Both the formation of insoluble salt for aliphatic diamines and the poor reactivity for aliphatic dianhydrides result in semi‐aromatic polyimide (SAPI) with low molecular weight and, thereby, in highly brittle SAPI films in nature. To solve the above problems, a cyclic‐olefin copolymer synthesized from norbornene and maleic anhydride is used as the third monomer (crosslinking agent) to prepare the crosslinked SAPI (cSAPI) films. The relative viscosity of the precursor solution of cSAPI is increased with the loading of cyclic‐olefin copolymer, giving rise to the improvement in mechanical and thermal properties of cSAPI films. The tensile modulus, tensile strength, and elongation at break of cSAPI film with 5 wt% cyclic‐olefin copolymer are increased to 4.49 GPa, 137 MPa, and 14.9% from 3.57 GPa, 111 MPa, and 7.6%, respectively, compared to those of the baseline SAPI film. Meanwhile, the glass transition temperature of cSAPI films is increased to 282 from 270 °C of the SAPI film, which is advantageous to better meet the requirement for high‐temperature manufacturing processes such as lead‐free solder reflowing. In addition, all cSAPI films exhibit good optical transparency in the entire visible region.

中文翻译：

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通过交联改善透明半芳族聚酰亚胺的机械和热性能

脂族二胺的不溶盐的形成和脂族二酐的不良反应性都会导致低分子量的半芳族聚酰亚胺（SAPI），从而导致自然界中的高脆性SAPI膜。为了解决上述问题，将由降冰片烯和马来酸酐合成的环烯烃共聚物用作第三种单体（交联​​剂），以制备交联的SAPI（cSAPI）薄膜。cSAPI前体溶液的相对粘度随环烯烃共聚物的添加而增加，从而改善了cSAPI膜的机械和热性能。具有5 wt％环烯烃共聚物的cSAPI膜的拉伸模量，拉伸强度和断裂伸长率分别从3.57 GPa，111 MPa和7.6％分别提高到4.49 GPa，137 MPa和14.9％。与基准SAPI影片相比。同时，cSAPI薄膜的玻璃化转变温度从SAPI薄膜的270°C升高到282°C，这有利于更好地满足高温生产工艺（例如无铅焊料回流）的要求。此外，所有cSAPI薄膜在整个可见光区域都具有良好的光学透明性。