关键词: 侧基取代, 羟基芴Cardo结构聚酰亚胺, 酰氧化, 硅醚化反应, 溶解性, 透光率, 介电性能

Abstract: The cardo-type polyimides containing hydroxyl groups (PI-OH) were synthesized with one-step chemical imidzation method by taking hydroxyl-containing fluorene diamine and 44′-(44′-Isopropylidenediphenoxy) diphthalic anhydride as substrates. Then, cardo-type polyimides with low polarity and bulky size propionyloxy side groups (PI-OA)/tert-butyldimethylsiloxy side groups (PI-OSi) were prepared by acyl oxidation or silyl ether reaction of side hydroxyl groups. The effects of side group substitution on the solubility, optical and dielectric properties, etc. of PI-OH were systematically investigated. The results show  that the polarity and size of side groups greatly impacts the performances of PI films. Compared with PI-OH, PI-OA and PI-OSi show better solubility, higher transmittances and lower dielectric constants. Both can dissolve in low polar solvents such as dichloromethane or acetone. Their transmittances at 450nm can reach 86.7% and 85.2%, their dielectric constants are as low as 2.75 and 2.63 (1MHz). PI-OA and PI-OSi exhibit lower glass transition temperature and higher thermal expansion coefficients due to the introduction of low polarity and bulky size substituent groups.

Key words: side group substitution, cardo-type polyimides containing hydroxyl groups, acyl oxidation, silyl ether reaction, solubility, transmittance, dielectric property