Substitution norbornenyl Imides

The present study reports the synthesis, characterization and thermal reactions of phenyl and carbomethoxy substituted norbornenyl imides. These substrates were designed to model the reactive end-caps of the PMR-15 resin and allow an assessment of the effect that conjugating substituents would have on the high temperature cure of such systems. The effect of these substituents on both monomer isomerization and polymerization is reported and a possible use of the phenyl substituent as a probe of polymer structure is suggested. 

Having established the effect of substitution on the rates of both monomer isomerization and polymerization, we addressed the question of polymer structure. Specifically, are norbornenyl imide units incorporated into the fully cured polymer with their norbornyl rings intact If so, does the polymer also reflect the equilibrium ratio of exo and endo ring fused monomers For our parent monomers, PN and PX, this question has been unanswerable. We have not found any direct probe that allows an unambiguous assessment of specific substructures within the cured polymer. We do, however, have some evidence bearing on this question for the phenyl substituted monomer. This evidence is attributable in part to our discovery of an unexpected side-reaction in the cure of the phenyl substituted monomer, and in part to the presence of a unique NMR diagnostic for phenyl substituted, endo norbornyl N-phenyl imides. Both of these results are detailed below. 

Our syntheses of these new materials showed that both hydrogenation and epoxidation occurred exclusively from the exo face of both VN and < >VX. This is consistent with extensive literature precedent for a variety of reactions on norbornenyl double bonds (9). H1 NMR spectroscopy of these materials also revealed an interesting pattern. All phenyl substituted compounds with endo imide rings (< >VN, HYVN, VNE) evidenced signals due to one of the ten aromatic protons (five on each phenyl ring) being shifted to unusually high field (6.4 +. 16). This is consistent with a field effect on a proton of one of... 

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