Azobenzene-containing block copolymers: the interplay of light and morphology enables new functions

Zhao, Yue; He, Jie

doi:10.1039/b821589h

Cited by 135 publications

(90 citation statements)

References 69 publications

(82 reference statements)

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“…The typical strategies employ the use of azobenzene derivatives in the main chain 51 or as side 52 groups. They have also been applied in the preparation of block copolymers 53 , hyperbranched polymers and dendrimers 54 .…”

Section: Spiropyran; (C) Fulgide; (D) Diarylethenementioning

confidence: 99%

Multi‐stimuli‐responsive Polymers Based on Calix[4]arenes and Dibenzo‐18‐crown‐6‐ethers

Wiktorowicz

Tenhu

Aseyev

2018

Temperature‐Responsive Polymers

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Section: Spiropyran; (C) Fulgide; (D) Diarylethenementioning

confidence: 99%

Multi‐stimuli‐responsive Polymers Based on Calix[4]arenes and Dibenzo‐18‐crown‐6‐ethers

Wiktorowicz

Tenhu

Aseyev

2018

Temperature‐Responsive Polymers

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“…In the years since, considerable data have been accumulated, and several reviews on this topic are now available. 5,19,[120][121][122][123][124] The orientations of azobenzene mesogenic groups and MPS cylinder domains have been found to be dependent on the film thickness. For poly(ethylene oxide) (PEO)-b-PAz (Figure 10), a critical thickness was determined to be 70 nm.…”

Section: Photoalignment Of Block Copolymer Thin Filmsmentioning

confidence: 99%

New strategies and implications for the photoalignment of liquid crystalline polymers

Seki

2014

Polym J

131

118

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The photoalignment of liquid crystalline materials has been studied extensively over the past two and a half decades and has recently become of technological importance in the liquid crystal display panel industry. This review introduces recent attempts at the photoalignment of liquid crystalline polymers and focuses on two aspects. First, strategies to ensure effective in-plane alignment of photoresponsive mesogens are highlighted. Despite the numerous investigations reported to date, film systems have not been well optimized in terms of realizing efficient photoreactions that consider the mesogen orientations. Second, new photoalignable systems composed of block copolymers with surface-grafted polymers and block copolymer films are introduced. The photoalignment processes in these mesoscopic systems involve strong cooperative motion of the different hierarchical size features. In the course of these approaches, a new strategic platform, photoalignment of liquid crystalline polymers via commanding from the free surface, is proposed. These approaches are expected to offer new concepts and possibilities for smart light-responsive materials and systems. Polymer Journal (2014) 46, 751-768; doi:10.1038/pj.2014.68; published online 13 August 2014 INTRODUCTIONPhotoreactions in ordered media have been the subject of numerous studies. In liquid crystal (LC) systems, molecules are packed with substantial motional freedom, and photoreactions trigger changes in the packing state or the collective molecular orientation. The effects can be amplified to the mesoscopic, microscopic and even macroscopic levels due to strong motional cooperativity. Photochromic reactions have frequently been incorporated in LC media because of their repeatability for controlling material properties. This approach has provided various types of smart, light-responsive materials 1 exhibiting surface-mediated photoalignment of LC materials, 2-6 photoinduced phase transitions, 7-12 photoorientation/addressing of polymer thin films, 13-18 photoinduced mass migrations, [19][20][21][22][23][24][25][26][27][28] phototactic sliding motions, 29-31 photo-driven motions and morphology of monolayers, 32-35 and macroscopic photomechanical deformations. [36][37][38][39][40][41][42][43][44][45][46] Photoalignment research and technology started in 1988 with the discovery of the reversible alignment control of nematic LCs by the photoisomerization of azobenzene on a substrate surface (Figure 1) by Ichimura et al. 47 It was demonstrated that the E/Z (trans/cis) photoisomerization of an azobenzene monolayer on a substrate can switch the alignment of nematic LC molecules between the homeotropic and planar modes. This active functional surface was dubbed a 'command surface' or 'command layer.' Shortly after this finding, Gibbons et al., 48 Dyadyusha et al. 49 and Schadt et al. 50 showed that angular selective excitation of an azo dye-doped polyimide or a photocrosslinkable polymer film with linearly

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“…Generally, the tuning of morphology can be achieved by virtue of external stimuli, such as a solvent or temperature annealing, casting, light, and so on (Segalman and Green, 1999;Zhao and He, 2009;Sriprom et al, 2010;Zhang et al, 2010;Ma et al, 2011;Okano et al, 2011). Light provides a flexible means to handle materials in a non-contact manner.…”

Section: Introductionmentioning

confidence: 99%

“…Light provides a flexible means to handle materials in a non-contact manner. To manipulate the surface morphology of a polymer film by light, photoresponsive chromophores usually are incorporated into polymers (Zhao and He, 2009). Azobenzene is a well-known photoresponsive molecule.…”

Section: Introductionmentioning

confidence: 99%

“…Azobenzene is a well-known photoresponsive molecule. In azobenzene-containing block copolymers, the reversible photoisomerization of azobenzene can serve as a means of modulating the surface morphology in polymer thin films (Zhao and He, 2009). Considerable work has been reported on the photoalignment and photopatterning of block copolymer films containing azobenzene moiety (Kadota et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

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Surface pattern based on an azobenzene-containing copolymer thin film and its light-driven morphology modulation

Zhang

Wang

2013

J. Zhejiang Univ. Sci. A

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Abstract:A type of azobenzene-containing block copolymer polymethyl methacrylate-b-poly (n-butylmethacrylate-co-6-(4-(phenylazo) benzoate) hexyl methacrylate) (PMMA-b-(PnBMA-co-PAzoMA)) was synthesized by the atom transfer radical polymerization (ATRP). Macroinitiator polymethyl methacrylate (PMMA) was prepared by ATRP and used to initiate the copolymerization of monomer n-butyl methacrylate (nBMA) and azobenzene-based methacrylate monomer (AzoMA). Herein, three block copolymers with different molecular weights and block volume fractions were obtained and spin-coated on a silicon substrate or quartz plate before annealing at 180 °C for 14 h. The surface morphologies in these annealed copolymer films were observed by atomic force microscopy (AFM). Bicontinuous stripe or island patterns with different sizes were formed dependent on the film thickness. These ordered patterns are considered to be formed arising from the dewetting process of the surface layer in the copolymer film. Photoisomerization of azobenzene units in the copolymer films changed the dewetting behaviors of the surface layer of the thin film. Therefore, some copolymer annealed films showed a reversible morphology conversion between bicontinuous stripe and island structure when exposed to UV light and upon being stored in the dark. It was found that the composition of the block copolymer had obvious influences on the photoinduced morphology conversion behaviors in these copolymer thin films. When the volumes of PnBMA and PAzoMA phases in the block copolymer were large enough, the surface morphology could be modulated by UV light irradiation and storage in the dark. This work proposes a new possibility for photoinduced control and design of the dewetting processes of thin films using a linear block copolymer.

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Azobenzene-containing block copolymers: the interplay of light and morphology enables new functions

Cited by 135 publications

References 69 publications

Multi‐stimuli‐responsive Polymers Based on Calix[4]arenes and Dibenzo‐18‐crown‐6‐ethers

Multi‐stimuli‐responsive Polymers Based on Calix[4]arenes and Dibenzo‐18‐crown‐6‐ethers

New strategies and implications for the photoalignment of liquid crystalline polymers

Surface pattern based on an azobenzene-containing copolymer thin film and its light-driven morphology modulation

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