超低收缩复合树脂的研制机理及性能设计与表征

It has been the focus to develop low shrinkage，high mechanical properties of dental composite resins in recent years. A major difficulty in developing low shrinkage dental restoration materials is that their deficiently mechanical properties cannot satisfy the clinical purpose. According to these unsatisfied performances of dental composite resins, a kind of superlow shrinkage of POSS nano hybrid composite resins will be developed. Based on the zirconia martensitic transformation mechanism, the conditions and place of zirconia martensitic transformation from metastable tetragonal phase to monoclinic phase will be confirmed. The volume shrinkage inhibition of the composite resins will be studied owing to volume expand caused by zirconia martensitic phase transformation (t→m). The microstructure and macro performance of the composite resins will be analysed and characterized comprehensively. And the influence on mechanical properties and volume shrinkage of composite resins by zirconia will be evaluated.We will clear the quantitative linkage between zirconia and composite resins interface and performances. Molecular dynamics model of zirconia martensitic phase transformation (t→m) will be established. Starting from the microscopic interaction, mesoscopic structural characteristics and macroscopic mechanical behavior will be quantitatively described. The zirconia martensitic phase transformation nature and the response mechniasm between zirconia and composite resins will be revealed. The ultra-low composite resins performance design and control will be realized. This study is quite important not only for developing superlow shinkage POSS nano hybrid composite resins but slao for developing novel dental materials. It will also supply the scientific theoretical basis for performence design and optimization of composite resins and the available research method for effective control the volume shrinkage and reinforcing and toughening of the polymers.

针对齿科复合树脂聚合收缩大、力学性能不足等现状，从氧化锆（ZrO2）马氏体相变出发，研制超低收缩POSS纳米杂化复合树脂。基于氧化锆马氏体相变机制，确定室温下氧化锆亚稳态四方相到单斜相的转变条件及相变场所，研究氧化锆马氏体相变伴随的体积膨胀对复合树脂聚合收缩的抑制作用。对复合树脂结构与性能进行全面分析表征，综合评价氧化锆对复合树脂收缩及力学性能影响，明确氧化锆与复合树脂界面及性能间定量联系。建立氧化锆马氏体相变的分子动力学模型，从微观相互作用出发定量描述体系细观结构特征与宏观力学行为，揭示氧化锆相变本质及与复合树脂性能的响应机理，实现超低复合树脂的性能设计与调控。该项研究不仅对开发超低收缩POSS纳米杂化复合树脂、发展新型齿科材料具有重要意义，而且为复合树脂的性能设计、结构优化等提供科学的理论依据，为有效控制聚合物体积收缩、增强增韧等提供切实可行的研究手段。

采用新型骨粘结剂——硅磷酸钙粉末做填料，研制出超低收缩复合树脂材料。硅磷酸钙粉末由硅酸钙及磷酸钙组成。硅酸钙遇水后会迅速发生水化反应，并伴随体积膨胀。本项目采用SEM、XRD等方法，研究了不同硅磷酸钙含量（质量比分别为0%，10%，20%）、不同浸水时间（0~180天）对复合树脂的微观结构的影响。研究结果表明，浸水180天后三种复合树脂的体积膨胀率分别为1.42%（0 wt.% CPSC）、2.79 vol.% （10 wt.% CPSC）和2.27 vol.% (20 wt.% CPSC）。同时，复合树脂的挠曲强度、弹性模量及硬度等力学性能，均满足临床的使用要求。因此，含有硅磷酸钙填料的复合树脂，在口腔环境中由于水化反应产生的体积膨胀，可以有效减小复合树脂的聚合体积收缩，最终得到超低收缩的复合树脂。.另一方面，本项目在复合树脂中引入了反应性纳米单体——甲基丙烯酸基多面低聚倍半硅氧烷(POSS-methacrylate)，合成出POSS杂化纳米复合树脂。研究了几种不同POSS含量的纳米复合树脂的力学性能，包括收缩率、弹性模量、挠曲强度、抗压强度、硬度及韧性等。结果表明，POSS可有效改善复合树脂的体积收缩，较全面地提高复合树脂的力学性能，增加材料的耐磨损性及使用寿命，其中POSS含量为2 wt.%的纳米复合树脂，表现出最佳的综合性能。.结合实验数据，构建了分子动力学模拟的计算模型并验证了计算方法的可行性。通过径向分布函数、内聚能、溶解度及均方位移等参数的计算结果，分析了POSS杂化纳米复合树脂的分子结构，以及多官能POSS-methacrylate纳米单体对复合树脂的微观结构的影响。在此基础上，利用分子动力学模拟的计算方法，对POSS杂化纳米复合树脂的主要力学参数进行了预报。此研究方法可以大大缩短研发时间、节省实验经费。