CHEM 4225 Polymer Chemistry - Copolymerization

Flashcards covering copolymerization, kinetics, terminal model, and reactivity ratios.

What is copolymerization?

Polymerization of two or more monomers.

Give examples of copolymerization.

poly(ethylene-co-propylene) (EP); poly(styrene-co-butadiene) (SBR)

If monomer (A) reacted with monomer (B), what are the possible structures of polymer formed?

Random, Alternating, Block, and Grafted.

How is a grafted copolymer made?

A polymer reacts with a different polymer.

Give examples of Grafted Copolymer.

High Impact Polystyrene (HIPS) and Acrylonitrile / Butadiene / Styrene (ABS)

What is the assumption of the Terminal Model in copolymerization kinetics?

Reactivity of the propagating species depends only on the monomer unit at the end of the chain.

According to the Terminal Model, what are the possible propagation reactions in copolymerization?

Monomers M1 and M2 can each add either to a propagating chain ending in M1 or to one ending in M2.

What does the copolymer composition depend on?

The copolymer composition depends on the co-monomer reactivity and concentration.

What does the instantaneous copolymer equation describe?

Describes the relative change in the monomer composition.

At steady state assumption, what happen to M1. and M2?

M1. and M2. are generated and consumed at equal rates.

What is the reactivity ratio for monomer 1 (r1)?

The ratio of propagation rate-constants for the addition of M1 and addition of M2 to a propagating radical chain with monomer 1 at the radical end, M1.

What is the reactivity ratio for monomer 2 (r2)?

The ratio of propagation rate-constants for the addition of M2 and addition of M1 to a propagating radical chain with monomer 2 at the radical end, M2.

What does it mean if both reactivity ratios are equal (k11 = k12 and k22 = k21)?

There is no preferential monomer incorporation into the propagating chain, and the copolymer is random.

What does it mean if both reactivity ratios are zero (k11 = k22 = 0)?

Alternating copolymers are formed.

What does it mean if both reactivity ratios are small but not exactly zero (k11 = k22 ≈ 0)?

Copolymers are highly alternating with some random placement.

What does it mean if both reactivity ratios are very much larger than unity (k11 >>> k22 or k22 >>> k11)?

Copolymers are homopolymers only or block copolymers only.

What is the limitation of the instantaneous copolymer equation?

Radical-chain concentrations is usually not known or easily measured.

What is the Mayo and Lewis equation used for?

Used the definition of reactivity ratios and obtain an equation in terms of r1 and r2.

What is the Q-e scheme?

Widely used model for predicting the behavior of monomers during copolymerization, similar to the reactivity ratios.

What is the Q-e scheme used for?

Used to predict the reactivity ratios.