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Optically Active Polymers Containing Side Chain Azobenzene Chromophores: Chiroptical Properties and Photochromic Behaviour of 4-Methacryloxyazobenzene/(−)-Menthyl Methacrylate Copolymers
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Angelina Altomare1), Carlo Carlini2), Francesco Ciardelli1) and Roberto Solaro1)
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1) Dipartimento di Chimica e Chimica Industriale, Centro CNR Macromolecole Stereordinate Otticamente Attive, University of Pisa
2) Dipartimento di Chimica Industriale e dei Materiali, University of Bologna
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ABSTRACT: Copolymers of trans-4-methacryloxyazobenzene (MAB) with (−)-menthyl methacrylate (MtMA) have been prepared by using AIBN as free radical initiator. The resulting polymer samples are characterized by a substantially random distribution of monomeric co-units, as evaluated from reactivity ratios. Kinetics of photoinduced trans to cis and thermally induced cis to trans back-isomerization of azobenzene side chains have been examined and the relevant kinetic parameters evaluated. Dependence of chiroptical properties on both copolymer composition and extent of cis/trans isomerization has been investigated. The circular dichroism induced on azobenzene chromophores has been shown to arise mainly from isolated MAB units, as the chiral perturbation is not appreciably transmitted along MAB sequences. The results have been discussed in terms of tertiary structure reversible variations connected to photoinduced change of local conformation.
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Keyword: (−)-Menthyl Methacrylate/ 4-Methacryloxyazobenzene/ Photochromic Polymers/ cis–trans Isomerization/ Chiral Polymers/ Chiroptical Properties/ Circular Dichroism
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Published online: April 08, 2005 |
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© Copyright, 2005 by The Society of Polymer Science, Japan |
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