Substituent effects on thermal and photo‐alignment behavior of poly(ethylene imine)s carrying azobenzene side groups
A new class of liquid‐crystalline poly(ethylene imine)s (PEIs) having four differently substituted (—CN,—C4H9,—OCH3 and—NO2) azobenzene side‐chain groups attached through alkyl spacer groups were successfully synthesized using a solution polycondensation reaction. The synthesized polymers were characterized using differential scanning calorimetry, polarized optical microscopy and X‐ray diffraction. The photochemical, thermo‐optical and photo‐orientational behavior of the polymers were investigated in detail. Spin‐coated films of PEIs with azobenzene groups having—C4H9,—OCH3 and—NO2 substituents showed out‐of‐plane molecular orientation on annealing. Except for the PEI with an azobenzene group having —NO2 substituent, all polymers exhibited good photoresponsive properties upon irradiation with UV and visible light. Films of PEIs with azobenzene side groups having—CN,—C4H9 and—OCH3 substituents showed reversible alignment behavior from random state to out‐of‐plane and from out‐of‐plane to random state on annealing and on irradiation with UV and non‐polarized visible light. The reversibility of the molecular orientation of PEIs from random state to out‐of‐plane and from out‐of‐plane to random state greatly depended on the substituent attached to the azobenzene side‐chain group. Copyright © 2010 Society of Chemical Industry
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Document Type: Research Article
Publication date: 01 May 2011
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