AA/AMPS水凝胶的交联聚合反应动力学及其机理

Crosslink polymerization kinetics of poly(acrylic acid-co-2-acrylamido-2-methylpropane sulfonic acid),AA/AMPS hydrogels, was investigated by using dilatometry in the presence of sodium persulfate as initiator and N,N'-methylene bis(acrylamide) as crosslinker. It was found that the reaction for the crosslink polymerization ofAA/AMPS hydrogels had orders of 0.58, 1.14, and 0.86 with respect to the initiator, AMPS, and AA, respectively.From the Arrhenius plots, the activation energy of the crosslink polymerization was found to be about 140 and 89 kJ.mol1 in the presence and absence of the crosslinker, respectively, in the temperature range from 45 to 65 ℃. It was noted that the crosslinker had effects on the reaction order of the initiator and the activation energy due to the formation of cross-linked networks, which was verified by Fourier transfer infrared (FTIR) spectrum. To further confirm the influences of the cross-linked network structure on kinetic parameters of the erosslink polymerization, a mechanism was proposed, which highlights the different termination routes between free radical polymerization and crosslink polymerization. These results suggest that dilatometry provides a convenient tool for crosslink polymerization study, and confirm that the cross-linked networks are formed in the crosslink polymerization.     

溶胶-凝胶制备ZnTiO3粉体及其表征

以钛酸丁酯、硝酸锌、乙醇和乙酸为原料,采用溶胶-凝胶工艺制备了纯净六方ZnTiO₃粉体.利用TG-DTA、XRD和FE-SEM等检测手段对前驱体凝胶的热分解、相变以及粉体结构和形貌进行研究.结果表明:ZnTiO₃凝胶前驱体热分解分3个阶段,第1阶段在262 ℃以下主要为有机物的分解过程;第2阶段为262~700 ℃,此时的粉体为非晶态立方相ZnTiO₃;六方ZnTiO₃相的生成发生在第3阶段700~900 ℃.获得纯净六方ZnTiO₃相的较为合适的工艺条件为:前驱体在60 ℃进行溶胶,然后在700~900 ℃煅烧2 h.      

聚酰亚胺气凝胶材料的制备及其应用

聚酰亚胺（polyimide，PI）由于具有较好的力学性能、优异的耐化学性、良好的介电性能和高温稳定性，被认为是一种应用前景广泛的高温工程聚合物。聚酰亚胺的各类制品如薄膜、涂料、胶黏剂、光电材料、先进复合材料、微电子器件、分离膜以及光刻胶等已经被广泛应用于电子信息、防火防弹、航空航天、气液分离以及光电液晶等领域。聚酰亚胺气凝胶（PIA）是由聚合物分子链构成的相互交联的三维多孔材料，结合了聚酰亚胺和气凝胶的优异性能，使其不但具有聚酰亚胺的优异特性，而且具有气凝胶的轻质超低密度、高比表面积、低导热系数以及低介电常数等突出特点，因此聚酰亚胺气凝胶材料迅速发展成为性能优异的有机气凝胶之一，并且在航空航天、电子通讯、隔热阻燃、隔音吸声以及吸附清洁等领域展示出广阔的应用前景。鉴于该材料的这些特质，本文对聚酰亚胺气凝胶的制备方法、影响因素（溶剂效应、单体结构和固含量）以及应用进行了论述，并对聚酰亚胺气凝胶材料的未来发展进行了展望。      

凝胶限域制备CdS/SiO2及其光催化产氢性能研究

利用凝胶限域—阴离子交换法制备了CdS/SiO2复合材料,采用XRD、SEM、HRTEM、BET、UV-vis和GC对其结构、物性及可见光催化产氢性能进行了表征,并与水热法及常温沉淀法制备的CdS纳米粒子进行了性能比较。结果表明,利用SiO2凝胶限域制备的CdS粒径为3~7 nm,CdS/SiO2比表面积可达68.99 m^2/g,其吸收带边红移至605 nm。在无助催化剂的条件下,CdS/SiO2的光催化产氢速率达到1925.29μmol/(h·g),分别为水热法及常温沉淀法的47倍和2.3倍,且光催化循环稳定性更优。     

