Outline the difference in the way in which polymerization occurs, stating a specific example of a polymer produced by each process.

Polymers can either soften when heated or remain rigid until they decompose or combust. Other than Kevlar, state the names of one polymer that softens and one that does not. Explain this difference on a molecular level.

Softening polymer:

Non-softening polymer:

Explanation:

Addition:

double bond converted to single bond forming new bonds to other monomers / OWTTE;

poly(e)thene / polyprop(yl)ene / PVC / polystyrene / Teflon/PTFE;

Accept suitable diagram.

Condensation:

monomer contains two functional groups;

small molecule/water produced when monomers join together / OWTTE;

polyester/Terylene/Dacron / nylon/polyamide/Kevlar;

Accept suitable diagram.

Softening polymer:

poly(e)thene / polypropylene / PVC / PET / polystyrene / Teflon/PTFE / polyester/Terylene/Dacron / nylon/polyamide;

Non-softening polymer:

phenol-urea/Bakelite / phenol-methanal/formaldehyde/Melamine;

Explanation:

rigid polymers have cross-links between polymer chains / polymers that soften do not have cross-links between polymer chains;

This was the best answered question in the option with many candidates being able to outline polymerization processes and examples of the products, though full marks were rare. The role of cross-linking and examples of polymers displaying this, was however very limited.

This was the best answered question in the option with many candidates being able to outline polymerization processes and examples of the products, though full marks were rare. The role of cross-linking and examples of polymers displaying this, was however very limited.