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Journal of Polymer Science Part A: Polymer Chemistry, Vol.36, No.16, 2827-2837, 1998
Stimuli-responsive polymers. III. Poly(aryl ether ketone amide)s with reversible trans <-> cis-4,4 '-azobenzene and fixed 2,2 '-binaphthyl kinking elements in the main chain
The low-temperature polycondensation of trans-azobenzene-4,4'-dicarbonyl chloride with (S)-(-)-1,1'-binaphthyl-2,2'-diamine and/or 1,4-bis(3-aminophenoxy-4'-benzoyl)benzene afforded a new series of poly(aryl ether ketone amide)s with both fixed and photoinducible kinking elements positioned randomly along the main chain. In their lower energy, trans-azobenzene configurations, the orange, film-forming materials were amorphous, highly tractable, and thermally stable under air or nitrogen up to about 420 degrees C. Variants endowed with higher loadings of the bent binaphthyl monomer were soluble in a variety of organic solvent media including THF and acetone. The introduction of cis-azobenzene backbone kinks into these materials was carried out by irradiating the polymer solutions with near-UV light. Up to 10% of the azobenzene moieties in these polymers were capable of assuming the higher energy cis-configuration, thus greatly increasing the number of bent or kinked sites positioned along each polymer backbone. In solution, reverse cis --> traits isomerization reactions were triggered thermally and were quantitatively tracked by both optical absorbance and H-1 NMR spectroscopies. Activation parameters calculated for cis --> trans reorganization of the polymer backbone were not dependent upon the chemical composition or molecularweight of the polymers but did exhibit a small dependence upon the nature of the solvent medium used to conduct the isomerization experiment.
Keywords:PHOTOSENSITIVE FUNCTIONALITIES, CHELATING COPOLYMERS;AZOBENZENE RESIDUES, POLYAMIDES, ISOMERIZATION, CHIRALITY;OLIGOMER