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Photo Actuation Performance of Nanotube Sheet Incorporated Azobenzene Crosslinked Liquid Crystalline Polymer Nanocomposite.

ABSTRACT: Crosslinked liquid crystalline polymers (CLCPs) containing azobenzene (AZO-CLCPs) are a type of promising material due to their significance in the design of light-driven smart actuators. Developing AZO-CLCP composites by incorporating AZO-CLCPs with other materials is an effective way of enhancing their practicability. Herein, we report an AZO-CLCP/CNT nanocomposite prepared by the in situ polymerization of diacrylates containing azobenzene chromophores on carbon nanotube (CNT) sheets. The liquid crystal phase structure of CLCP matrix was evidenced by the two-dimensional X-ray scattering. The prepared pure AZO-CLCP films and AZO-CLCP/CNT nanocomposite films demonstrated strong reversible photo-triggered deformation under the irradiation of UV light at 366 nm of wavelength, as a result of photo-induced isomerization of azobenzene moieties in the polymer network. But compared to pure AZO-CLCP films, the AZO-CLCP/CNT nanocomposite films could much more rapidly return to their initial shapes after the UV light irradiation was removed due to the elasticity effect of CNT sheets. The deformation behavior of AZO-CLCP/CNT nanocomposite films under the light irradiation was also different from that of the pure AZO-CLCP films due to the interfacial interaction between a polymer network and CNT sheet. Furthermore, incorporation of a CNT sheet remarkably increased the mechanical strength and robustness of the material. We also used this AZO-CLCP/CNT nanocomposite as a microvalve membrane actuator, which can be controlled by light, for a conceptual device of a microfluidic system. The results showed that this AZO-CLCP/CNT nanocomposite may have great potential in smart actuator applications for biological engineering, medical treatment, environment detection and microelectromechanical systems (MEMS), etc.

SUBMITTER: Bi M

PROVIDER: S-EPMC6523392 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Photo Actuation Performance of Nanotube Sheet Incorporated Azobenzene Crosslinked Liquid Crystalline Polymer Nanocomposite.

Bi Meng M He Yifan Y Wang Yuchang Y Yang Wenlong W Qin Ban B Xu Jiaojiao J Wang Xiuxiu X Wang Binsong B Dong Yinmao Y Gao Yachen Y Li Chensha C

Polymers 20190423 4

Crosslinked liquid crystalline polymers (CLCPs) containing azobenzene (AZO-CLCPs) are a type of promising material due to their significance in the design of light-driven smart actuators. Developing AZO-CLCP composites by incorporating AZO-CLCPs with other materials is an effective way of enhancing their practicability. Herein, we report an AZO-CLCP/CNT nanocomposite prepared by the in situ polymerization of diacrylates containing azobenzene chromophores on carbon nanotube (CNT) sheets. The liqu ...[more]

PMID: 31018552

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Project description:Embedding nanomaterials into polymer hydrogels enables the design of functional materials with tailored chemical, mechanical, and optical properties. Nanocapsules that protect interior cargo and disperse readily through a polymeric matrix have drawn particular interest for their ability to integrate chemically incompatible systems and to further expand the parameter space for polymer nanocomposite hydrogels. The properties of polymer nanocomposite hydrogels depend on the material composition and processing route, which were explored systematically in this work. The gelation kinetics of network-forming polymer solutions with and without silica-coated nanocapsules bearing polyethylene glycol (PEG) surface ligands were investigated using in situ dynamic rheology measurements. Network-forming polymers comprised either 4-arm or 8-arm star PEG with terminal anthracene groups, which dimerize upon irradiation with ultraviolet (UV) light. The PEG-anthracene solutions exhibited rapid gel formation upon UV exposure (365 nm); gel formation was observed as a crossover from liquid-like to solid-like behavior during in situ small-amplitude oscillatory shear rheology. This crossover time was non-monotonic with polymer concentration. Far below the overlap concentration (c/c* ≪ 1), spatially separated PEG-anthracene molecules were subject to forming intramolecular loops over intermolecular cross-links, thereby slowing the gelation process. Near the polymer overlap concentration (c/c* ∼ 1), rapid gelation was attributed to the ideal proximity of anthracene end groups from neighboring polymer molecules. Above the overlap concentration (c/c* > 1), increased solution viscosities hindered molecular diffusion, thereby reducing the frequency of dimerization reactions. Adding nanocapsules to PEG-anthracene solutions resulted in faster gelation than nanocapsule-free PEG-anthracene solutions with equivalent effective polymer concentrations. The final elastic modulus of nanocomposite hydrogels increased with nanocapsule volume fraction, signifying synergistic mechanical reinforcement by nanocapsules despite not being cross-linked into the polymer network. Overall, these findings quantify the impact of nanocapsule addition on the gelation kinetics and mechanical properties of polymer nanocomposite hydrogels, which are promising materials for applications in optoelectronics, biotechnology, and additive manufacturing.

Project description:BACKGROUND AND PURPOSE:The photo-isomerizable local anaesthetic, quaternary ammonium-azobenzene-quaternary ammonium (QAQ), provides rapid, optical control over pain signalling without involving genetic modification. In darkness or in green light, trans-QAQ blocks voltage-gated K+ and Na+ channels and silences action potentials in pain-sensing neurons. Upon photo-isomerization to cis with near UV light, QAQ blockade is rapidly relieved, restoring neuronal activity. However, the molecular mechanism of cis and trans QAQ blockade is not known. Moreover, the absorption spectrum of QAQ requires UV light for photo-control, precluding use deep inside neural tissue. EXPERIMENTAL APPROACH:Electrophysiology and molecular modelling were used to characterize the binding of cis and trans QAQ to voltage-gated K+ channels and to develop quaternary ammonium-ethylamine-azobenzene-quaternary ammonium (QENAQ), a red-shifted QAQ derivative controlled with visible light. KEY RESULTS:trans QAQ was sixfold more potent than cis QAQ, in blocking current through Shaker K+ channels. Both isomers were use-dependent, open channel blockers, binding from the cytoplasmic side, but only trans QAQ block was slightly voltage dependent. QENAQ also blocked native K+ and Na+ channels preferentially in the trans state. QENAQ was photo-isomerized to cis with blue light and spontaneously reverted to trans within seconds in darkness, enabling rapid photo-control of action potentials in sensory neurons. CONCLUSIONS AND IMPLICATIONS:Light-switchable local anaesthetics provide a means to non-invasively photo-control pain signalling with high selectivity and fast kinetics. Understanding the mode of action of QAQ and related compounds will help to design of drugs with improved photo-pharmacological properties. LINKED ARTICLES:This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.

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Photo Actuation Performance of Nanotube Sheet Incorporated Azobenzene Crosslinked Liquid Crystalline Polymer Nanocomposite.

Publications

Photo Actuation Performance of Nanotube Sheet Incorporated Azobenzene Crosslinked Liquid Crystalline Polymer Nanocomposite.

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