基板效應對高分子微米球型態轉變之影響

Abstract

比起球形高分子粒子來說，非球形的高分子粒子因其廣泛的應用性在近年來備受關注。相關的製備技術如相分離法、溶劑揮發法、複合粒子移除法等皆為當前製備非球形奈米材料的主流技術。但上述的製備方式皆涉及溶液的參與，鮮少有在非溶液的系統下製備。若製備球形奈米材料的系統涉及溶劑的參與，會出現形貌不易控制的問題。為了使產物的形貌能夠被準確得控制，我們必須要找出一個沒有溶劑的系統。因此在這裡我們將探討一個不需在溶液系統下的製備方式，而是以玻璃基板及高分子膜的加熱系統，利用各材料間表面能的差異達到形變的效果，進而成功製得目標物。 本論文主要是在探討高分子微米球在不同高分子膜厚的環境下熱退火後的形貌變化，其中高分子球為市售的10 μm polystyrene (PS)微米球，將其配製成溶液之後，再利用旋轉塗佈的方式將微米球置於poly(methyl methacrylate) (PMMA) 高分子膜上，隨後再將此系統放入加熱器中均勻加熱。我們將加熱溫度設定為240 °C，高於PMMA以及聚苯乙烯的玻璃轉移溫度。聚苯乙烯微米球在加熱的過程中會逐漸陷進PMMA高分子膜內部且其形貌會轉變成半球形。此外，我們也探討了不同膜厚對微米球形貌的影響，在厚膜環境下會產生半球形態的高分子粒子，在薄膜環境下則會製備出扁盤形貌的高分子粒子。 探討該反應的機制，由於PS對PMMA的表面能低於PS對空氣的表面能，因此在加熱的過程中為了使整體系統的能量趨於穩定，PS奈米球會陷入PMMA膜中增加其與PMMA膜的接觸面積以減少與空氣的接觸面積進而降低系統的表面能。此外，PS奈米球的形貌亦會隨高分子的膜厚而有所差異。在厚膜系統中，因微米球在加熱過程中並未碰觸到膜較厚時，其形貌愈接近球形，膜較薄時，則愈接近盤狀。 本研究為一項新穎的非球形奈米材料製備技術，該技術由於僅需藉由加熱即可製得，並未涉及過多複雜的步驟，可精準控制實驗變因，實驗結果再現性高。此外，此技術具新穎性、簡便性、精準性，期許該技術往後能在相關領域能有更進一步且突破性的發展。

Compared to spherical polymer particles, non-spherical polymer particles recently have drawn great attention due to their wide applications. Various fabrication techniques such as phase-separation, solvent-evaporation, and composite particles removal method have been developed to prepare non-spherical polymer particles. These methods, however, are all related to polymers in a solution state. The presence of solvent adds more complexity in controlling the particle shape. There are less techniques developed without the use of solvents. Here, we develop a new method to fabricate non-spherical polymer particles, in which solvents are not used. Spherical polymer particles are placed on top of a polymer film. After thermal annealing, the spherical polymer particles transform into non-spherical particles and finally embedded in the polymer film. In this work, commercial polystyrene (PS) microspheres with an average diameter of 10 μm are used. Then the PS microspheres are spin-coated on poly(methyl methacrylate) (PMMA) films. Subsequently, the samples are annealed at 240 °C, which is higher than the glass transition temperatures of both polymers. The PS microspheres gradually sink into the PMMA film and transform into non-spherical PS particles. We also change the thickness of the PMMA film to study the thickness effect. For thicker PMMA films, the PS microspheres transform into hemispherical PS particles. For thinner films, the PS microspheres transform into disc-like PS particles. In conclusion, we develop a novel method to fabricate non-spherical polymer particles. This method is easy and requires no solvent. In the future, we will explore the applications of these polymer particles.