Easily crosslinkable side-chain azobenzene polymers for fast and persistent fixation of surface relief gratings

Han, Guang; Zhang, Hongtao; Chen, Jing; Sun, Qian; Zhang, Yuying; Zhang, Huiqi

doi:10.1039/c4nj01658k

Cited by 17 publications

(17 citation statements)

References 80 publications

(175 reference statements)

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“…Importantly, these films are very uniform, adherent to one another, and present a scalable way to make variable thickness STECs not limited by the spin‐coating approach. This engineering concept presents further opportunities to incorporate cross‐linking units onto the azobenzenes themselves in order to increase STF loading or to construct co‐polymers with cross‐linkable moieties, where the ratio of STF to cross‐links may be precisely controlled.…”

Section: Resultsmentioning

confidence: 99%

Solid‐State Solar Thermal Fuels for Heat Release Applications

Zhitomirsky

Cho

Grossman

2015

Advanced Energy Materials

109

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56 Wh kg −1 ) employing ruthenium with higher cyclability have been developed, [5][6][7] but remain prohibitively expensive for wide adoption. With the availability of accurate computational tools, new approaches have leveraged carbon nanostructures and insights into the steric interaction of STFs to increase energy density employing highly cyclable and modest energy density (60-70 Wh kg −1 ) azobenzene derivatives. [ 8,9 ] While demonstrating a per-molecule increase in energy density via templating, [ 10 ] these approaches require complex multistep reactions, have low yields, and the resulting material has low solubility in most organic solvents (<1 g L −1 ). More recently, it was possible to develop liquid azobenzene fuels at room temperature by attaching bulky ligands to the molecule, [ 11 ] and with several computational works detailing the possibility of increasing its energy density through functionalization of the benzene rings, [ 12 ] this platform holds much promise for future STF developments. With such rapid progress in STF materials, it is perhaps surprising that the solid-state platform and related applications have remained largely unexplored, with only recent studies on semi-solid photoliquefi able ionic crystals reaching energy densities of 35 Wh kg −1 . [ 13 ] Transitioning fully to the solid-state offers the possibility of integrating STF materials into a multitude of existing solid-state devices such as coatings for deicing, or novel applications such as solar blankets and other consumer oriented heating equipment.We took the view that if properly engineered on the molecular level, STF materials could be controllably tailored within the solid-state, and that until now, there has not been an efficient method to accomplish this. For one, the most recent STF reports have relied on carbon scaffolds [ 10,14 ] that simultaneously increase synthesis complexity, cannot be deposited into uniform fi lms, contribute to the optical density without resulting in photocharging, and introduce uncontrollable morphological effects that may limit charging and reversible switching in the solid-state. [ 15 ] Similarly, single-molecule thin fi lms do not make homogenous layers, can often result in crystallization, and melt at low temperatures (≈70 °C for azobenzene) thus limiting their utility in the solid-state. Fortunately, a wealth of literature exists on azobenzene-based materials in solid-state applications for microswitches, microactuators, and sensors. [16][17][18][19][20][21] We postulated that the ideal material class to form solid-state STF coatings would need to (1) form smooth fi lms with controllable thickness, (2) be resilient at high temperatures, (3) preserve the heat release properties of Closed cycle systems offer an opportunity for solar energy harvesting and storage all within the same material. Photon energy is stored within the chemical conformations of molecules and is retrieved by a triggered release in the form of heat. Until now, such solar thermal fuels (STFs) have been largely unavailable...

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Section: Resultsmentioning

confidence: 99%

Solid‐State Solar Thermal Fuels for Heat Release Applications

Zhitomirsky

Cho

Grossman

2015

Advanced Energy Materials

109

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“…Note that neither of the constituents contains any flexible chains that are conventionally used in designing small-molecule liquid-crystalline complexes, which in combination with the presence of the dimethylamino group should promote the surface patterning efficiency. 1043 , 1044 The high-temperature LC phase, in turn, should promote photoalignment. 1045 , 1046 The photoresponsive properties of the complex were indeed unique.…”

Section: Functional Systemsmentioning

confidence: 99%

The Halogen Bond

et al. 2016

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The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

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“…The occurrence of the crosslinking in the blend films was confirmed by the difference of solubility between the crosslinked film and the uncrosslinked one (Figure S2, Supporting Information) . In addition, it has been demonstrated that the optical transparency of most of the azobenzene polymer films is hardly affected by the post‐crosslinking process, which is highly important for their practical applications . The PAZO/PU blend films mentioned below are crosslinked unless otherwise specified.…”

