Questions from class - Lecture 1

Question 1

What kind of macromolecule is a polymer?

Answer 1

A polymer is a macromolecule consisting of many repeating units known as monomers.

Question 2

Which conformation does a polymer typically have?

Answer 2

It typically has a random coil conformation.

Question 3

Which parameters define a polymer?

Answer 3

It’s end-to-end distance R, mean end-to-end , it’s radius of gyration R_g, it’s molar mass M (number average, weight average), degree of polymerization N, isomerism, architecture.

Question 4

What is the degree of polymerization?

Answer 4

The number of monomers attached to make the chain, denoted N.

Question 5

Which types of isomerism define the microstructure of a polymer?

Answer 5

Stereoisomerism (tacticity), sequence isomerism (head-to-tail, head-to-head), and structural isomerism (cis, trans, vinyl).

Question 6

Which architectures have been synthesized?

Answer 6

Linear, star, branched, comb, dendrimer, cyclic

Question 7

Why do polymers feature a molar mass distribution?

Answer 7

Due to the statistical nature of polymer synthesis, it is difficult to control exactly how many monomers are attached to a chain. Thus, the chains will vary in size, giving different molar masses.

Question 8

Which mean average molar masses are currently used?

Answer 8

The number-average molar mass and the weight-average molar mass. Can define the k-th moment molar mass for higher k.

Question 9

How is the polydisperisty index defined?

Answer 9

It is defined as the ratio between the weight average molar mass and the number average molar mass. For monodisperse polymer is this 1, for all other is this more than 1.

Question 10

Which typical distributions are observed?

Answer 10

Two typical distributions:
Schulz-Zimm distribution (for step polymerization like polycondensation)
Poisson distribution (for chain polymerization, like anionic polymerization)