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Polydopamine‐Graphene Oxide Flame Retardant Nanocoatings Applied via an Aqueous Liquid Crystalline Scaffold 下载免费PDF全文
Hanim Kim Dae Woo Kim Vivek Vasagar Heonjoo Ha Sergei Nazarenko Christopher J. Ellison 《Advanced functional materials》2018,28(39)
A highly effective flame retardant (FR) nanocoating was developed by conducting oxidative polymerization of dopamine monomer within an aqueous liquid crystalline (LC) graphene oxide (GO) scaffold coating. Due to its high water content, the LC scaffold coating approach facilitated fast transport and polymerization of dopamine precursors into polydopamine (PDA) within the water swollen interlayer galleries. Uniform and periodically stacked (14.5 Å d‐spacing) PDA/GO nanocoatings could be universally applied on different surfaces, including macroporous flexible polyurethane (PU) foam and flat substrates such as silicon wafers. Remarkably, PDA/GO coated PU foam exhibited highly efficient flame retardant performance reflected by a 65% reduction in peak heat release rate at 5 wt% PDA/GO loading in an 80 nm thick coating. While many physically mixed flame retardants are usually detrimental to the mechanical properties of the foam, the PDA/GO coating did not affect mechanical properties substantially. In addition, the PDA/GO coatings were stable in water due to the intrinsic adhesion capability of PDA and the transformation of GO to the more hydrophobic reduced GO form. Given that PDA is produced from dopamine, a molecule prevalent in nature, these findings suggest that significant opportunities exist for new polymeric FRs derived from other natural catechols. 相似文献
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Woongbi Cho Jisoo Jeon Wonsik Eom Jae Gyeong Lee Dong-Gyun Kim Yong Seok Kim Tae Hee Han Jeong Jae Wie 《Advanced functional materials》2021,31(31):2102106
In recent years, the “Kirigami” have been exploited to engineer stretchable electronics that exhibit enhanced deformability without sacrificing their mechanical and electrical properties. However, kirigami-inspired engineering is often limited to passive mechanical stretching for 3D shape morphing. To counter this problem, in this study, azobenzene-functionalized liquid crystalline polymer networks (azo-LCNs) are monolithically integrated with patterned reduced graphene oxide (rGO), called azo-LCN/rGO, to achieve on-demand shape reconfiguration in response to external stimuli (UV, NIR, solar rays, and portable light); in addition, the azo-LCN/rGO exhibit highly enhanced mechanical and electrical properties. The cross-sectional area and thickness of rGO patterns are controlled using a masking technique and evaporative self-assembly. By the spatial patterning of rGO, insulating azo-LCNs are converted into electrically conducting structures (381.9 S cm−1). The elastic modulus of <2 µm thick azo-LCN can be tailored in the range of 1.3–6.4 GPa by integration with rGO layers of thickness less than 2 µm. Upon UV irradiation, azo-LCN/rGO exhibit both for/backward in-plane bending as well as out-of-plane chiral twisting, thus overcoming the typical trade-off relationship between elastic modulus and deformability. Finally, an on-demand contactless shape reconfiguration in azo-LCN/rGO by UV irradiation in conjunction with passive mechanical strain is demonstrated. 相似文献
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Yijie Hu Hao Zhuo Yu Zhang Haihong Lai Jiwang Yi Zehong Chen Xinwen Peng Xiaohui Wang Chuanfu Liu Runcang Sun Linxin Zhong 《Advanced functional materials》2021,31(51):2106761
Stretchable and tough hydrogels are highly required for various flexible devices. Liquid metal (LM) emerges as an attractive applicant in preparing functional hydrogels due to its unique features. However, the high fluidity of LM and incompatibility between LM and polymer matrix make it hard to fabricate tough hydrogels. Herein, inspired by the function of ligaments in biological structure, graphene oxide (GO) nanosheets are introduced to encapsulate LM droplets. GO nanosheets form strong interaction with both LM and polymer matrix to create a stable shell that prevents LM droplet from fracture and exudation to polymer network. The flexible LM/GO core–shell microstructure avoids phase separation and produces a tough hydrogel with stress of high up to 303 kPa at 1240% elongation. It also shows notch insensitivity and strong adhesion to various surfaces. This study opens the possibility of using LM in stretchable and tough hydrogels. 相似文献
