Flashcards in D6 Basic Polymer Properties 2 Deck (25)
Three things water soluble polymers are potentially able to do
What does this make water soluble polymers good for?
Increase viscosity of solvents
Adsorb at surfaces
Makes good suspending agents
In order to dissolve in water, what must a polymer be?
What kind of polymer is capable of forming a thin film and what are the uses of this?
Uses : tablet coating, wound dressing, membranes etc
The rate of dissolution of a water soluble polymer is depended on the ______________.
Higher molecular weight = Stronger ________
What does this result in?
Forces holding chains together therefore more energy required to force chains apart
Velocity of penetration (S) equation
K and A are constants
M = polymer weight
What does the velocity of penetration tell us?
The rate at which dissolved, considering the polymer weight
How do polymers control drug delivery effectively?
Bulk solvent (water) --> Difffusion layer (as in NaCl solid) --> Gel Layer --> Infiltration layer --> Polymer
Rather than dissolving, cross-linked water soluble polymers can become ______?
Large quantities of water become imbided leading to increased volume
The ________ of a polymer impacts viscosity by effecting ____________.
What does better polymer - solvent interactions mean for the shape of the structure ?
A more open, expanded polymer structure
What is the results of greater polymer - polymer interactions?
Polymer is likely to coil up
What is a theta solvent?
Ideal conditions, all interactions cancel
How does charge affect shape?
Describe a charged polymer compared to a neutral polymer.
Affects shape and therefore flow and viscosity
Neutral is contracted, lower viscosity
Charged groups, expanded and higher viscosity
What is intrinsic viscosity?
Determined by polymer molecular weight and the type of solvent - extrapolate grapg back to C=0 / y axis
How to calculate intrinsic viscosity
ns = viscosity of polymer solution
no = viscosity of the solvent ONLY
What is this equation n = KM^a and what are the components?
How can it be calculated from a graph?
n = intrinsic viscosity
K and a are constants
M = molecular weight
Calculate from a grapph
y = mx +c
ln [n] = ln K + a ln [M]
The a constant is a reflection of the _________ of the polymer
a = 0 for spheres
a = 0.5-0.8 random coils
a = 1.8 rods
What happens to viscosity when polymer concentration increases?
What forms when polymer concentration continues to increase?
Gel precipitate forms - viscous cross linked system
Two ways polymer gels can be formed
1 swelling of cross linked solid polymer
2 making dissolved polymer less soluble, (increasing polymer polymer interactions)
What is a critical gelation concentration?
System when a gel forms from solution contrains a CGC
Below this concentration a gel will not exist
Type 1 and Type 2 gels
1. irreversible covalent systems e.g, contact lenses
2. heat reversible e.g. agar
What does solubility parameter tell us?
Essentially a measure of cohesion between molecules