Photo-triggered assembly/disassembly of macroscopically ordered monodomain lamellar structure in side-chain liquid crystalline polymer containing strong polar azobenzene mesogens

Photocontrol of molecular alignment is an exceptionally-intelligent and useful strategy. It enables us to control optical coefficients, peripheral molecular alignments, surface relief structure, and actuation of substances by means of photoirradiation. Azobenzene-containing polymers and functionalized liquid crystalline polymers are well-known photocontrollable materials. In this paper, we introduce recent applications of these materials in the fields of mechanics, self-organized structuring, mass transport, optics, and photonics. The concepts in each application are explained based on the mechanisms of photocontrol. The interesting natures of the photocontrollable materials and the conceptual applications will stimulate novel ideas for future research and development in this field.

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“…The contrast between the clear and opaque phase within the films is a remarkable phenomenon, as shown in the literatures [162,200,201].…”

Section: Other Applicationsmentioning

confidence: 92%

Optical and Physical Applications of Photocontrollable Materials: Azobenzene-Containing and Liquid Crystalline Polymers

2012

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“…The synthesis and characterization of the side‐chain LCP was reported in our previous work (Liu et al , 2011). The films were obtained by casting a solution of 5 wt% polymer‐THF onto the glass slides.…”

Section: Methodsmentioning

confidence: 99%

“…Recently, we observed an interference figure appeared from an in‐plane oriented film, which showed a centered black‐cross. This figure is similar to an interference figure that obtained from a perpendicularly orientated film (Liu et al , 2011). However, little attention has been paid on identifying the in‐plane or perpendicularly orientated films via the conoscopic observation methods.…”

Section: Introductionmentioning

confidence: 99%

Distinguishing the parallel and vertical orientations and optic axis characteristics determination of azobenzene mesogen by conoscopic polarized microscopy

Liu

Wang

Dong

et al. 2011

Journal of Microscopy

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SummaryOrientational behaviours under the action of linearly polarized light and circularly polarized light of a side-chain azobenzene containing polymer were studied by conoscopic polarized microscopy. The results suggest that the linearly polarized light (473 nm, 20 mW cm −2 ) results in an in-plane orientation of the azobenzene groups. The irradiation with circularly polarized light (473 nm, 20 mW cm −2 ) leads to a tilt orientation (out-of-plane) of the azobenzene groups with the long axis of mesogens aligned along the propagation direction of the actinic light. Characteristic features of the in-plane and out-of-plane orientated films were obtained from their interference figures. The in-plane orientated film shows an interference cross consisting of a broad fuzzy bar, and the cross-centre lies in the centre of view field. In-plane orientated film also yields a flash figure upon a less than 10 • rotation of the sample under polarized microscopy. The interference figures yielded from the out-of-plane orientated films consist of narrow bar cross. The locations of those interference figures depend on the oblique angle of the irradiation light. A method for distinguishing the in-plane orientation of the mesogens from the vertically out-of-plane orientation is demonstrated, which is based on comparing the bar width of their interference figures, and by whether they can produce a flash figure upon a small angle rotation of the film. The liquid crystalline film is identified as positive and uniaxial anisotropy after annealing of the perpendicularly irradiated film.

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Reversible Photoinduced Switching of Permeability in a Cast Non‐Porous Film Comprising Azobenzene Liquid Crystalline Polymer

Liu¹,

Wang²,

Dong³

et al. 2011

Macromol. Rapid Commun.

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Permeation characteristics of an azobenzene-containing liquid crystalline (LC) non-porous film are investigated using a metallic corrosion method. Thin films (300 nm) are fabricated by the solution casting of an azobenzene side-chain LC polymer on freshly polished carbon steel coupons. Coated coupons are treated under the following conditions: a) gradual annealing at a cooling rate lower than 1 °C · min(-1) from 150 °C (above its Tg ) to room temperature, and b) irradiation at 465 nm (20 mW · cm(-2) ) with either circularly polarized light (CPL) or non-polarized light (NPL). The morphology of these films is characterized using X-ray diffraction, polarized optical microscopy, and transmission measurements. The results suggest that the annealing treatment resulted in the formation of a polydomain structure consisting of locally ordered small smectic domains that lack mutual orientation. Ordered micro domains are surrounded by disordered phases. CPL and NPL irradiation generates a monodomain orientated structure and an isotropic liquid crystal glass, respectively. The permeability of these non-porous films treated by CPL, NPL, and annealing are found to be 6.14 × 10(-4) , 1.92 × 10(-2) , and 1.56 × 10(-3) cm(3) · m(-2) · d(-1) . An orientation-dependent structure model is constructed to explain the permeation phenomenon, considering the ordered phase is impermeable, only the disordered phase is accessible to penetrating molecules. Fast switching of gas permeation is demonstrated by alternative irradiation of the film with CPL and NPL, which results in an approximately 30-fold difference in the permeability of the non-porous film.

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Photo-triggered assembly/disassembly of macroscopically ordered monodomain lamellar structure in side-chain liquid crystalline polymer containing strong polar azobenzene mesogens

Cited by 10 publications

References 53 publications

Optical and Physical Applications of Photocontrollable Materials: Azobenzene-Containing and Liquid Crystalline Polymers

Optical and Physical Applications of Photocontrollable Materials: Azobenzene-Containing and Liquid Crystalline Polymers

Distinguishing the parallel and vertical orientations and optic axis characteristics determination of azobenzene mesogen by conoscopic polarized microscopy

Reversible Photoinduced Switching of Permeability in a Cast Non‐Porous Film Comprising Azobenzene Liquid Crystalline Polymer

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