Nanocomposite hydrogel consisting of Na‐montmorillonite with enhanced mechanical properties

A new kind of nanocomposite (NC) hydrogel with Na‐montmorillonite (MMT) is presented in this article. The NC hydrogels were synthesized by free radical copolymerization of acrylamide and (3‐acrylamidopropyl) trimethylammonium chloride (ATC) in the presence of MMT and N,N′‐methylene‐bis‐acrylamide used as chemical cross‐linker. Due to the cation‐exchange reaction between MMT and ATC (cationic monomer) during the synthesis of NC hydrogels, MMT platelets were considered chemical “plane” cross‐linkers, different from “point” cross‐linkers. With increasing amount of MMT, the crosslinking degree enhanced, causing a decrease of the swelling degree at equilibrium. Investigations of mechanical properties indicated that NC hydrogels exhibited enhanced strength and toughness, which resulted from chemical interaction between exfoliated MMT platelets and polymer chains in hydrogels. Dynamic shear measurements showed that both storage modulus and loss modulus increased with increasing MMT content. The idea described here provided a new route to prepare hydrogels with high mechanical properties by using alternative natural Na‐MMT. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1020–1026     

A note on the Chern-Simons invariant of hyperbolic 3-manifolds

In this note we study how the Chern-Simons invariant behaves when two hyperbolic 3-manifolds are glued together along incompressible
thrice-punctured spheres. Such an operation produces many hyperbolic 3-manifolds with different numbers of cusps sharing the same volume and the same Chern-Simons invariant. The results in this note, combined with those of Meyerhoff and Ruberman, give an algorithm for determining the unknown constant in Neumann's simplicial formula for the Chern-Simons invariant of hyperbolic 3-manifolds.

     

分散共聚法制备特殊形态高分子微球的研究

以聚乙二醇 (PEG)大分子单体为反应性稳定剂 ,在丙烯腈的分散共聚反应中添加少量苯乙烯以形成疏水性核 ,制备得到了亚微米级高分子微球 .透射电子显微镜研究表明 ,该高分子微球具有特异的形态结构 .同时研究了分散共聚体系中各种反应因素对微球形态和直径的影响 ,结果表明 ,苯乙烯单体的添加量、PEG大分子单体的浓度及分子量、混合溶剂的组成对微球直径和形态均有明显的影响 .X 射线光电子能谱 (XPS)研究结果表明 ,微球表面聚集有亲水性PEG链 ,核为疏水的聚 (丙烯腈 苯乙烯 ) ,即形成的特异形态的PEG接枝高分子微球亦为复合型结构     

Interpenetrating Network Hydrogels based on Nanostructured Conductive Polymers for Flexible Supercapacitor

Flexible conductive polymer hydrogels are unique material that synergize the features of conductive polymers and hydrogels. They are excellent candidates for the flexible supercapacitor electrodes. In this paper, flexible conductive polymer hydrogels were prepared with poly(vinyl alcohol) as soft skeleton through cyclic freezing-thawing method. Firstly, phytic acid-doped polyaniline with crosslinked network was prepared using phytic acid as the dopant and crosslinking agents. Hydrogels with interpenetrating binary network nanostructure were then formed by freezing-thawing method. The interpenetrating binary network structure endowed the hydrogel reliable mechanical properties with decent flexibility and compressive strength of 3.64 MPa. More importantly, this unique structure enable them to maintain highly specific capacitance (314 F/g at the current density of 0.5 A/g).     

Effect of partial crosslinking on morphology and properties of the poly(β-hydroxybutyrate)/poly(d,l-lactic acid) blends

Poly(β-hydroxybutyrate) (PHB) is a bio-based and biodegradable aliphatic polyester, however its application is limited by some disadvantages such as high price, brittleness, poor processability and low melt-strength due to serious thermal degradation. Partial crosslinking initiated by dicumyl peroxide (DCP) was applied in this work to improve the performance of poly(β-hydroxybutyrate)/poly(d,l-lactic acid) (PHB/PDLLA) blends. The partial crosslinking of the blends and its effect on the properties, morphology, rheology and thermal behavior of the blends were investigated. The tensile strength and impact toughness of the PHB were increased by incorporation of the PDLLA, which were improved further after the partial crosslinking because of an increased compatibility between the PHB and the PDLLA phases. The rheological study revealed that the storage modulus (G′) and complex viscosity (η*) of the blends were increased after addition of the DCP. On the other hand, the crystallization of PHB in the blends was restricted to a certain extent by the formation of partially crosslinked network while its crystal form was not modified.     

