Photocrosslinking of polymers, prepared from cinnamic acid derivatives, by chemical modification of poly(viny1 alcohol) or polycondensation of difunctional cinnamic acid derivatives has been studied. With Michler's ketone (sytem. name: 4,4'-bis(dimethylamino)benzophenone), crosslinking of copolymers is improved. 2-Nitrofluorene or 9-xanthenone have little effect on the crosslinking rate. Photocrosslinking of poly(a-cyano-4-vinylcinnamic acid), poly(ethy1 a-cyano-4-vinylcinnamate) and their copolymers is enhanced in the presence of 2-hydroxy-2-methylpropiophenone, but the effect is lowered in the case of its acrylic esters or their (co)polymers.

Polymers containing cinnamic acid units were obtained by chemical modification of poly(viny1 alcohol) by cinnamic acid derivatives with a carbon-carbon double bond in para position. The reactivity of the acid chloride is lowered by the inductive effect of the double bond. Polycondensation of these derivatives, when difunctional, leads to low-molecular-weight polyamides and polyesters with good yields. The introduction of acrylic or methacrylic groups on photosensitizers has also been studied, leading to monomers which can be polymerized by a radical process, or copolymerized with the previous monomers, the polymer bearing then the photosensitizer and the cinnamic double bond on the same chain.

The synthesis of cinnamic acid derivatives with a carbon-carbon double bond in para position was studied by a Knoevenagel reaction with p-chloromethylstyrene. The latter was obtained via a several-step reaction from 2-phenylethanol. The monomers can be polymerized by a free-radical process without affecting the cinnamic group. Copolymerization is effective only with monomers such as maleic anhydride, p-vinylbenzaldehyde or methyl methacrylate, having a n-acid character like the cinnamic acid derivatives used in our study. 0 1990, HUthig & Wepf Verlag, Basel CCC 0025-116X/90/%03.00