聚丙烯酰胺/聚异丙基丙烯酰胺互穿网络水凝胶的制备与性能

采用分步法用电子加速器辐射合成了聚丙烯酰胺(PAAm)/聚异丙基丙烯酰胺(PNIPAAm)互穿网络水凝胶,并考察了温度、pH值、离子强度对其溶胀性能的影响.研究表明:互穿水凝胶具有温度敏感性,且其体积相变与互穿网络中PAAm和PNIPAAm含量有关,随着网络中PAAm含量的增加水凝胶的体积相变趋于平缓,可以通过改变PAAm和PNIPAAm的组成比来控制水凝胶的体积相变行为.此外,互穿水凝胶还具有pH敏感性和一定的抗盐性.     

银离子对结冷胶/聚丙烯酰胺双网络水凝胶的增强作用

首先,以结冷胶(GG)为基体,丙烯酰胺(AAm)为单体,N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,通过"一锅法"制备GG/PAAm双网络水凝胶(GG/PAAm DN);然后将GG/PAAm DN浸泡在硝酸银溶液中制得Ag~+增强的GG/PAAm DN(GG-Ag~+/PAAm DN)。通过扫描电子显微镜、流变仪、原子吸收光谱仪、力学性能测试等手段研究了AAm、MBA用量及Ag~+对水凝胶流变性能、微观形貌、力学性能的影响。结果表明:与GG/PAAm DN相比,GG-Ag~+/PAAm DN的储能模量升高,力学性能明显增强,压缩强度由4.88 MPa增大到11.8 MPa,,断裂伸长率由236%增大到320%,断裂强度由0.1MPa提高到0.26MPa。抗菌实验表明GG-Ag~+/PAAm DN具有良好的抗菌性能。     

制备参数对聚乙烯醇水凝胶-玻璃基板摩擦行为的影响

采用不同方法制备了聚乙烯醇(PVA)水凝胶,研究了制备参数对水凝胶/玻璃摩擦体系的影响.结果表明,混合溶剂有利于凝胶均匀网络的形成,制备的凝胶强度较高;冷冻解冻次数的增加有利于PVA水凝胶强度的提高;超高相对分子质量聚氧化乙烯(PEO)的加入,可使PVA形成更为致密、均匀的网络,显著提高PVA水凝胶的模量(E).低滑动速率(v)时,高E的水凝胶具有较高的摩擦力(f),但易在较低v下形成流体动力润滑,使其在较高v(10-1~100m/s)时反而呈现出较低的摩擦力,该速率范围与人体正常行走时膝关节软骨的运动速率相当.PEO的加入可降低较高v时的f,而低v区f的降低与加入的PEO浓度有关.     

聚乙烯醇/羧甲基壳聚糖共混水凝胶的辐射合成及性能

采用电子加速器辐照法制备了聚乙烯醇(PVA)/羧甲基壳聚糖(CMCH)共混水凝胶;研究了PVA与CMCH的配比、辐照剂量、温度以及pH值对PVA/CMCH共混水凝胶性能的影响.实验发现,PVA与CMCH在辐照剂量为40 kGy、配比为w(PVA)/w(CMCH)=5/1的条件下可得到强度较好的PVA/CMCH共混水凝胶,该水凝胶具有一定的温度和pH敏感性:在5~20℃时具有较高的溶胀率,温度在20℃以上溶胀率较低;水凝胶在pH<4.0和pH>6.0时溶胀率均较大,而当pH为4.0~6.0时溶胀率较小.     

多孔PVA水凝胶的组成、形貌及泊松比等力学性能研究

制备了不同含量的纯聚乙烯醇(PVA)水凝胶和不同表面活性剂含量的多孔PVA水凝胶,采用数字散斑测量其泊松比,并使用电镜和显微镜观察其微观结构,探讨了纯PVA水凝胶与多孔PVA水凝胶组成、微观结构、泊松比、压缩模量和体积模量的变化及相互关系.研究发现,采用表面活性剂成孔,反复冷冻成型制备的闭孔结构水凝胶,其泊松比随应力应变增加而减小;随PVA含量增加而泊松比值减小;随表面活性剂含量增加,孔径变大,泊松比值减小.PVA水凝胶泊松比值与压缩模量和体积模量的比值成正比.     

