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193 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What is a polymer? |
A polymer is a large molecule that is made up of very long chain molecules which are composed of smaller units called monomers. |
They are very big! |
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What is a monomer? |
A monomer contains a double bond that reacts with a radical to form a chain or carbon-carbon linkages. |
They form polymers! |
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What is a polymer gel? |
A solid that has a large fluid component that is intimately mixed. The solid is made up of cross links that form a 3D network throughout the structure. This connection can be physical or covalent. |
It’s physical connection makes it a solid! |
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What are the properties of polymer gel? |
Polymer gels have liquid and solid character, (viscoelasticity). They mimic the properties of living tissues. |
Not a liquid has liquids don’t remember it’s shape! |
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What are the applications of polymer gels? |
They are biocompatible, so good for drug delivery. They can be good for filtration and insulation. They are cheap and easy to make. They are can be made responsive to stimuli. They are biodegradable and their properties are tuneable. Also good for cell growth and respiration. |
Think about the biocompatibility! |
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Xerogels |
Gels that have been dried out and the solid network has been left behind. Good for filtration and insulation. |
Think about the name “Xero” |
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Aerogels |
This is where the liquid component of the gel has been replaced with gas. Ultra light. |
They can balance on top of a blade of grass! |
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What are the commercial applications of gels? |
Contact lens, skin care, absorbing liquids ( nappies, soils, etc), foods, drug release, analysis (DNA, protein electrophoresis), growing cells, wound healing. |
What are some everyday gel products you see? |
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What are the disadvantages of gels? |
Not environmentally stable so can dry out or swell with liquid. They are usually very weak or brittle and can tear. Solvents also add weight with little functionality. |
Think about the limitations of everyday gels. |
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What is cross linking? |
Form a kind of mesh that acts as a sieve, filters out large molecules. Form the network that makes up the solid component of the gel. Bifunctional or multifunctional monomers that have two or more double bonds in FRP. There are 6 common types of cross linking. Which are covalent, ionic, entanglement, salt formation, H-bonding, hydrophobic interaction. |
What contributes to the solid network? |
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What are the two ways to prepare polymer gels? |
1st way: most common and easiest way is by free radical polymerisation (FRP) which happens in the presence of crosslinker and monomer. 2nd way: start with a polymer solution and add crosslinker |
Think about radical sources! |
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What are the three steps in FRP? |
1st step: initiation - production of new radicals which then add onto the monomer. 2nd step: propagation - addition of a growing chain onto a monomer. 3rd step: termination - the radical at the end of the chain is destroyed by some process. Usually involves a H from a solvent, monomer or another polymer chain.
This technique doesn’t mind water and can be initiated by heat, light and electrochemically. Does not like oxygen and thiols. Length of chains are determined by rate of propagation/termination. |
Can be done with a wide range of double bonds. Think about how you would end a long chain. |
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What are the two types of photo initiators in FRP? |
Type 1- absorbs the light and then fragments into radicals, undergoes direct photodissociation. Aka Norris type 1 reaction. Type 2- photochemical intramolecular abstraction of a hydrogen atom or electron from a donor molecule to produce radicals as a primary product. Has two ingredients. Aka Norrish type 2 reaction. |
Which one has two ingredients? |
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What is the advantage of photo initiation over thermal initiation? |
-light abundance, clean and green, sustainable, environmentally friendly, allows for a greater amount of spatial and temporal control, safer. |
Think about the sustainability |
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What is the requirement for polymers to be water soluble? |
-to form a hydrogel that polymer must be soluble in water. For water solubility, polymer must have lots of polar and/or hydrophilic groups such as OH-, NH3+, CO2-, SO3-. Most natural polymers are water soluble (except cellulose and citin). |
Think about common charged groups and common polar groups. |
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Gelatin |
-prepared by thermal denaturalisation of collagen, which is abundant in fish skin, animals, bones and cartilage. Collagen, which is an insoluble protein, can be broken up through hydrolysis to form Gelatine. Which becomes a gel when it cools. |
Think about collagen |
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Gelatin |
-prepared by thermal denaturalisation of collagen, which is abundant in fish skin, animals, bones and cartilage. Collagen, which is an insoluble protein, can be broken up through hydrolysis to form Gelatine. Which becomes a gel when it cools. |
Think about collagen |
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Starch |
-used for energy storage in plants, this is largely 1,4 linked polyglucose structure. Highly branched starches are water soluble while more linear starches are only soluble in hot water. Gel when cooled through partial crystallisation. |
Think about how plants use it |
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Alginates |
-used as alternatives for gelatine for vege boys. They are 1,4 linked polysaccharide with carboxylic groups extracted from seaweed. Can be cross linked by forming gels by adding calcium ions which form salt cross links between the carboxylate ions. |
Think about the salt formation cross links! |
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Hyaluronic acid |
-complex polysaccharide with carboxylic groups. It is the main component of the extra cellular matrix between cells and joints. Used in skin care products. Also to treat arthritis and as a dermal filler in cosmetic surgery. |
What part of the body does this come from? |
