polymers Flashcards
what are polymers
very large molecules made from nay repeat units bonded together
what are the uses of polymers in pharmaceuticals
- adjuvants
- suspending agents
- emulsifying agents
- flocculating agents
- adhesives
- packaging
= coating - drug delivery
- wound dressing
how are polymers made
polymerisation
steps
1. initiation
2. propagation.
3 termination
what is degree of polymerisation
- this is the amount of monomers that the polymer has
and this will determine some of its chemical properties
what is polydispersity
it refers to the variation in size, shape or molecular weights of particles
- a metaerial with a high degree of polydispersity will have a wide range of particles sizes whereas low dispersing means they are more uniform in size
polydispersity affects the mechanical properties, processability and performance of the polymers
in colloids it affects the stability and behaviour of colloidal particles
hwo do you calculate the number average modular weight
- this is determined by chemical analysis such as gel permeation, chromatography or osmotic pressure measurements
symbol : Mn
how is weight average molecular weight
- it is determined through light scattering or gel permeation chromatography - this is biased towards larger molecules
symbol - Mw
what is polydispersity index (PDI)
polydispersity index (PDI) = Mw/Mn
PDI = 1 is monodisperse
PDI > 1 is polydisperse
what are the two classes of plyemsrs
homopolymers - made from one type of monomers
copolymers - made from more than one type
what are the different types of homopolymers
- linear homopolymers
-branched homopolymers
- cross linked homopolymers
what are the different types of copolymers
- linear alternating polymers
- linear random polymers
- linear block polymers
- graft copolymers
difference and similarities between amorphous, crystalline and semi-crystalline polymers
- amorphous polymers have no long range order - they lack a sharp melting point, they soften with an increase in temperature, they are thermoplastics
- crystalline polymers - long range order, more structured, they have sharp melting points
- semi regions of crystallinity - they have regions of crystalline and amorphous, they also have sharp melting points
what are the different states of matter for polymers
- mobile liquid
- viscous liquid
- rubber
- tough plastic
- crystalline solid
- partially crystalline plastic
- tough plastic
polymers i solitons
-the way a polymer will interact with solvents depend on its properties such as the type of chemical structures it has
- poor solubility - this is when the polymer would rather interact with its self than the solvent so it forms a ball
- theta solvent - this is when the polymer doesn’t want to interact with its self or the solvent so there is no net interaction - so there is random movement
good solvent - this is when there is net polymer and solvent interaction, so it starts to extend out
rigid rod - this is when the polymer prefers the sole vent so it will extend itself to make sure that it has all contact with the solvent
no a = poor solvent
a = 0.5 = theta solvent
a= 0.8 = good solvent
a = 2 = rigid rod
polymer solubility
water soluble polymers - are used to increase viscosity, adsorb at interfaces or gels (however some polymers may have a high MW- molecular weight, high degree of crystalinityy or cross linking can decrease the rate of solution )
water insoluble polymers- are used to form coats, filtration membranes and packaging
ionic polymers are more likely to be water soluble - because it is polar and water is polar to they will interact
