【作者】 张明祖；

【导师】 闻荻江；

【作者基本信息】 苏州大学 ， 材料学， 2010， 博士

【摘要】 两亲性聚合物作为乳化剂,具有低分子的表面活性同时,也具有很多独特的物理化学性质,使用时具备很多小分子乳化剂或复配体系所不具备的优点。对分散体系的稳定作用及其在(细)乳液聚合和分散聚合中的应用则是该类聚合物最引人注目的应用研究之一。两亲性聚合物的种类之一是无规型两亲性聚合物,其合成方法简便易行,单体种类选择和组成的范围变化多样,通过化学合成手段可得到表面活性高低不同、不同结构的、一定分子量的两亲性聚合物,作为乳化剂应用于相关的乳液聚合中,其聚合产物结构或性能有不少独特的优点。本论文合成了两种新型两亲性无规共聚物:(1)利用BPO引发甲基丙烯酸(MAA)、甲基丙烯酸十八烷基酯(SMA)和聚乙二醇甲基丙烯酸酯(PEGMA),合成了两亲性共聚物Poly(MAA-co-SMA-co-PEGMA),其具有离子型表面活性剂和非离子表面活性剂的特点。(2)利用AIBN引发SMA、DMA(甲基丙烯酸(N, N-二甲氨基)乙酯)单体,合成了分子量分布窄的两亲性无规共聚物Poly(SMA-co-DMAEMA),其具有阳离子表面活性剂的特点。这两种两亲性共聚物作为后续(细)乳液聚合的乳化剂。与此同时,将已合成的聚甲基丙烯酸(N, N-二甲氨基)乙酯[poly(DMAEMA)]Y-型大分子单体作为细乳液聚合反应的乳化剂和共聚大分子单体。对它们相应的(细)乳液聚合的体系和聚合产物做了相关研究。得到了如下重要的结论:1.Poly(MAA-co-SMA-co-PEGMA)共聚物(MAA:SMA:PEGMA = 45:25:30)的CMC(临界胶束浓度)为0.003g/ml左右,其浊点温度69.1°C,水溶液的表面张力最低值为48 mN/m左右,而低分子表面活性剂SDS(十二烷基硫酸钠)则为40 mN/m。Poly(MAA-co-SMA-co-PEGMA)共聚物(以下简称HS)与低分子表面活性剂SDS(以下简称LS)复配增强其表面活性、提高其浊点,当HS:LS=5:5后,体系的表面张力和临界胶束浓度都有所降低,接近于低分子表面活性剂,且有明显的CMC值,浊点温度大于100℃。作为丙烯酸酯乳液聚合的复配乳化剂,其聚丙烯酸酯乳液的稳定性好,成膜后吸水性低,很容易达到平衡,且最终的吸水率也比较低,比低分子表面活性剂体系聚丙烯酸酯膜吸水率降低100%以上,耐水性好。2.Poly(SMA-co-DMAEMA)是以DMA:SMA=8:2,9:1(摩尔比)两种比例,制备出两种结构精致,分子量分布较窄的大分子乳化剂。在乳液中亲水链伸向水相,形成聚苯乙烯为“核”乳化剂为“壳”的聚合物粒子。细乳液聚合动力学研究表明,随着固含率增大,聚合反应速率、转化率增加;随着大分子乳化剂用量的增加,聚合反应速率、转化率增加;随着体系pH值变化,在pH=3-5范围内,细乳液聚合具有较高的稳定性、反应速率和转化率;而在pH=7时,细乳液聚合稳定性、反应速率和转化率都较低。FTIR和1HNMR分析,结果表明:大分子乳化剂吸附在苯乙烯的微球上,而把它们的亲水链伸向水中,形成“毛发型”聚合物微球。对反应中的细乳液的粒径进行跟踪测试,结果显示,粒径基本不变,表明大分子乳化剂具有良好的乳化效果。对聚合物粒子的形态进行透镜分析,结果表明:在酸性介质中,粒子大小均匀,说明大分子乳化剂所形成的阳离子型聚电解质或部分质子化对苯乙烯细乳液聚合有明显影响。3.以聚甲基丙烯酸(N, N-二甲氨基)乙酯[poly(DMAEMA)]Y-型大分子单体作为细乳液聚合反应的乳化剂和共聚大分子单体。细乳液聚合动力学研究结果表明:随着大分子单体用量的增加,聚合反应速率增加。随着体系pH值增大,在pH=3-5范围内,细乳液聚合速率较快,转化率较高;而在pH=7时,最终单体的转化率仍很低。FTIR和1H NMR分析,结果表明:大分子单体以共价键形式与苯乙烯微球相结合,而把它们的两条亲水链伸向水中。形成“毛发型”聚合物微球。DSC分析结果表明:每一样品只有一个玻璃化转变温度和单一吸热分解峰,证明体系中poly(DMAEMA)与聚苯乙烯合为一体。对聚合物粒子的形态进行透射电镜分析,结果表明:随着体系中大分子用量的增大,聚合物微球粒径变得均匀。在酸性介质中,粒子大小均匀;而在中性pH介质中,粒子大小不均匀。说明poly(DMAEMA)所形成的阳离子型聚电解质或部分质子化对苯乙烯细乳液聚合有明显影响。更多还原