溶胶-凝胶法制备TiO2/硅藻土复合材料及其光催化性能

采用焙烧、酸洗等工艺预处理硅藻土，以改性硅藻土和钛酸丁酯为前驱体，采用溶胶-凝胶法制备TiO₂/硅藻土复合材料，采用XRD、SEM、FT-IR、TG等手段对其进行分析表征，以甲基橙为降解对象考察其光催化性能。结果表明：硅藻土表面均匀负载着锐钛矿型的二氧化钛，晶粒尺寸为35.76 nm。负载比2∶1、pH为>2～3、焙烧温度500℃制备的TiO₂/硅藻土复合材料的光催化性能最好，热稳定性良好。当TiO₂/硅藻土复合材料投入量为1 g/L,对60 mL(10 mg/L)的甲基橙溶液60 min内的降解率达到92%。     

TiC_p/30CrNi4Mo复合材料的制备及其摩擦磨损性能

采用高能球磨与热压相结合的方法制备含体积分数30%TiC增强颗粒的30CrNi4Mo复合材料,观察复合材料的显微组织、颗粒分布情况,检测复合材料的力学性能,并探讨复合材料在不同状态下的摩擦磨损行为。结果表明:50 MPa压力下,1 100℃热压烧结获得的复合材料中TiC颗粒较均匀地分布在基体中,与基体结合牢固,基体为珠光体、铁素体以及少量残余奥氏体;复合材料相对密度达97.6%,密度仅为6.83 g/cm3,抗拉强度达1 083MPa,伸长率为1.0%,硬度为53 HRC;高含量TiC颗粒的加入可极大提高TiCp/30CrNi4Mo复合材料的耐磨损性能,干摩擦和油摩擦条件下都表现出了优异的耐磨损性能,且在高速高载荷下显示了更为显著的优势,200 N载荷下400 r/min干摩擦30 min,TiCp/30CrNi4Mo复合材料的质量磨损量仅为铸态30CrNi4Mo材料的1/16左右;400 N载荷下200 r/min干摩擦30 min,TiCp/30CrNi4Mo复合材料的质量磨损量仅为30Cr Ni4Mo的1/10左右。干摩擦时载荷增加,TiCp/30Cr Ni4Mo复合材料的摩擦因数先上升后下降,随滑动速度增加,摩擦因数减小。干摩擦时,在不同载荷和滑动速度下,TiCp/30CrNi4Mo复合材料主要表现为轻微的磨粒磨损,显示出良好的耐磨损性能。     

水雾化制备FeSiCr软磁粉末磁性能研究

采用水雾化工艺制备FeSiCr软磁合金粉末,经筛分合批后制成粒径(D50)5～40μm的样品.研究了不同粒径FeSiCr软磁粉末对磁性能的影响,为产品应用提供指导性实验.研究结果表明,随着粉末粒径的增大,粉心的磁导率逐渐增大,在100～1000 kHz的频段范围内,磁导率衰减幅度小于5％,具有较好的频率特性.随着粉末粒...     

尿素水热法制备Mg/Al/Fe多元水滑石及其阻燃性能研究

采用尿素水热法制备出形貌规整的层状镁铝铁氢氧化物（MgAlFe-CO3LDHs）。通过XRD、SEM、粒度分析表明,MgAlFe-CO3LDHs粉体具有较高的结晶度、较为规整的形貌特征和较窄的粒度分布。采用熔融共混法制备了不同配比的EVA复合材料,系统研究了不同元素组分对EVA阻燃性能的影响。实验结果表明LDHs的阻燃作用优于氢氧化镁和氢氧化铝的混合物。MgAlFe-CO3LDHs系列样品的性能优于MgAl-CO3LDHs,不同元素有不同的阻燃作用模式,含Fe的LDHs作用可能涉及气相自由基捕捉及能量阻隔作用。适当的引入Fe可以明显的提高材料的UL94级别、高温稳定性并减少CO释放量。     

金刚石/硅复合材料的制备和导热性能

为探索新型热沉用散热材料,采用高温高压方法烧结制备了金刚石/硅复合材料,并研究了金刚石大小粒度混粉、金刚石含量、渗硅工艺以及金刚石表面镀钛对复合材料的致密度和导热性能的影响.结果表明:在大粒度金刚石粉中掺入小粒度金刚石粉、渗硅和金刚石表面镀钛处理都可提高金刚石/硅复合材料的致密度和热导率;随着金刚石含量增大,复合材料热导率提高;其中75/63μm镀钛金刚石颗粒与40/7μm金刚石颗粒的混粉,当混粉质量分数为95%时,在4～5GPa、1400℃高温高压渗硅烧结,金刚石/硅复合材料的热导率可高达468.3W·m^-1·K^-1.     

