Photopolymerization reaction in di n‐propyl ester of dicyano p‐phenylene diacrylic acid crystal is shown to be mediated by exciton–phonon coupling. Raman phonon spectra suggest that at the initial stage of reaction progress, the reactant and the product form a solid solution. In the later stage, the reactant segregates out and forms its own lattice. The polymer lattice is shown to maintain a good degree of order. Infrared and Raman spectra confirm that the polymerization occurs by cyclobutane ring formation. © 1994 John Wiley & Sons, Inc.

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