利用熱拉伸技術製備 異向性高分子粒子及其形貌探討

Abstract

在過去與粒子科學（Particle science）相關的研究中，等向性（Isotropic）高分子微球因為製備簡易，早已有許多深入的研究，然而因為等向性微球的表面積／體積比較低加上高對稱性的形貌，使其應用受到限制。為了拓展高分子粒子的應用廣度，異向性高分子粒子的研究必定是不可或缺的。本論文的主軸即是利用熱拉伸法，發展出多個成本低、簡便、快速的異向性高分子粒子製備技術。 本論文可分為三個部分。在第一部分，我們改良了傳統熱拉伸法，利用常見的實驗室器具，如長尾夾、砝碼、高溫烘箱，取代昂貴的訂製拉伸機具，可拉伸鑲嵌在聚乙烯醇膜中的聚苯乙烯微球，製備出異向性聚苯乙烯粒子。在第二部分中，我們在異向性聚苯乙烯粒子懸浮液中加入四氫呋喃，可降低聚苯乙烯粒子的黏度，而聚苯乙烯粒子的形狀會朝著使表面能最低的圓球形狀開始變形，藉此可簡便的控制聚苯乙烯粒子的形貌。在第三部分中，我們提出一種新方法可同時製備出不同形貌的異向性聚苯乙烯粒子，我們利用熱退火處理分散有聚苯乙烯微球的聚乙烯醇薄膜，再用長尾夾限制聚乙烯醇膜的收縮方向，在聚乙烯醇膜的不同位置上製備出不同長寬比的聚苯乙烯異向性粒子，分別為扁圓球、長寬比為1.2的扁橢球和長寬比為1.5的扁橢球。本論文不只改良了舊有的熱拉伸法，也提出了簡便的方法控制聚苯乙烯異向性粒子的形貌和提出可以一次得到多種形貌的異向性高分子粒子的製備方法，有效提升了製備異向性高分子粒子的效率。

To broaden the applications of polymer particles, it is desired to increase its anisotropy. This thesis mainly focuses on developing novel methods, which are based on a thermal stretching technique, to fabricate anisotropic polymer particles. This thesis is divided into three parts. In the first part, we improve the old thermal stretching method to fabricate anisotropic polystyrene particles by stretching poly(vinyl alcohol) （PVA） films embedded with polystyrene microspheres. In the second part, we develop a simple approach to manipulate the shapes of anisotropic particles. By adding tetrahydrofuran into the anisotropic polystyrene particle suspensions, the viscosities of the polystyrene particles are decreased. The anisotropic polystyrene particles gradually transform into polystyrene spheres, which possess lower surface and interfacial energies. In the third part, we develop a new method to fabricate different kinds of anisotropic particles simultaneously. By thermal annealing-induced PVA film contraction, the polystyrene spheres are stretched to anisotropic particles. Polystyrene oblate spheroids and polystyrene prolate spheroids with aspect ratios of 1.5 and 1.2 can be observed on the PVA films. This thesis improves the traditional thermal stretching technique, increases its efficiency to fabricate multiple anisotropic particles simultaneously, and provides a novel method to control particle shapes.