ε-己内酯/丙交酯可控共聚及生物降解薄膜材料的研究

Polycaprolactone (PCL) shows good flexibility，good resistance to radiation, slow degradation rate, and has complementary advantages with the rigid PLA in many aspects. The combination of the two polymers is an ideal combination for development of new, high performance biodegradable materials. However, PCL and PLA are not compatible with each other, and directly combining the two by melt-blending will lead to degradation in material performance due to the phase separation. This project aims to synthesis block, gradient and random PCL-co-PLA copolymers with controllable structures by changing the catalysts, monomer feeding sequence and polymerization conditions, etc. On one hand, study the effects of the molecular structure on film blowing processability of the copolymer materials. On the other hand, use the PCL-co-PLA copolymers as compatibilizers for PCL/PLA melt-blending system, in order to prepare microheterogeneous polymer alloys. Copolymers will be labeled with fluorescein, in order to solve the problem of being difficult to track in the blending systems.The microscopic distribution of copolymers compatibilizers will be observed by using the laser scanning confocal microscope. And their effects on the microscopic phase separation, interface compatibility, crystallization behavior as well as the macroscopic properties of the polymer alloys will be systematically studied. By comparing the properties of the plastic films produced by copolymerization and blending methods, the influence of copolymer molecular structure on film products will be investigated. And more attention will be paid to the correlation between the transmittance, anti-radiation property, gas barrier property，degradation period of the films and the composition of the resins. This project will provide theoretical and practical support for development of biodegradable plastic films with excellent mechanical properties as well as controllable degradation period.

聚己内酯（PCL）柔韧性好、抗辐射、降解慢，与刚性聚乳酸（PLA）优势互补，二者结合是开发新型可降解材料的理想配对。然而，PCL与PLA互不相容，两者简单共混容易分相，材料性能反而下降。本项目拟通过改变催化剂、单体投料顺序及聚合条件等，实现嵌段、渐变及无规PCL-co-PLA共聚物的可控合成。一方面研究分子结构对共聚物材料吹膜性能的影响；另一方面以共聚物作为PCL/PLA共混增容剂，制备微观非均相聚合物合金。为解决共聚物在共混体系不易示踪的难题，拟对其进行荧光标记，利用激光共聚焦显微镜观察共聚物在共混体系的微观分布；系统研究共聚物增容剂对聚合物合金微观分相、界面相容性、结晶行为乃至宏观性能的影响。对比研究共聚物结构对两种方法所得吹塑薄膜性能的影响,重点关注树脂组成与薄膜透光率、抗辐射性、气体阻隔性及降解周期的相关性，为开发性能优异、降解周期可控的生物降解薄膜提供理论和实践依据。

聚乳酸（PLA），作为一种重要的生物基、可降解人工合成聚酯材料，在强度、模量等性能方面与众多石油基塑料表现相当，使其成为替代传统非降解高分子材料的理想替代产品。在食品包装、方便餐具、无纺纤维、医疗器械、农用薄膜以及一次性耗材等方面有着广阔的应用前景。然而，单纯的PLA树脂也存在一些不足，包括熔体强度低、热稳定性差、易脆裂，很难吹塑成高品质的薄膜产品，限制了其应用范围。基于聚己内酯（PCL）柔韧性好、抗辐射、降解慢，与刚性PLA优势互补，二者结合是开发新型可降解材料的理想配对。然而，PCL与PLA互不相容，两者简单共混容易分相，材料性能反而下降。本项目从改变催化剂、单体投料顺序及聚合条件等方面入手，实现了一系列嵌段、渐变及无规可降解聚酯共聚物的可控合成。以这些可降解共聚物作为PLA树脂共混改性体系的增容剂，制备微观非均相聚合物合金。深入研究了共聚物增溶剂在共混体系的微观分布，以及共聚物增容剂对聚合物合金微观分相、界面相容性、结晶行为乃至宏观性能的影响。对比研究共聚物结构对吹塑薄膜性能的影响,为开发性能优异、降解周期可控的生物降解材料提供理论和实践依据。此外，项目研究过程中我们发现分子结构可控的可降解共聚物材料不仅可以作为增容剂改性共混材料，而且可以通过功能化接枝，实现可降解抗菌材料的制备。利用商用席夫碱锰Mn催化剂，我们设计出一种可切换的催化共聚合体系，并首次将其应用于酸酐、环氧化物、CO2和ε-己内酯多种单体混合物的一锅法选择性共聚，精确合成了AB、ABA以及ABC型嵌段共聚物。通过理论计算对这种独特的可控开关共聚过程进行了理论阐述。通过对不同环氧化合物的选择性反应，实现了多达5种单体的可控切换共聚，得到了结构多样性、功能性良好的多嵌段共聚物。利用炔基功能侧链引入季铵盐片段，成功实现了具有抗菌活性的可降解聚合物合成。