Date of Award


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University or Center

Atlanta University (AU)

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A low molecular weight po1y-S-a1anine (350 row) was prepared by thermal po1ycondensation of S-a1anine ethyl ester. In thermal analysis, six transitions occurred in the initial polymer in approximate order of increasing temperature: glass transition temperature (Tg), crysta1- crystal transition, cold crystallization, melt crystallization, crystalline disorientation, and melting. Isothermal annealing of this polymer at 200 0 followed by quenching provided structures which exhibited multiple melting peaks in thermal analysis. In this work reasons are proposed for the dual endotherm. By prolonged annealing only, before analysis, part of the recrystallization exotherm can be observed in the differential scanning calorimetry (DSC) scan. DSC thermo grams obtained at varying heating rates on samples showing po1y-S-a1anine endotherms supported the assignment of superheating as the cause of the shift to higher peak temperatures with increasing heating rate. To further support the structural assignment, the infrared absorption showed typical polyamide bands, and the nuclear magnetic resonance spectrum gave two methylene peaks of equal intensity.

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