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Chitin |
-main material in shells of crustaceans and insects. Highly insoluble and crystalline. Can form chitosan by hydrolysing the N acetamide group with a strong base to an amine. |
One of the few natural polymers that are insoluble |
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Chitin |
-main material in shells of crustaceans and insects. Highly insoluble and crystalline. Can form chitosan by hydrolysing the N acetamide group with a strong base to an amine. |
One of the few natural polymers that are insoluble |
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Chitosan |
-is soluble in mild acid (which protonates the amines). When protonated it is mildly antimicrobial as positive charge disrupts the negative charged microbial walls. |
Think about the amine groups on this polymer. |
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Chitin |
-main material in shells of crustaceans and insects. Highly insoluble and crystalline. Can form chitosan by hydrolysing the N acetamide group with a strong base to an amine. |
One of the few natural polymers that are insoluble |
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Chitosan |
-is soluble in mild acid (which protonates the amines). When protonated it is mildly antimicrobial as positive charge disrupts the negative charged microbial walls. |
Think about the amine groups on this polymer. |
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Cellouse |
-main component of plant cell walls. Not soluble, too crystalline, it can be broken up by cellouse derivatives to make it more soluble. Derivatives are methyl cellulose, carboxymethylcellose. Both used as water thickeners in food and pharmaceuticals. |
One of the few natural polymers that are insoluble |
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Chitin |
-main material in shells of crustaceans and insects. Highly insoluble and crystalline. Can form chitosan by hydrolysing the N acetamide group with a strong base to an amine. |
One of the few natural polymers that are insoluble |
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Chitosan |
-is soluble in mild acid (which protonates the amines). When protonated it is mildly antimicrobial as positive charge disrupts the negative charged microbial walls. |
Think about the amine groups on this polymer. |
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Cellouse |
-main component of plant cell walls. Not soluble, too crystalline, it can be broken up by cellouse derivatives to make it more soluble. Derivatives are methyl cellulose, carboxymethylcellose. Both used as water thickeners in food and pharmaceuticals. |
One of the few natural polymers that are insoluble |
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Heparin |
-densely sulphated and a naturally occurring glycosaminoglycan. Known as a potent anticoagulant. Derived from mucosal tissues of meat animals such as pig intestines. Not sheep! |
Think gross lol |
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Cerium salt cross linking method |
-Cerium salts (such as ceric ammonium nitrate) are used to cleavage the 1,2 diols to produce free radicals. Then add the di-function crosslinker to generate chemical crosslinking. Many natural polymers have diol groups in sugar backbones so common method to join natural polymers with synthetic polymers and cross link natural polymers. |
Think about the diols in sugar backbones. |
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Imine (schiff base) linkage cross linking method |
-An imine is formed between an amine and an aldehyde or ketone and works even in water. So can oxidate a hydroxyl group to an aldehyde group then add the di- amine or multi amine crosslinker to generate chemical crosslinking. Used for nasal surgery where they react with a solution of chitosan derivatives with a solution of oxidised polysaccharide that contains aldehyde groups. |
Think about nasal surgery |
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Imine (schiff base) linkage cross linking method |
-An imine is formed between an amine and an aldehyde or ketone and works even in water. Used for nasal surgery where they react with a solution of chitosan derivatives with a solution of oxidised polysaccharide that contains aldehyde groups. |
Think about nasal surgery |
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Amide linkage crosslinking method |
-amides are very nucleophilic and react with a variety of electrophiles. This way is used to couple amines and carboxylic acids in water to form amides. To link two amine containing polymer chains you would use a diacid cross linker. You use the EDC carboamide for aqueous cross linking and the water insoluble DCC carboamide for non-aqueous synthesis. DCC is not widely used as contains toxic leftovers. |
How are amides formed? |
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Imine (schiff base) linkage cross linking method |
-An imine is formed between an amine and an aldehyde or ketone and works even in water. Used for nasal surgery where they react with a solution of chitosan derivatives with a solution of oxidised polysaccharide that contains aldehyde groups. |
Think about nasal surgery |
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Amide linkage crosslinking method |
-amides are very nucleophilic and react with a variety of electrophiles. This way is used to couple amines and carboxylic acids in water to form amides. To link two amine containing polymer chains you would use a diacid cross linker. You use the EDC carboamide for aqueous cross linking and the water insoluble DCC carboamide for non-aqueous synthesis. Both EDC and DCC activate the carboxylic acid group which can then be cross linked with di amine or poly amine. DCC is not widely used as contains toxic leftovers. |
How are amides formed? |
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NHS coupling crosslinking method |
-used as an activating reagent for carboxylic acids to form active esters. Then crosslink with di amine or poly amine. More stable than the intermediates from EDC and DCC. |
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Method for crosslinking thiol containing polymers |
-first add a mild oxidant such as peroxide or iodine which forms dithiol linkages. This occurs in nature to internally stabilise protein structures. Oxygen can initiate this reaction making the polymers difficult to store without gelling. Thiols make good nucleophiles and can target double bonds in a Michael addition. This can be catalysed by radicals or base. To gel a mixture of double bonds and thiols, use a radical source (eg peroxide) and heat or a photo initiator and light or a change in pH. |
This is where Michael addition comes into play |
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Click chemistry |
