Flashcards · 9701 · A Level Topic 35

Polymerisation (A Level) flashcards

12 cards on A Level Topic 35, subtopics 35.1 to 35.3. Pick a subtopic or study them all.

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Condensation polymerisation: Monomers, each with two functional groups, join with the elimination of a small molecule (usually H₂O, or HCl from an acyl chloride) at every linkage.
Polyester and polyamide: monomers and linkage: Polyester: diol + dicarboxylic acid (or diacyl chloride); ester link –COO–. Polyamide: diamine + dicarboxylic acid (or diacyl chloride); amide link –CONH–. Or one monomer with both groups (hydroxy acid, amino acid).
Repeat unit from ethane-1,2-diol and benzene-1,4-dicarboxylic acid: –OCH₂CH₂OOCC₆H₄CO– (a polyester); one H₂O lost per ester link.
Why are polyamides generally stronger than polyesters?: Amide groups form hydrogen bonds between chains; ester groups only give permanent dipole–dipole attractions.
How do you deduce the monomers from a section of a condensation polymer?: Find the repeating ester or amide links, break each one and add back H₂O (–OH to the C=O side, –H to the O or N side) to regenerate the diacid and the diol or diamine.

Which monomers give addition and which give condensation polymers?: A C=C double bond: addition, no small molecule lost. Two reactive groups per monomer (–OH, –NH₂ with –COOH or –COCl): condensation, losing H₂O or HCl.
How can you tell from a polymer section how it was made?: A continuous saturated carbon backbone: addition polymer. Repeating ester or amide links in the chain: condensation polymer.
Addition vs condensation polymerisation: by-product and atom economy: Addition: nothing eliminated, 100% atom economy. Condensation: H₂O or HCl eliminated, atom economy below 100%.

Why are poly(alkenes) difficult to biodegrade?: They are chemically inert: the non-polar C–C backbone has no bonds that water or enzymes can attack.
Why are polyesters and polyamides biodegradable?: Their polar ester or amide links can be hydrolysed by acid or alkali (and by enzymes), breaking the chain into monomers.
Products of acid and alkaline hydrolysis of polyesters and polyamides: Polyester: acid → carboxylic acid + alcohol; alkali → carboxylate salt + alcohol. Polyamide: acid → carboxylic acid + ammonium salt; alkali → carboxylate salt + amine.
Photodegradable polymer: A polymer with bonds or additives that absorb UV light and break, fragmenting the material. This is a different process from biodegradation by hydrolysis.