【作者】 倪克钒；

【导师】 翁志学； 单国荣；

【作者基本信息】 浙江大学 ， 化学工程与技术， 2006， 博士

【摘要】 有机.无机杂化纳米粒子和微胶囊兼具高分子材料和无机材料的优点,可提高和拓宽单一材料的性能,在控制释放、生物制药等前沿领域有广阔的应用前景。本论文选用常用单体苯乙烯和功能单体甲基丙烯酸-3-三甲氧基硅丙酯（MPS）,进行核壳乳液共聚（或细乳液共聚）,方便地制得了有机-无机杂化核-壳结构的纳米粒子和纳米微胶囊。 深究反应机理,认为上述杂化粒子是自由基共聚和MPS中SiOR基团的水解-缩合反应耦合的结果,MPS在乳液体系中粒子相和水相的分配以及水解-缩合速率是影响过程的关键因素,并在反应温度（70℃）下,实验测得了这两方面数据。发现MPS加入量小于PS种子的11wt%时,体系处于非饱和状态,粒子相和水相中的MPS浓度随加入量的增加而线性增长。达到饱和状态后,粒子相和水相中的MPS浓度不再变化,分别为0.37、0.014mol/L,且乳胶粒粒径、化学组成对MPS的分配行为影响很小。MPS在粒子相与水相间以及在单体液滴与水相间都有恒定的分配系数k^p、k^d,分别为k^p=φ^p/φ^w=[M]^p/[M]^w=25.8、k^d=φ^d/φ^w=[M]^d/[M]^w=364。同时,用²⁹Si核磁共振谱测定了MPS的水解和缩合速率常数,发现该值随pH值均呈马鞍型变化,可用下式表述:k_h=k_H10^-pH+k_OH10^pH-14,k_c=k_H,c10^-pH+k_OH,c10^pH-14,最小值分别在pH=7和pH=4处。 通过反应过程分析,并根据乳胶粒形态的热力学判据,设计了核-壳结构的有机-无机杂化纳米粒子,指导实验的实施。即经乳液聚合先合成聚苯乙烯种子,继而在种子核外生成苯乙烯与MPS的共聚物,利用MPS中硅氧烷基的水解-缩合反应,再形成杂化的壳。pH值和MPS的饱和程度是影响制备过程及乳胶粒形态结构的重要因素:pH=7时,MPS的水解-缩合反应并不剧烈,乳胶粒中自由基共聚处于主导地位,MPS迅速吸附在乳胶粒相表面,发生反应,逐渐形成核-壳结构,同时SiOR基团轻微水解,生成SiOH基团,得到聚合物与氢键交联的杂化结构;pH=8.5、体系中MPS非饱和时,水相中MPS浓度较小,苯乙烯和MPS及其水解缩合产物的共聚反应仍能在乳胶粒表面发生,但产物中SiOR基团的水解、缩合程度较大,形成了以共聚物为主链、伴有大量Si-O-Si缩合产物为侧链的复杂结构;pH=8.5、体系处于MPS饱和状态时,水相中MPS浓度和水解缩合速率（缩合速率相对更快）都较高,使MPS在水相中迅更多还原