-must have very high yielding coupling reaction, ideally more than 99% -couple under mild conditions eg water at room temperature with minimal side products and ideally no catalysts or other reagents needed. |
Think quick and easy |
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Copper catalysed azide alkyne cycloaddition |
-to make a gel, mixing polymers containing both azide and alkyne functionalities with a trace amount of copper catalyst. Example of click chemistry |
It’s in the name lol |
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What is self-healing gel? |
Self-healing gels are gels that are formed by dynamic covalent bonds which have cross links that are not fixed so that any force can be absorbed by breaking the temporary crosslink and then reforming it. |
Dynamic covalent bonds |
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What are the 5 non-covalent bond crosslink/dynamic covalent bond methods? |
Imine bond, boronate ester bond, disulfide, acylhydrazone, DA reaction. |
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What is H bonded gel design? |
-by incorporating hydrogen bonding units, gels can be made very tough as the reversible bonds can absorb energy and reform any damage. |
In the name! |
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What are Zwitterionic gels? |
-are ionic gels that are held together by electrostatic forces, which can work in water. A zwitterion, contains an equal number of positively and negatively charged functional groups. They are generally weak as they don’t have enough intermolecular attraction as most of the attraction is intramolecular. Super hydrophilic and bio compatible. |
Also called an inner salt |
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Ampholytic gels |
A type of Zwitterionic gel. They contain both positive and negative monomers that have been copolymerised and require no crosslinker as the ionic bonds form the crosslinker. Mobile counter ions (Na+) need to be removed as will dissolve the gel since it screens the reaction. The solution must be very concentrated or not enough attractive forces to hold gel together. Displays self healing, as ionic linkages can reform. |
Think about ionic bonds |
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Suparmolecular gel |
When small molecules (LMWGs) aggregate to form long fibres which gel the system. Other shapes precipitate out. Found in nonaqueous systems. Responds to heat, light and fluoride ions. |
Think about long strands |
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low molecular weight gelators (LMWGs) |
The gelatos molecules have a polar and a non polar region. One part will aggregate away from the solvent and the other part will like the solvent and the control of the aggregation so it forms fibres. This can be controlled by temperature, solvent polarity, pH etc. |
Think about polarity |
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What is the general structure of a RAFT agent? |
Reactive C=S double bond that captures free radical (addition). Weak S-C single bond to be homolytic cleavage (fragmentation). And a modifier attached to the C=S, modifies addition and fragmentation rates. |
Lots of S |
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What is the general structure of a RAFT agent? |
Reactive C=S double bond that captures free radical (addition). Weak S-C single bond to be homolytic cleavage (fragmentation). And a modifier attached to the C=S, modifies addition and fragmentation rates. |
Lots of S |
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RAFT polymerisation mechanism |
A type of living polymerisation invoking a conventional radical polymerisation which is mediated by a RAFT agent. Monomers must be capable of radical polymerisation. The steps are initiation, pre-equilibrium, re-initiation, main equilibrium, propagation and termination. RAFT adduct radical is sufficiently hindered such that it does not undergo termination reactions. Monomer, solvent, radical, and polymer. |
Think about typical FRP |
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What is MAM and LAM |
MAM is a class of monomers that means more activated and LAM means less activated |
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Living polymer network |
-able to grow in size and mass. Parent network refers to the network between the end of formation and prior any further growth, daughter networks are those which have been grown or modified from a progenitor parent network. |
In the name |
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Uncontrolled vs controlled |
Uncontrolled: simple to implement and low cost. Broader molecular weight, limited control over polymer structure and end group, dead polymer, uncontrolled initiation, propagation, and termination. Controlled: narrow mw disperity, predetermined mw, dormant polymer, can be reactivated and further growth. Need to select a RAFT agent, slower polymerisation kinetics. |
Dead vs living polymers |
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PET-RAFT |
-stands for photo induced electron energy transfer. It is superior to the original RAFT. Used for continuous and consistent polymer production. Carried out by a photoredox catalyst and chain transfer agent, initiated by light. |
Think about light |
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PET-RAFT |
-stands for photo induced electron energy transfer. It is superior to the original RAFT. Used for continuous and consistent polymer production. Carried out by a photoredox catalyst and chain transfer agent, initiated by light. |
Think about light |
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Tensile modulus |
Ratio is stress and strain which is a measure of how stiff the material is. Modulus employs a hooke’s law calculation. E = stress/strain. |
Stress vs strain |
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Difference between toughness and stiffness |
Stiffness is how well a material resists deformation, the force need to stretch by a certain amount. Toughness is the ability of material to absorb energy before failure. Stiffness can be probed through measuring the stress/strain relationship. Stress is how much pressure is applied and strain is how much the object is affected by stress. Toughness is related to cracking. |
Think about the lab. |
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Examples of how to make gels tougher |
-make the chain lengths between crosslinks longer and more even in length so there are no short chains to break early -include a mechanism to absorb extra energy from the crack to stop spreading -use roxtaxanes for crosslinks makes the structure more flexible and more sliding movement along the chains |
Longer chains |
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Double network gel |