INFLUENCE OF FRICTION ON THE MOTION OF BASE WITH AN ECCENTRIC ROTOR

偏心转子惯性力引起的底座运动受到地面摩擦的影响,与光滑情形的理论结果存在定性差异。转子逆时针匀速旋转的惯性力若小于构件总重,则底座随摩擦因子增加而出现连续、一次停顿和两次停顿的振动及完全静止的4种状态。因惯性力对正压力及摩擦力的影响,底座在连续及一次停顿的振动时右向位移较大;而底座跳起时如``蛤蟆夯'则整体向左移动。     

基于壳聚糖衍生物的蛋白质药物载体材料的制备及性能

在离子液体均相体系中合成了一种新型两亲性窄分子量分布的低聚壳聚糖衍生物月桂基-琥珀酰化壳聚糖(LSCOS). 以LSCOS为载体材料, 以牛血清蛋白(BSA)为模板蛋白, 以戊二醛为交联剂, 用油包水(W/O)乳化交联法制备了包载BSA的BSA/LSCOS缓释载药微球. 通过扫描电子显微镜(SEM)、 透射电子显微镜(TEM)及紫外-可见光谱(UV-Vis)研究了BSA/LSCOS比率和戊二醛/LSCOS比率对微球的形貌结构、 包埋率、 载药率和体外药物释放特性的影响. 结果表明, 在离子液体中合成的LSCOS包覆了BSA, 形成的微球粒径约为1 μm, 微球表面随BSA用量的增加变得光滑, 随戊二醛用量的增加变得粗糙. BSA的累积释放率与BSA包载量成正比, 与交联剂添加量成反比, 因此, 可通过控制蛋白质药物的添加比率和交联剂用量来控制蛋白质药物体外释放率.     

沉淀法高效制备聚多巴胺纳米粒子

为得到分散性和稳定性较好的聚多巴胺纳米粒子,利用“沉淀-再分散法”高效制备了聚多巴胺纳米粒子水分散液。 首先利用溶液氧化法制备了分散在水/乙醇中的聚多巴胺纳米粒子,然后向分散液中加入丙酮使聚多巴胺纳米粒子絮凝。 收集沉降物,用丙酮冲洗并干燥后,加水重新分散得到纯化的聚多巴胺纳米粒子水分散液。 丙酮沉淀法得到的聚多巴胺纳米粒子形貌规整,分散性好,粒径分布在250 nm左右,在水中具有良好的储存稳定性和光热性能,与传统的超速离心提纯法相比,产率可提高57.4%。 此方法为其之后在药物载体及光热治疗等方面的应用研究提供了便利。     

Thermal conductivity of nanofluids and size distribution of nanoparticles by Monte Carlo simulations

Nanofluids, a class of solid–liquid suspensions, have received an increasing attention and studied intensively because of their anomalously high thermal conductivites at low nanoparticle concentration. Based on the fractal character of nanoparticles in nanofluids, the probability model for nanoparticle’s sizes and the effective thermal conductivity model are derived, in which the effect of the microconvection due to the Brownian motion of nanoparticles in the fluids is taken into account. The proposed model is expressed as a function of the thermal conductivities of the base fluid and the nanoparticles, the volume fraction, fractal dimension for particles, the size of nanoparticles, and the temperature, as well as random number. This model has the characters of both analytical and numerical solutions. The Monte Carlo simulations combined with the fractal geometry theory are performed. The predictions by the present Monte Carlo simulations are shown in good accord with the existing experimental data.