【作者】 张立彬；

【导师】 孔祥正；

【作者基本信息】 济南大学 ， 高分子化学与物理， 2010， 硕士

【摘要】 本文采用异凝聚法以制备具有特殊表面微观结构的聚合物复合微粒,并探讨可有效控制这种微观结构的有效方法。本文的研究内容分为三个方面:阳离子胶粒的制备及粒径控制;阴离子胶粒的制备及粒径控制;复合微粒的制备及结构控制。首先以1-溴代十六烷和N,N-二甲基氨基甲基丙烯酸乙酯为原料,合成阳离子功能单体甲基丙烯酰氧乙基十六烷基二甲基溴化铵(DMHB)。利用红外光谱仪、核磁共振氢谱仪、元素分析仪、表面张力仪和电导率仪对DMHB进行相关表征,确定其分子结构中带有反应活性的双键,临界胶束浓度(CMC)为6.7×10-4 mol/L。使用阳离子自由基引发剂,改变阳离子功能单体DMHB的量与苯乙烯(St)进行乳液聚合获得不同粒径的P(St-DMHB)阳离子纳米胶粒。结果表明,随DMHB用量增加,最终乳胶粒粒径规律性变小,干态胶粒粒径可控变化范围为28~74nm;而乳胶粒ζ电位随DMHB用量增加先增大,尔后至DMHB用量占总单体质量的2%后不再变化。然后,通过批量法乳液聚合,用过硫酸钾(KPS)引发甲基丙烯酸甲酯(MMA)或St聚合制备不同粒径的阴离子亚微米胶粒。研究了引发剂用量、聚合温度、乳化剂用量及单体性质等影响因素。结果显示,提高引发剂用量有利于提高聚合反应速率,但对乳胶粒粒径影响不大;提高聚合反应温度有利于提高聚合反应速率,降低乳胶粒粒径;在无任何乳化剂下获得的PMMA乳胶粒的干态粒径可控变化范围为150~220nm;当使用乳化剂时,通过调节乳化剂用量可制得干态粒径可控变化范围介于75~200nm之间的PMMA乳胶粒,及干态粒径可控变化范围为90~800nm的PSt乳胶粒。采用半连续乳液聚合法制备聚(St-丙烯酸丁酯)胶粒时,减少乳化剂用量,有利于获得较大的乳胶粒,二次成核几率减小;不断滴加单体可使乳胶粒不断长大,但胶粒长大到一定程度后较易产生粘连,水化粒径可控变化范围在54~172nm。胶粒所载负电荷由引发剂残基引入,ζ电位不随聚合条件改变而变化,基本恒定在-48mV左右。最后,采用基于静电相互作用的异凝聚法将上述两种带有相反电荷的胶粒进行组装,可获得表面粗糙的草莓型复合微粒,随着壳层阳离子胶粒粒径的减小,复合微粒表面粗糙度变低。对异凝聚过程中复合液透光率和微粒大小及分布进行跟踪测试,并通过透射电子显微镜和扫描电子显微镜观察阳离子胶粒、阴离子胶粒以及复合微粒的形态、大小及表面形貌。结果显示,通过改变阴离子乳胶粒和阳离子乳胶粒的比例可以实现单位复合微粒表面的阳离子胶粒数在一定范围内可控变化。将具有不同表面形态的微粒沉积在聚合物膜上,测定膜表面水接触角变化。结果显示,沉积草莓型聚合物颗粒的膜的表面接触角比沉积光滑聚合物颗粒的膜的表面接触角大,说明表面二次结构有利于增强膜材料的表面憎水性能。更多还原

【Abstract】 A series of raspberry-like polymer composite particles with peculiar surface microstructure were prepared by electrostatic heterocoagulation, and their surface microstructure were adjustable under controlled. This work can be presented in 3 parts: Preparation of cationic particles with controlled size; preparation of anionic particles with controlling size; and heterocoagulation using the cationic and anionic particles with objective to control the microstructure of the obtained composite paticles.A polymerizable surfactant, methacryloxyethylhexadecyl dimethylammonium bromide (DMHB) was first synthesized with dimethylaminoetyl methacrylate and n-hexadecane bromide. The molecular structure of DMHB was characterized by FTIR, 1HNMR and element analysis. The surface activity of DMHB was measured by tensiometer. and its aqueous solution conductivity was tested. A series of styrene (St) and DMHB emulsion copolymerization with different level of the cationic monomer DMHB were carried out using 2,2′-azobis(2-methylpro-pionamide) dihydrochloride as a cationic initiator, cationic particles with particle size varied from 28 to 74 nm were obtained. It clearly revealed that the hydrodynamic diameter of the final latex particles decreased from 105 to 43 nm when DMHB content changed from 0.25% to 15%; on the same time, a slight increase inζpotential of the particles varied from 37 to 46 mV was observed when DMHB content changed from 0.25% to 2%, thisζpotential was kept relatively constant with further DMHB content increase.Anionic latex particles of poly(methyl methacrylate) (PMMA) or of PSt with different size were prepared by batch process using potassium peroxydisulfate as initiator. Several process parameters, such as concentration of initiator, polymerization temperature, concentration of emulsifier and the type of monomers, were preliminarily studied. It was shown that polymerization rate was enhanced at higher temperature and higher initiator concentration. Anionic PMMA particles with particle size varied between 150 to 220 nm were obtained by changing polymerization temperature from 90 to 60°C without any emulsifier. When using surfactant at varied concentrations, anionic PMMA particles with size between 75 to 200 nm and anionic PSt particles with size between 90 to 800 nm were readily obtained. A series of anionic poly(St-butyl acrylate) (P(St-BA)) particles with different hydrodynamic particle size from 54 to 172 nm were also prepared by seed emulsion polymerization with different levels of emulsifiers and different monomers ratios. Since the immobile negative charge of anionic particles was provided by initiator fragment, aζpotential of about -48mV for all anionic particles was detected regardless of polymerization processes.Heterocoagulation was then attempted using the cationic particles of different size and the anionic particles based on electrostatic interaction. Light transmittance, particle size upon heterocoagulation and its distribution were followed in order to understand the assembly of the 2 types of the particles of opposite charge. Transmission electron microscope (TEM) and Scanning electron microscope (SEM) were used to observe the morphology of cationic latex particles, anionic latex particles and the composite particles. Results showed that the coverage of larger anionic particle surface by smaller cationic particles was adjustable at limited extent by controlling the ratio of the anionic and cationic latex particles. Finally, the composite particles obtained through heterocoagulation were deposited on a film of P(St-BA). It was found that the surface contact angle on the composite particles coated film was much larger than that on P(St-BA) film, which illuminated that the surface coated with the composite particles with designed microstructure contributed greatly to enhancement of hydrophobicity of the surface.更多还原