Synthesis Of Photosensitive Polyimide Via Atom Transfer Radical Polymerization

Photosensitive polyimide(PSPI) as one kind of excellent performance materialexhibits high mechanical properties, good chemical, thermal, radiation,flame resistanceand electronic insulating, low dielectric constant, also possesses a photographicproperties.This work aims to synthesize a series of the photo-crosslinkable graftedpolyimide through ATRP technique, using chloromethyl polyimide as macroinitiator, thephotosensitive4-Methacryloyloxystyryl phenyl letone (MSPK) as monomer.We used sodium hydroxide as catalyst to synthesize4-Hydroxychalcone (HSPK)via traditional Claisen-Schmidt condensation. And then react with methacryloylchloride to synthesize another photosensitive monomer that can be used as the monomerof ATRP,4-Methacryloyloxystyryl phenyl letone (MSPK). HSPK and MSPK werecharacterized by the means of FT-IR,1H NMR and UV-Vis.We used chloromethyl ether as chloromethylation reagent, SnCl4as catalyst tomake the polyimide have active groups chloromethyl. We get the differentchloromethylation ratios of chloromethylated polyimide(CMPI) by controlling thedosage of chloromethyl ether and the reaction time. We synthesize two kinds of CMPIthat the chloromethylation ratios were50%and95%that can be used as macroinitiatorof ATRP. Both of the polymers were characterized by the means of FT-IR and1H NMR.We used50%and95%CMPI as macroinitiator, CuCl and bpy as catalyst,complexing agent to initiate MSPK for ATRP to synthesize the photo-crosslinkablegrafted polyimide (PI-g-PMSPK) containing chalcone in side chain. We discussed andanalysised the effect of the initiators, complexing agent, reaction temperature andreaction time on ATRP, the structure of the products were characterized by FT-IR and1HNMR. The most approprite catalyst system was CuCl/bpy, the most appropritetemperature was100℃for this ATRP reaction, and the conversion of monomerincreased with the increasing of reaction time and degree of chloromethylation.ThisATRP reaction was first-order kinetics reaction, and molecular weight increases linearlywith the conversion in this reaction. The results showed that the reaction has thecharacteristics of living polymerization.The polymers have high photosensitivity, it would happen photo-crosslinkingreaction between the molecules under UV irradiation, the maximum extent ofphotoreaction for the polymer film was about80.12%. The polymers have goodsolubility, were soluble in many organic solvents such as CHCl3、THF、DMF、DMAcand so on. After UV irradiation, they were insoluble in any organic solvent. Meanwhile, the polymers have good thermal stability, Tg＞121.6℃, their initial thermaldecomposition temperature were greater than210℃.