氧代氮代苯并環己烷：合成改善、機制及其固化物微結構之研究

Abstract

本論文透過A-A及B-B聚縮合合成途徑，避免一般曼尼希縮合(Mannich condensation)製程中的副反應發生，成功製備出高分子量的主鏈高分子型氧代氮代苯並環己烷(benzoxazine, Bz)預聚物，P(BF-bapp)-1。另合成三種結構相似、分子量相異之預聚物，探討分子量差異對其固化物物性與微結構之影響。 為探討Bz的開環聚合(ring-opening polymerization, ROP)機制，本論文合成三種不同結構的主鏈高分子型Bz預聚物，分別為雜環上氧及氮原子鄰位(ortho)皆無甲基取代的PBz-0M；雜環上氧原子鄰位受甲基取代的PBz-2M；雜環上氧及氮原子鄰位皆受甲基取代的PBz-6M。透過微差掃描熱分析(DSC)、傅立葉轉換紅外線光譜(FTIR)以及熱性質分析，我們發現，ROP可透過雜環上氮原子的鄰位(ortho)進行，並提出其反應機制進行解釋。 Bz/氰酸酯混膠共聚合反應機制已在多篇文獻中被探討，並有文獻指出Bz開環的結構為混膠中氰酸酯快速三環化的主因。然而，近來我們意外發現將4,4’-oxyaniline/phenol-based Bz (P-oda)以及雙酚A氰酸酯(BACY)以溶劑溶解配置成膠後，靜置於室溫24小時，溶液將形成凝膠(gel)。在此環境下，Bz開環聚合的可能性極低，因此我們認為催化效應來自與Bz本身的結構，本論文將透過Model reaction尋找凝膠化(gelation)之主因，並提出Bz於氰酸酯三環化中之催化機制進行解釋。

A main chain-type polybenzoxazine precursor, P(BF-bapp)-1, with high molecular weight (MW) was prepared through a strategy of A-A and B-B polycondensation, avoiding by-reaction that occurred in Mannich condensation. To discuss the effect of the MW of benzoxazine on the properties and microstructure of the resulting thermoset, anthother three structurally similar benzoxazines with difference MW were syntheized in this work. To discuss the mechanism of ring-opening polymerization (ROP) of benzoxazine, three polybenzoxazine precursors were prepared. Among the polybenzoxazine precursors, free ortho positions to the O and N of oxazine are available for PBz-0M. The ortho positions to the O of oxazine are blocked by methyl group for PBz-2M. The ortho positions to the O and N of oxazine are blocked by methyl group for PBz-6M. According to DSC, IR, and thermal analysis, we found that the ROP of PBz-2M can be carried out through free ortho positions to the N of oxazine. A reaction mechanism was proposed to explain the polymerization in this work. Blends of cyanate ester and benzoxazine have been independently studied by several researchers, some of them suggest that the rapid trimerization of cyanate ester in the blend is related to the ring-opened structure of benzoxazine. Recently, we unexpectedly observe that gelation occurred in solution of P-oda/BACY blend after 24 h at room temperature. However, the possibility of ring-opening polymerization for benzoxazine at room temperature is rare. Therefore, it is highly likely that the catalytic effect results from the benzoxazine itself. We tried to find the reason of gelation through model reaction in this work, and proposed a catalytic mechanism of benzoxazine for the trimerization of cyanate ester.