Photochromism of 4-cyanophenylazobenzene in liquid crystalline-coil AB diblock copolymers: the influence of microstructure

Moriya, Keiichi; Seki, Takahiro; Nakagawa, Masaru; Mao, Guoyong; Ober, Christopher K.

doi:10.1002/1521-3927(20001201)21:18<1309::aid-marc1309>3.0.co;2-1

Cited by 32 publications

(7 citation statements)

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“…Block copolymers with azobenzene-containing side chains were also synthesized by various other groups. [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] However, less data were given concerning holographic experiments utilizing thick films, in particular regarding angular multiplexing. In thick films, the optical density of the entire sample has to be sufficiently low.…”

Section: Introductionmentioning

confidence: 99%

Blends of Poly(methacrylate) Block Copolymers with Photoaddressable Segments

et al. 2007

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The paper presents the synthesis of azobenzene-functionalized block copolymers based on a poly-(methyl methacrylate) (PMMA) segment and an azobenzene-functionalized poly(hydroxyethyl methacrylate) segment, and a basic study of blending these block copolymers with homopolymers is given. Two diblock copolymers, prepared via different routes, were synthesized by a living anionic polymerization followed by a polymer analogous reaction to attach the azobenzene side groups. Self-assembly of the block copolymers resulted in phase-separated morphologies on the nanometer scale. The photoaddressable azobenzene segments are dispersed in the PMMA matrix and locally confined. Special focus is given to the preparation and characterization of block copolymer blends with PMMA homopolymer in order to dilute the phase-separated azobenzene morphology and reduce the optical density while maintaining the confinement. The block copolymer blends were characterized with respect to their morphology and initial holographic experiments were performed.

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Section: Introductionmentioning

confidence: 99%

Blends of Poly(methacrylate) Block Copolymers with Photoaddressable Segments

et al. 2007

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“…For films of the G0 and G2 LDBCs in their LC states, the l max exhibited the largest blue shift to 300 nm which may be explained by the regular lamellar organization of azobenzene chromophores, as suggested in Fig. [86][87][88]91 While it has been reported that the H-aggregation thus the spectral hypsochromic shift of azobenzene chromophores was remarkably suppressed in block copolymers confined by the microphase segregated structure, 90 whereas the obvious H-aggregation formation in our LDBC system may mainly be attributed to the flexible ten-methylene spacer which effectively decoupled the aggregation of azobenzene mesogenic units from the motion of the dendritic PAMAM segment and PEG block and thus favoured the formation of assembled liquid crystalline superstructures from various generation LDBCs. Whereas for those of G1 and G3 LDBCs, with a weight fraction of azobenzene chromophores 47.2% and 69.5%, respectively, the radial organization of chromophores in the majority matrix phase as shown in Fig.…”

Section: Generation-dependent Photophysical Behavior Of Azobenzene Chmentioning

confidence: 78%

“…6. It has been well documented that azobenzene chromophores in homopolymers with LC nature show a strong tendency to form H-aggregates, such as liquid crystalline polymethacrylate with azobenzene moieties reported by Iyoda et al 21 and Ober et al, 90 in addition to liquid crystalline dendrimers. 6(B, D) to form the strongest H-aggregation.…”

Section: Generation-dependent Photophysical Behavior Of Azobenzene Chmentioning

confidence: 96%

Self-assembled hierarchical structure evolution of azobenzene-containing linear-dendritic liquid crystalline block copolymers

