基于生物可降解材料的高分子结晶实验教学

Experimental teaching of polymer crystallization based on biodegradable materials

该结晶综合实验通过差示扫描量热(DSC)、正交偏光显微镜(POM)、小角激光散射(SALS)等实验方法,研究了丁二酸丁二酯/甲基丁二酸丁二酯无规共聚物(PBSMS)中非晶共聚单元甲基丁二酸丁二酯含量对共聚物热性能、结晶动力学和结晶形态等的影响。整个实验包括实验设计、小组合作、汇总实验结果、进行数据分析、建立物理模型等环节,最后得出了研究结论。实验研究结论与理论知识和文献报道结果一致,加深了学生对理论知识的理解和掌握。通过本实验,学生的实验设计能力、综合分析能力和科研思维都得到了很好的训练。

[Objective]To enhance students’understanding of polymer crystallization and cultivate their research and innovation skills,three traditional independent experiments,namely differential scanning calorimetry(DSC),polarizing microscope(POM),and small-angle laser scattering(SALS),have been integrated into a systematic crystallization study.Our study focuses on biodegradable polymer polybutylene succinate(PBS),allowing for a comprehensive investigation of the crystallization process and characteristics from multiple perspectives.[Methods]This study investigates how the amorphous copolymer unit,butylene 2-methylsuccinate(BMS),affects the thermal properties,crystallization kinetics,and morphology of poly(butylene succinate-co-butylene 2-methylsuccinate)(PBSMS).The research was conducted collaboratively,with each team initially performing literature reviews and designing experiments tailored to their respective topics.Subsequently,each team formulated an experimental plan based on instructor feedback.During the experimental phase,they sequentially executed DSC,POM,and SALS experiments as per their assigned tasks.The data collected was then analyzed across teams working on similar topics to comprehensively assess the crystallization process.This analysis aimed to explore the impact of BMS on the crystallization behavior of PBSMS and to derive research conclusions.The findings from the study were systematically compiled into laboratory and course reports.During DSC experiments,a heating rate of 10℃/s was chosen after eliminating the thermal history of the sample.The experiment was conducted at three set temperatures:160℃,20℃,and 160℃.A small amount of polymer powder(about 0.3 mg)was heated between two glass slides and melted at 160℃for 3 min,then rolled into a bubble-free film.These films were subsequently observed and photographed using POM at appropriate intervals.In the photographs,three fixed spheroids were selected,and their radii at different times were determined using the three-point method.These data were then fitted to obtain the average spheroid growth rate.Additionally,the films were observed using SALS to calculate the spheroid radius and ring spacing using the corresponding formulas.[Results]The study revealed the following:1)As the BMS content decreased(0%–10%),the peak crystallization temperature and melting point of the polymer increased;2)Within the 75℃–80℃range,the spheroid radial growth rate of PBSMS decreased as the BMS content increased at the same isothermal crystallization temperature;3)At the same isothermal crystallization temperature,PBSMS with less amorphous copolymerization units exhibited larger,irregular zonal spherulites;4)Different BMS concentrations(0%–10%)had different effects on the spheroid radius of PBSMS.[Conclusions]Through a series of comparative experiments and detailed analyses,we demonstrated that changes in BMS content significantly affect the peak crystallization temperature,melting point,spheroid morphology,and average growth rate during the isothermal crystallization of the PBSMS.The experimental results align with the theoretical knowledge and literature,enhancing understanding and mastery of the subject.Through these integrated experiments,students improved their skills in experimental design,data analysis,and scientific reasoning.Moreover,the course facilitated advanced research topics,guiding students to conduct scientific research training in teaching experiments and achieving the goal of integrating research with teaching.