铜/钛双金属复合管的热旋锻制备及其界面组织性能

铜/钛双金属复合管兼具铜的导热性和钛的耐海水腐蚀性,是海军舰船、滨海电站的各类海水管路和蒸汽管路系统理想材料。本文采用热旋锻方法成功制备了界面结合性能良好的铜/钛双金属管,重点研究了变形温度、道次变形量等重要工艺参数对管材结合性能的影响,明确了旋锻过程中双金属的结合机制。研究结果表明,在旋锻温度600~900℃,道次变形量45%~70%的制备工艺条件下可成功制备界面冶金结合、结合性能优异的铜/钛双金属复合管,且旋锻温度越低,所需道次变形量越大。在旋锻温度800℃,变形量54.6%条件下制备的铜/钛复合管的平均界面结合强度为13.3 N·mm~(-1),最大剥离强度可达26.5 N·mm~(-1),整管抗拉强度为303.1 MPa,断后伸长率为23.5%,复合界面在极大的压扁弯曲变形下仍不会分层,变形协调性优异。分析认为热旋锻方法制备双金属复合管的界面结合机制为:两金属表面碰撞接触的瞬间氧化膜因表层金属的流动而破裂,新鲜金属基体互相咬合,实现物理结合,同时界面两侧的原子在高温热激活作用下产生相互扩散,达到冶金结合。     

Preparation and stability testing of a hydrogel for topical analgesia

With the commercial availability of a cream (EMLA) containing a eutectic mixture of local anaesthetics, 2.5% (w/w) lidocaine and 2.5% (w/w) prilocaine, effective topical anaesthesia of the intact skin is possible without the need for subcutaneous injections or exposure to high concentrations of local anaesthetics. In our hospital a topical anaesthetic product was designed for the same purpose. The home-made product contains a eutectic mixture of a local anaesthetic (5% w/w) and l-menthol (1% w/w). Prilocaine was used as the local anaesthetic because it is known for its safety and its well investigated analgesic effects. The eutectic mixture of prilocaine and l-menthol was mixed with a carbopol hydrogel (1% w/w). Preliminary testing of this anaesthetic hydrogel in our hospital has yielded satisfactory results. The anaesthetic hydrogel was found to be stable after at least 3 months' storage at ambient temperature.     

Preparation of hydrogel microspheres by coacervation of aqueous polyphosphazene solutions

A new method of preparing ionically cross-linked polyphosphazene hydrogel microspheres which enables effective control over microsphere size distribution has been developed. The synthesized microspheres can be used in protein delivery and, especially, as vaccine delivery vehicles. A new technique utilizes the ability of aqueous solutions of poly[di(carboxylatophenoxy)phosphazene] (PCPP) to form coacervate microdroplets upon addition of sodium chloride. These microdroplets are then stabilized via polymer cross-linking with calcium ions. It was demonstrated that the method enables efficient microencapsulation of proteins. It was also shown that microsphere size can be controlled through the manipulation of microencapsulation conditions. The process is simple, highly reproducible and generates microspheres with a narrower microsphere size distribution, compared to the previous technologies.     

Growth factor release from amylopectin hydrogel based on copper coordination

This paper describes a biodegradable hydrogel matrix releasing basic fibroblast growth factor (bFGF) on the basis of protein metal coordination with the protein drug. The biodegradable hydrogel was prepared from amylopectin by its crosslinking with ethylene glycol diglycidyl ether, followed by introduction of diethylenetriaminepentaacetic acid (DTPA) residues for copper chelation. When bFGF was incorporated into the DTPA-introduced amylopectin hydrogel after chelation with Cu2+, an insignificant amount of bFGF was released from the hydrogel in buffered solution, in contrast to that without Cu2+ chelation. An increased ionic strength in the solution did not affect the bFGF release, indicating the occurrence of coordinate bonding of bFGF to the DTPA-introduced hydrogel through Cu2+ chelation. An implantation study with 125I-labeled amylopectin hydrogels demonstrated that they underwent degradation in the back subcutis of mice. Cu2+ chelation of hydrogels enabled bFGF to remain in the mouse back for a long time period, irrespective of DTPA introduction. However, DTPA residues were necessary to induce significant neovascularization by the Cu2+-chelating hydrogels incorporating bFGF. The DTPA-introduced amylopectin prevented Cu2+-induced deactivation of bFGF, again in marked contrast to DTPA-free amylopectin. It was concluded that biologically active bFGF could be incorporated to DTPA-introduced amylopectin through Cu2+ chelation in a stabilized state and was released as a result of hydrogel biodegradation, resulting in prolonged neovascularization.     

