Problem 1 (total points: 25, a)-f) 3.5, g) 4) Given the information about the in

Question

Problem 1 (total points: 25, a)-f) 3.5, g) 4) Given the information about the influence of the various structural parameters on T of polymers, assign a number to the SYNTHETIC polymers listed below marking its relative position on the T, scale starting with the lowest Tg (1) and ending with the highest T (6). Justify what made you order the polymers the way you did it. For your convenience the chemical structures of the polymers are provided in the "Chemical stockroom" a) Polyethylene (PE) b) poly(4-bromo styrene) (PBrS) c) alternating copolymer of poly(ethylene-alt-propylene) (PEP) d) poly(dimethyl siloxane) (PDMS) NETWORK e) polyimide (PI) f Poly(carbonate) (PC) g) Where on the T, scale would you put the DNA in aqueous solution?

Explanation / Answer

Relative order of glass transition temperature(in Kelvin) of the given polymers is

PDMS(156K) <POLYTHENE(193K)<PEP(214K)<DNA in aqoues solution(223K)<PBrS(411K)<Polycarbonate(420K)<Polyimide(673K)

Glass transition temperature (Tg) can be defined as the temperature of molecular chain start to move by external force. When the polymerr molecular structure becomes more ordering the movement of chains are constrained. Presence of Benzene in the main chain reduced the Tg, whereas having long branched chain in the monomer increses the Tg. That is Tg of Poly(4-Bromostyrene) has lowest Tg value .Symmetry in the polymeric chain also reduced the Tg value.syndiotactic polymers have higher Tg value than isotactic . Secondary bonding like hydrogen bonds and prsence of polar groups increases the Tg value. That is why polyimides have highest Tg value.

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