Abstract
Abstract The glass transition temperatures Tg, sub-glass transition temperatures sub-tg, melting points Tm, and apparent melting enthalpies δHf have been measured for poly-N-(n-octadecyl)maleimede (PMI-18) fractions having number-average molecular weights between 1.25×103 and 1.9×105 by using differential scanning calorimetry. The results showed a dependence of the galss transition temperature on molecular weight similar to that observed for conventional linear polymers. The variation of Tg of PMI-18 fractions with molecular weight cannot be conveniently represented by any of the usual equations. On the other hand, the variation of Tg with molecular weight can be described very precisely by means of the Ellis equation, which leads to a value of Tg(∞)=387.6 K. An analysis of the present data on Tg, in conjuntion with a similar treatment due to Cowie, has shown that a plot of Tg against log X n (where X n is the number average bacbone bond number of main chain segments, namely, number of backbone carbon ato...
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