气相沉积法制备聚酰亚胺薄膜的热环化研究

采用两种单体同时蒸发沉积聚合方法制备得到聚酰亚胺（PI）薄膜。对不同温度下和不同恒温时间的聚酰胺酸（PAA）薄膜进行了红外分析，将300 ℃恒温3 h以上的薄膜脱膜，用白光干涉仪测量了PI薄膜热环化前后表面质量。采用热重分析仪在不同升温速率条件下对薄膜进行了分析。结果表明，在热环化过程中，随着温度增加亚胺化程度逐渐增加。在300 ℃时随着恒温时间增加亚胺化程度逐渐增加，恒温3 h以上薄膜亚胺化较为完全，可以获得完整且不易破损的自支撑薄膜。在热环化过程中，升温速率较低时薄膜的亚胺化程度在低温区转化率提高，过量单体蒸发更完全，故一般选择较小的升温速率，约10 ℃/min甚至更低。采用上述热环化工艺得到了亚胺化程度较高且不易破损的PI薄膜，其表面均方根粗糙度为9.8 nm。

Investigation on curing process of vapor-deposited polyimide thin films

Using vapor deposition polymerizatioin method, polyimide(PI) thin films were successfully fabricated in different curing conditions. Poly (amic acid) (PAA) thin films at different temperatures and for different retention times at 300 ℃ were analysed by FTIR. The thin films held at 300 ℃ for 3 h were taken off from KBr substrate, and photograghed in interferometry microscope. Also, the thin films were analysed by thermogravimetry (TG) at different heating rates. The results show that the extent of imidization increases with temperature increasing in curing process and retention time increasing at 300 ℃. The thin films can be taken off from KBr for the retention time of 3 h. After curing process surface, the roughness of thin film is good, but R_q is 9.8 nm. The heating rate has a little influence on the ultimate extent of imidization, and low heating rates, 10 ℃/min or even lower, are preferred.