Flashcards in Polymer 2: Properties of polymer Deck (20):
What are the two different states of polymers?
Describe the properties of crystalline state?
1. Highly ordered arrays of molecules and atoms
2. Definite melting point
3. Anisotropic: orientations are all in different directions
Describe the properties of Amorphous state?
1. Randomly orientated molecules and atoms
2. No definitive melting point
3. Some properties typical for liquids
4. Isotropic properties: orientations are in the same direction
What is left after evaporation of KCl and a polymer like chitosan?
1. Crystals formed through low organic salts
2. Solution of chitosan will never form crystals (jelly like material)
How do the ranges of crystallinity range from 0% to 90%?
1. 0% Amorphous
2. 90% crystalline
What do the factors of crystallinity depend upon?
1. Chemical structure
3. Processing conditions
4. Molecular Weight
What are the only polymer that can be completely crystallised?
Proteins have a perfect order at any level
What are the three different states for amorphous crystalline solids?
1. Glassy state
2. Rubbery state
3. Liquid state
How can you test the different states for amorphous crystalline solids?
Hanging a weight from the polymer and seeing how far they stretch
What does glass state temperature (Tg) mean?
The temperature required to turn glass from hard (glassy) to soft state (rubber)
Give two examples when Tg is -75 and Tg is 100?
1. Tg= -75 represents the material that forms catheters (polyisoprene)
2. Tg=100 represents polystyrene
What is plasticisation and what effect does it have on the glass state temperature?
1. When a substance is added that makes the material more soft such as water
2. Decreases glass transition temperature
When a polymer has a glass transition state of above 100 degrees and below it, what state does it bring?
1. Above Tg=100 means it's soft and rubbery
2. Below 100 degrees means it hard and glassy
What is addition polymerisation and give an example?
1. When you form a large macromolecule from the addition of many monomers with double bonds
2. This can be many repeating groups which leads to Poly being added to the front of the chemical name
Example: Vinyl acetate becomes poly (vinyl acetate)
What is step growth polymerisation?
1. When the polymer is added to water (hydrolysis)
2. Products formed are then used
Example: breast implants
What is Ring Opening Polymerisation?
1. Unstable ring is added alongside a catalyst and heated
2. Ring opening is formed
3. Biodegradable polymer is then formed which has applications in drug delivery
What is chitin?
1. Natural polymer that's found in animals such as crustaceans, fungi, insects and molluscs
2. Highly insoluble
What is chitosan?
1. Pharmaceutical excipient
2. Soluble in water under slightly acidic conditions as the NH2 reacts
3. Used to form capsules
How do you form chitosan from chitin?
1. You replace one functional group with NH2 in chitin