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| 1. |
Which of the following polymers are long chain and which of them are cross-linked condensation polymers? Explain. (1) Ethylene glycol (2) Glycerol (3) Terephthalic acid |
| Answer» Ethylene glycol `HO-(CH_2)_2 -OH` and terephthalic acid `(HOOC-C_6H_4 -COOH)` , each possesses two active bifunctional groups. Hence, they undergo polycondensation to form a long straight chain polymer known as polyester. Glycerol `(HOCH_2 -CHOH - CH_2OH)` contains three functional groups. Hence, polycondensation of glycerol withterephthalic acid forms a network polymer. During polycondensation, two - OH groups of glycerol react with the acid to form an ester. The remaining - OH groups hanging inthe polymer chain fo rm a polyester as a result of the polycondensation. Thus, the hanging -OH groups are bonded to the - OH groups of the adjacent polymer chain forming a cross-link and a network polymer is formed. | |