N-乙烯基单体辅助熔融接枝研究及其接枝聚合物表面性能

Tailoring the surface properties of a polymer is desired for a broad range of applications. Reactive extrusion melt grafting method can avoid the shortcoming of surface modification method, i.e., the as-prepared samples are not subjected to the further processing such as melting processing. However, the grafting degree of the reactive extrusion is generally low, and the graft chains in the as-prepared graft polymer are not easy to enrich onto its own surface, thus the surface properties of the material are not significantly changed. In this proposal, the graft chains consisting of fluoride and biocompatible component are immobilized onto polymer backbones by reactive extrusion grafting procedure in the presence of the biocompatible N-vinyl monomer as promoter. Firstly, the grafting kinetics and mechanism are elucidated by use of low molecular weight compounds as model to simulate the grafting process, and the N-vinyl monomer-assisted melt grafting system is constructed. Secondly, the relationships between the molecular structure parameters of the graft polymer as well as film-forming conditions and the migration of the graft chain are investigated, thus the migration mechanism of the graft chain is elucidated, and a method which can regulate the surface performance of graft polymers is developed. Thirdly, the interactions between the surface of the graft polymer and proteins, blood cells as well as somatic cells are investigated, thus the biocompatible surface of the graft polymer is prepared. The innovation of this proposal is summarized as follows. The graft polymer with a satisfied grafting yield is prepared via the N-vinyl monomer-assisted melt grafting method. The method, which can build the thermodynamically stable surface of a graft polymer, is established. Thus, the shortcoming of surface modification is avoided. The proposal will facilitate the application of good-performance and low-cost biomedical polymer in the high-grade field of implantable and interventional medical devices.

聚合物表面性能的调控是拓展其应用的重要手段。反应挤出熔融接枝可避免表面化学改性法制备的样品不能进行熔融加工等二次处理的缺点，但由于其接枝率一般较小，且接枝链很难在表面富集，表面性能难以显著改变。本项目拟采用N-乙烯基单体为反应挤出辅助接枝剂，将含氟且具有生物相容性的接枝链引入到聚合物分子链上，同时利用低分子化合物模拟接枝过程，以阐明接枝反应的动力学和机理，进而构建新的辅助接枝体系；通过研究接枝聚合物的分子结构参数和成膜条件与接枝链迁移间关系，揭示接枝链表面迁移机制，发展调控接枝聚合物表面性能的方法；通过研究表面性质与蛋白质、血细胞和体细胞间的相互作用，制备出具有生物相容性的接枝聚合物表面。创新为：利用N-乙烯基单体辅助接枝法制备出接枝率理想的接枝聚合物，发展一种利用接枝聚合物构建热力学稳定的聚合物表面的方法，避免表面改性法存在的不足，推动性能优、成本低的医用高分子用于植入、介入等高端领域。

聚合物表面性能的调控是拓展其应用的重要手段。反应挤出熔融接枝可避免表面化学改性法制备的样品不能进行熔融加工等二次处理的缺点，但由于其接枝率一般较小，且接枝链很难在表面富集，表面性能难以显著改变。本项目采用N-乙烯基单体为反应挤出辅助接枝剂，将含氟且具有生物相容性的接枝链引入到聚合物分子链上，获得了高效接枝体系。.主要研究内容。. ①N-乙烯基单体辅助接枝研究; ②接枝聚合物接枝链表面迁移机制; ③接枝聚合物表面生物相容性.重要结果、关键数据等及其科学意义或应用前景. ①N-乙烯基单体辅助接枝研究. 在NVP的辅助下，丙烯酸酯类单体对基体聚合物的接枝率提高5倍以上。接枝聚合物没有出现明显的降解或交联，力学性能优良。其辅助接枝机理为：基体聚合物形成大分子自由基后，首先引发NVP的接枝反应，相对于SEBS•，生成的SEBS-g-NVP•更易与丙烯酸酯类单体发生共聚反应，从而显著地提高了丙烯酸酯类单体的接枝率。.②接枝聚合物接枝链表面迁移机制. 接枝聚合物膜的表面亲水性与成膜溶剂密切相关，选用亲水PEG的择优性溶剂氯仿成膜，PEG接枝链更易于在表面富集。在水相环境下，接枝聚合物表面会发生表面重组，亲水性接枝链进一步向表面伸展。fPEG接枝链可自发在接枝聚合物表面富集，富集率与fPEG的分子结构以及成膜溶剂相关。YfPEG的表面富集率相对略低，受成膜溶剂影响较大；LfPEG的表面富集率超过11倍，且不受成膜溶剂的影响。. ③接枝聚合物表面生物相容性. 相比基体聚合物，接枝聚合物膜的纤维蛋白原吸附量降低了75%左右，血小板粘附受到明显地抑制。可能源于含氟碳链的疏水性，亲水性接枝链较短及其含量较低等原因，fPEG表面血液相容性不及PEG接枝表面。. 采用N-乙烯基单体辅助熔融接枝方法对苯乙烯类热塑性弹性体进行接枝改性，制备的含氟且具有生物相容性的接枝料，具有接枝链向表面自动迁移性能，可用于自润滑、抗菌类医疗器械。该研究成果得到企业产业化项目的支持，部分类别接枝料在威高集团得到了应用。