凝胶网络中溶剂性质的分子动力学模拟

本文利用分子动力学(MD)方法模拟了三种不同结构的凝胶网络系统,对系统的压力、溶剂的自扩散系数以及溶剂在凝胶不同区域的密度分布等进行了考察。模拟结果表明,被吸收进入凝胶网络的溶剂的性质与纯溶剂的性质有很大的差别,但凝胶结构的不均匀性对凝胶网络中溶剂的性质几乎没有什么影响。     

基于定向冷冻超双疏NFC气凝胶的构筑

以纳米纤维素(NFC)为原料,分别以纯水和水与二甲基亚砜混合溶剂(H₂O-DMSO)为分散介质通过定向冷冻的方式使NFC悬浮液凝固,经冷冻干燥和化学气相沉积后得到具有超双疏性能NFC气凝胶。接触角测试分析表明：在一定浓度范围内,NFC气凝胶接触角随着NFC浓度的增加而增加;而以H2O-DMSO为溶剂制备的NFC气凝胶(FNDA-Ds)较同NFC浓度下纯水溶剂制备的样品接触角明显增大,且当NFC浓度为2%(wt)时,包括水、乙二醇、甘油、蓖麻油和十六烷在内的各液体接触角均达150°以上,表明冷冻干燥过程中DMSO的存在优化了气凝胶表面的纳/微多级粗糙结构,显著提升了其疏液性能。     

毛竹纳米纤丝化纤维素球形气凝胶的制备和表征

以毛竹(Phyllostachys heterocycla cv.Pubescens)为原料,采用落球法制备纳米纤丝化纤维素(NFC)球形水凝胶,溶剂置换和超临界CO2干燥后得到了NFC球形气凝胶。通过透射电子显微镜(TEM)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)和BET对NFC球形气凝胶的微观形貌、化学态、结晶结构和孔隙结构进行表征分析。研究结果表明,NFC水凝胶和气凝胶均为球形,其化学组成和结晶结构均与天然纤维素一致,NFC气凝胶的骨架通过丝状纳米纤丝化纤维素缠绕和聚集形成三维网络结构,NFC气凝胶具有较高的比表面积和孔隙体积,分别为173 m2/g和0.62 cm3/g。     

制备树脂基RF/RDX含能材料的溶剂选择研究

间苯二酚-甲醛气凝胶(RF)是一种重要的树脂材料,以RF作为骨架的纳米复合含能材料RF/RDX兼具有含能材料、纳米材料及复合材料的三重特性。本文从表界面化学基础理论出发,对纳米RF/RDX制备过程中涉及的炸药溶剂进行研究,达到选择最佳溶剂的目的。通过测定溶剂的黏度值及其与基体材料的接触角,并采用毛细渗透法计算了材料的表面能,考虑了溶剂本身在材料上的流动性、溶剂与材料的界面接触程度两方面的影响因素,给出了实验数据,经过对比得出结论,选择了三氯乙烯、N,N-二甲基甲酰胺、乙腈作为RDX的备选溶剂。最后以N,N-二甲基甲酰胺为溶剂,采用溶胶-凝胶法制备出了纳米RF/RDX材料,电镜扫描结果表明使用超临界干燥RF凝胶网格尺寸在20～100 nm之间,在制备出的RF/RDX复合物中RDX填充较满,粒度在36～38 nm之间,分布较为均匀,验证了该溶剂可用于纳米RF/RDX的制备。     

常压制备SiO_2气凝胶的温度控制研究

以正硅酸乙酯(TEOS)为先驱体,乙醇(EtOH)为溶剂,盐酸和氨水为酸碱催化剂,N,N-二甲基甲酰胺(DMF)为干燥控制化学添加剂,通过溶胶-凝胶法制备SiO_2醇凝胶,经异丙醇(IPA)/正己烷(Hexane)溶剂置换,三甲基氯硅烷(TMCS)/正己烷表面改性等工艺,最后经常压干燥制备完整,低密度,高比表面积,超疏水的SiO_2气凝胶块体。研究了各工艺阶段温度变化对气凝胶性能的影响。研究发现:水解温度为35℃,凝胶温度为室温,老化温度为50℃,分步溶剂置换中前4步为50℃,第5步为35℃,改性温度为35℃,清洗温度为50℃,制备的SiO_2气凝胶块体,比表面积高达892.33 m~2/g,密度0.142 g/cm~3,疏水角140°。     

薄膜材料的制备方法

文章详细介绍了薄膜材料制备的各种方法,包括真空蒸发法、真空溅射法、脉冲激光沉积法、分子束外延法、化学气相沉积法、化学浴沉积法、电沉积法、溶胶一凝胶法、连续离子层吸附与反应法、分子自组装技术法、模板合成法、溶剂热法。     

