Changes in polyvinylpyrrolidone coil dimensions by complexation with organic anions: effect of chain length

Changes in polyvinylpyrrolidone (PVP) coil dimensions by complexation with small organic anions were studied by dilure solution viscometry Intrinsic viscosity provides a convenient measure of the dimensions assumed by a flexible polymer chain in solution as a result of interactions with all components in its environment. Molecular interactions between PVP and sodium benzoate and salicylate were investigated over a range of low concentrations of each anion, from 2.5 to 90 mM, and as a function of five molecular weight grades of PVP. This study showed that both contraction and expansion of polymer coils were sensitive to the concentration and chemical structure of the cosolute. In addition, at high anion concentrations changes in polymer conformation by complexation were dependent on both the chain length of PVP and charge density of bound anions through excluded volume effects. Experimental results demonstrating these observations are presented in a three-dimensional surface plot of intrinsic viscosity ratio, polymer size, and anion concentration. A distinct local minimum in the surface plane was exhibited for each cosolute.     

聚合物对非离子十二烷基聚氧乙烯聚氧丙烯醚浊点的影响

测定了水溶性高分子聚乙二醇(PEC1000、PEG2000、PEG6000)和聚乙烯吡咯烷酮(PVP-K30、PVP-K90)对三种非离子表面活性剂十二烷基聚氧乙烯聚氧丙烯醚C12H25O(EO)m(PO)nH(LS36,m=3,n=6;LS5,m=4,n=5;LS54,m=5,n=4)浊点的影响.结果表明,聚乙二醇(PEG)可使三种表面活性剂水溶液浊点降低;而聚乙烯吡咯烷酮(PVP)随其浓度增加,表面活性剂溶液浊点先升高然后又下降;浊点下降程度与聚合物浓度和分子量有关.     

SDS与PVP对碘化银溶胶稳定性的影响

研究了SDS、PVP及二者的混合物对AgI溶胶稳定性的影响。SDS主要通过表面活性负离子在AgI质点表面上的吸附使ζ电势升高,提高溶胶的稳定性。低浓度的PVP使AgI溶胶敏化,高浓度时又通过吸附层的空间稳定效应使其稳定。在PVP与SDS的混合溶液中,AgI溶胶的稳定性显著增加。根据PVP与SDS在固液界面上的相互作用讨论了这一增效作用。     

聚乙烯吡咯烷酮/黏土纳米复合水凝胶的制备及表征

通过原位聚合法, 以N-乙烯基吡咯烷酮(NVP)和黏土为原料制备了生物相容性有机-无机纳米复合水凝胶, 通过黏度、透明度、XRD及力学性能等研究了水凝胶体系的性质和微观结构. 结果显示, 单体NVP通过氢键作用吸附于黏土粒子周围, 从而有效阻止黏土颗粒的凝胶化; 通过对聚合过程透明度的变化、凝胶吸水性能以及拉伸力学性能分析发现, 其反应机理与丙烯酰胺类体系不同. 黏土颗粒间网链较短, 导致吸水率和断裂伸长率明显低于聚丙烯酰胺/黏土体系, 但模量和拉伸及压缩强度明显增加; XRD结果显示, 干凝胶中黏土颗粒呈有序排列, 随着黏土含量增加, 黏土粒子间距变小, 而在含水复合凝胶中, 黏土颗粒以剥离态均匀分散; 对于凝胶表面的细胞形态观察初步检验了此类纳米复合凝胶的细胞相容性, 未观察到显著不良影响.     

PVP/HEC分子间缔合作用机理探讨

通过粘度、紫外光谱、红外光谱和DSC谱的测定,探讨了PVP/HEC分子间的缔合机理.结果表明,PvP/HEC复合体系相对于单一体系产生了粘度的负协同效应,NaCl的加入使单一体系和复合体系的粘度均下降;在紫外可见吸收光谱中,PVP/HEC复合体系的最大吸收波长λmax相对于PVP、HEC各自的λmax都发生红移;PVP/HEC复合物的红外光谱在2370 cm-1出现新的吸收峰;DSC谱中复合物的峰温高于简单混合物,而其焓变低于简单混合物,这一切均证明HEC与PVP之间未发生疏水缔合,而是HEC的羟基与PVP的羰基之间通过氢键缔合成复合物,复合物的分子链排列较为紧密.     

