硅烷偶联剂MPS对SiO2-聚丙烯酸酯复合微球接枝交联结构及剪切取向能力的影响

为了探究γ-甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)对SiO₂-聚丙烯酸酯(PAcr)复合微球结构与性能的影响，在丙烯酸丁酯与甲基丙烯酸甲酯的自由基悬浮共聚合体系中加入MPS、MPS偶联改性的SiO₂(MPS-SiO₂)纳米粒子或MPS偶联改性SiO₂纳米粒子的原始分散液，分别考察了非偶联MPS的量、偶联MPS的量、偶联与非偶联MPS的相对含量对SiO₂-PAcr复合微球交联程度和交联结构的作用规律，并进一步对比了具有不同交联结构复合微球的剪切取向能力。通过TEM观察发现，非偶联MPS会水解自缩聚产生直径约6 nm的颗粒（即MPS水解颗粒），表面带有可聚合双键，能起到交联作用。MPS偶联改性SiO₂纳米粒子原始分散液除含有MPS-SiO₂纳米粒子外，还含有MPS水解颗粒，因而能构筑双重交联结构。具有这种双重交联结构的复合微球在HAAKE转矩流变仪中经熔融剪切可形成平均长径比高达12.0的取向体，而单独以MPS水解颗粒或MPS-SiO₂纳米粒子为交联点的微球经相同的熔融剪切过程只能形成平均长径比分别为9.1和8.8的取向体。这表明，偶联和非偶联MPS所构造的两种不同尺度的交联结构对SiO₂-PAcr复合微球剪切取向能力的提高有着显著的协同作用。 

Effect of silane coupling agent MPS on crosslinking structure and shear orientation ability of SiO2-polyacrylate composite particles

In order to reveal the effect of γ-methacryloxypropyl trimethoxysilane (MPS) on the structure and property of SiO₂-polyacrylate (PAcr) composite particles, MPS, MPS modified SiO₂ (MPS-SiO₂) nanoparticles, and the raw dispersions obtained from the modification of SiO₂ nanoparticles with MPS were used as the additives in the radical suspension copolymerization of butyl acrylate and methyl methacrylate. The influence of the amount of coupled and uncoupled MPS and the ratio of coupled MPS to uncoupled MPS on the crosslinking degree and crosslinking structure of SiO₂-PAcr composite particles was investigated, and the shear orientation abilities of the composite particles with different crosslinking structures were compared. TEM observation shows that some irregular particles with diameter at about 6 nm are formed by the hydrolytic condensation of uncoupled MPS (i.e. MPS condensed particles). The MPS condensed particles can act as the crosslinking points owing to the double bonds on their surface. By adding the raw dispersions from MPS modification of SiO₂ nanoparticles, dual-crosslinking structure can be formed in the SiO₂-PAcr composite particles because both coupled and uncoupled MPS are included in the polymerization system. The as-prepared dual-crosslinked particles can be deformed into the orientated structure with a high aspect ratio of 12.0 in HAAKE torque rheometer. However, the aspect ratio after the same shear orientation process can only reach 8.8 and 9.1 with coupled or uncoupled MPS as additives, respectively. The coupled and uncoupled MPS can lead to two different kinds of crosslinking structures, which improves the shear orientation ability of SiO₂-PAcr composite particles synergistically.