【摘要】 利用GPC、原位FT-IR技术研究了聚酰胺酸(BPADA-BAPS)在不同热处理过程中的热环化,结果表明,升温过程中,聚合物分子链断裂成酐、胺端基这一动态平衡的平衡常数在175℃～200℃段趋于最大;初始热环化温度(Tonset)随升温速率的递增而升高,推测其受溶剂与酰胺酸基团间的氢键和酰胺酸基团自身的构象调整难易程度、速率的影响;恒温热环化过程中,聚合物的Tg不断升高。当Tg达到反应温度时,聚合物即转入玻璃态,各链段的迁移受到限制,结果聚合物的环化及分子链的断裂同时缓和下来。更多还原

【Abstract】 The thermal imidization behavior of a linear polyamic acid for the different kinds of treatments was investigated by GPC and FT-IR. The results show that the PAA chain bonds trend to break into anhydride and amine end groups during the heating-up treatment, which is a dynamic equilibrium reaction and its equilibrium constant of the amine-anhydride/amic acid system toward the direction of amine-anhydride reaches the biggest at the temperature range of 175 ℃~200 ℃. The initial imidization temperature (T(onset)) of PAA increases with the increase of the heating-up rate during the continuous heating-up treatment, which is, to a large extent, due to the hydrogen bond between the solvent(DMF) and amide as well as the rate of the conformation changes of amide. For the isothermal imidization, T_g of the polymer increases with the increase of the imide content. When the T_g reaches the reaction temperature, the polymer is transformed from rubbery to a glassy state, and segment motion almost ceases. As a result, both the imidization and the chain cleavage almost ceased simultaneously.更多还原