Copolymer of polyimide oligomers and terephthalonitrile N,N-dioxide and their methods of preparation

Abstract

We have disclosed a new class of thermosetting copolymers derived from terephthalonitrile N,N'-dioxide and polyimide oligomer that cure through addition reactions to form essentially void-free cured resins that exhibit outstanding high temperature stability. These copolymers may be formed from either acetylene terminated polyimide oligomers or nitrile terminated polyimide oligomers. Copolymers prepared in accordance with our invention exhibit little or no outgassing during cure and are extremely useful in the preparation of laminates where high temperature stability and high strength is required.

We claim: 
     
       1. Copolymers of addition cured polyimides formed from the reaction of aromatic bis(nitrileoxides) and cyano- or acetylene-substituted polyimide oligomers and consisting essentially of the following general formula: ##STR11## where X=CO, O, CH 2 , SO 2 , or --CF 2  ) n   Y=CH or N, and   R=--C 6  H 4  OC 6  H 4  --, --C 6  H 4  OC 6  H 4  OC 6  H 4  --, or --C 6  H 4  OC 6  H 4  OC 6  H 4  OC 6  H 4  -- and where ##STR12## may be replaced by ##STR13##     
     
     
       2. The copolymers of claim 1 wherein the dinitrile dioxide is terephthalonitrile N,N'-dioxide. 
     
     
       3. The copolymers of claim 1 wherein the polyimide oligomers consist of acetylene substituted materials having the following structure: ##STR14## where X=CO, O, CH 2 , SO 2  or CF 2 , and where   R=C 6  H 4  OC 6  H 4  --, --C 6  H 4  OC 6  H 4  --, or --C 6  H 4  OC 6  H 4  OC 6  H 4  OC 6  H 4  --, and wherein ##STR15## may be replaced by ##STR16##     
     
     
       4. The copolymers of claim 2 wherein the polyimide oligomers are acetylene substituted polyimide oligomers. 
     
     
       5. The copolymers of claim 1 wherein the polyimide oligomers consist of cyano substituted compounds having the following structure: ##STR17## wherein X=CO, O, CH 2 , SO 2  or CF 2 , and wherein   R=C 6  H 4  OC 6  H 4  --, --C 6  H 4  OC 6  H 4  OC 6  H 4  --, or --C 6  H 4  OC 6  H 4  OC 6  H 4  OC 6  H 4  --, and wherein ##STR18## may be replaced by ##STR19##     
     
     
       6. The copolymers of claim 2 wherein the polyimide oligomers consist of cyano substituted polyimide oligomers. 
     
     
       7. A copolymer of claim 4 wherein X is CO and R is --C 6  H 4  OC 6  H 4  OC 6  H 4  --. 
     
     
       8. A copolymer of claim 6 wherein X is CO and R is --C 6  H 4  OC 6  H 4  OC 6  H 4  --. 
     
     
       9. A method for preparing copolymers of bis(nitrileoxides) and acetylene substituted polyimide oligomers comprised of the steps of: a. forming a solution of the polyimide oligomer in an organic solvent;   b. adding the bis(nitrileoxide) to said solution under constant agitation to form a mixture;   c. allowing said mixture to gel, whereby the desired resin is formed;   d. separating said resin from said gel by applying an alcoholic solvent; and   e. causing said resin to be dried.   
     
     
       10. The method of claim 9 wherein the solvent employed to form the solution is sulfolane.