Hydrogels that contain 80 to 90 percent weight of water yet are both hard and strong with mechanical properties comparable to that of rubbers and cartilages. Consist of two interpenetrating polymer network with different mechanical properties. First network is highly stretched and densely cross linked, making it stiff and brittle. The second network is flexible and sparsely cross linked, making is soft and stretchable. |
Two solid polymer networks |
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How is double network gels prepared. |
Highly crossed linked network is first polymerised then a loose lightly cross linked network of a different monomer is formed around. They are slow to make as after the first polymerisation the second monomer and initiator must be slowly diffused into the first gel, ready for second polymerisation. |
By normal methods, just done twice. |
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Gelation process |
When gelation occurs, a dilute or more viscous polymer solution is converted into a system of infinite viscosity, i.e. a gel. |
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Gelation process |
When gelation occurs, a dilute or more viscous polymer solution is converted into a system of infinite viscosity, i.e. a gel. |
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Gel point |
The point is an abrupt change in the viscosity of a solution containing polymerisable components. At this point, a solution undergoes gelation as reflected in a loss of fluids and an infinite 3 dimensional network is formed. |
Change from liquid to solid |
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Reaction time |
Formation process of synthetic polymer gels such as the polymerisation of multifunctional monomers or the reaction between a linear polymer and crosslinking agent. Gel point being treated as a function of reaction time. Gel point is the time when the gel starts forming after the time the reaction started. |
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Reaction time |
Formation process of synthetic polymer gels such as the polymerisation of multifunctional monomers or the reaction between a linear polymer and crosslinking agent. Gel point being treated as a function of reaction time. Gel point is the time when the gel starts forming after the time the reaction started. |
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Temperature |
At which the gel is formed by increasing or decreasing the temperature. |
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Reaction time |
Formation process of synthetic polymer gels such as the polymerisation of multifunctional monomers or the reaction between a linear polymer and crosslinking agent. Gel point being treated as a function of reaction time. Gel point is the time when the gel starts forming after the time the reaction started. |
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Temperature |
At which the gel is formed by increasing or decreasing the temperature. |
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Solution concentration |
The minimum necessary amount of solute molecules in solvent. |
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Inverse test tube method |
Predicts the gel point by keeping aqueous solution of gelatin in an ice bath for 24 h. Melting point determined when the gel is dropped to the bottom of the glass tube. Determines the melting point with the data obtained. The equation derived from the Vant Hoff equation used to express the linear relationship. |
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Viscoelasticity |
Have viscous properties and elastic properties. In a solid if one applies an oscillatory strain and measures the stress, the difference between the peak strain and the stress is zero in a perfect elastic solid. In a liquid a different behaviour is found. The force (stress) needed is not proportional to the displacement (strain) but 90 out of phase with it. G’ storage modulus (in phase solid property), G’’ loss modulus ( 90 out of phase, liquid property) when G’=G’’ this is the gelation point. |
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Viscoelasticity |
Have viscous properties and elastic properties. In a solid if one applies an oscillatory strain and measures the stress, the difference between the peak strain and the stress is zero in a perfect elastic solid. In a liquid a different behaviour is found. The force (stress) needed is not proportional to the displacement (strain) but 90 out of phase with it. G’ storage modulus (in phase solid property), G’’ loss modulus ( 90 out of phase, liquid property) when G’=G’’ this is the gelation point. |
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Rheological test |
Used for product quality control as a measurement of the elastic recovery in polymer melts and their compounds. Measures the swell or shrinkage of materials undergoing extrusion. Solids and liquids behave differently on this test. Shear produced by the test is measured. |
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Viscoelasticity |
Have viscous properties and elastic properties. In a solid if one applies an oscillatory strain and measures the stress, the difference between the peak strain and the stress is zero in a perfect elastic solid. In a liquid a different behaviour is found. The force (stress) needed is not proportional to the displacement (strain) but 90 out of phase with it. G’ storage modulus (in phase solid property), G’’ loss modulus ( 90 out of phase, liquid property) when G’=G’’ this is the gelation point. |
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Rheological test |
Used for product quality control as a measurement of the elastic recovery in polymer melts and their compounds. Measures the swell or shrinkage of materials undergoing extrusion. Solids and liquids behave differently on this test. Shear produced by the test is measured. |
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Driving force between gel elasticity |
Entropy. As there are a trillion ways for the chains to wander between the endpoints which means in an increase in entropy (states) on going from a stretched chain to a more folded one. The enthalpy doesn’t change much as the chain changes conformation so as G will become more negative (favourable) as the stretched chain contracts out due to increasing S. |
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Viscoelasticity |
Have viscous properties and elastic properties. In a solid if one applies an oscillatory strain and measures the stress, the difference between the peak strain and the stress is zero in a perfect elastic solid. In a liquid a different behaviour is found. The force (stress) needed is not proportional to the displacement (strain) but 90 out of phase with it. G’ storage modulus (in phase solid property), G’’ loss modulus ( 90 out of phase, liquid property) when G’=G’’ this is the gelation point. |