冷冻/解冻制备的聚乙烯醇水凝胶的结构和流变性研究

研究了冷冻/解冻法制备的不同浓度(5wt%～25wt%)聚乙烯醇(PVA)水凝胶的结构和流变行为之间的关系.由XRD确定了凝胶中PVA的结晶度和晶粒尺寸.用应力流变仪研究了凝胶的流变行为,包括动态模量和蠕变等.在频率为1Hz和低应力的条件下,测量了凝胶的储能模量和损耗模量.在该试验条件下,PVA水凝胶的形变是完全可以回复的.低频率区和低应变区的储能模量随浓度增加而变大,但当浓度超过20wt%时,储能模量增加速率明显降低.由PVA水凝胶在1Hz时的储能模量和结晶度的数据,理论分析得到了形成PVA水凝胶的最低PVA浓度和最小结晶度.当PVA浓度低于15wt%时,储能模量主要由PVA的微晶控制,分子链间的氢键影响很小.通过低应变区储能模量的数值计算出了凝胶网孔尺寸的结构参数.同时对不同温度下PVA水凝胶的储能模量数据进行了标度分析.PVA水凝胶的蠕变行为显示,随浓度提高,凝胶的蠕变黏弹性由线性向非线性转变.     

PVA-PAMPS-PAA三元互穿网络型水凝胶的合成及其性能研究

以2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、丙烯酸(AA)以及聚乙烯醇(PVA)为原料,制备了PVA-PAMPS-PAA三元互穿网络型(T-IPN)水凝胶.红外分析表明,PVA与PAA以及PAMPS之间形成了较强的氢键,使得PVA分子上的C—O伸缩震动吸收峰移向了低波数处.X射线衍射以及电镜分析表明,当PVA用量较低时,PVA能均匀的穿插于凝胶网络中,形成完善的互穿网络结构,当PVA用量过高时,部分的PVA结晶而使得凝胶出现相分离.研究了该三元互穿网络型水凝胶的溶胀性能,结果表明,该水凝胶的平衡溶胀比在200至340之间,并且随着AA以及AMPS用量的增加,凝胶的溶胀速率以及平衡溶胀比均升高.该三元互穿网络型水凝胶在酸性溶液中和在碱性溶液中表现出截然不同的消溶胀性能;并且随着溶液pH的升高,凝胶在pH=9.0附近出现体积突变,表现出pH敏感性.通过研究T-IPN水凝胶的抗压缩性能发现,利用线型高分子、柔性高分子网络以及刚性高分子网络制备的三元互穿网络型水凝胶能在高溶胀比下保持较高的强度.溶胀比为180的T-IPN水凝胶,其最大抗压缩强度可达12.1 MPa.进一步研究发现,凝胶的组成以及溶胀比均对凝胶的抗压缩强度和压缩应变均存在较大的影响.     

溶致液晶作模板水凝胶的制备及其表征

以表面活性剂Brij 58溶致液晶(LLC)为模板, 采用光聚合的方法合成了结构规整的新型溶致液晶型聚丙烯酰胺(PAAm)水凝胶, 并对其结构、形貌和性能进行了研究. 扫描电镜结果表明活性剂Brij 58用量为10%～40%时, 可形成结构规整、孔径均一的LLC型水凝胶, 其孔径为1～2 µm, 约为普通水凝胶的1/40. 当Brij 58浓度大于50%时, 体系发生相分离, 此时合成的水凝胶含水量及孔隙率下降. 傅立叶变换红外光谱(FTIR)显示, LLC型水凝胶中羰基和氨基的红外吸收向低波数方向移动, 表明其中形成了大量的分子间氢键. 同时, LLC型PAAm水凝胶还保持了普通水凝胶的pH敏感性, 相同条件下, 其溶胀比大于普通水凝胶.     

