D6 Basic Polymer Properties 2

Question 1

Three things water soluble polymers are potentially able to do
What does this make water soluble polymers good for?

Answer 1

Increase viscosity of solvents
Swell/change shape
Adsorb at surfaces
Makes good suspending agents

Question 2

In order to dissolve in water, what must a polymer be?

Answer 2

Sufficiently polar

Question 3

What kind of polymer is capable of forming a thin film and what are the uses of this?

Answer 3

Insoluble polymers

Uses : tablet coating, wound dressing, membranes etc

Question 4

The rate of dissolution of a water soluble polymer is depended on the ______________.

Answer 4

Molecular weight

Question 5

Higher molecular weight = Stronger ________

What does this result in?

Answer 5

Forces holding chains together therefore more energy required to force chains apart

Question 6

Velocity of penetration (S) equation

Answer 6

S=KM^-A
K and A are constants
M = polymer weight

Question 7

What does the velocity of penetration tell us?

Answer 7

The rate at which dissolved, considering the polymer weight

Question 8

How do polymers control drug delivery effectively?

Answer 8

Bulk solvent (water) –> Difffusion layer (as in NaCl solid) –> Gel Layer –> Infiltration layer –> Polymer

Question 9

Rather than dissolving, cross-linked water soluble polymers can become ______?
What happens?

Answer 9

Swollen

Large quantities of water become imbided leading to increased volume

Question 10

The ________ of a polymer impacts viscosity by effecting ____________.

Answer 10

Shape

Flow properties

Question 11

What does better polymer - solvent interactions mean for the shape of the structure ?

Answer 11

A more open, expanded polymer structure

Question 12

What is the results of greater polymer - polymer interactions?

Answer 12

Polymer is likely to coil up

Question 13

What is a theta solvent?

Answer 13

Ideal conditions, all interactions cancel

Question 14

How does charge affect shape?

Describe a charged polymer compared to a neutral polymer.

Answer 14

Affects shape and therefore flow and viscosity
Neutral is contracted, lower viscosity
Charged groups, expanded and higher viscosity

Question 15

What is intrinsic viscosity?

Answer 15

Determined by polymer molecular weight and the type of solvent - extrapolate grapg back to C=0 / y axis

Question 16

How to calculate intrinsic viscosity

Answer 16

[(ns-no)/no] /C
ns = viscosity of polymer solution
no = viscosity of the solvent ONLY

Question 17

What is this equation n = KM^a and what are the components?

How can it be calculated from a graph?

Answer 17

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]

Question 18

The a constant is a reflection of the _________ of the polymer

Examples

Answer 18

Shape

a =  0 for spheres
a = 0.5-0.8 random coils 
a = 1.8 rods

Question 19

What happens to viscosity when polymer concentration increases?

Answer 19

Increases

Question 20

What forms when polymer concentration continues to increase?

Answer 20

Gel precipitate forms - viscous cross linked system

Question 21

Two ways polymer gels can be formed

Answer 21

1 swelling of cross linked solid polymer

2 making dissolved polymer less soluble, (increasing polymer polymer interactions)

Question 22

What is a critical gelation concentration?

Answer 22

System when a gel forms from solution contrains a CGC

Below this concentration a gel will not exist

Question 23

Type 1 and Type 2 gels

Answer 23

1. irreversible covalent systems e.g, contact lenses

2. heat reversible e.g. agar

Question 24

What does solubility parameter tell us?

Answer 24

Essentially a measure of cohesion between molecules

Question 25

Solubility parameter equation

Answer 25

S = [(delta Hv - RT)/V] ^1/2 
S = solubility parameters 
R gas constant 
delta Hv = molar enthalpy of vaporisation 
T absolute temperature 
V molar volume