Diblock copolymer–azobenzene complexes through hydrogen bonding: Self‐assembly and stable photoinduced optical anisotropy. Issue 8 (5th January 2013)

• Record Type: Journal Article
• Authors: del Barrio, Jesús; Blasco, Eva; Oriol, Luis; Alcalá, Rafael; Sánchez‐Somolinos, Carlos
• Is Part Of: Journal of polymer science. Volume 51:Issue 8(2013:Apr.)
• Page Start: 1716
• Page End: 1725
• Publication Date: 2013-01-05
• Subjects: 547
• DOI: 10.1002/pola.26523
• Languages: English
• ISSNs: 0887-624X

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>We have demonstrated the preparation of a series of photoaddressable supramolecular block copolymers by mixing a carboxy‐terminated azobenzene derivative, 6‐[4‐(4′‐cyanophenylazo)phenyloxy]hexanoic acid (AZO), and two polystyrene‐<italic>b‐</italic>poly(4‐vinylpiridine) (PS‐<italic>b</italic>‐P4VP) block copolymers. AZO can be selectively attached to the P4VP block of PS‐<italic>b</italic>‐P4VP through hydrogen bonding interactions. The assembly of AZO with vinylpyridine group‐containing polymers was initially investigated on a model system composed of P4VP homopolymer and AZO. Homogeneous liquid crystalline materials were obtained for ratios of AZO to vinylpyridine repeating unit, <italic>x</italic>, lower or equal to 0.50. Mixtures with higher <italic>x</italic> resulted in heterogeneous materials showing clear macrophase separation. Accordingly, a series of hydrogen‐bonded complexes of PS‐<italic>b</italic>‐P4VP and AZO, PS‐<italic>b</italic>‐P4VP(AZO)<italic><sub>x</sub></italic>, with <italic>x</italic> = 0.25 and <italic>x</italic> = 0.50 were prepared. Lamellar and spherical morphologies were observed for the complexes based on PS24‐<italic>b</italic>‐P4VP9.5 (<italic>M</italic><sub>n, PS</sub> = 24, 000, <italic>M</italic><sub>n, P4VP</sub> = 9500) and PS24‐<italic>b</italic>‐P4VP1.9 (<italic>M</italic><sub>n, PS</sub> = 24, 000, <italic>M</italic><sub>n, P4VP</sub> = 1900), respectively. Photoinduced orientation of the azobenzene units was obtained in films of P4VP(AZO)<italic><sub>x</sub></italic> and PS‐<italic>b</italic>‐P4VP(AZO)<italic><sub>x</sub></italic> with <italic>x</italic> = 0.25 and 0.50 by using 488 nm linearly polarized light and characterized through birefringence and dichroism measurements. This investigation shows a versatile and less laborious approach to azobenzene‐containing polymer materials with low chromophore content, of interest in optical application. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013</p> </abstract>