新型無乳化劑乳化聚合技術開發:製備活性共聚乳膠及均一粒徑有機/無機混成乳膠

Development of Novel Surfactant-Free Emulsion Polymerization Techniques: Preparation of Living Block Copolymer and Monodisperse Organic/Inorganic Hybrid Latexes

周奕辰(I-Chen Chou)

指導教授 ： 邱文英

國立臺灣大學/工學院/化學工程學研究所/博士(2013年)

https://doi.org/10.6342/NTU.2013.01340

摘要

在本研究中，吾人以各種無乳化劑之乳化聚合配合各種新型無乳化聚合技術之開發，製備活性共聚乳膠及均一粒徑有機/無機混成乳膠，並探討其反應機制。本論文共分為三大部分。第一部份使用1,1-對二苯乙烯 (1,1-diphenylethylene，DPE) 控制活性自由基聚合以及製備其團聯共聚物，並使用Pickering 乳化進行油相內之活性自由基聚合研究。第二部分為研究不穩定狀態下Pickering乳化聚合時所生成的均一粒徑乳膠顆粒之研究。此外並使用無乳化劑固體粒子穩定聚合法一步驟製備均一粒徑之高分子/二氧化矽之 (核/殼)奈米複合乳膠。第三部份為使用分散聚合(dispersion polymerization)，在無乳化劑的狀態下開發新型製備均一微米級乳膠顆粒之技術及分析，並使用無乳化劑分散聚合包覆碳黑奈米粒子。
第一部份包含第二、三章。在第二章中利用1,1-對二苯乙烯 (1,1-diphenylethylene，DPE) 控制活性自由基聚合。實驗發現在較低溫的聚合系統中，不論改變1,1-對二苯乙烯的量、起始劑的量，分子量皆不隨著單體轉化率升高而成長。藉由提高反應溫度且預熱起始劑的處理，在DPE控制活性自由基聚合的系統中也能得到傳統活性自由基聚合的特徵。反應溫度、預熱步驟等變因對於分子量、分子量分佈的影響將在這個部分討論。最後利用DPE-capped PMMA當巨起始劑，成功的製備 聚(甲基丙烯酸甲酯)-聚(丙烯酸丁酯) 團聯共聚物，並探討引入溶劑的量及對反應速率、活性自由基聚合控制效果、分子量及其分佈之影響。
第三章將此DPE控制活性自由基聚合引入Pickering乳化系統中進行反應，在水熱法環境下利用親水性高分子電解質聚苯乙烯磺酸鈉鹽 (Poly(sodium 4-styrenesulfonate, PSS-NA) 協同合成具懸浮性的親水奈米氧化鋅粒子作為Pickering乳化之穩定粒子。藉由使用不同分子量的PSS-NA和改變其用量，研究對於Pickering乳化聚合時之型態、懸浮穩定性、油水介面性質、及DPE活性自由基聚合行為之影響。
第二部份包含第四章以及附錄。吾人發現在不穩定的Pickering乳化聚合中，特定條件下能得到部分穩定的次微米級均一粒徑乳膠顆粒。吾人對於此現象進行一系列研究並提出一個凝聚誘導(Coalescence induce)的聚合機制用於闡述此均一乳膠例子之合成路徑，並延伸此研究至沒有穩定粒子存在之無乳化劑系統，對於諸多變因進行探討。因生成的乳膠粒子其產率(yield)較低，故安排於附錄內。第四章中則是探討使用市售表面負電荷之二氧化矽奈米粒子，使用無乳化劑乳化聚合由帶正電起始劑AIBA起始一步驟合成均一粒徑之高分子乳膠/二氧化矽之核/殼奈米複合乳膠粒子，並探討二氧化矽粒子濃度、水相酸鹼度等對此核殼結構合成之影響。
第三部份包含第五、第六章。第五章中，吾人在醇相中進行無乳化劑之分散聚合，使用帶電之起始劑合成無乳化劑包覆之乳膠顆粒。然而，單獨使用帶電起始劑並無法獲得完全均一粒徑以及大於微米級之乳膠粒子。為了克服此問題，使用了帶電/不帶電的混合起始劑系統，發現藉由加入此不帶電的起始劑能得到數微米大小之均一粒徑乳膠顆粒。吾人對於此新型研究路徑之各種變因作一系列探討。 第六章中，使用無乳化劑醇/水相分散聚合，製備包覆奈米碳黑粒子之複合材料。首先使用溶膠凝膠法對市售碳黑表面做反應官能基之接枝反應同時並增加其長時間分散性使其均勻分散於溶劑中，隨後進行無乳化劑之分散聚合，成功製備高分子乳膠顆粒包覆之碳黑/高分子之核/殼奈米複合乳膠，並探討碳黑表面接枝量、使用起始劑種類、溶劑極性等因素對包覆之影響。

關鍵字

Pickering 乳化聚合 ； 1,1-對二苯乙烯 ； 控制活性自由基聚合 ； 有機/無機複合乳膠顆粒 ； 均一粒徑 ； 分散聚合 ； 無乳化劑乳化聚合 ； 核/殼結構

