Flashcards · 9620 · A Level Topic 30

Polymers (A Level) flashcards

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Condensation polymer: A polymer formed when monomers with two reactive groups join, giving off a small molecule (usually water) at each new link.
Monomers of Terylene, nylon 6,6 and Kevlar: Terylene: ethane-1,2-diol + benzene-1,4-dicarboxylic acid. Nylon 6,6: hexane-1,6-diamine + hexanedioic acid. Kevlar: benzene-1,4-diamine + benzene-1,4-dicarboxylic acid.
Polyester vs polyamide: linkage and monomers: Polyester: ester link –COO–, from a diol and a dicarboxylic acid. Polyamide: amide link –CONH–, from a diamine and a dicarboxylic acid (or from amino acids).
Repeating unit of nylon 6,6: –[CO–(CH₂)₄–CO–NH–(CH₂)₆–NH]–, with 2n H₂O formed for n units.
Strongest forces between chains in polyesters and in polyamides: Polyesters: permanent dipole–dipole forces between C=O groups. Polyamides: hydrogen bonds from N–H on one chain to the C=O oxygen of another (very many in Kevlar, whose flat rigid chains line up).
Uses of Terylene, nylon 6,6 and Kevlar: Terylene: polyester fabric, bottles. Nylon 6,6: rope, carpet, clothing. Kevlar: bulletproof vests, armour.

Why are polyesters and polyamides biodegradable but polyalkenes are not?: Ester and amide links have a δ+ carbonyl carbon that water or OH⁻ can attack, so they hydrolyse. Polyalkenes have only non-polar C–C and C–H bonds, so they are chemically inert.
Products of hydrolysing a polyamide with acid and with alkali: Dilute acid, heat: dicarboxylic acid + diammonium salt. Aqueous alkali, heat: dicarboxylate salt + diamine.
Landfill vs incineration of waste polymers: Landfill: cheap, no sorting; but uses land, and polyalkenes last a very long time. Incineration: reduces volume, heat can generate electricity; but releases CO₂, and toxic gases such as HCl from chlorinated polymers must be removed.
Advantages and disadvantages of recycling polymers: Conserves crude oil and energy, and reduces landfill. But collection, sorting by polymer type and cleaning cost money and energy, and mechanically recycled material is lower quality.