溶剂对顺丁橡胶凝胶的溶胀研究

凝胶是聚丁二烯分子发生歧化、交联反应,生成的不溶于任何溶剂的网状结构的橡胶大分子。本文利用不同溶剂对顺丁橡胶凝胶样品进行溶胀实验,研究浸泡时间、溶剂种类对凝胶溶胀过程中体积、质量、外观形貌的影响规律。研究表明,用两种溶剂浸泡的凝胶,其规律都是随着浸泡时间的延长,凝胶的质量、体积增幅都是先快速增加,达到最大值后趋于平缓并有所下降。且凝胶含量越高,凝胶胀大越明显。但用甲苯溶剂对凝胶溶胀的速率和尺寸更大,且溶胀后的凝胶呈透明状。     

无机非金属材料的软化学合成

本文系统地介绍无机非金属材料制备中的软化学方法，评论溶胶－－凝胶法、沉淀－煅烧法、水热合成法、蒸发溶剂法，乳化剂法等各种软化学方法的工艺原理、优点及存在问题等。     

丙烯酸十八酯与甲基丙烯酸共聚物凝胶的合成及其性能

以无水乙醇为溶剂,N,N’-亚甲基双丙烯酰胺(MBAA)为交联剂,在50℃下将丙烯酸十八酯(ODA)与甲基丙烯酸(MAA)进行共聚,合成了丙烯酸十八酯(ODA)与甲基丙烯酸(MAA)的共聚物凝胶：研究了共聚组成对凝胶性能的影响。结果表明：经二甲亚砜(DMSO)平衡溶胀后的凝胶,在[ODA]：[MAA]摩尔比为1：3时,具有较高的规整性和较高的溶胀倍率。DSC测定表明在温度交化过程中聚合物凝胶存在有序．无序结构的转交。将共聚物凝胶在由不同极性的溶剂环己醇和DMSO组成的混合溶剂中溶胀,发现聚合物凝胶在极性溶剂DMSO中的规整性最高,随着小极性溶剂环己醇的比例加大,混合溶剂的极性下降,聚合物凝胶在混合溶剂中的规整性逐渐降低,相交温度向低温迁移,吸热和放热量降低,至环己醇含量≥40％后,在升温-降温过程中其吸放热量均为0,不发生相交,这说明溶剂的极性对聚合物凝胶的规整性有较大的影响。     

科技纵横

杜邦生产可生物降解溶剂杜邦公司开发出一种经生物路线生产二甲基 2 哌啶酮的方法。二甲基 2 哌啶酮主要用于清洗计算机电路中的金属和电子元件 ,是一种可生物降解的溶剂。这种溶剂商品名为Xolvone ,是由细菌细胞与 2 甲基戊二腈 (MGN) (尼龙生产的联产品 )反应制得的。该公司在试验时发现 ,与化学反应相比 ,细菌反应的收率更高 ,产生的杂质更少。工艺的关键环节是包封细菌细胞 ,可使用细菌与MGN反应而成的凝胶涂层来进行包封。反应在较低温度的水中进行 ,比化学催化方法产生的毒性小。细菌细胞直径为 2～ 3微米 ,而凝胶形成小球涂…     

Rheological analysis of the gelation behavior of tetraethylorthosilane/ vinyltriethoxysilane hybrid solutions

The gelation behavior of tetraethylorthosilane (TEOS) sol in the presence of a silane coupling agent vinyltriethoxysilane (VTES) was investigated experimentally. Specifically, the gel time and gel structure were analyzed by the rheological multiwave test of Fourier transform mechanical spectroscopy (FTMS) for the mixtures of TEOS/ VTES with various molar ratios at different temperatures. Gelation was accomplished through the sol-gel reactions of the silicon alkoxide TEOS in aqueous acidic solution. The results showed that, at elevated temperatures, the gel point was scattered and obscured by the noise in low frequencies owing to the enhanced thermal agitations. In this case, the statistical method was used to find the exact gel time. The activation energy of gelation and the gel exponent ranged from 25 to 30 kJ/mol and from 0.581 to 0.771, respectively, depending on the TEOS/VTES composition. The fractal dimension was estimated from the gel exponent and indicated the gel structure and that the TEOS/VTES solutions formed a relatively open and coarse gel structure.     

Reformation of Fumed Silica Gel After Being Broken

The reorganization of fumed silica gel formed in sulphuric acid medium after being broken has been studied using rheological measurements including thixotropy, gelling time, and gel strength determination according to the falling rod method. The original gel formed by fumed silica particles was also studied for comparison. The results showed that the segments yielded after the original gel was broken can reorganize into a new gel although its ability was weaker than that of fresh particles. The dispersed size of silica particles influenced both the formation of the original gel and the reorganization behavior. The smaller silica particles favored a prolonged gelling time but yielded a gel with relatively low strength. Comparatively, the tendency to reorganize was weaker than in the original gel formation. The standing temperature during the fresh gel formation showed less of an effect on the reorganization process.     

