Process for making photopolymerizable aromatic polyamic acid derivatives

Claim 1

A process for the synthesis of photosensitive polyamicacid derivatives which are polyimide precursors comprising the sequential steps: (1) forming a solution in aprotic solvent of aromatic dianhydride and monomer(s) corresponding to the formula RZH, wherein R is an ethylenically unsaturated moiety capable of addition polymerization and Z is --O--, --S-- or --NR'-- wherein R' is --H or C 1-4 alkyl, the amount of monomer being 0-40 equivalent %, basis dianhydride, and maintaining the solution for a time and temperature sufficient to effect partial reaction of the aromatic dianhydride with substantially all of the monomer; (2) admixing with and dissolving in the aromatic dianhydride-containing reaction solution of step (1) aromatic diamine while maintaining the reaction solution below 50° C. to effect condensation polymerization of the unreacted anhydride and the amine moieties to form the corresponding polyamic acid(s); (3) admixing with and dissolving in the polyamic acid(s)-containing reaction solution of step (2) an isoimidization agent selected from the group consisting of N,N'-dihydrocarbyl-substituted carbodiimides, trifluoroacetic acid anhydride and mixtures thereof to convert the polyamic acid(s) to the corresponding polyisoimide(s); (4) admixing with and dissolving in an aprotic solution of the polyisoimide(s) of step (3) a molar excess of monomer corresponding to the formula RZH and maintaining the solution for a time and temperature sufficient to effect substantially complete esterification of the carboxylic acid moieties of the polyisoimide(s) with monomer and converting the polyisoimide(s) to the corresponding polyamic acid derivatives; and (5) separation of polyamic acid derivatives from the reaction solution of step (4).