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Rouhollah Jalili Seyed Hamed Aboutalebi Dorna Esrafilzadeh Roderick L. Shepherd Jun Chen Sima Aminorroaya‐Yamini Konstantin Konstantinov Andrew I. Minett Joselito M. Razal Gordon G. Wallace 《Advanced functional materials》2013,23(43):5345-5354
Key points in the formation of liquid crystalline (LC) dispersions of graphene oxide (GO) and their processability via wet‐spinning to produce long lengths of micrometer‐dimensional fibers and yarns are addressed. Based on rheological and polarized optical microscopy investigations, a rational relation between GO sheet size and polydispersity, concentration, liquid crystallinity, and spinnability is proposed, leading to an understanding of lyotropic LC behavior and fiber spinnability. The knowledge gained from the straightforward formulation of LC GO “inks” in a range of processable concentrations enables the spinning of continuous conducting, strong, and robust fibers at concentrations as low as 0.075 wt%, eliminating the need for relatively concentrated spinning dope dispersions. The dilute LC GO dispersion is proven to be suitable for fiber spinning using a number of coagulation strategies, including non‐solvent precipitation, dispersion destabilization, ionic cross‐linking, and polyelectrolyte complexation. One‐step continuous spinning of graphene fibers and yarns is introduced for the first time by in situ spinning of LC GO in basic coagulation baths (i.e., NaOH or KOH), eliminating the need for post‐treatment processes. The thermal conductivity of these graphene fibers is found to be much higher than polycrystalline graphite and other types of 3D carbon based materials. 相似文献
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Seyed Hamed Aboutalebi Mohsen Moazzami Gudarzi Qing Bin Zheng Jang‐Kyo Kim 《Advanced functional materials》2011,21(15):2978-2988
A novel process is developed to synthesize graphene oxide sheets with an ultralarge size based on a solution‐phase method involving pre‐exfoliation of graphite flakes. Spontaneous formation of lyotropic nematic liquid crystals is identified upon the addition of the ultralarge graphene oxide sheets in water above a critical concentration of about 0.1 wt%. It is the lowest filler content ever reported for the formation of liquid crystals from any colloid, arising mainly from the ultrahigh aspect ratio of the graphene oxide sheets of over 30 000. It is proposed that the self‐assembled brick‐like graphene oxide nanostructure can be applied in many areas, such as energy‐storage devices and nanocomposites with a high degree of orientation. 相似文献
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棒状液晶分子相变问题的机械旋转模型研究 总被引:2,自引:1,他引:1
综述一种关于棒状液晶材料的分子结构与液晶相的相关关系的研究成果。介绍了有关液晶分子的机械旋转模型。该模型将液晶分子视作一种高速旋转的转子,通过分子参数计算,对液晶材料的相变温度和分子结构之间的关系给出了一种全新的解释。最新研究表明,含氟三苯液晶材料的分子结构中存在slim和fat现象,能够对液晶材料的相变进行合理解释。该模型能够通过简单的模型方法对新型液晶材料的分子设计与合成提供有用的信息。 相似文献
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Jie Xiao Xiaojian Wang Xiao‐Qing Yang Shidi Xun Gao Liu Phillip K. Koech Jun Liu John P. Lemmon 《Advanced functional materials》2011,21(15):2840-2846
Nanocomposites comprised of poly(ethylene oxide), molybdenum disulfide, and graphene were prepared by the hydrolysis of lithiated molybdenum disulfide in an aqueous solution of PEO and graphene. Structural analysis by XRD shows the nanocomposites are disordered with an expansion of ~6 Å in the interlayer spacing. During the first discharge, the nanocomposites electrochemically dissociates irreversibly into Li2S and Mo and are able to continously cycle as Li2S +Mo/Lix ? S + Mo + Lix+2 as shown by XRD of the discharged electrodes at different depth of discharge (DOD), cyclic voltammetry (CV), and high resolution TEM. A significant increase of the reversible capacity is found in as‐prepared MoS2/PEO/graphene composite. The results suggest a new electro‐interaction between lithium and molybdenum metal that only occurs in the nanoregime and is enhanced by PEO. The addition of 2 wt% of graphene to the nanocomposites greatly increases the rate capability with rates as high as 10000mA g?1 yielding > 250mAh g?1 and recovering to > 600 mAhr g?1 at 50mA g?1. 相似文献