Temperature‐, pH‐, and ion‐stimulus‐responsive swelling behaviors of poly(dimethylaminoethyl methacrylate) gel containing cholic acid

Poly(dimethylaminoethyl methacrylate) hydrogels containing cholic acid (PDMAEMA–CA) were synthesized by radiation crosslinking. The introduction of 10 and 20 mol% cholic acid (CA) into the poly(dimethylaminoethyl methacrylate) (PDMAEMA) hydrogel decreased the maximum swelling ratio (SR) of the gel from 40 to 6 and 5, respectively. The incorporation of CA with dimethylaminoethyl methacrylate led to a decrease in the lower critical swelling temperature of the gel from 44 to 42°C but did not exert big influence on the ion‐stimulus‐responsive properties of the gel. However, the pH sensitivity of the PDMAEMA–CA gel was quite different from that of PDMAEMA gel. The SR of PDMAEMA gel decreased at pH 2.5, whereas the SRs of the PDMAEMA–CA gels showed a convex‐upward function of pH; that is, SR of the PDMAEMA–10% CA gel first increased (pH 1.2–3.2) and then decreased (pH 3.2–11.9) with increasing pH. The pH‐stimulus‐responsive swelling behavior of the PDMAEMA–20% CA gel was similar to that of the PDMAEMA–10% CA gel except for the unique swelling behavior exhibited in the lower pH region. The unique decrease in SR in strong acidic solutions was attributed to aggregations driven by the hydrophobic interactions between CA molecules. Phase separation of the gel in strongly acidic solutions was observed; that is, the margin of the swollen gel was transparent and elastic (cellular structure), whereas the core of it was opaque (aggregated structure) as recorded by scanning electron microscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39998.     

Adsorption of ammonium and nitrate ions by poly(N‐isopropylacrylamide) gel and poly(N‐isopropylacrylamide‐co‐chlorophyllin) gel in different states

The adsorption of ammonium and nitrate by temperature‐stimulus‐responsive poly(N‐isopropylacrylamide) (NIPA) gel and poly(N‐isopropylacrylamide‐co‐chlorophyllin) (NIPA‐CH) gel in different states was investigated. Both the NIPA gel and NIPA‐CH gel could adsorb ammonium and nitrate in a swollen state (swollen gel) and a swelling state (swelling gel), and they adsorbed ammonium more than nitrate. When the gels were shrinking (shrinking gel), they could adsorb a little ammonium from solution, but when the gels were in a shrunken state (shrunken gel), they hardly adsorbed ammonium. The adsorption of both ammonium and nitrate increased for the swelling NIPA gel in comparison with the swollen gel. The NIPA‐CH gel was the opposite in this respect. The difference in the amounts of adsorption of ammonium and nitrate by the swollen and swelling NIPA‐CH gels was more significant than that of the NIPA gels. It was suggested that ions such as ammonium and nitrate could not diffuse into the gels freely. The adsorption of ammonium and nitrate was affected not only by the phase transitions of the gels but also by the electrical charges. The experimental results for the adsorption of ammonium and nitrate during the volume changes of the gels imply that if the gels are applied to the immobilization of microorganisms, they may improve mass transfer between the immobilization matrix and bulk liquid under cyclic temperature changes and promote reactions of the immobilized microorganisms, especially the nitrification of nitrifying bacteria immobilized by the NIPA‐CH gel. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2367–2372, 2005     

介孔硅胶负载次氯酸脱除柴油中的硫化物

采取介孔硅胶负载次氯酸脱除硫含量为150μg·g-1的4,6-二甲基二苯并噻吩模型柴油中的硫化物,考察孔结构和脱硫条件对介孔硅胶负载次氯酸脱除模型柴油硫化物的影响,研究再生条件对脱硫剂再生效果的影响。通过红外光谱和N2等温吸附对硅胶进行表征,N2等温吸附分析结果表明,实验选用的3种硅胶均为介孔硅胶;红外光谱分析结果表明,不同孔结构的介孔硅胶均可以负载次氯酸并将模型柴油中4,6-二甲基二苯并噻吩氧化为砜并吸附在介孔硅胶上。SGA型硅胶脱硫率较低;而在反应温度35℃和剂油质量比0.050条件下,使用次氯酸负载质量分数为90.7%的SGB型硅胶,脱硫率达97.3%,使用次氯酸负载质量分数为79%的SGC型硅胶,脱硫率达99.0%。在反应温度30℃和剂液质量比0.19条件下,分别清洗10次,清洗时间5 min,SGC型硅胶的脱硫率下降幅度很小,而SGB型硅胶的脱硫率明显下降。大孔径有利于介孔硅胶负载次氯酸脱除柴油中的硫化物,而且有利于脱硫剂的再生。     

