关键词: 液-液转变, 无规聚甲基丙烯酸甲酯, 退火

Abstract: Effects of annealing temperature( T_a) and annealing time( t_a) on the liquid liquid transition and transition intensity of atactic poly(methyl methacrylate) were studied by means of differential scanning calorimetry. With the increase of T_a from 393 to 443 K, T_ll shifted to higher temperature with the decrease in transition intensity, on the contrary, when Ta was over 443 K, T_ll declined and transition intensity increased. When T_a kept constant with the increase of t_a, T_ll and transition intensity varied as the results described above. Moreover, the variation extent of T_ll and transition intensity increased with the increase of T_a, in other words, the time needed reaching the maximum extent of variation of the two parameters was decreased with the increase of T_a. The dependence of T_ll and transition intensity on annealing conditions may be explained by the formation of local ordered structure, i.e. stereocomplex, during the annealing process by means of Van der Waals forces between isotacitic and syndiotactic segments of the same or different chains of atactic poly(methyl methacrylate).

Key words: Liquid-liquid transition, Atatic poly(methyl methacrylate), Annealing