基于超分子作用的聚合物-SiO2复合粒子的设计合成、表面SiO2解离和性能研究

In recent years, considerable effort has been devoted to the elaboration of colloidal polymer-silica nanocomposite particles with defined morphologies. Most of the colloidal nanocomposite syntheses are based on the polymerization of organic monomer in the presence of pre-formed SiO2 colloidal particles. However, it is still a challenge to control the surface SiO2 composition in this method. The goal of the proposal is aimed to develop a novel method to synthesize of polymer-silica colloidal nanocomposite particles based on cucurbit[8]uril (CB[8]) supramolecular interactions. CB[8] is capable of simultaneously encapsulating two guest molecules inside its cavity, forming a stable yet dynamic ternary complex. CB[8] will first precomplex with azo--functionalized silica nanoparticles to form azo-SiO2/CB[8], then copolymerization of 1-methyl-1-(4-vinylbenzyl)- [4,4’-bipyridine]-1,1’-diium chloride iodide (St-MV) and vinyl monomer (e.g., styrene) will be conducted in the presence of azo-SiO2/CB[8] using a free-radical initiator in aqueous media. The resulting polymer will complex with the azo-SiO2/CB[8] based on host-guest interactions. Commercial ultrafine aqueous silica sol will be used and the most possible morphology of the composite particles will be raspberry or currant-bun. The noncovalent nature of supramolecular interactions offers an opportunity to reversibly control the complexation. The azo-SiO2/CB[8]/polymer ternary complexes could be dissociated upon addition of a competitive guest, resulting in composite particles without silica composition or with controllable SiO2 composition on the surfaces. This proposed approach represents a new paradigm in the synthesis of polymer colloids. Potential applications for these new nanocomposite particles include abrasion-resistant coatings.

聚合物-SiO2纳米复合粒子具有广泛的应用前景。目前，这类复合粒子的制备大多是基于单体在SiO2粒子存在下的原位聚合，但现有方法不能实现对其表面SiO2组分的有效调控。本项目将基于超分子作用发展一种原位聚合制备聚合物-SiO2复合粒子的新方法，即选择能同时与两种客体分子结合而形成三元复合物的葫芦8脲(CB[8])作为聚合物和SiO2之间的超分子连接物。CB[8]预先与偶氮苯功能化的SiO2纳米粒子(azo-SiO2)进行复合，然后在得到的azo-SiO2/CB[8]的存在下，进行甲基紫精功能化的苯乙烯与乙烯基单体的原位无皂乳液共聚，所生成的聚合物将基于主-客体作用而与azo-SiO2/CB[8]结合形成复合粒子；接着，通过加入竞争性客体调控复合粒子表面SiO2与CB[8]的解离，将得到表面SiO2组分可控的复合粒子。本项目不但具有重要的理论意义，而且在制备耐磨涂料方面也具有潜在的应用价值。

聚合物-SiO2纳米复合粒子具有广泛的应用前景。目前，这类复合粒子的制备大多是基于单体在SiO2粒子存在下的原位聚合。另一方面，在聚合物-无机复合粒子的制备过程中需解决的最重要问题之一是消除聚合物和无机物之间的不相容性，这通常需要在它们之间的界面建立物理化学的或者化学的联系，使聚合物和无机物表面之间具有显著的亲和力。本项目利用葫芦8脲(CB[8])超分子作用发展了一种原位聚合制备聚合物-SiO2复合粒子的新方法，这是基于CB[8]可以相继与含有缺电子的甲基紫精组分的客体和含有富电子的偶氮组分的客体相结合而形成三元复合物， 从而可以作为聚合物和SiO2之间的超分子连接物。本项目首先研究了苯乙烯和甲基紫精功能化的苯乙烯(StMV)的无皂乳液共聚，然后在此基础上研究了苯乙烯与StMV在偶氮苯功能化的SiO2纳米粒子(azo-SiO2, 20~24nm)和CB[8]的存在下的无皂乳液共聚。结果表明，在适当的条件下，所生成的聚合物能基于主-客体作用而与azo-SiO2结合形成聚集状的复合粒子。对比实验证实azo-SiO2和CB[8]二者缺一不可。本项目首次实现了基于CB[8]超分子作用来制备聚合物-SiO2复合粒子。