Molecular cloning of a DEG/ENaC sodium channel cDNA from human testis

The number of members of the recently defined DEG/ENaC sodium channel superfamily is increasing. Their importance in Na transport, taste perception, acid sensing, and mechanotransduction has been implicated. We have cloned a new member of this superfamily from human testis, which was named hTNaC1 (for human testis sodium channel 1). The hTNaC1 has 532 amino acid residues with two hydrophobic transmembrane domains. It has the highest identity (82%) with a rat H(+)-gated Na channel specific for sensory neurons (DRASIC) and a low identity (29%) with an epithelial isoform (alpha-ENaC) of this superfamily. Northern blot of human tissues revealed its selective expression in testis (7 kb) and absence in other tissues. The identification of a new member of Na channel specifically expressed in testis will expand the role of this channel family to the reproduction physiology.     

Electrophysiological and biochemical evidence that DEG/ENaC cation channels are composed of nine subunits

Members of the DEG/ENaC protein family form ion channels with diverse functions. DEG/ENaC subunits associate as hetero- and homomultimers to generate channels; however the stoichiometry of these complexes is unknown. To determine the subunit stoichiometry of the human epithelial Na+ channel (hENaC), we expressed the three wild-type hENaC subunits (alpha, beta, and gamma) with subunits containing mutations that alter channel inhibition by methanethiosulfonates. The data indicate that hENaC contains three alpha, three beta, and three gamma subunits. Sucrose gradient sedimentation of alphahENaC translated in vitro, as well as alpha-, beta-, and gammahENaC coexpressed in cells, was consistent with complexes containing nine subunits. FaNaCh and BNC1, two related DEG/ENaC channels, produced complexes of similar mass. Our results suggest a novel nine-subunit stoichiometry for the DEG/ENaC family of ion channels.     

Coupled influence of substratum hydrophilicity and surfactant on epithelial cell adhesion

The influence of substratum surface hydrophilicity and of a surfactant on human epithelial cell adhesion and protein adsorption was investigated. Therefore, tissue culture grade polystyrene (TCPS) and bacteriological grade polystyrene (BGPS) substrata were treated with different media, with or without Pluronic F68 [a poly(ethylene oxide) and poly(propylene oxide) triblock copolymer surfactant], and with or without type I collagen as a typical extracellular matrix protein. The conditioned substrata were submitted to XPS analysis and assayed for cell adhesion by inoculating Hep G2 cells in a chemically defined nutritive medium. The presence of collagen at the substratum surface is required to obtain attachment and spreading of Hep G2 cells. With PS substrata, treating with a solution of collagen does not promote cell adhesion if the solution contains Pluronic; XPS data show that this is due either to prevention of collagen adsorption or to its desorption by rinsing. With less hydrophobic TCPS substrata, the presence of Pluronic in the conditioning solution does not preclude cell adhesion, nor collagen adsorption. The effect of BGPS and TCPS substrata on Hep G2 cell adhesion is thus mediated by the presence of a surfactant that affects the adsorption of collagen.     

Selective adsorption of uranyl ion on ion-imprinted chitosan/PVA cross-linked hydrogel

An interpenetration network (IPN) ion-imprinting hydrogel (IIH) was synthesized using uranyl ions as template for adsorption and removal of uranyl ions from aqueous solutions. The IIH was obtained via cross-linking of blended chitosan/polyvinyl alcohol (PVA) using ethylene glycol diglycidyl ether (EGDE). The ability of the IIH to adsorb and remove uranyl ions from aqueous solutions was assessed using a batch adsorption technique. The maximum adsorption capacity was observed in the pH range of 5.0-6.0. The adsorption process could be well described by both the Langmuir and Freundlich isotherms and the maximum adsorption capacity calculated from Langmuir equation was 156 mg/g. Equilibrium was achieved within 2 h. The kinetic data, obtained at optimum pH 5.0 could be fitted with to a pseudo-second order equation. The selectivity coefficient of uranyl ion and other metal cations on IIH indicated an overall preference for uranyl ions which was much higher compared with the non-imprinted hydrogel. This suggests that the IIH is a promising sorbent material for the selective removal of uranyl ions from aqueous solutions.     

