MChem Master of Chemistry Polymer Chemistry 2

Question 1

Which of the following is an example of a condensation (step-growth) polymer?

Accepted Answer

Nylon-6,6

Answer

Polyethylene

Answer

Polystyrene

Answer

Polyisoprene

Question 2

What does the Carothers equation predict in step-growth polymerization?

Accepted Answer

The number-average degree of polymerization as a function of monomer conversion

Answer

The rate constant of chain initiation

Answer

The glass transition temperature from monomer structure

Answer

The dispersity as a function of initiator concentration

Question 3

In atom transfer radical polymerization (ATRP), what component serves as the persistent radical?

Accepted Answer

The Cu(II) complex (oxidized metal halide)

Answer

The carbon-centered propagating radical

Answer

The alkyl halide initiator

Answer

The ligand coordinated to copper

Question 4

Which analytical method directly measures the absolute molecular weight of a polymer without calibration standards?

Accepted Answer

Multi-angle light scattering (MALS)

Answer

GPC with refractive index detection

Answer

Viscometry using the Mark-Houwink equation

Answer

Matrix-assisted laser desorption ionization (MALDI) for all molecular weights

Question 5

What structural feature distinguishes an isotactic polymer from an atactic polymer?

Accepted Answer

Isotactic polymers have all pendant groups on the same side of the backbone

Answer

Isotactic polymers have no stereocenters along the backbone

Answer

Isotactic polymers have alternating R and S stereocenters

Answer

Isotactic polymers are cross-linked while atactic polymers are linear

Question 6

The Mark-Houwink-Sakurada equation [η] = KM^α relates intrinsic viscosity to molecular weight. What does the exponent α indicate about polymer-solvent interactions?

Accepted Answer

α values between 0.5 and 0.8 indicate a good solvent where chains are expanded

Answer

α = 0 indicates theta solvent conditions

Answer

α = 1 always indicates rod-like rigid polymers

Answer

α < 0 indicates poor solvent conditions where chains collapse

Question 7

What is the primary advantage of reversible addition-fragmentation chain-transfer (RAFT) polymerization over conventional free-radical polymerization?

Accepted Answer

It provides controlled molecular weights and narrow dispersity by reversible chain-transfer equilibria

Answer

It requires no initiator, making it purely thermally driven

Answer

It completely eliminates oxygen sensitivity

Answer

It can only polymerize acrylates, giving excellent selectivity