中文摘要：

采用细乳液聚合制备了不同接枝链长度和密度的聚苯乙烯按枝二氧化硅纳米复合粒子（SiO2-PS）．利用傅里叶红外光谱（FTIR）、透射电子显微镜（TEM）、示差扫描量热（DSC）、热失重（TGA）与凝胶渗透色谱仪（GPC）考察了SiO2-PS粒子接枝结构特征．采用TEM研究了接枝链聚合度（N）和接枝密度（σ）对SiO2·PS填充PS体系纳米粒子空间分布的影响规律．结果显示，N基本不变，σ越高，纳米粒子越易均匀分散；而接枝链过长易使长链相互缠结，起到反浸润作用，粒子聚集，不利于均匀分散．纳米粒子热力学稳定分散状态仅与N、σ有关，与粒径无关．通过调控Ⅳ和盯可得到特定的纳米粒子分散形貌．对比考察了SiO2-PS填充聚甲基丙烯酸甲酯（PMMA）体系结果，揭示了接枝链与基体分子链相容性对纳米粒子空间分布的贡献．

英文摘要：

A recurring challenge in the field of polymer nanocomposites （PNCs） is to control the spatial distribution of nanoparticles （NPs） throughout a polymer matrix and thereby optimize the desired macroscopic performance of PNCs. In this study, polystyrene-grafted silica （ SiO2-PS） NPs with different grafted chain length and grafting density were prepared via miniemulsion polymerization. The grafted structure of SiO2-PS NPs was characterized via combination of Fourier transform infrared spectroscopy （FTIR） , transmission electron microscopy （TEM） , differential scanning calorimeter （DSC） , thermogravimetric analysis （TGA） and gel permeation chromatography （GPC）. The core-shell structure of SiO2-PS NPs that consisted of different polymerization degrees of grafted chains （N） and grafting density （σ） can be synthesized by tuning various reaction conditions. The effect of N and σ on spatial distribution of SiO2-PS NP filled PS matrix was investigated by TEM observation. The results reveal that tunable specific spatial distribution of grafted NPs can be obtained through the control of N and tr. In the ease of that N is basically the same,grafted particles with higher σ are miscible with PS matrix chains,leading to more homogeneous dispersion of NPs. While when N is very high for grafted NPs with roughly the same σ the grafted chains and the matrix chains are dewetting between each other, which is not effective for uniform dispersion. The thermodynamics stable state of NP distribution is merely related to N and σ and independent of the particle size. Furthermore, by comparing the results of SiO2-PS NP filled PS and polymethyl methacrylate （PMMA） matrices, the contribution of the chemical structure differences and compatibility between grafted chains and matrix chains on spatial distribution of NPs are also discussed. The phase separation behavior between the PMMA matrix and grafted PS chains makes a great difference to the spatial distribution of the grafted NPs.