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Stable graphene oxide-based lyotropic liquid crystals for interfacial lubrication

Friction 2024年第5期12卷 954-967页

作者： Yumei GUO Hanglin LI Jiusheng LI Xiangqiong ZENG Laboratory for Advanced Lubricating Materials Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai201210China University of Chinese Academy of Sciences Beijing100049China

lyotropic liquid crystals have lubricating properties due to their ordered assembly and fluidity,whose mesogens are often characterized by amphiphilic properties.Despite the attention that graphene oxide(GO)has been studied as a novel amphiphilic lyotropic mesogen this decade,and GO applied as a lubrication additive has been demonstrated in both oil and water-based systems,little research reveals the interfacial lubrication of GO liquid crystals yet.This work reports that GO aqueous dispersion can form lyotropic liquid crystals above a specific critical concentration of 5.00 mg/mL,providing a form of stable water-based lubricant,which can keep stable for several months and can reduce friction by 37.3%and wear by 25.24%.The liquid crystal phase was verified by polarizing microscope and synchrotron radiation small-angle X-ray scattering,and its rheological properties and viscoelasticity were studied by interfacial rheometer.The formation of lyotropic liquid crystals can enhance the stability of GO aqueous dispersions at high density,simultaneously ensuring friction decrease and anti-wear effect.It is attributed to the stable nematic network by the ordered GO sheets.The ordered assembly structure bears vertical shear force,therefore,reducing the wear.It is also assumed that the wide lateral size of graphene oxide promotes the nematic phase thus smoothes the graphene oxide film composed spontaneously under the coincidence of lamellar liquid crystal and 2D layered material.Through this work,the interlayer lubrication of GO was optimized,and the problem of GO dispersion sedimentation was solved by self-assembly.The range of interfacial lubrication of GO aqueous dispersion has been expanded and the synergistic effect is conducive to the environmentally friendly lubricants.

关键词： lyotropic liquid crystal graphene oxide aqueous lubrication tribological behavior

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lyotropic liquid crystalLINE BEHAVIOR OF FIVE CHITOSAN DERIVATIVES

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Chinese Journal of Polymer Science 1999年第1期17卷 65-70页

作者：董炎明 Department of Chemistry Xiamen University Xiamen 361005 China

Five chitosan derivatives, i.e. O-butyryl chitosan, O-benzoyl chitosan, N-phthaloyl chitosan, N-maleoyl chitosan and O-cyanoethyl chitosan, were prepared from chitosan. All of them had better solubility than chitosan, and demonstrated lyotropic liquid crystalline behavior in various solvents. The critical liquid crystalline behavior of three O-substituted chitosan derivatives was evidently different from two N-substituted analogues. Typical fingerprint textures of cholesteric phase were only observed in three O-substituted derivatives. The critical concentration (v/v%) of three O-substituted derivatives does not depend on the acidity of acidic solvents.

关键词： chitosan derivatives lyotropic liquid crystal

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STUDIES ON CRITICAL CONCENTRATION OF liquid crystalLINE ETHYLCELLULOSE

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Chinese Journal of Polymer Science 1996年第2期14卷 134-141页

作者：董炎明张世英 Department of Chemistry Xiamen University Xiamen 361005

Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than ten solvents were determined using both Abbe refractometer and polarized microscopy. Critical concentration C-crit of forming liquid crystal phase decreased with increasing solubility parameter delta of solvent until approaching the delta of polymer. Although the alcohols used as solvents had the same variation rule, the critical concentration values of their solutions were much higher, due to their excessive large hydrogen bond component of delta. The experiments of using mixed solvents which showed good linear relation between C-crit and delta also proved this rule. A technique of Transmission Optical Analysis was first used to estimate the concentration dependence of critical phase transition temperature T-crit of EC, and a T-C phase diagram could be drawn.

关键词： ethyl cellulose lyotropic liquid crystal critical concentration solubility parameter Transmission Optical Analysis phase diagram

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Hierarchical ordering of charged supramolecular helices

Hierarchical ordering of charged supramolecular helices

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中国化学会2017全国高分子学术论文报告会

作者：黄宁东李良彬中国科学技术大学

螺旋结构在水溶液超分子自组装中很常见,但其在多级自组装（水相超分子液晶）中的作用常常被忽略。合成离子型BTA分子在水溶液中能自发形成螺旋管状结构并进一步有序排列成中心四方晶格,基于这一多级自组装体系,我们研究了螺旋结构之间... 详细信息

螺旋结构在水溶液超分子自组装中很常见,但其在多级自组装（水相超分子液晶）中的作用常常被忽略。合成离子型BTA分子在水溶液中能自发形成螺旋管状结构并进一步有序排列成中心四方晶格,基于这一多级自组装体系,我们研究了螺旋结构之间静电相互作用的角向关联对超分子液晶长程有序形成的影响。溶液中的长程液晶有序由X射线小角散射来测量,螺旋管间的角向关联（角向旋转有序）由X射线中角散射来测量。小角散射测得的不同分子浓度的变化说明体系中有一个自由度处在窘组的状态,中角散射实验进一步证明角向关联的变化与小角的变化是一致的。结合理论预计的DAN体系中角向关联的构象和中心四方晶格的消光原理,我们提出了超分子多级结构中可能的角向旋转构象。In-situ小角散射跟踪溶液中四方有序的形成,说明具体的角向关联并不影响长程位置有序的形成,反而是角向关联由结晶过程来决定。

关键词： helical charge distribution azimuthal correlation X-ray scattering lyotropic liquid crystal

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