聚乙烯吡烙烷酮修饰碳糊电极-双通道毛细管电泳安培法测定环境中的硝基酚

建立了几种硝基酚的聚乙烯吡烙烷酮修饰碳糊电极-双通道毛细管电泳安培检测的新方法.采用双工作电极和两台伏安仪,将样品的检测电位分别设定在氧化电位(+0.5V_vs.SCE)和还原电位(-1.4V_vs.SCE),在一个检测池中同时获得所有样品的氧化和还原信息,以还原电流和氧化电流值之比(Nc=ir/io)作为定性依据,对样品的纯度进行确证.通过优化工作电极、检测电位、缓冲溶液、β-CD和乙醇浓度等实验参数,实现了几种硝基酚的分离检测,同时采用样条小波最小二乘法对样品数据信号进行处理,并将此法应用于实际样品的测定.     

PVP-b-PLA修饰Fe_3O_4磁性纳米粒子的制备与表征

通过硅烷偶联剂与Fe3O4磁性纳米粒子偶合在其表面引入C C端基,进一步与N-乙烯基吡咯烷酮(NVP)加成聚合制备含端羟基PVP包裹的磁体,再引发丙交酯(LA)开环聚合制得PVP-b-PLA修饰的Fe3O4纳米粒子.通过XRD、GPC、FTIR、SEM、TG、DSC和激光粒度仪等,对产物进行分析和表征,结果表明,纳米Fe3O4与PVP以及PVP与PLA之间均为化学键联,PVP和PLA是以嵌段共聚物的形式存在且两者之间存在明显的微相分离,纳米Fe3O4表面聚合物包覆率为35%,厚度约13 nm.此外,该PVP-b-PLA包覆的磁性纳米粒子比饱和磁化强度为53 emu/g,与未包覆相比下降约25%.     

Sonochemical synthesis of silver nanoparticles coated copper wire for low-temperature solid state bonding on silicon substrate

The rapid and efficient preparation of silver-copper wire by sonochemical assisted reduction method for high antioxidant performance and low melting temperature. Good ohmic contact between Ag-Cu wire and Si substrate can be achieved at temperature as low as 320℃.     

Electro-oxidation of Ascorbic Acid on PVP-stabilized Graphene Electrode

Polyvinylpyrrolidone-stabilized graphene(PVP-graphene) was synthesized and investigated as a modifier for the determination of ascorbic acid(AA).With PVP acting as stabilizer and dispersant,the resulting PVP-graphene material could disperse well into water.And the PVP-graphene modified glassy carbon electrode(PVP-graphene-GCE) showed an obvious electrocatalytical activity toward the oxidation of AA in a phosphate buffer solution(PBS,pH=7.0) with an oxidation potential of AA at 0.052 V vs.Ag|AgCl(sat.KCl).The calibration curve for AA was linear in a concentration range from 1.0×10-5 to 5.0×10-4 mol/L with a correlation coefficient of 0.9998.And the detection limit was found to be 1μmol/L.During the oxidation of AA,the π-π interaction of graphene plane with conjugated hexenoic acid-lactone in AA molecules might play a key role.As a result,an obvious decrease of overpotential was achieved at such a PVP-graphene electrode through a possible adsorption/enrichment process,which will probably trigger potential applications for the electroanalysis of some aromatic and heterocyclic compounds.     

Aqueous-phase exfoliation of graphite in the presence of polyvinylpyrrolidone for the production of water-soluble graphenes

Treatment of crystalline graphite fine powder with an aqueous solution of the harmless and versatile substance polyvinylpyrrolidone under sonication results in water-soluble, polymer-protected graphene single layers without oxidation or destruction of the sp² character of the carbon core. The liquid-phase extraction of graphene monolayers was evidenced by TEM and AFM techniques, while their graphitic character was checked with Raman spectroscopy. Besides PVP, the water-soluble biopolymers albumin and sodic carboxymethylcellulose were also employed successfully in the aqueous-phase exfoliation of graphite, thereby supporting the generic character of the present method using a variety of suitable polymeric extractants.