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Rheological test |
Used for product quality control as a measurement of the elastic recovery in polymer melts and their compounds. Measures the swell or shrinkage of materials undergoing extrusion. Solids and liquids behave differently on this test. Shear produced by the test is measured. |
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Driving force between gel elasticity |
Entropy. As there are a trillion ways for the chains to wander between the endpoints which means in an increase in entropy (states) on going from a stretched chain to a more folded one. The enthalpy doesn’t change much as the chain changes conformation so as G will become more negative (favourable) as the stretched chain contracts out due to increasing S. |
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What two forces determine the amount of swelling? |
Osmotic pressure- is the minimum pressure needed to be applied to solution to prevent the inward flow of its pure solvent across a semipermeable membrane. Also the tendency of a solution to take its pure solvent by omosis. Elastic energy- is the energy stored in the configuration of a material or physical system as it is subjected to elastic deformation by work performed upon it. The energy needed to stretch the gel is balanced by osmotic energy gained by swelling the gel. Has unfavourable S decrease. This determines the amount of swelling. |
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How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
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How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
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Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
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How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
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Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
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Basic strategy for pH sensitive |
-form hydrogels with weak acid groups, these groups will be unionised in low pH and deprotonated and charged at high pH. This increased charge makes them more hydrophilic and thus they swell more. |
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How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
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Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
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Basic strategy for pH sensitive |
-form hydrogels with weak acid groups, these groups will be unionised in low pH and deprotonated and charged at high pH. This increased charge makes them more hydrophilic and thus they swell more. |
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Strategy for redox sensitive |
Is to instal redox capable groups which can be oxidised or reduced which will change their polarity of charge causing swelling or deswelling. Oxidation causes swelling and reduction causes deswelling. |
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How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
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Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
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Basic strategy for pH sensitive |
-form hydrogels with weak acid groups, these groups will be unionised in low pH and deprotonated and charged at high pH. This increased charge makes them more hydrophilic and thus they swell more. |
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Strategy for redox sensitive |
Is to instal redox capable groups which can be oxidised or reduced which will change their polarity of charge causing swelling or deswelling. Oxidation causes swelling and reduction causes deswelling. |
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Electro conductive gels |
Add conductive material to the gel, could be conductive polymers, graphene, carbon nanotubes, ions, etc. Used as soft strain sensors. |
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How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
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Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
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Basic strategy for pH sensitive |
-form hydrogels with weak acid groups, these groups will be unionised in low pH and deprotonated and charged at high pH. This increased charge makes them more hydrophilic and thus they swell more. |
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Strategy for redox sensitive |
Is to instal redox capable groups which can be oxidised or reduced which will change their polarity of charge causing swelling or deswelling. Oxidation causes swelling and reduction causes deswelling. |
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Electro conductive gels |
Add conductive material to the gel, could be conductive polymers, graphene, carbon nanotubes, ions, etc. Used as soft strain sensors. |
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LCST behaviour of PNIPAAm |
It is soluble when cold and insoluble when put in hot water. Have a hydrophilic and hydrophobic part. The hydrophilic part makes the polymer compatible in the first place but the water doesn’t like the hydrophilic part so it’s structures around it, these molecules are more ordered than normal water, accounting for negative entropy. |
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How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
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Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
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Basic strategy for pH sensitive |
-form hydrogels with weak acid groups, these groups will be unionised in low pH and deprotonated and charged at high pH. This increased charge makes them more hydrophilic and thus they swell more. |
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Strategy for redox sensitive |
Is to instal redox capable groups which can be oxidised or reduced which will change their polarity of charge causing swelling or deswelling. Oxidation causes swelling and reduction causes deswelling. |
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Electro conductive gels |
Add conductive material to the gel, could be conductive polymers, graphene, carbon nanotubes, ions, etc. Used as soft strain sensors. |
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LCST behaviour of PNIPAAm |
It is soluble when cold and insoluble when put in hot water. Have a hydrophilic and hydrophobic part. The hydrophilic part makes the polymer compatible in the first place but the water doesn’t like the hydrophilic part so it’s structures around it, these molecules are more ordered than normal water, accounting for negative entropy. |