Section: Methodsmentioning

confidence: 86%

“…Thus in the PAZO/PU blend films, PU as the host material can provide favorable mechanical properties for the whole blend system. It should be mentioned that poly(methacrylate)‐type azobenzene polymers have rigid characteristics because of their backbones . Compared with the pure PU film, blend films (PAZO/PU = 9/91) show higher Young's modulus but smaller tensile strength.…”

Section: Resultsmentioning

confidence: 99%

“…Remarkably, the post‐crosslinking method provides an opportunity to give a feasible and ingenious way to prepare CLCP/polymer blend films. Zhang and co‐workers reported a series of CLCPs and homopolymers with N ‐hydroxysuccinimide carboxylate‐substituted azobenzene groups, which enables the post‐crosslinking of polymer chains with 1,6‐hexanediamine under mild conditions after a film‐formation process . Our group synthesized a block copolymer PEO‐ b ‐PAZO bearing an easily crosslinkable azobenzene mesogen.…”

Section: Introductionmentioning

confidence: 99%

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Photo‐Induced Bending Behavior of Post‐Crosslinked Liquid Crystalline Polymer/Polyurethane Blend Films

Pang

Qing

et al. 2017

Macromol. Rapid Commun.

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a variety of practical applications and definitely merit further investigations. The incorporation of azobenzene chromophore into CLCPs gives rise to photoinduced deformations such as uniaxial contraction/expansion and high-speed bending. [13][14][15][16][17][18][19][20][21][22] The photo mechanical effect resulting from photo responsive CLCP is useful in the development of actuators.There has been growing interest in designing and studying photo responsive composite films by combining CLCPs with commercial polymers, which will reduce cost and enlarge the scopes of the applications of CLCPs. [23,24] Ikeda and co-workers reported various doublelayer films through the lamination of azobenzene-containing CLCP layers on the flexible polyethylene (PE) plastic sheets. As a result, the rotation of a light-driven plastic motor as well as 3D movements such as an inchworm walk and a flexible robotic arm motion was successfully achieved. [25,26] Additionally, a visible-light-driven plastic microrobot composed of CLCP/PE bilayer films could manipulate the object that is about ten times heavier than its own weight effectively. [27] However, these photoresponsive double-layer actuators with an adhesive layer generally suffer from delamination of the two layers after long-term exposure to light source, which results in a decreased lifetime.In fact, another useful method has also been proposed to prepare the photoresponsive composite films by dispersing liquid crystalline polymers (LCPs), LC molecules, or azo compounds in the amorphous polymers. Yu and co-workers achieved the photomechanical conversion in polymer-dispersed LCs (PDLCs) like hybrid films with LCP particles dispersed in polyvinyl alcohol (PVA), yet the responsive rate was very low because of the high glass transition temperature of LCP. [28,29] They prepared various photomobile composite films via doping LC molecules or azo compounds to the polymer. Owing to the immiscibility between the small molecule and the polymer, the poor dispersion inevitably occurred in the hybrid film, which further dramatically decreased the mechanical properties of the composite films and impeded their applications to some degree. [29][30][31] Undoubtedly, the improvement of the miscibility between a photoabsorbent and the polymer matrix will bring the promotion of mechanical properties and bending behaviors of the resulted blend films. Involvement of photoresponsive CLCP to polymer substrate by the dispersion method will provide Photoresponsive Actuators Photoresponsive blend films with post-crosslinked liquid crystalline polymer (CLCP) as a photosensitive component and flexible polyurethane (PU) as the matrix are successfully fabricated. After being uniaxially stretched, even at low concentration, the azobenzene-containing CLCP effectively transfers its photoresponsiveness to the photoinert PU matrix, resulting in the fast photo-induced bending behavior of whole blend film thanks to the effective dispersion of CLCP. Specifically, the blend film shows photo-induced deformations upon ex...

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Easily crosslinkable side-chain azobenzene polymers for fast and persistent fixation of surface relief gratings

Cited by 17 publications

References 80 publications

Solid‐State Solar Thermal Fuels for Heat Release Applications

Solid‐State Solar Thermal Fuels for Heat Release Applications

The Halogen Bond

Photo‐Induced Bending Behavior of Post‐Crosslinked Liquid Crystalline Polymer/Polyurethane Blend Films

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