PVA增强P(AAEA-co-AA)温度敏感性水凝胶的合成及其性能研究

以4-乙酰基丙烯酰乙酸乙酯(AAEA)、丙烯酸(AA)以及PVA为原料, 通过自由基溶液聚合法, 制备了PVA-P(AAEA-co-AA)半穿网络型(s-IPN)水凝胶. 红外分析表明, AAEA主要以烯醇式结构存在, 并且由于PAAEA, PAA以及PVA之间较强的氢键作用, 使得PAAEA以及PVA分子上的C-O伸缩振动吸收峰移向了低波数处. 电镜分析表明, PVA能贯穿于P(AAEA-co-AA)交联网络中, 从而有效阻碍凝胶的相分离|而XRD研究发现, 当PVA用量较少时, PVA能均匀的贯穿于凝胶网络中, 形成完善的互穿网络结构, 当PVA用量过高时, PVA不能有效地贯穿于聚合物交联网络中而出现结晶. 采用DSC对s-IPN水凝胶的体积相转变进行了研究, 结果表明, 该s-IPN水凝胶的体积相转变温度(VPTT)在54.0至57.8 ℃之间, 并且随着PVA用量的增加, 凝胶的VPTT逐渐升高. 研究了该s-IPN水凝胶的抗压缩性能, 结果表明, PVA与P(AAEA-co-AA)形成的半互穿网络结构能有效提高凝胶的抗压缩强度, 其最大抗压缩强度可达8.4 MPa. 对凝胶的温度敏感性研究发现, 当外界温度低于VPTT时, 凝胶能保持溶胀状态|而当温度高于VPTT时, 凝胶的平衡溶胀度迅速下降, 表现为温度敏感性.     

聚电解质盐三聚磷酸钠对聚乙烯醇凝胶的Hofmeister效应研究

聚乙烯醇(PVA)物理微晶水凝胶由于化学稳定性好、无毒、生物相容性好等特点，近年来成为物理微晶凝胶研究的模板聚合物。但其力学性能较差，如何提高凝胶的力学性能，拓展其应用范围一直是水凝胶领域的研究难点和热点。Hofmeister盐析效应是提升凝胶力学性能一种高效、绿色的制备手段，但之前的研究多集中在小分子无机盐对凝胶性能的影响，对聚电解质盐的盐析效应鲜见报道。本文研究了三聚磷酸钠(STPP)聚电解质对PVA凝胶性能的影响，系统比较了其与氯化钠及氢氧化钠处理的PVA凝胶；重点从微观形态和结晶结构两方面研究了聚电解质盐与小分子盐引起PVA凝胶的微观结构差异，并分析了结构与性能间的响应关系。聚电解质STPP处理的PVA凝胶薄膜应力达到了23 MPa,应变高达1 100%,断裂韧性(110 MJ/cm³),比纯水凝胶提升55倍之多，并兼具良好的阻燃性能。     

Surface Changes at Platinized Platinum Based Hydrogen Gas Electrodes Following Use in Highly Saline Aqueous Solutions

Platinized platinum based hydrogen gas electrodes, Pt(Pt)|H₂(g)|H⁺(aq), and silver‐silver chloride electrodes, Ag|AgCl|Cl^? (aq), make up the Harned cell, without transfer, working in the potentiometric mode at Cl^? concentrations and ionic strengths, I, below 0.1 mol kg^?1, for assigning primary pH values to reference pH buffer solutions. This work reports on experiments performed at higher I and Cl^? solutions up to 0.7 mol kg^?1, aiming at addressing seawater conditions with results of equally high quality. In the course of measurements, the occasional occurrence of highly unstable potentials denoted electrode malfunction; Pt metal surfaces observed by SEM/EDS and XRD exhibit strong Ag and Cl peaks corresponding to the presence of AgCl crystals deposited at both surfaces.     