|
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|
How to tune LCST temperature |
By changing the size of the alkyle group the LCST temperature can be raised or lowered. The less polar the more water has to structure around it, making S even more negative, further lowering the LCST. |
|
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|
How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
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|
Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
|
|
|
Basic strategy for pH sensitive |
-form hydrogels with weak acid groups, these groups will be unionised in low pH and deprotonated and charged at high pH. This increased charge makes them more hydrophilic and thus they swell more. |
|
|
|
Strategy for redox sensitive |
Is to instal redox capable groups which can be oxidised or reduced which will change their polarity of charge causing swelling or deswelling. Oxidation causes swelling and reduction causes deswelling. |
|
|
|
Electro conductive gels |
Add conductive material to the gel, could be conductive polymers, graphene, carbon nanotubes, ions, etc. Used as soft strain sensors. |
|
|
|
LCST behaviour of PNIPAAm |
It is soluble when cold and insoluble when put in hot water. Have a hydrophilic and hydrophobic part. The hydrophilic part makes the polymer compatible in the first place but the water doesn’t like the hydrophilic part so it’s structures around it, these molecules are more ordered than normal water, accounting for negative entropy. |
|
|
|
How to tune LCST temperature |
By changing the size of the alkyle group the LCST temperature can be raised or lowered. The less polar the more water has to structure around it, making S even more negative, further lowering the LCST. |
|
|
|
Photo cleavage |
Useful for releasing things from gel, or for breaking up a gel so it dissolves. Eg type 1 photoinitiators or coumarin to o - nitrobenzyle |
|
|
|
How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
|
|
Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
|
|
|
Basic strategy for pH sensitive |
-form hydrogels with weak acid groups, these groups will be unionised in low pH and deprotonated and charged at high pH. This increased charge makes them more hydrophilic and thus they swell more. |
|
|
|
Strategy for redox sensitive |
Is to instal redox capable groups which can be oxidised or reduced which will change their polarity of charge causing swelling or deswelling. Oxidation causes swelling and reduction causes deswelling. |
|
|
|
Electro conductive gels |
Add conductive material to the gel, could be conductive polymers, graphene, carbon nanotubes, ions, etc. Used as soft strain sensors. |
|
|
|
LCST behaviour of PNIPAAm |
It is soluble when cold and insoluble when put in hot water. Have a hydrophilic and hydrophobic part. The hydrophilic part makes the polymer compatible in the first place but the water doesn’t like the hydrophilic part so it’s structures around it, these molecules are more ordered than normal water, accounting for negative entropy. |
|
|
|
How to tune LCST temperature |
By changing the size of the alkyle group the LCST temperature can be raised or lowered. The less polar the more water has to structure around it, making S even more negative, further lowering the LCST. |
|
|
|
Photo cleavage |
Useful for releasing things from gel, or for breaking up a gel so it dissolves. Eg type 1 photoinitiators or coumarin to o - nitrobenzyle |
|
|
|
Photo dimerization |
Two molecules that are photo excited are joined together. Many of these are reversible (at different wavelengths) so can be basis for photo cleavage as well. Might be used to form gels using light, or make existing gels stiffer by adding extra crosslinks. |
|
|
|
How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
|
|
Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
|
|
|
Basic strategy for pH sensitive |
-form hydrogels with weak acid groups, these groups will be unionised in low pH and deprotonated and charged at high pH. This increased charge makes them more hydrophilic and thus they swell more. |
|
|
|
Strategy for redox sensitive |
Is to instal redox capable groups which can be oxidised or reduced which will change their polarity of charge causing swelling or deswelling. Oxidation causes swelling and reduction causes deswelling. |
|
|
|
Electro conductive gels |
Add conductive material to the gel, could be conductive polymers, graphene, carbon nanotubes, ions, etc. Used as soft strain sensors. |
|
|
|
LCST behaviour of PNIPAAm |
It is soluble when cold and insoluble when put in hot water. Have a hydrophilic and hydrophobic part. The hydrophilic part makes the polymer compatible in the first place but the water doesn’t like the hydrophilic part so it’s structures around it, these molecules are more ordered than normal water, accounting for negative entropy. |
|
|
|
How to tune LCST temperature |
By changing the size of the alkyle group the LCST temperature can be raised or lowered. The less polar the more water has to structure around it, making S even more negative, further lowering the LCST. |
|
|
|
Photo cleavage |
Useful for releasing things from gel, or for breaking up a gel so it dissolves. Eg type 1 photoinitiators or coumarin to o - nitrobenzyle |
|
|
|
Photo dimerization |
Two molecules that are photo excited are joined together. Many of these are reversible (at different wavelengths) so can be basis for photo cleavage as well. Might be used to form gels using light, or make existing gels stiffer by adding extra crosslinks. |
|
|
|
Photo isomerization |
These are molecules that bend or change shape on exposure to light. Might be useful in changing a gels overall shape or polarity. Many are reversible, so can switch back and forth. |
|
|
|
How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
|
|
Photo ionisation |
These may release or take in ions on irradiation, resulting in a change in pH. This can cause ionic gel to expand or contract. |
|
|
|
Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
|
|
|
Basic strategy for pH sensitive |
-form hydrogels with weak acid groups, these groups will be unionised in low pH and deprotonated and charged at high pH. This increased charge makes them more hydrophilic and thus they swell more. |
|
|
|
Strategy for redox sensitive |
Is to instal redox capable groups which can be oxidised or reduced which will change their polarity of charge causing swelling or deswelling. Oxidation causes swelling and reduction causes deswelling. |
|
|
|
Electro conductive gels |
Add conductive material to the gel, could be conductive polymers, graphene, carbon nanotubes, ions, etc. Used as soft strain sensors. |
|
|
|
LCST behaviour of PNIPAAm |
