【作者】 贾光伟；

【导师】 许湧深；

【作者基本信息】 天津大学 ， 材料化学工程， 2009， 博士

【摘要】 微滴乳液聚合技术诞生于20世纪70年代。单体珠滴内成核占主导的特征,大大拓展了乳液聚合的应用范围。因此,对该工艺的理论及应用研究,具有重要的理论价值和现实意义。本论文首先以十二烷基硫酸钠(SDS)为表面活性剂和十六烷(HD)为助稳定剂,实施了苯乙烯单体的微滴乳液聚合。运用动态光散射分析(DLS)和透射电镜(TEM)表征了单体珠滴与乳胶粒的尺寸。进而采用估算乳胶粒数目与单体珠滴数目的比值和计算表面活性剂的覆盖率相结合的方法,研究了微滴乳液体系的成核机理及聚合动力学。实验结果表明,微滴乳液聚合体系的成核机理及聚合速率,主要受表面活性剂浓度以及助稳定剂用量变化的影响;通过调节实验条件,可以轻易地实现珠滴成核占主导,并制备了形貌规整的微纳米乳胶粒。同时,利用该体系的单体珠滴为反应器,原位实施了自由基聚合和溶胶凝胶反应,开发了制备聚合物基纳米复合材料的新工艺。并用动态光散射分析、红外光谱分析(FTIR)、差示扫描量热分析(DSC)、透射电镜测试等手段,对产物的性能和结构进行了表征。结果表明,制备了复合材料乳胶粒;随着无机相含量的增大,复合材料的玻璃化转变温度逐渐增大;通过控制两个反应的速率,可以制备不同形貌的乳胶粒。为克服上述体系十六烷在复合材料中的残留问题,本论文又开发了以液体聚丁二烯(LPB)为助稳定剂的微滴乳液体系,并与HD助稳定剂体系进行了比较。实验结果表明,LPB可以单独作为助稳定剂,实施微滴乳液聚合;LPB对单体珠滴尺寸、乳胶粒尺寸以及动力学的影响,与HD类似;由于LPB具有聚合物的性质,能够延长小珠滴存在的时间,所以LPB为助稳定剂的微滴乳液体系的珠滴成核比例高于上述的HD体系,反映了LPB在聚合过程中更优异的抑制单体分子扩散的能力。然而,由于LPB的粘性大于HD,所以同等条件下,LPB微滴乳液体系得到的单体珠滴尺寸大于HD体系,在制备小尺寸单体珠滴方面,LPB的能力要低于HD。此外,差示扫描量热分析结果表明,液体聚丁二烯对聚合物起到改性作用。测试结果表明,LPB为助稳定剂的微滴乳液体系的单体珠滴,可以用于制备复合材料的新工艺,实现了对新工艺的优化。微纳米反应器的区室化效应,很好的将两相之间混合限制在了纳米尺度,增强了两相的复合程度。更多还原

【Abstract】 Miniemulsion polymerization was developed in 1970s. Due to their small size, monomer droplets are the main nucleation locis in miniemulsion polymerization. This will extend the application of conventional emulsion polymerization. Therefore, any effort on the development of this new technique will be urgent and meaningful.In present study, the miniemulsion polymerizations of styrene emulsified by sodium dodecyl sulphate (SDS) and co-stabilized with hexadecane (HD) were carried out. The sizes of monomer droplets and latexes were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). According to these data, the surface coverage and ratio of latexes number and droplets number (Np/Nm) were both calculated. Then the dependence of nucleation mechanism and kinetics on the process parameters was investigated. Results show that, the nucleation mechanism and polymerization rate are mainly affected by SDS concentration and HD level. The dominant droplet nucleation can be achieved by careful operation. And perfect polymer particles in nanosize can be easily synthesized. Furthermore, the new technique on preparing polymer nanocomposite was developed based on these monomer droplets. The sol-gel process and radical polymerization were conducted spontaneously in monomer droplets (nano reactors) of miniemulsion. Dynamic light scattering (DLS), Fourier transform infrared (FTIR), Differential scanning calorimetry (DSC), and TEM were employed to characterize the structure and property of the products. Results indicate that the nanocomposite can be easily prepared in one step. Glass transition temperature (Tg) of composite is enhanced by increasing the inorganic content. Composites latexes with different structure can be prepared by tailoring the reaction rates of these two reactions.In order to solve the deleterious effects of HD on the properties of composite, a new miniemulsion system co-stabilized by liquid polybutadiene was developed in the second part. Moreover, the comparison of these two systems was discussed. The dependence of monomer size, latex size and knetics on LPB level is same with that of HD case. Due to the polymeric property of LPB, which can preserve the small droplets, the proportion of monomer nucleation in LPB system is higher than that of HD system. However, due to its higher viscosity, the LPB is less efficient than HD in preparing small monomer droplets. The size of monomer droplets in former system is larger than that of latter one. The results of DSC measurement indicate that LPB is chemically incorporated in the product, showing the modification on the product. The results of FTIR, DSC, Thermogravimetry (TG), X-ray diffraction (XRD) show that nanocomposite can be prepared using the LPB-costabilized miniemulsion system. This will optimize the new technique in preparing polymer composite, developed in present study. The compartment effect of the reactors (monomer droplets) enables the blending in nano size, strengthening the interaction of these two phases. Therefore, this new technique exhibits great potential in preparing polymer nanocomposite.更多还原