以新型杯[6]衍生物为探针的银离子选择性电极研究

以新型杯芳烃衍生物 ( 5,1 1 ,1 7,2 3 ,2 9,3 5-六 [( 4-苯甲酸 )偶氮基 ]-3 7,3 8,3 9,40 ,41 ,42 -六羟基杯 [6 ]芳烃 )为探针构成 PVC膜离子选择性电极 ,发现该探针对银离子有选择性 ,该电极在 1 .0× 1 0 - 5～ 2 .0× 1 0 - 2 mol·L- 1范围内有典型的 Nernst响应。对常见碱金属、碱土金属和过渡金属离子有很好的选择性 ,而 Hg2 + 、Cr3 + 、Cs+、Na+、Fe2 +有一定程度的干扰 ;此电极稳定且重复性好 ,作为指示电极已成功地应用于 Na Cl滴定 Ag NO3 体系     

Anion-selective properties of alkali metal-free lead phosphate glasses containing silver chloride and their application in an ion-selective electrode

Alkali-free lead phosphate glasses containing silver chloride have been developed for anion responsive sensors. From measurements of the final glass compositions by electron probe microanalysis, it became clear that some of chloride ions in the glass bulk were not volatilized during the glass melting process. Compared with phosphate glasses containing silver oxide, the new glass electrodes containing silver chloride could respond more rapidly, although the response behaviour for anionic species were similar. From the electrode potential vs. time curve for the anionic species, the potential rapidly reached equilibrium when these concentrations varied from 10^?5 to 10^?2 M. The response times, t₉₅, to thiocyanate of the new glass electrode and the phosphate glass electrode containing silver oxide were 30 and 110 s, respectively. Moreover, the response time required for an initial potential change with a concentration jump of thiocyanate with the new glass electrode was found to be independent of the membrane thickness within about 2 mm and of the measuring temperature between 15 and 40°C. It is concluded that the diffusion process of species such as silver ion in the glass bulk does not take part in the initial part of the response behaviour.     

The microporous structure of silver/silver chloride electrodes and the implications for Harned cell operation

The stability of silver/silver chloride reference electrodes when moved between different electrolyte solutions is limited by the small amount of solution transferred. The time required for the Ag/AgCl electrode potential to stabilize has been shown to increase with electrode size in an empirical fashion. The results presented suggest the presence of a microporous structure in the electrodes that limits the rate at which traces of any previous solutions are diluted by any new solution environment. Operational implications for the stability and accuracy of the Harned Cell used as the primary standard for pH measurements and the certification of primary reference buffers are discussed. Presented to the CCQM Electrochemical Analysis Working Group, Paris, April 2004.     

Cyanide ion-selective electrodes based on thin electroplated membranes of silver chalcogenides: Part I. Membrane preparation and characterization

Cyanide-responsive ion-selective electrodes have been developed based on thin tellurium-doped silver selenide membranes electrodeposited on platinum substrates. The chemical composition of the electroplated film membranes could be expressed by the general formula Ag_2+δSe_1?xTe_x (where 0.2 < δ < 0.8 and 0.2 ? × ? 0.1). These electrodes exhibit a linear response in cyanide solutions with concentrations ranging from 10^?2 to 10^?6 M, with a slope of the electrode function of about 90 mV (pCN)^?1 (i.e., lower than the theoretically predicted double-Nernstian slope). These electrodes showed very stable behaviour during long-term investigation (several months). The conditions for the electrochemical preparation of cyanide-responsive silver chalcogenide membranes are discussed both from theoretical and practical points of view. X-ray diffraction, energy-dispersive x-ray fluorescence microanalysis (EDAX) and scanning electron microscopy (SEM) were used to examine the membrane composition, structure and surface morphology.     

