A NEW METHOD FOR FABRICATING HIGH-PERFORMANCE POLYMERIC THIN-FILMS BYCHEMICAL-VAPOR POLYMERIZATION

A vacuum deposition method is presented in which copolymer films are g rown from a vinylic monomer chosen for desirable properties and paraxy lylene. The concentration of paraxylylene in the final copolymer can b e negligibly small if proper deposition conditions, presented here for the first time, are employed. Films of paraxylylene with N-phenyl mal eimide deposited at 40 degrees C, for example, showed thermal stabilit y and FTIR spectra nearly identical with homopolymers of poly(N-phenyl maleimide). Different rate-limiting steps are proposed to explain fil m composition; paraxylylene is under surface reaction control, while t he comonomer obeys mass now control, This results in a deposition envi ronment extremely rich in comonomer. Growth rates and compositions wer e consistent with predictions. The initiation reaction did not appear different from homopolymerization of paraxylylene. The general method presented here allows fabrication of vapor-deposited thin films with p roperties limited primarily by tile comonomer employed.