RING RETENTION VIA PULSED PLASMA POLYMERIZATION OF HETEROCYCLIC AROMATIC-COMPOUNDS

Polymerization of two isomeric heterocyclic monomers, 3-methyl-1-vinyl pyrazole and 1-allylimidazole, was investigated under pulsed plasma co nditions. Large-scale, progressive variations in polymer compositions were observed with sequential changes in the plasma duty cycles employ ed, all other plasma variables being held constant. In particular, unu sually linear polymers (by normal plasma polymerization standards) are achieved at exceptionally low average power inputs, employed when the pulsed plasma technique is operated at low duty cycles. With both mon omers, a pronounced increased retention of their aromatic rings is obs erved in the plasma-synthesized polymers as the duty cycle employed du ring film formation is reduced. Overall, a higher ring retention is ac hieved with the imidazole, compared to the pyrazole, reflecting bond e nergy differences in these two isomers. This study also includes synth esis and spectral characterization of a conventionally prepared linear poly(3-methyl-1-vinylpyrazole) which was employed to assess the degre e of ring retention in the plasma polymers. On the basis of the result s of this study, it appears that relatively linear polymers of fairly complex molecules are readily synthesized using the low duty cycle pul sed plasma technique. according-ly, this approach is useful in extendi ng the utility of plasma polymerizations which have heretofore tended to focus on synthesis of unique, relatively highly cross-linked materi als. The pulsed technique provides synthesis of these polymers while m aintaining the many inherent advantages of the plasma polymerization t echnique, including particularly the pinhole-free, conformal, and adhe sive qualities of these films.