Shi

Chen

et al. 2012

Soft Matter

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In this paper, the phase behaviors and self-assembled structures of a series of liquid crystalline lineardendritic block copolymers (LDBCs) in the bulk state have been systematically investigated in combination with DSC, POM, SAXS, WAXS, and TEM. The LDBCs consist of a linear poly(ethylene glycol) (PEG) block (degree of polymerization, DP ¼ 49) and dendritic polyamidoamine (PAMAM) segments of generation G0 to G3, functionalized with photoactive azobenzene mesogenic units bearing an octyloxy tail and a flexible ten-methylene spacer (AZO). An unprecedented hierarchical structure evolution with increasing dendron generation has been demonstrated for this series of azobenzenecontaining LDBCs in bulk. Well-defined lamellar structures are formed for liquid crystalline LDBCs of G0, G1, and G2 with only a slight change in layer spacing between 12.2 and 13.0 nm. A simple lamellar structure is generated by mPEG-G0-(AZO) 2 , while tetragonal-within-lamellar and lamellar-withinlamellar hierarchical structures are created in mPEG-G1-(AZO) 4 and mPEG-G2-(AZO) 8 , respectively, due to further suborganization between PAMAM and AZO segments within the dendritic blocks. For the highest generation copolymer investigated in this work, mPEG-G3-(AZO) 16 , the structure changes dramatically from lamellar for lower generations into rectangular columnar with lattice parameters a ¼ 8.5 nm and b ¼ 6.5 nm or higher temperature disordered columnar mesophases. The introduction of the alkyloxy tail in the azobenzene mesogenic unit is of crucial importance for constructing such hierarchical structures. Moreover, those complex lamellar mesophases transform into micellar or network cubic structures upon cooling to ambient solidification temperature with PEG crystallization showing a complete inverse phase change tendency in virtue of the curvature effect as a result of the specific linear-dendritic architecture. Very interestingly, the films of azobenzene-containing liquid crystalline LDBCs exhibit generation/morphology dependent photophysical characteristics, which may afford a convenient way for designing and fine-tuning novel optical storage materials. ; Tel: +86-10-62758126 † Electronic supplementary information (ESI) available: Tables of SAXS/WAXS data assignments of the series LDBCs in their LC states and supplementary SAXS profiles of various generation LDBCs in their solid states at room temperature; Variable temperature SAXS/WAXS profiles and POM textures of the precursor azobenzene mesogenic compound and various generation LDBCs; and representative UV-vis spectra in solution; DSC curves of mPEG-G3-(AZO) 16 . See

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“…Some years later in 1989, Angeloni et al compared the spectroscopic properties of main chain and side chain azobenzene polymers with the corresponding monomers and found that the substitution pattern has the largest effect on the excitation maximum [44]. This effect is also shown for block copolymers consisting of a polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(β-acetyl galactose ethyl methacrylate) or poly(ethylene glycol) (PEG) block in combination with various polymeric azobenzenes [45,46,47,48,49]. In that regard, the first block copolymer containing a photo-responsive azobenzene segment was synthesized by Se et al in 1997 using side chain modification of a polystyrene- block - N,N -dimethyl-4-vinylphenethylamine block copolymer prepared by sequential anionic polymerization with p,p’ -Bis(chloromethyl)azobenzene [50].…”

Section: λ-Dependent Photo-response In Block Copolymer Nanostructumentioning

confidence: 99%

Micellization of Photo-Responsive Block Copolymers

2017

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This review focuses on block copolymers featuring different photo-responsive building blocks and self-assembly of such materials in different selective solvents. We have subdivided the specific examples we selected: (1) according to the wavelength at which the irradiation has to be carried out to achieve photo-response; and (2) according to whether irradiation with light of a suitable wavelength leads to reversible or irreversible changes in material properties (e.g., solubility, charge, or polarity). Exemplarily, an irreversible change could be the photo-cleavage of a nitrobenzyl, pyrenyl or coumarinyl ester, whereas the photo-mediated transition between spiropyran and merocyanin form as well as the isomerization of azobenzenes would represent reversible response to light. The examples presented cover applications including drug delivery (controllable release rates), controlled aggregation/disaggregation, sensing, and the preparation of photochromic hybrid materials.

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Photochromism of 4-cyanophenylazobenzene in liquid crystalline-coil AB diblock copolymers: the influence of microstructure

Cited by 32 publications

References 9 publications

Blends of Poly(methacrylate) Block Copolymers with Photoaddressable Segments

Blends of Poly(methacrylate) Block Copolymers with Photoaddressable Segments

Self-assembled hierarchical structure evolution of azobenzene-containing linear-dendritic liquid crystalline block copolymers

Micellization of Photo-Responsive Block Copolymers

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