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SynopsisNovel polyamides from trans-Pocten-l,8-dioic acid (POD) and truns-%trans-&octadien-1,S-dioic acid (2,GODD) ad linear aliphatic diamines or piperasine were prepared in good yields by low-temperature polycondensation. The polymers obtained were investigated by infrared spectroscopy, x-ray diffraction, and differential scanning calorimetry. Polyamides from 4-OD show high molecular weights and crystallinities and T, above 500"K, whereas those from 2,6-ODD are very weakly crystalline and decompose without melting in nitrogen a t temperatures higher than 550'K. DSC studies revealed in the case of 4-OD polymers with odd diamines, a multiple peak phenomenon in the melting region, strongly dependent from the heating rate. Some hypotheses consistent with this behavior are briefly discussed, and it is concluded that the phenomenon arises from melt recrystallization occurring during the DSC scan. HOOCCH2 CH CH,

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Copolyesters derived from adipic acid, trans-3-hexenedioic acid and 1, ldhexadecanediol were prepared and investigated by means of X-ray diffraction and DSC techniques. From the X-ray results an isomorphous replacement of the saturated and unsaturated diacid units has been suggested. The equilibrium melting temperature 7", and the heat of fusion AH, were slightly dependent on the copolyester composition. The crystallization process was analyzed by means of Hoffman's kinetic crystallization theory for a lamellar type crystal growth. The values of the free energy of formation of a nucleus of critical dimensions A@* and the free energy of folding a, were found to decrease regularly with increasing amount of double bonds, varying from 110 to 83 kJ/mol for A@* and from 171 to 127 erg/cm2 for ue. This effect has been interpreted on the basis of an increase of chain flexibility owing to the presence of the trans double bonds.