It is soluble when cold and insoluble when put in hot water. Have a hydrophilic and hydrophobic part. The hydrophilic part makes the polymer compatible in the first place but the water doesn’t like the hydrophilic part so it’s structures around it, these molecules are more ordered than normal water, accounting for negative entropy. |
|
|
|
How to tune LCST temperature |
By changing the size of the alkyle group the LCST temperature can be raised or lowered. The less polar the more water has to structure around it, making S even more negative, further lowering the LCST. |
|
|
|
Photo cleavage |
Useful for releasing things from gel, or for breaking up a gel so it dissolves. Eg type 1 photoinitiators or coumarin to o - nitrobenzyle |
|
|
|
Photo dimerization |
Two molecules that are photo excited are joined together. Many of these are reversible (at different wavelengths) so can be basis for photo cleavage as well. Might be used to form gels using light, or make existing gels stiffer by adding extra crosslinks. |
|
|
|
Photo isomerization |
These are molecules that bend or change shape on exposure to light. Might be useful in changing a gels overall shape or polarity. Many are reversible, so can switch back and forth. |
|
|
|
How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
|
|
Photo ionisation |
These may release or take in ions on irradiation, resulting in a change in pH. This can cause ionic gel to expand or contract. |
|
|
|
Additive manufacturing |
A process of making 3D products through adding material layer by layer, synonymous with 3D printing. Which allows design freedom, less waste, quick production, on demand manufacturing. |
The basis of 3D printing |
|
|
Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
|
|
|
Basic strategy for pH sensitive |
-form hydrogels with weak acid groups, these groups will be unionised in low pH and deprotonated and charged at high pH. This increased charge makes them more hydrophilic and thus they swell more. |
|
|
|
Strategy for redox sensitive |
Is to instal redox capable groups which can be oxidised or reduced which will change their polarity of charge causing swelling or deswelling. Oxidation causes swelling and reduction causes deswelling. |
|
|
|
Electro conductive gels |
Add conductive material to the gel, could be conductive polymers, graphene, carbon nanotubes, ions, etc. Used as soft strain sensors. |
|
|
|
LCST behaviour of PNIPAAm |
It is soluble when cold and insoluble when put in hot water. Have a hydrophilic and hydrophobic part. The hydrophilic part makes the polymer compatible in the first place but the water doesn’t like the hydrophilic part so it’s structures around it, these molecules are more ordered than normal water, accounting for negative entropy. |
|
|
|
How to tune LCST temperature |
By changing the size of the alkyle group the LCST temperature can be raised or lowered. The less polar the more water has to structure around it, making S even more negative, further lowering the LCST. |
|
|
|
Photo cleavage |
Useful for releasing things from gel, or for breaking up a gel so it dissolves. Eg type 1 photoinitiators or coumarin to o - nitrobenzyle |
|
|
|
Photo dimerization |
Two molecules that are photo excited are joined together. Many of these are reversible (at different wavelengths) so can be basis for photo cleavage as well. Might be used to form gels using light, or make existing gels stiffer by adding extra crosslinks. |
|
|
|
Photo isomerization |
These are molecules that bend or change shape on exposure to light. Might be useful in changing a gels overall shape or polarity. Many are reversible, so can switch back and forth. |
|
|
|
How to calculate cross link density. |
By mixing a polymer and solvent which can be approximated to by a simple flory huggins solution theory. One way to experimentally estimate the crosslink density is to see how much they swell. |
Swelling increase as cross density goes down (mw between crosslinks increase) or solvent gets better, flory huggins parameter. |
|
|
Photo ionisation |
These may release or take in ions on irradiation, resulting in a change in pH. This can cause ionic gel to expand or contract. |
|
|
|
Additive manufacturing |
A process of making 3D products through adding material layer by layer, synonymous with 3D printing. Which allows design freedom, less waste, quick production, on demand manufacturing. |
The basis of 3D printing |
|
|
Subtractive manufacturing |
A process of making material by removing from a solid object. Well known process with a long history. Also simple to manufacture. |
|
|
|
Responsive gel |
Gels that respond to their environment by changing a physical attribute. Common stimuli- temperature, water, voltage, light, magnetic field, ions, pH, organic solvent, enzymes Common effects- shape change, colour change, mechanical properties, fluorescence, degradation, surface energy change, piezoelectricity, chemical spawn, growth, self-healing. |
|
|
|
Basic strategy for pH sensitive |
-form hydrogels with weak acid groups, these groups will be unionised in low pH and deprotonated and charged at high pH. This increased charge makes them more hydrophilic and thus they swell more. |
|
|
|
Strategy for redox sensitive |
Is to instal redox capable groups which can be oxidised or reduced which will change their polarity of charge causing swelling or deswelling. Oxidation causes swelling and reduction causes deswelling. |
|
|
|
Electro conductive gels |
Add conductive material to the gel, could be conductive polymers, graphene, carbon nanotubes, ions, etc. Used as soft strain sensors. |
|
|
|
LCST behaviour of PNIPAAm |
It is soluble when cold and insoluble when put in hot water. Have a hydrophilic and hydrophobic part. The hydrophilic part makes the polymer compatible in the first place but the water doesn’t like the hydrophilic part so it’s structures around it, these molecules are more ordered than normal water, accounting for negative entropy. |
|
|
|
How to tune LCST temperature |
By changing the size of the alkyle group the LCST temperature can be raised or lowered. The less polar the more water has to structure around it, making S even more negative, further lowering the LCST. |
|
|
|
Photo cleavage |
Useful for releasing things from gel, or for breaking up a gel so it dissolves. Eg type 1 photoinitiators or coumarin to o - nitrobenzyle |
|
|
|
Photo dimerization |
Two molecules that are photo excited are joined together. Many of these are reversible (at different wavelengths) so can be basis for photo cleavage as well. Might be used to form gels using light, or make existing gels stiffer by adding extra crosslinks. |
|
|
|
Photo isomerization |
These are molecules that bend or change shape on exposure to light. Might be useful in changing a gels overall shape or polarity. Many are reversible, so can switch back and forth. |
|
|
|
Brief history of 3D printing |
1981, Hideo Kodama made first prototype. 1984, Charles Hull, inventing stereolithography. Which lets designers create 3D models using digital data. |
