D6 Basic Polymer Properties 2 Flashcards

1
Q

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

A

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

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2
Q

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

A

Sufficiently polar

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3
Q

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

A

Insoluble polymers

Uses : tablet coating, wound dressing, membranes etc

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4
Q

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

A

Molecular weight

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5
Q

Higher molecular weight = Stronger ________

What does this result in?

A

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

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6
Q

Velocity of penetration (S) equation

A

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

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7
Q

What does the velocity of penetration tell us?

A

The rate at which dissolved, considering the polymer weight

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8
Q

How do polymers control drug delivery effectively?

A

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

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9
Q

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

A

Swollen

Large quantities of water become imbided leading to increased volume

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10
Q

The ________ of a polymer impacts viscosity by effecting ____________.

A

Shape

Flow properties

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11
Q

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

A

A more open, expanded polymer structure

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12
Q

What is the results of greater polymer - polymer interactions?

A

Polymer is likely to coil up

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13
Q

What is a theta solvent?

A

Ideal conditions, all interactions cancel

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14
Q

How does charge affect shape?

Describe a charged polymer compared to a neutral polymer.

A

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

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15
Q

What is intrinsic viscosity?

A

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

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16
Q

How to calculate intrinsic viscosity

A

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

17
Q

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

How can it be calculated from a graph?

A

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]

18
Q

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

Examples

A

Shape

a =  0 for spheres
a = 0.5-0.8 random coils 
a = 1.8 rods
19
Q

What happens to viscosity when polymer concentration increases?

A

Increases

20
Q

What forms when polymer concentration continues to increase?

A

Gel precipitate forms - viscous cross linked system

21
Q

Two ways polymer gels can be formed

A

1 swelling of cross linked solid polymer

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

22
Q

What is a critical gelation concentration?

A

System when a gel forms from solution contrains a CGC

Below this concentration a gel will not exist

23
Q

Type 1 and Type 2 gels

A
  1. irreversible covalent systems e.g, contact lenses

2. heat reversible e.g. agar

24
Q

What does solubility parameter tell us?

A

Essentially a measure of cohesion between molecules

25
Q

Solubility parameter equation

A
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