侧基取代对羟基芴Cardo结构聚酰亚胺性能的影响

Effect of Side Group Substitution on the Properties of Cardo-Type Polyimides Containing Hydroxyl Groups

以含羟基芴Cardo结构的二胺和双酚A型二酐为基材,通过一步化学亚胺化法制备出羟基芴Cardo结构聚酰亚胺(PI-OH),再通过其侧羟基的酰氧化或硅醚化反应制备出低极性、大体积的丙酰氧侧基芴Cardo结构PI(PI-OA)和叔丁基二甲基硅醚侧基芴Cardo结构PI(PI-OSi),系统研究了侧基取代对PI-OH溶解性、光学性能和介电性能等的影响。结果表明:侧基的极性和体积较大程度影响了PI薄膜的各项性能,相较于PI-OH,PI-OA和PI-OSi表现出更好的溶解性能、更高的透光率和更低的介电常数,二者可溶于二氯甲烷、丙酮等低极性低沸点溶剂,在450 nm的透光率分别高达86.7%和85.2%,介电常数分别低至2.75和2.63(1 MHz);由于低极性、大体积取代基团的引入,PI-OA和PI-OSi的玻璃化转变温度下降、热膨胀系数增大。

The cardo-type polyimides containing hydroxyl groups(PI-OH)were synthesized with one-step chemical imidzation method by taking hydroxyl-containing fluorene diamine and 44′-(44′-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 450 nm can reach 86.7%and 85.2%,their dielectric constants are as low as 2.75 and 2.63(1 MHz).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.