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FDM 3D |
3D printing technology that is based on material extrusion. A fused deposition melts a plastic filament and extrudes it through a nozzle. The material is laid down layer by layer. Usually the cheapest 3D printing option. But has a lack of fine details. |
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Polylactic acid for FDM |
Environmentally friendly, biodegradable as made from corn starch or sugar cane, print temperature 180 C - 230 C, odourless, even sweet smelling, a bit brittle, deform around temperatures of 60 C |
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Polylactic acid for FDM |
Environmentally friendly, biodegradable as made from corn starch or sugar cane, print temperature 180 C - 230 C, odourless, even sweet smelling, a bit brittle, deform around temperatures of 60 C |
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|
Acrylonnitrile butadiene styrene (ABS) for FDM |
Good general purpose 3D printer filament, print temperature; 210 C - 250 C. Print bed temperature 80 C - 110 C, tough and moderately flexible. |
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Polyethylene terephthalate (PET) |
Similar to ABS, but possible food safe. Print temperature 220 C - 250 C. Print bed temperature 50 C - 75 C. Susceptible to moisture. |
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Thermoplastic polyurethane (TPU) for FDM |
Extremely flexible, bendable, stretchable, compressible. Print temperature: 210 C - 230 C. Difficult to print, slow print speed. |
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Thermoplastic polyurethane (TPU) for FDM |
Extremely flexible, bendable, stretchable, compressible. Print temperature: 210 C - 230 C. Difficult to print, slow print speed. |
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Nylon for FDM |
High strength, high flexibility, high durability. Print temperature 240 C - 260 C. Print bed temperature 70 C - 100 C. Typically expensive. |
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Thermoplastic polyurethane (TPU) for FDM |
Extremely flexible, bendable, stretchable, compressible. Print temperature: 210 C - 230 C. Difficult to print, slow print speed. |
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|
Nylon for FDM |
High strength, high flexibility, high durability. Print temperature 240 C - 260 C. Print bed temperature 70 C - 100 C. Typically expensive. |
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Polycarbonate (PC) for FDM |
Strongest 3D printer filament, resistant to heat and physical impact. Very high print temperature 270 C - 310 C. Print bed temperature 90 C - 110 C. Absolutely not food safe. |
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Stereolithography (SLA) |
This machine builds parts out of a liquid photopolymer through polymerisation activated by a later (usually 405nm). Parts are built on to a build platform inside a vat filled with the liquid photo polymer. The laser is line by line scanning the surface of the vat which is photopolymerised and solidifying. The build platform is lowered into the vat and the part is built layer by layer. Only works with photo polymers. Very good accuracy and fine details. |
|
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|
Stereolithography (SLA) |
This machine builds parts out of a liquid photopolymer through polymerisation activated by a later (usually 405nm). Parts are built on to a build platform inside a vat filled with the liquid photo polymer. The laser is line by line scanning the surface of the vat which is photopolymerised and solidifying. The build platform is lowered into the vat and the part is built layer by layer. Only works with photo polymers. Very good accuracy and fine details. |
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|
Digital light processing (DLP) |
A DMD (digital micro mirror device) is a key component which is made of thousands of micro mirrors used for navigating the light beam projected by the digital light projector. Similar to SLA but instead projects an entire image at once to cure a photo polymer. Also needs photo polymerisation. |
|
|
|
Stereolithography (SLA) |
This machine builds parts out of a liquid photopolymer through polymerisation activated by a later (usually 405nm). Parts are built on to a build platform inside a vat filled with the liquid photo polymer. The laser is line by line scanning the surface of the vat which is photopolymerised and solidifying. The build platform is lowered into the vat and the part is built layer by layer. Only works with photo polymers. Very good accuracy and fine details. |
|
|
|
Digital light processing (DLP) |
A DMD (digital micro mirror device) is a key component which is made of thousands of micro mirrors used for navigating the light beam projected by the digital light projector. Similar to SLA but instead projects an entire image at once to cure a photo polymer. Also needs photo polymerisation. |
|
|
|
Continuous liquid interface production (CLIP) |
Is a variety of vat polymerisation, which uses an oxygen permeable film to inhibit polymerisation at the surface close to the UV source and as a result remove the need for an intermediate recoating step for each layer. CLIP is faster than DLP. |
|
|
|
Stereolithography (SLA) |
This machine builds parts out of a liquid photopolymer through polymerisation activated by a later (usually 405nm). Parts are built on to a build platform inside a vat filled with the liquid photo polymer. The laser is line by line scanning the surface of the vat which is photopolymerised and solidifying. The build platform is lowered into the vat and the part is built layer by layer. Only works with photo polymers. Very good accuracy and fine details. |
|
|
|
Digital light processing (DLP) |
A DMD (digital micro mirror device) is a key component which is made of thousands of micro mirrors used for navigating the light beam projected by the digital light projector. Similar to SLA but instead projects an entire image at once to cure a photo polymer. Also needs photo polymerisation. |
|
|
|
Continuous liquid interface production (CLIP) |
Is a variety of vat polymerisation, which uses an oxygen permeable film to inhibit polymerisation at the surface close to the UV source and as a result remove the need for an intermediate recoating step for each layer. CLIP is faster than DLP. |
|
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|
Two photon polymerisation for 3D micro printing. |
Enables three dimensional fabrication in the 100 nm regime. Is a non linear optical process based on the simultaneous absorption of two photons in a photosensitive material. Two photon absorption is proportional to the square of the intensity. |
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