New photoresponsive (meth)acrylate (co)polymers containing azobenzene pendant sidegroups with carboxylic and dimethylamino substituents .1. Synthesis and characterization of the monomers

New azobenzene-based (az.b.) monomers with CO2H (acid) or N(CH3)(2) (basic) substituents were synthesized. For some of these compounds new synthetic routes had to be developed, especially for the az.b. monomers with a CO2H substituent (azoacids) where their synthesis, purification and (thermal) characterization turned out to be rather difficult. The monomers with a N(CH3)(2) substituent (azobases) were rather easy to synthesize. but were unexpectedly sensitive to acidic moisture. When exposed to air, the originally yellow powders slowly turned green. This problem was solved by addition of a small amount of piperidine to the recrystallizing solutions. Satisfactory yields and purity were achieved for all az.b. monomers. As could be expected from the molecular structure of the az.b. monomers, a liquid crystalline behaviour was found in a few cases. Copyright (C) 1996 Elsevier Science Ltd