【Abstract】 Nanoparticles and nanocapluses with organic-inoragnic hybrid structure can exhibit the excellent properties of both inorganic and polymer materials. They can be used in some pioneer fields, such as controlled release, biotechnology, medicine etc. In this thesis, a special functional comonomer, 3-trimethoxysilyl propyl methacrylate （MPS）, is copolymerized with styrene in the seeded emulsion （or miniemulsion） polymerization process to prepare the organic-inoragnic hybrid nanoparticles with core-shell morphology or nanocapluses.It is found that this process is determined by the coupling reaction of free radical polymerization and hydrolysis-condensation. Therefore, partition and hydrolysis/condensation rates of MPS are the key factors determining the reaction process. In the thesis, MPS partition behavior is characterized by gas chromatography （GC）. It is found that MPS concentration both in water and particle phase increase linearly up to the saturated concentration when MPS addition amount is about 11%wt of polymer seeds. Then the concentrations in these two phases keep constant at the saturated concentration, which are 0.37 and 0.014 mol/L in particle and water phases, respectively. The MPS partitions in each phase have constant coefficients, which can be expressedas: Meanwhile, the hydrolysis andcondensation rate constants are measured at different pH value with ²⁹Si liquid-state NMR. It is found that the hydrolysis and condensation rate constants-pH plots show inverted bell-type with a lowest value at pH=7 and 4, respectively. A formula is presented to correlate the hydrolysis and condensation rate constants at different pH value as:Based on the reaction mechanism and the thermodynamic criterion governing the final morphology of the particles, organic-inorganic hybrid core-shell nanoparticles are designed and synthesized by seeded emulsion polymerization. Through morphology design, polystyrene, as seeded cores, are synthesized firstly;then MPS is added to form MPS-styrene copolymer shell on the surface of polystyrene core;and finally the organic-inorganic hybrid shell is formed through sol-gel process via the hydrolysis-condensation of organic alkoxysilane groups in MPS. The operation conditions, such as pH value, saturation degree of MPS, etc, have great influence on the latexmorphology and microstructures: the hydrolysis-condensation rates are quite slow at pH=7, free radical polymerization is the dominated reaction in the system and MPS enter into particles very quickly, only a little parts of SiOR groups are hydrolyzed to form slightly hydrogen bonded crosslink;in the case of pH=8.5 and unsaturation, high hydrolysis-condensation rate constants will lead the copolymer shell to have C-C main polymer chain with side chains of Si-O-Si oligomers or cyclic molecules;and in the case of pH=8.5 and saturation with MPS, higher MPS concentration and higher hydrolysis-condensation rates in water phase will promote the growing up and agglomeration of the Si-O-Si oligomers or cyclic molecules in the water and make the emulsion unstable finally;at pH=2, the extreme high hydrolysis rate （much higher than condensation rate） leads to the formation of multi-SiOH resultants, which act as crosslinker and cause the gelation of the system.A monomer partition model was developed firstly using constant partition coefficients;then a free radical emulsion polymerization model with the monomer partition was presented. On the base of these two models and the features of hydrolysis-condensation reaction for organosilane at various phases in the heterogeneous system, a complete kinetic model of emulsion polymerization with the participation of hydrolysis-condensation reaction was derived. This model is used in the emulsion copolymerization system of MPS and styrene, and are compared with the experimental data obtained by GC and solid-state ²⁹Si NMR. It is found that the model predicted results are in good agreement with the experimental data. It is concluded that the characteristic parameter f of the heterogeneous system is determined by the surface area and the difficulty of functional groups diffusingonto the particle surface, and can be estimated byBy using the synthetic hybrid core-shell nanoparticles, nanocapsules can be obtained after removing the polystyrene core through centrifuge-redisperse or dialysis methods. However, morphology of the nanocapsules obtained by centrifuge-redisperse method is greatly destroyed because of the strong mechanic force during the produced process. The dialysis process can produce perfect nanocapsules, but it consumes quite a long time and the core cannot be removed completely. Therefore, miniemulsion process is used to synthesize hybrid nanocapsules by only one step with using low molecular weight droplets as template. In this process, styrene and MPS are copolymerized on the surface of the well-dispersed isooctane droplets to form capsules. It is found that the micelles and homogenous nucleation methods in the synthetic process must be avoided, so that theaddition amount of surfactant must be less than its critical micelle concentration （3.3g/L） and hexadecane used as costabilizer. It is also found that the initial volume fraction of the monomer in the recipe must be lower than 0.36 to obtain capsules, because less monomer fraction in droplets is in favor of the phase separation after polymer is produced, and higher MPS fraction is favor in the formation of capsules, but too higher MPS content in capsules will lead to collapse.The kinetics of the penetrative process is researched by ultraviolet-visible spectrum （UV）, it is found that the diffuse behavior is consisted with diffuse model in themicroporous media: cw - coe B r ’, DB =Da￡/r2 . The diffusion coefficients andtortuosities are calculated and suggest that the diffusion velocity is increased with higher MPS content in capsules due to the larger porosity;the tortuosity is less in cresol red-methanol system than that in anthracene-THF system, and nearly didn’t change with the MPS content in capsules. The loading of the anthracene is proved by FTIR, and the release velocity is much slower than the loading velocity because the special microstructure of the hybrid nanocapsules.更多还原