胶冻强度与明胶α组分关系的研究

用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)法测定了明胶的α组分含量;用胶冻强度测定仪测定了它们的胶冻强度。结果表明,这两组数据的比值呈线性的对应关系。作者曾在“α_1组分含量最高的明胶”一文中推测,胶冻强度与明胶α组分含量之间存在相互的影响,这一推测在本文的研究中得到证实。     

高浓度超高相对分子质量聚乙烯冻胶流变行为的研究

应用Rosand RH7D型双料筒毛细管流变仪,研究了以白油为溶剂的高浓度超高相对分子质量聚乙烯(UHMWPE)冻胶的流变特性,以及冻胶浓度、温度对高浓度冻胶的流变曲线、非牛顿指数和结构黏度指数的影响。结果表明:高浓度UHMWPE冻胶属于宾汉流体,不同浓度的UHMWPE冻胶非牛顿指数随温度的升高先增大后减小,结构黏度指数随UHMWPE冻胶浓度及温度的增高而减小。     

Gelation performance of poly(ethylene imine) crosslinking polymer–layered silicate nanocomposite gel system for potential water‐shutoff use in high‐temperature reservoirs

Polymer gels have been widely used for water shutoff in mature oil fields. In this paper, polyacrylamide (PAM)–montmorillonite (MMT) nanocomposites (NC) were prepared through in situ intercalative polymerization. Fourier transform infrared spectroscopy and X‐ray diffraction were conducted to characterize the prepared PAM/MMT nanocomposites. The gelation performance of poly(ethylene imine) (PEI) crosslinking PAM/MMT nanocomposite gel system (NC/PEI gel system) was systematically investigated by bottle testing and viscosity measurement methods. The results showed that the gelation performance of the NC/PEI gel system was greatly affected by the total dissolved solids, PAM/MMT nanocomposite concentration, and PEI concentration. The NC/PEI gel system exhibited much better thermal stability and gelation performance than the PAM/PEI gel system at the same conditions. The gelation performance after flowing through porous media of the NC/PEI gel system before injection and that of the subsequently injected gel system was different. The gel strength decreased and the gelation time was delayed after the gel system before injection was flowed through porous media. However, the gel strength of the subsequently injected gel system did not decrease, and only the gelation time was delayed after flowing through porous media. This study suggests that the NC/PEI gel system can be used as a potential water‐shutoff agent in high‐temperature reservoirs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44243.     

Effect of ionizing irradiation and blending of natural rubber latex on polyvinylalcohol gelation by using chemical and freezing–thawing processes for use in the field of construction engineering

The aim of this work is to study the gelation behavior of polyvinylalcohol (PVA) and natural rubber latex (NRL) using two methods: The first was chemical gelation by adding sodium borate as a crosslinking to obtain a modeling clay gel able to draw easily under tension (using drum mill) or by using hand pressing. Irradiation was then applied at 2.5 Mrad to possess more crosslinking effect, where stable and rubbery‐gel shape in the dimension was obtained. The second method, where samples of liquid PVA were frozen and thawed for three consecutive cycles. The obtained gel was quite rubbery but completely soluble in hot water at 70°C. Irradiation was performed at 2.5 Mrad to produce a highly rubbery gel and resistant to boiled water. Also, blending of NRL with PVA induced a significant increase in gel‐elasticity and resistivity to boiled water. Factors affecting the properties of the prepared gel such as gel draw ability and gel strength were studied. The study was supported with thermal and scanning electron microscopy (SEM) to investigate the modification of PVA‐gel behavior through irradiation and blending with NRL processes. The results indicated that the PVA‐gel obtained by chemical method or blended with NRL through freezing–thawing gelation gave a superior ability for cement loading. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

ESR study of radiation-induced polymerization of styrene adsorbed on silica gel

The effect of the specific surface area of silica gels on the radiation-induced polymerization of styrene adsorbed on silica gel was studied by ESR. The same radicals were generated on the silica gels regardless of the specific surface area, but the stability of the radicals at room temperature depended on the specific surface area. This means that the decay of the radicals proceeded mainly on the surface of the silica gel. Almost all the radicals generated by irradiation were initially in the bulk of the silica gel and migrated from the interior to the surface of the gel. When styrene monomer was adsorbed on the surface of the silica gel, the silica gel radicals interacted with the monomer and initiated polymerization and then generated polymer. The rate of migration of the silica gel radical was rather fast in the case of silica gel with a large specific surface area. Thus, the polymerization behavior of styrene adsorbed on silica gel greatly depended on the specific surface area of the gel.