並列摘要

In this research, we developed several kinds of novel surfactant-free polymerization along with various known surfactant-free polymerization techniques for preparing living block copolymer organic/inorganic hybrid latexes as well as monodisperse latexes. This research was divided into three main parts. In the first part, 1,1-diphenylethene(DPE) controlled radical polymerization was performed and used to synthesize living block copolymer, further extended the system to Pickering emulsion polymerization. In the second part, we studied the formation of monodisperse latexes derived from unstable Pickering emulsion polymerization. Besides, monodisperse polymer/silica core/shell nanocomposites were prepared by emulsifier-free solid stabilized polymerization. In the third part, surfactant-free alcoholic dispersion polymerization was conducted for monodisperse latexes as well as nanoparticles encapsulation.
Chapter 2 and 3 were contained in the first part. In chapter 2, controlled free radical polymerizations by 1,1-diphenylethene(DPE) were demonstrated. In our previous study, the DPE controlled radical polymerization with constant molecular weight throughout the polymerization was caused by the intrinsically low reactivation rate constant (k2) of DPE-capped dormant chains at lower temperatures. By using a preheating treatment of initiators followed by a living polymerization of monomers at higher temperatures, a continuous growing of polymers with unimodal molecular weight distribution and a relatively small polydispersity index was observed. The reaction temperature, and preheating treatment to the molecular weight also molecular weight distribution were discussed. Moreover, we prepared poly(methyl methacrylate-block-n butyl acrylate) (PMMA-b-PBA) block copolymers using DPE-capped PMMA as a macroinitiator through bulk and solution polymerization. The influences of solvent and polymerization methods on the polymerization rate, controlled living character, molecular weight (Mn) and molecular weight distribution (PDI) throughout the polymerization were studied and discussed. In chapter 3, Pickering emulsion polymerization in the presence of a novel suspension of zinc oxide/ Poly(sodium 4-styrenesulfonate) (ZnO/PSS-) nanocomposite particles was applied to prepare ZnO/living block copolymer latexes. In the emulsion system, 1,1-diphenylethene(DPE) controlled radical polymerization of poly(methyl methacrylate)-b-poly(butyl acrylate) was proceeded in oil phase. The influences of hydrophilicity of the ZnO/PSS- nanocomposite as well as the ratio between ZnO/PSS- and oil phase on the polymerization, controlled living character, molecular weight (Mn), and molecular weight distribution (PDI) of living block copolymers throughout the Pickering emulsion polymerization has also been elaborated. To the best of our knowledge, this was the first solid stabilized emulsion with a controlled/living radical polymerization inside.
Chapter 4 and Appendix were contained in the second part. We discovered that monodisperse latexes (MLs) ranging from nanometers to micrometers with a clean surface and acceptable colloidal stability can be obtained under unstable Pickering emulsion polymerization conditions. A coalescence-induced Pickering emulsion polymerization route for the MLs was proposed. Furthermore, we extended this polymerization system to coalescence induced surfactant-free emulsion polymerization in the absence of any particulate stabilizers and studied various parameters thoroughly. Due to the relatively low latex production yields with respect to the monomer input from the coalescence follows creaming, we arranged this part into Appendix. In chapter 4, we conducted the emulsifier-free polymerization in the presence of commercial grade negatively charged colloidal silica. Well-defined vinyl polymer core/silica shell with near monodisperse distributions could be readily obtained in a single step using cationic AIBA as initiator. Various syntheses parameters such as the pH of the solution, the kind of initiator employed into the polymerization, the amount of silica, and the ratio between the monomer and the silica were studied.
Chapter 5 and 6 were contained in the third part. In chapter 5, we propose a new strategy for preparing high solid content, surfactant-free charge stabilized monodisperse latex particles via alcoholic dispersion polymerization by means of a mixed ionic/non-ionic initiator system, which produces hundreds of nanometer up to several micron sized latex particles with a clean surface in a single batch process. It was observed that no truly monodisperse latexes could be obtained using ionic initiators alone in alcoholic dispersion polymerization, therefore a mixed initiation approach was proposed. The effect of various factors on this new approach is investigated, and a specific mechanism is also presented. In chapter 6, we describe a new method based on surfactant-free aqueous/alcoholic dispersion polymerization, which enables the polymeric encapsulation of nanoparticles. Mechanism of this approach is investigated in the context of the preparation of polystyrene encapsulated carbon black (CB) nanocomposite latex particles. Commercial grade MOGUL® L CB is first grafted with reactive silane coupling agents through sol-gel reaction and is finely dispersed in the polar medium with dissolved monomer, then the ionic initiator is added to the system to start the polymerization. The reactive functional groups introduced onto the CB nanoparticles enable its participation into the nucleation also surface polymerization, leading to the well-defined latex-encapsulated nanocomposite structure. Various synthesis parameters such as the grafting amount of silane coupling agent, the initiator employed into the polymerization, and solvency to the encapsulation were investigated.

並列關鍵字

Pickering emulsion polymerization ； 1,1-diphenylethene ； controlled radical polymerization ； organic/inorganic composite latex ； monodisperse ； dispersion polymerization ； surfactant-free emulsion polymerization ； core/shell structures

參考文獻

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