Methacrylic polymers containing permanent dipole azobenzene chromophores spaced from the main chain: synthesis and characterization

✍ Scribed by Altomare, Angelina; Andruzzi, Luisa; Ciardelli, Francesco; Gallot, Bernard; Solaro, Roberto

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 268 KB
• Volume: 47
• Category: Article
• ISSN: 0959-8103
• DOI: 10.1002/(sici)1097-0126(199812)47:4<419::aid-pi78>3.0.co;2-m

✦ Synopsis

Three photochromic monomers containing a permanent dipole photochromic azobenzene group separated from the methacryloyl moiety by a polymethylene spacer, namely 4-(4-oxy-4@-cyanoazobenzene)but-1-yl methacrylate, 6-(4-oxy-4@-cyanoazobenzene)hex-1-yl methacrylate, and 8-(4-oxy-4@-cyanoazobenzene)oct-1-yl methacrylate, were synthesized in three steps starting from 4-cyanoaniline. These monomers were homopolymerized and copolymerized with an optically active monomer, ([)-menthyl methacrylate, in the presence of AIBN as a radical initiator. The polymeric materials, having a molar content of photochromic units comprised between 5 and 100% and molecular weights of about 15 000, were characterized by an almost random distribution of monomeric units and a glass transition temperature ranging from 35 to 131¡C. Polymer samples having a content of aromatic units larger than 75% were characterized by a thermotropic liquid crystalline structure, as evidenced by optical microscopy, X-ray di †raction and DSC measurements. Two-dimensional correlations spectroscopy (COSY) allowed an appreciable contribution by intramolecular charge transfer mesomers to the electronic distribution of the azobenzene chromophore to be highlighted.