經由Photo-Fries’重排反應的新高分子型光安定劑之研究

Abstract

高分子材料經常在戶外長期使用，因此材料的耐候性就變得很重要，維持高分子的光安定化有許多方法，例如：加入UV遮蔽劑、激發態的去活化劑、自由基的消除劑及UV吸收劑。UV吸收劑會將所吸收的UV光能消耗並轉成不會傷害材料的熱能，降低輻射能的不利影響，故較常被使用。一些已商業化的光吸收劑，大半都是低分子量的鄰羥基苯酮或其衍生物，當高分子材料使用這些低分子量的UV吸收劑時，常會出現的缺點，例如長期在戶外使用時會滲出表面或加工時受熱揮發，如果提高添加量，卻又會造成材料機械物性下降。為了改進這些缺失，本篇研究加入新穎性高分子型的光安定劑，第一章首先研究PPA及PMPA，結果顯示，PPA及PMPA會進行Photo-Fries重排反應，在分子主結構上產生具光安定效果的鄰羥基苯酮，兩者的反應速率常數不同，並且以PMPA的光安定效果較佳。在第二章則將PPA及PMPA加入PET中，觀察它們對PET的光安定效果及保謢作用，並證實有效。這個觀念亦可推廣應用到於熱固性聚合物，因此在第三章中以環氧乙烷及二丙烯酸雙苯酚A酯形成IPN聚合物，經UV照光後亦同樣產生鄰羥基苯酮，因此可達到IPN聚合物的光安定化效果。另外環氧乙烷和甲基丙烯酸基環氧乙烷形成的IPN聚合物也具有類似的保護效果。 Photo-Fries重排反應亦存在於芳香族聚合物，第五章合成芳香族聚酯、交替型及無規則型芳香族共聚酯、交替型及無規則型芳香族共聚醯胺酯等五種聚合物，經UV照光後可在分子主鏈上生成鄰羥基苯酮。其中以聚對苯二甲酸雙酚A酯擁有最快的Photo-Fries反應速率。第六章則研究將這些芳香族聚合物加入PET中來確認它們對PET光安定作用之功效。本論文的研究結論，確實可達到以Photo-Fries重排反應產生新穎性聚合物級的光安定劑，並具有良好的安定化效果。

Long term out-door uses of polymers are very common. Therefore, the weatherability of polymers becomes an important consideration. Photostabilization of polymers can be achieved by different means. These include screen of ultraviolet light, deactivation of excited states, addition of radical scavengers, and uv absorbers. Use of uv absorbers to dissipate the photo energy and convert it into a harmless heat, and therefore, to retard the adverse effect of irradiation is widely applied in polymer technology. However, most commercial uv absorbers are low molecular weight derivatives of o-hydroxybenzophenone. When these low molecular weight uv absorbers are incorporated into polymers, many drawbacks occur quite often, such as leaching problem during long term out-door application and evaporation problem during thermal processing. Furthermore, when these uv absorbers are incorporated into polymer in large quantities, drawback of mechanical properties are often observed. In order to avoid these drawbacks, we are interested in innovative high molecular weight polymeric types of photostabilizers. In a kinetic and mechanism study of photo-fries’ rearrangement for poly(phenyl acrylate) (PPA) and poly(p-methylphenyl acrylate) (PMPA), both acrylic polymers underwent photo-fries’ rearrangement, leading to the production of o-hydroxybenzophenone moiety at the pendant group in different rate constants, and both were expected to be inherent photostabilizers, with PMPA a better one (chapter 1). Both PPA and PMPA were then used to protect thermoplastics against photodegradation and their protection to PET was confirmed (chapter 2). The same idea also applied to thermosetting polymers. Thus, an interpenetrating polymer networks (IPN) based on epoxy and bisphenol-A diacrylate was proved to produce o-hydroxybenzophenone moiety when this material was under uv irradiated. And its photostabilization of IPN materials was successfully achieved (chapter 3). This application also extended to the IPN material of epoxy and methacrylated epoxy, and was again proved successful (chapter 4). Considering a similar photo-fries’ rearrangement, aromatic polyester, random and alternating copolyesters, and random and alternating copolyester-amides were investigated under accelerated uv irradiation, o-hydroxybenzophenone moiety could be found at the main chain of these polymers, with poly(bisphenol-A terephthalate) possessing the highest rate constant of photo-fries’ reaction (chapter 5). Confirmation of the photostabilization capability for these polymeric type phtostabilizers by blending each one with PET were performed by kinetic studies (chapter 6). In conclusions, innovative polymeric types of photostabilizers via photo-fries’ rearrangement has been successfully developed in this research.