【Abstract】 Amphiphilic polymers are promising surfactants due to their unique physicochemical properties such as excellent emulsion ability, high stability, etc. The application in (mini)emulsion polymerization and dispersed polymerization is one of the most notable applications of amphiphilic polymers. Among these amphiphilic polymers, random ones are very intriguing because of their easy processing, various monomers and compositions. Furthermore, various amphiphilic random polymers with different compositions, molecular weights, and surface activity can be synthesized and used in emulsion polymerization.In this work, two kinds of amphiphilic random copolymers were synthesized: (1) Amphiphilic random copolymer poly(MAA-co-SMA-co-PEGMA) was prepared by the conventional radical polymerization of methacrylic acid (MAA), stearyl methacrylate (SMA), and poly(ethylene glycol) monomethacrylate (PEGMA) using BPO as the initiator; (2) Amphiphilic random copolymer poly(SMA-co-DMAEMA) was synthesized by the radical polymerization of (N, N-dimethylamino)ethyl methacrylate (DMAEMA) using AIBN as the initiator. Subsequently, both these amphiphilic copolymers were used as macromolecular surfactants in (mini)emulsion polymerization. Moreover, Y-shaped macromonomer based on poly[(N, N-dimethylamino)ethyl methacrylate] (PDMAEMA) with a narrow molecular weight distribution was synthesized via oxyanion-initiated polymerization and then utilized in the miniemulsion polymerization of styrene. This macromonomer acted well both as a comonomer carrying a reactive C=C double bond in its central section and as a pH-responsive polycationic surfactant in media with different pH values. The following conclusions can be obtained from this work:1.The CMC value of poly(MAA-co-SMA-co-PEGMA) (MAA:SMA:PEGMA=45:25:30) is about 0.003 g/ml, and its clouding point is about 69.1°C, while the lowest surface tension of this copolymer aqueous solution is about 48 mN/m comparing with the 40 mN/m for low molecular weight surfactant SDS. The mixed surfactant system of poly(MAA-co-SMA-co-PEGMA) (denoted HS) and SDS (denoted LS) can be used to strengthen the surface activity and increase the clouding point. The surface tension and CMC value of the mixed surfactant system decreased when the HS:LS is 5:5, and the clouding point was more than 100°C. The polyacrylate emulsion stabilized by the mixed surfactants possesses good stability and water resistibility, comparing with the system stabilized by low molecular weight surfactant.2.Two kinds of macromolecular surfactants poly(SMA-co-DMAEMA) copolymers were successfully prepared with the molar ratio of DMAEMA:SMA are 8:2 and 9:1, respectively. The strongly hydrophobic PSMA chains could be anchored in the surface of monomer droplets and the miniemulsion polymerization of styrene was then conducted. The kinetics studies showed that the polymerization rate and monomer conversion increased with the increase of solid content and the amount of macromolecular surfactant. Furthermore, the pH value of aqueous media also influenced the miniemulsion polymerization. The miniemulsion polymerization possessed high stability, reaction rate and monomer conversion at pH 3-5, while the system became unstable and the reaction rate and monomer conversion were also decreased at pH 7. FTIR analysis demonstrated that the macromolecular surfactant was adsorbed on the polystyrene microspheres and the hydrophilic chains extended to the aqueous phase, resulting in the“hairy”microspheres. Particle size analysis and TEM measurements showed that these amphiphilic copolymers are efficient surfactants and the polymer microspheres were relatively uniform under acidic media.3.Y-shaped macromonomer based on poly[(N, N-dimethylamino)ethyl methacrylate] (PDMAEMA) was an efficient surfactant for the miniemulsion polymerization of styrene. The kinetics studies showed that the reaction rate increased with the increasing amount of macromonomer. The miniemulsion polymerization possessed higher reaction rate and monomer conversion at pH 3-5, while the monomer conversion was very low at pH 7 medium. FTIR and 1H NMR analyses the macromonomer was linked with the polystyrene microsphere by covalent bond, while the hydrophilic PDMAEMA chains extended to the aqueous phase. DSC analysis showed that only one Tg was obtained for the samples, which indicated that the poly(DMAEMA) was bonded with polystyrene microspheres. TEM measurements demonstrated that the polymer microspheres became uniform with the increase of the amount of macromolecular surfactant. The microspheres were uniform under acidic condition, indicating that the protonated polycation strongly influenced the miniemulsion polymerization of styrene.更多还原