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An ex situ strategy for fabrication of graphene oxide (GO)/metal oxide hybrids without assistance of surfactant is introduced. Guided by this strategy, GO/Al2O3 hybrids are fabricated by two kinds of titration methods in which GO and Al2O3 colloids are utilized as titrant for hybrids of low and high GO content respectively. After sintered by spark plasma sintering, few‐layer graphene (FG)/Al2O3 nanocomposites are obtained and GO is well reduced to FG simultaneously. A percolation threshold as low as 0.38 vol.% is achieved and the electrical conductivity surpasses 103 Sm?1 when FG content is only 2.35 vol.% in FG/Al2O3 composite, revealing the homogeneous dispersion and high quality of as‐prepared FG. Furthermore, it is found that the charge carrier type changes from p‐ to n‐type as graphene content becomes higher. It is deduced that this conversion is related to the doping effect induced by Al2O3 matrix and is thickness‐dependent with respect to FG. 相似文献
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光响应液晶嵌段共聚物综合了光响应性液晶和嵌段聚合物两类材料的优异特性,是一种多功能性的新型材料。其中以偶氮苯为代表的光响应基团作为液晶基元的嵌段共聚物是其目前研究的主体。本文对光响应液晶材料和嵌段聚合物分别做了简要介绍,阐述了它们各自的优势和特点。对于光响应液晶嵌段共聚物的光响应机理、相分离过程和有序化调控手段进行了重点探讨。在此基础上,介绍了其在光子学、有机纳米模板和聚合物胶束等方面的研究进展。 相似文献
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Hyun Kim Jae Ah Lee Cedric P. Ambulo Ha Beom Lee Shi Hyeong Kim Vinay V. Naik Carter S. Haines Ali E. Aliev Raquel Ovalle‐Robles Ray H. Baughman Taylor H. Ware 《Advanced functional materials》2019,29(48)
Strategies for obtaining materials that respond to external stimuli by changing shape are of intense interest for the replacement of traditional actuators. Here, a strategy that enables programmable, multiresponsive actuators that use either visible light or electric current to drive shape change in composites comprising carbon nanotubes (CNTs) in liquid crystal elastomers (LCEs) is presented. In the nanocomposites, the CNTs function not only in the traditional roles of mechanical reinforcement and enhancers of thermal and electrical conductivity but also serve as an alignment layer for the LCEs. By controlling the orientation, location, and quantity of layers of CNTs in LCE/CNT composites, programmed, patterned actuators are built that respond to visible light or electrical current. Photothermal LCE/CNT film actuators undergo fast shape change, within 1.2 s using 280 mW cm?2 light input, and complex, programmed localized deformations. Furthermore, twisting LCE/CNT composite films into a fiber increases uniaxial muscle stroke and work capacity for electrothermal actuation, thereby enabling about 12% actuation strain and 100 kJ m?3 of work capacity in response to an applied DC voltage of 15.1 V cm?1. 相似文献
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Graphene Nanocomposites: Sandwich‐Type Nanocomposite of Reduced Graphene Oxide and Periodic Mesoporous Silica with Vertically Aligned Mesochannels of Tunable Pore Depth and Size (Adv. Funct. Mater. 47/2017) 下载免费PDF全文
Zheng‐Ming Wang Wenqin Peng Yoshiko Takenaka Noriko Yoshizawa Katsunori Kosuge Wendong Wang Geoffrey A. Ozin 《Advanced functional materials》2017,27(47)
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Achieving Outstanding Mechanical Performance in Reinforced Elastomeric Composite Fibers Using Large Sheets of Graphene Oxide 下载免费PDF全文
Mohammad Ziabari Seyedin Joselito M. Razal Peter C. Innis Rouhollah Jalili Gordon G. Wallace 《Advanced functional materials》2015,25(1):94-104
A simple fiber spinning method used to fabricate elastomeric composite fibers with outstanding mechanical performance is demonstrated. By taking advantage of the large size of as‐prepared graphene oxide sheets (in the order of tens of micrometers) and their liquid crystalline behavior, elastomeric composite fibers with outstanding low strain properties have been fabricated without compromising their high strain properties. For example, the modulus and yield stress of the parent elastomer improved by 80‐ and 40‐fold, respectively, while maintaining the high extensibility of ~400% strain inherent to the parent elastomer. This outstanding mechanical performance was shown to be dependent upon the GO sheet size. Insights into how both the GO sheet size dimension and dispersion parameters influence the mechanical behavior at various applied strains are discussed. 相似文献
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采用紫外光聚合诱导相分离方法制备了聚合物分散胆甾相液晶膜,系统研究了固化光强和固化温度等制备条件对薄膜的相形态的影响,并探讨了薄膜相形态与反射率的关系。研究表明:固化光强较低时相分离较完全,产生的液晶微滴尺寸较大,聚合物与液晶的界面非常光滑;增加光强会使液晶微滴尺寸变小,界面变粗糙,膜反射率逐步降低。相形态与固化温度的关系较为复杂:在温度较低时,液晶以圆形液滴的形式分散在聚合物基体中;随着固化温度升高,液晶液滴逐渐变大,并在40℃时形成了连续的液晶层和聚合物层的分层结构;进一步升高温度,则形成了三维的聚合物网络结构,液晶相贯穿其间。膜的反射率先随着固化温度的升高逐渐升高,而后又降低。固化光强为0.01mW/cm2,固化温度为40℃时,反射率达到最大值32.2%。 相似文献
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