IMMOBILIZATION OF RETINOIC ACID BY CATIONIC POLYELECTROLYTES

Retinoic acid was immobilized by precipitating its complexes with cati onic polyelectrolytes from aqueous solution. Polyelectrolytes with dif ferent architectures, such as poly(ionene-6,3 bromide), poly(dimethyl- diallylammonium chloride), and poly(N-methyl-4-vinylpyridinium chlorid e), form self-assembling complexes containing retinoic acid (70% (w/w) ). All these complexes are thermodynamically stable and can be process ed into mesomorphously ordered films with interesting physical propert ies. In contrast to the brittle crystalline retinoic acid the complexe s with polyelectrolytes are highly deformable viscoelastic materials. All materials show lamellar mesophase structures; their T-g value stro ngly depends on the polyelectrolyte. It is suggested that these materi als have great potential as pharmaceutical agents as well as models fo r the investigation and the mimicking of chromophores in visual pigmen ts and photosynthetic bacteria. The properties of the complexes are ex amined by X-ray diffraction, differential scanning calorimetry, polari zation optical microscopy, UV-vis spectroscopy, and stress-strain meas urements.