Polymers

Question 1

Name one of the ways we classify polymers.

Answer 1

Molecular characteristics - repeating monomer units affect the polymer characteristics, and are influenced by size, or shape.
The structure of the polymer is important in the classification, is it linear? Branched? is there crosslinkage/network formation?

Question 2

Name the three classifications of Homopolymers.

Answer 2

1. Linear, 2. Branched, 3. Crosslinked

Question 3

Name the four types of Copolymers structure

Answer 3

1. Statistictically random, 2. Alternating, 3. block polymer, and 4. graft polymer (the branches is a monomer groups, while the main linear backbone is a different monomer group.

Question 4

What is the difference between Homopolymers and Copolymers?

Answer 4

Homopolymers contain one repeating monomer unit, while co-polymers contain two ro more monomer units.

Question 5

Name some natural polymers.

Answer 5

Proteins - amino acids are the monomer units.
Polysaccharides - sugar monmer units
Natural Rubbers - Isoprene (that has been crosslinked)

Question 6

Describe the difference between Thermoplastics and Thermosets

Answer 6

Thermoplastics soften upon heating and harden when cooled, making them easy to mould and usually flexible.
Thermosets become permenantly hard once formed. The polymer is crosslinked after it is melted into a mould, causing a high degree of ridgidity.

Question 7

Describesome of the improvemnts provided by crosslinking.

Answer 7

Improves dimensionaly stability
Increases solvent resistance
Resists thermal distortion

Question 8

Name the three types of synthetic polymers

Answer 8

1. plastics - change shape upon application of a force and retain this shape when the force is removed
2. Fibers - polymeric materials forcibly drawn in one dimension, changing their propterties and giving greater strength in drawn direction
3. Elastomers - Rubber like materials, which return to the origional shape when a force is removed.

Question 9

What is the tensisle stress of a property and how is it determined?

Answer 9

The tensile strength is the breaking point of a polymer, which is determined by stretching a strip of polymer in one direction.

Question 10

What are the equations for stress and strain of a property?

Answer 10

Stress = Force/Initial area cross section
Strain = Delta l  / origional l of property

Question 11

The initial graph of stress v. strain shows a straight rise called the elastic region. What is the peak of this region called?

Answer 11

The yield point. This is where the alteration to the polymer is irriversable, and causes changes to the polymer structure. This starts the plastic region of the graph.

Question 12

explain the difference between brittle plastics, fibres and elastomers.

Answer 12

Brittle plastics have a high youngs moduleus, and little elongation
Fibres have a high modulus and little eloncation as well, but a higher yeild stregth than plastics
Elastomers have an initially low modulus but it increases when streched.

Question 13

When do polymer names not have prackets in their name?

Answer 13

When they are named after a single worded monomer

Question 14

What is the difference between Poly(ethylene oxide), and Poly(ethlyene gycol)

Answer 14

structurally nothing. PEO is made through the ring openening of ethylene oxide, while PEG is from the condensation of 1,2-dihydroxal ethane.
PEG usually has a lower molecular weight, and the molecule’s end groups are significant, while PEO has a higher olecular weight and it’s end groups are insignificant.

Question 15

Name the four rules for IUPAC nomenclaure

Answer 15

1. Selecet the constitutional repeating unit (usually the monomer)
   The name is placed in brackets, and prefized with poly
2. CRU is assigned on a basis of senority, heterocyclic rings/chains with heteroatoms/carboxylic rings/carboxylic chains.
3. Then labled from left to right.

Question 16

Draw Poly(oxyethylene)

Answer 16

[-O-CH2-CH2-]n

Question 17

Name this

[-O-CH(CH3)-CH2)-]n

Answer 17

poly(oxy-1-methylethylene)

Question 18

Name some methods of weight determinations for polymers

Answer 18

Light scattering
Osmetry
Gel permeation
viscosity
titration of end groups
mass spec

Question 19

Why is mass spec not a good method for determination of the weight of polymers?

Answer 19

Gel permeation Polymers don’t fragment properly, do the the strong bonds formed.

Question 20

What is the difference between the number of average molecular weight and the weight average molecular weight?

Answer 20

Mn is sensitive to the number of chains in a polymer, and is a measure of the average chain length, and is not influenced by the size of chains. Mw is a measure of the number of chains and the size of them, and is hense more useful.