A comparative study of four 20-membered N2S4-crown ethers as ionophores for polymeric membrane silver

Four 20-membered N2S4-monoazathiacrown ethers have been synthesized and explored as neutral ionophores for Ag+-selective electrodes.Potentiometric responses reveal that the flexibility of the ligands has great effect on the selectivity and sensitivity to Ag+ions.The electrode based on ionophore 9,10,20,25-tetrahydro-5H,12H-tribenzo[b,n,r][1,7,10,16,4,13]tetrathiadiaza cycloicosine6,13-(7H,14H)-dione(C)with 2-nitrophenyl octyl ether(ο-NPOE)as solvent in a poly(vinyl chloride)(PVC)membrane matrix shows a measuring range of 1.0 × 10-6 to 1.0 × 10-3 mol/L with a Nemstian slope of 54.9 ± 0.3 mV/decade.This electrode has high selectivity for Ag+with negligible interference from many other cations and can be used in a wide pH range of 3.6-9.2.     

纳米银自组装电极的制备及对高氯酸二茂铁的电化学响应

采用自组装的方法制备了纳米银粒子修饰金电极,并运用循环伏安法、交流阻抗谱探讨了该电极的电化学特性.研究了高氯酸二茂铁在该修饰电极上的直接电化学行为.实验结果表明,高氯酸二茂铁在该修饰电极上具有良好的电流响应.用示差脉冲法测定高氯酸二茂铁,其氧化峰电流与浓度在4.0×10-6～5.0×10-4 mol/L范围呈良好线性关系,线性方程为:Ip(μA)=0.0236c(μmol/L)-0.0975,线性相关系数为0.9982,检出限为2.3×10-7 mol/L(信噪比为3).     

A comparative study of four 20-membered N2S4-crown ethers as ionophores for polymeric membrane silver selective electrodes

<正>Four 20-membered N_2S_4-monoazathiacrown ethers have been synthesized and explored as neutral ionophores for Ag~+-selective electrodes.Potentiometric responses reveal that the flexibility of the ligands has great effect on the selectivity and sensitivity to Ag~+ ions.The electrode based on ionophore 9,10,20,25-tetrahydro-5H,12H-tribenzo[b,n,r][1,7,10,16,4,13]tetrathiadiaza cycloicosine 6,13-(7H,14H)-dione(C) with 2-nitrophenyl octyl ether(o-NPOE) as solvent in a poly(vinyl chloride)(PVC) membrane matrix shows a measuring range of 1.0×10~(-6) to 1.0×10~(-3) mol/L with a Nernstian slope of 54.9±0.3 mV/decade.This electrode has high selectivity for Ag~+ with negligible interference from many other cations and can be used in a wide pH range of 3.6-9.2.     

硫脲与多种阴离子共吸附行为的拉曼光谱研究

在电化学的研究与应用中，因硫豚（1’川可用作电镀添加剂、金属的缓蚀剂和一些电极反应的催化剂［‘］而受到人们的广泛重视．早在三十年代初就开展了有关水溶液和非水溶液体系中硫豚在不同金属电极表面的吸附行为的研究【’，’］、随着光谱电化学技术的建立、发展和不断完善     

Analysis of the differential capacity at the silver / lithium perchlorate aqueous solution interface

Analysis of the differential capacity of ideally polarized Ag electrodes without specific adsorption is presented. The capacity was measured for three crystal faces of Ag [(111), (100) and (110)] and for polycrystalline Ag in aqueous solutions at different concentrations of LiClO₄. The inner layer contribution C _i was analysed for all the systems studied according to Grahame's concept. Moreover, using the procedure proposed by Amokrane and Badiali, several contributions to C _i, i.e. the metal (C _m), the solvent (C _s) and dipole orientation (C _dip), were calculated. The influence of the kind of crystal face of the Ag electrode on the values of these contributions is discussed. Received: 21 May 1999 / Accepted: 19 November 1999