PA封端对ODPA/ODA聚酰亚胺薄膜热稳定性的影响

制备了经邻苯二甲酸酐(PA)封端的理论数均分子量为10000和30000的聚酰亚胺(PI)薄膜,通过差示扫描热分析(DSC)测定薄膜高温热处理前后玻璃化温度的变化,研究了PA封端对ODPA/ODA聚酰亚胺薄膜热稳定性能的影响.结果表明,封端可有效阻止分子链的无序增长,使聚酰胺酸(PAA)分子量分布变窄;且可明显减少分子链在高温下的反应,表现为热处理前后封端薄膜Tg变化明显小于未封端的薄膜.随着高温热处理时间的延长,短链薄膜Tg增长趋势减缓,长链薄膜的Tg变化直线上升.从高温再聚合、交联反应和端基活动性出发,解释了Tg升高和PA封端有利于提高PI薄膜热稳定性的原因.

The Effect on Thermal Stability of Polyimide Films Based on Phthalimide End-capped ODPA and ODA

Polyimide films capped with nonreactive phthalimide end groups were synthesized with theoretical number average molecular mass of 10000 and 30000 calculated using the Carothers equation.The effect of end-capper on the thermal properties was studied by investigating the change of the glass transition temperature(T_g) of films after cured at high temperature.The Gel Permeation Chromatography(GPC) results indicated that the molecular distribution of end capped PAA was smaller than that of the no end-capped one.The Differential Scanning Calorimetry(DSC) results showed PA end-capped polyimide films exhibited slower rising range of the T_g compared to no end cappers films'.With the increasing of curing time,the T_g of the short chain film increased slowly,which of the long chain film increased straightly.The end capper's effect was explained based on polymerization at high temperature,chain branching/crossing-linking reactions and molecular activity.