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....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 T a 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).展开更多
采用新疆奇台风化煤为原料,通过表面引发原子转移自由基聚合(SI-ATRP)方法制备腐植酸钠-聚甲基丙烯酸甲酯接枝共聚物(HA-Na-PMMA),通过正交实验确定了SI-ATRP最佳合成工艺条件:反应时间8 h,溴化亚铜∶溴化铜∶2,2-联吡啶质量比为20∶4∶...采用新疆奇台风化煤为原料,通过表面引发原子转移自由基聚合(SI-ATRP)方法制备腐植酸钠-聚甲基丙烯酸甲酯接枝共聚物(HA-Na-PMMA),通过正交实验确定了SI-ATRP最佳合成工艺条件:反应时间8 h,溴化亚铜∶溴化铜∶2,2-联吡啶质量比为20∶4∶20,物料质量比∶体积比为1 g∶10 m L,反应温度80℃。通过SI-ATRP制备的HA-Na-PMMA的接触角为84°,比HA-Na的接触角增大了54°,表明HA-Na的SI-ATRP接枝共聚效果显著。以HA-Na-PMMA为吸附剂,研究其对Cr(Ⅵ)的吸附性能,同时建立了HA-Na-PMMA对Cr(Ⅵ)的等温吸附模型,研究了其吸附热力学和吸附动力学。HA-Na-PMMA对Cr(Ⅵ)具有良好的吸附性能,其等温吸附模型符合Freundlich模型。吸附焓变为-0.2849 k J/mol,ΔGθ<0,所以吸附是自发的放热反应。常温下吸附速率常数KL为0.9113 mg/(g·min),表明其吸附动力学模型遵循Langmuir模型和Bingham模型。展开更多
基金National "Shi Wu"Supporting Key Item of China(No.2004BA720A15)Health Department Priority Supporting Item of Clinic Subject of China [No.(2004)468]Shenzhen Scientific Planning Supporting Item of China(No.200602099)~~
文摘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 T a 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).
文摘采用新疆奇台风化煤为原料,通过表面引发原子转移自由基聚合(SI-ATRP)方法制备腐植酸钠-聚甲基丙烯酸甲酯接枝共聚物(HA-Na-PMMA),通过正交实验确定了SI-ATRP最佳合成工艺条件:反应时间8 h,溴化亚铜∶溴化铜∶2,2-联吡啶质量比为20∶4∶20,物料质量比∶体积比为1 g∶10 m L,反应温度80℃。通过SI-ATRP制备的HA-Na-PMMA的接触角为84°,比HA-Na的接触角增大了54°,表明HA-Na的SI-ATRP接枝共聚效果显著。以HA-Na-PMMA为吸附剂,研究其对Cr(Ⅵ)的吸附性能,同时建立了HA-Na-PMMA对Cr(Ⅵ)的等温吸附模型,研究了其吸附热力学和吸附动力学。HA-Na-PMMA对Cr(Ⅵ)具有良好的吸附性能,其等温吸附模型符合Freundlich模型。吸附焓变为-0.2849 k J/mol,ΔGθ<0,所以吸附是自发的放热反应。常温下吸附速率常数KL为0.9113 mg/(g·min),表明其吸附动力学模型遵循Langmuir模型和Bingham模型。