PCL微/纳米纤维弹性性能在弯曲实验中的尺度效应研究

介绍了一种聚乙内酯(PCL)微/纳米纤维在弯曲实验中弹性性能的尺度效应模型。该模型是基于非局部理论的一种考虑非局部效应的微尺度模型,通过该模型可以计算出纤维材料的弹性性能在弯曲变形中的两种尺度效应:一种跟纤维的直径相关(D-SD),另外一种跟纤维的长度相关(L-SD)。采用原子力显微镜对PCL微/纳米纤维进行测试,对比PCL微/纳米纤维的三点弯曲实验数据与理论模型的计算结果,说明该模型可以解释纤维弹性性能的尺度效应,并且也适用于其他高分子纤维材料的微尺度弹性力学性能分析。     

Characterization and assessment of a novel poly(ethylene oxide)/polyurethane composite hydrogel (Aquavene) as a ureteral stent biomaterial

Although endothelium-derived hyperpolarizing factor (EDHF) activity has been demonstrated in arteries from various species, EDHF has not been chemically identified, nor its mechanism of action characterized. To elucidate this mechanism, we tested the effect of EDHF on large-conductance Ca2+-activated K+ (K(Ca)) channels in porcine coronary artery smooth muscle cells. By using a patch-clamp technique, single-channel currents were recorded in cultured smooth muscle cells; the organ bath also contained a strip of porcine coronary with endothelium, which served as the source of endothelium-derived relaxing factor(s) including EDHF. Exposure of endothelium to 10(-6) M bradykinin activated K(Ca) channels in cultured smooth muscle cells in cell-attached patches. When the experiment was performed in the presence of 10 microM indomethacin and 30 microM N(G)-nitro-L-arginine (L-NNA), which block the generation of prostaglandin I2 (PGI2) and NO, respectively, K(Ca) channel activity was stimulated by bradykinin, indicating the direct involvement of EDHF in K(Ca) channel stimulation. Neither 10 microM methylene blue nor 25 microM Rp-cAMPS inhibited bradykinin-induced K(Ca) channel activity. In inside-out patches, the addition of bradykinin to the solution was without effect on K(Ca) channel activation. However, in the presence of 0.5 mM guanosine triphosphate (GTP) and 1.0 mM adenosine triphosphate (ATP) in the bath solution, K(Ca) channels was activated by bradykinin. In outside-out patches, the addition of bradykinin also increased K(Ca) channel activity, when GTP and ATP were added to the pipette solution. The addition of GDP-beta-S (100 microM) in the cytosolic solution completely blocked the activation K(Ca) channels induced by bradykinin in inside-out and outside-out patches. Pretreatment with 30 microM quinacrine, a phospholipase A2 inhibitor, or 3 microM 17-octadecynoic acid (17-ODYA), a cytochrome P450 inhibitor, in addition to indomethacin and L-NNA, abolished bradykinin-stimulated K(Ca) channel activity in cell-attached patches. Both 14,15-epoxyeicosatrienoic acid (EET) and 11,12-EET increased the open probabilities of K(Ca) channels in cell-attached patches. These results suggest that EDHF, released from endothelial cells in response to bradykinin, hyperpolarizes smooth muscle cells by opening K(Ca) channels. Furthermore, our data suggest that EDHF is an endothelium-derived cytochrome P450 metabolite of arachidonic acid. The effect of EDHF on K(Ca) channels is not associated with an increase of cAMP and cGMP. The activation of K(Ca) channels appears to be due to the activation of GTP-binding protein.     

CaF2--SiO2型硅传感器辅助电极的制备及其定硅性能

以CaF₂＋SiO₂作为硅传感器辅助电极材料,将其均匀涂覆于ZrO₂（MgO）固体电解质表面,在高纯Ar气保护下,1400℃焙烧30min制备得到定硅传感器.利用X射线衍射仪、扫描电子显微镜以及能量色散谱仪系统研究了制备条件对于焙烧后形成的辅助电极膜层组成、物相和微观形貌的影响.膜层中不存在CaF₂,而是以SiO₂固体颗粒、CaO·MgO·2SiO₂固溶体及ZrSiO₄为主.另外,探讨了辅助电极膜层中物相的变化对于膜层黏结性以及定硅性能的影响.在1450℃下对铁液中硅含量进行测试,传感器响应时间在10s左右,稳定时间在20s以上,而且传感器的重复性也很理想.当铁液中硅质量分数在0.5%~1.5%时,硅传感器测量值与化学分析法分析值相吻合.