chapter 6

Question 1

what are the 4 types of copolymers?

Answer 1

1. random co
2. alternating co
3. block co
4. grafted co

Question 2

polycation

Answer 2

when the monomers are all positively charged

Question 3

polyanion

Answer 3

when all monomer are negatively charged

Question 4

polyampholytes

Answer 4

when macromolecule have postive and negative charged monomers

Question 5

why does a ideal flexible chain take on different configurations?

Answer 5

Due to their thermal energy. The solvent molecules bounce against various parts of the chain.

Question 6

how come polymers have limited flexibility?

Answer 6

1. fixed bond angles
2. rotation can be limited due to side chains
3. depends on beta which is determined by the cosine of the fixed bond and rotation angle

Question 7

what are the differences between polymers and monomers?

Answer 7

• monomers can flow next to each other
• polymers are more viscous than monomers

Question 8

what happens for a polymer when it is dissolved in
a) theta solvent
b) good solvent
c) bad solvent

Answer 8

a) : interactions between segments and solvent are very close to interactions between segments. End up with the same ideal behaviour as we did before
b) interactions between segment and solvent are more favourable than between segments. There is a higher dependency which means they expand slightly more
c) interactions between segment and solvent are less favourable than between segments. There is a weaker dependency, the polymer becomes smaller

Question 9

A solution is prepared of a flexible polymer, just below c*. Explain why this solution has a much higher viscosity than a solution of monomers with the same
concentration

Answer 9

Even at low concentrations, these
coil structures start to overlap, and the solution is actually concentrated.
At these low concentrations monomers can slide easily past each other, giving a much lower viscosity than a polymer solution

Question 10

A solution is prepared of a flexible polymer, just below c*; , explain why this solution displays elastic
behavior

Answer 10

Mechanical stretching results in ΔS<0, so stretching is entropically unfavorable. When stretching force is removed the polymer will retract and again form a coil structure