Finite deformation swelling of a temperature-sensitive hydrogel cylinder under combined extension-torsion

The swelling behavior of a temperature-sensitive poly-N-isopropylacrylamide(PNIPAM) hydrogel circular cylinder is studied subjected to combined extension-torsion and varied temperature. In this regard, a semi-analytical solution is proposed for general combined loading. A finite element(FE) analysis is conducted, subjecting a hydrogel cylinder to the combined extension-torsion and the varied temperature to evaluate the validity and accuracy of the solution. A user-defined UHYPER subroutine is developed and verified under free and constrained swelling conditions. The FE results illustrate excellent agreement with the semi-analytical solution. Due to the complexity of the problem, some compositions and applied loading factors are analyzed. It is revealed that for larger cross-linked density and larger ending temperature, the cylinder yields higher stresses and smaller radial swelling deformation. Besides, the radial and hoop stresses increase by applying larger twist and axial stretch. The hoop stresses intersect at approximately R/Rout = 0.58, where the hoop stress vanishes. Besides, the axial force has direct and inverse relationships with the axial stretch and the twist, respectively. However, the resultant torsional moment behavior is complex, and the position of the maximum point varies significantly by altering the axial stretch and the twist.     

Facile synthesis of temperature-sensitive ABA triblock copolymers by dispersion RAFT polymerization

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Synthesis of dual pH- and temperature-sensitive poly(N-isopropylacrylamide-co-acrylic acid)/sewage sludge ash hydrogel with the simultaneously high performance of swelling and deswelling

An advanced dual pH- and temperature-sensitive hydrogel (NASH2.5) was optimally synthesized through modification of N-isopropylacrylamide (NIPAM) hydrogel with introducing 5 mol% acrylic acid (AA) and 2.5 wt% sewage sludge ash (SSA). The swelling kinetic results showed that NASH2.5 exhibited both high equilibrium swelling ratio and swelling rate, which was attributed to the higher porous structure as shown in scanning electron microscope, and the more hydrogen bonding formed inside of the hydrogel as investigated in Fourier transform infrared spectrometer. In addition, its curve was better fitted to the pseudo-second-order model, indicating that the water absorption process was dominated by chemisorption through forming the hydrogen bonding among the water molecules and carboxyl/silanol groups of the hydrogel. Compared with the pure NIPAM hydrogel, the water transport mechanism switched from Case I diffusion to Case II diffusion by introduction of AA and further SSA. Furthermore, through the results of the deswelling kinetics in pH value change (from 9 to 4 and 2, respectively), temperature value change (from 25 to 40, 50, and 60°C, respectively), and dual pH and temperature values changes, NASH2.5 not only presented a high pH sensitivity, but also showed high sensitive to temperature by achieving high water recovery ratio in rapid dehydrated rate. Therefore, the dual stimuli-sensitive hydrogel with the simultaneously high performance of swelling and deswelling would provide a suitable alternative for specific applications such as pollutant adsorption.     

Cationic and temperature-sensitive liposomes loaded with eugenol for the application to silk

Silk has been widely used in the clothing industry due to their soft and smooth features, good biocompatibility, good heat dissipation, warmth and ultraviolet resistance. The application of fragrance to silk can significantly improve the performance of silk. However, there are two key scientific problems that need to be solved: slowing down the release rate of fragrances and increasing the scent lasting time of silk. In this study, cationic and temperature-sensitive liposomes were designed and prepared to encapsulate eugenol. These fragrance-loaded liposomes significantly slowed down the release rate of the fragrance and controlled the release rate of the fragrance in a thermo-sensitive manner. The liposomes adhered to the silk through electrostatic adsorption interaction. The positive charge on the fragrance-loaded liposomes neutralized much negative charge on silk and thereby increasing the adhesion efficiency.     

Release Property of Alginate Beads Coated with Poly(N-isopropylacrylamide-co-dimethylaminoethylmethacrylate)

Alginate beads were coated with copolymers of N-isopropylacrylamide and dimethylaminoethylmethacrylate (P(NIPAM-co-DMAEMA)s) by taking advantage of electrostatic interaction between alginate and the copolymer. The copolymers, of which DMAEMA contents in the feed for the copolymerization were 5.0% (PND 5) and 15.0% (PND 15), were employed for the coatings of alginate beads. The adsorption curve of PND 5 and PND 15 on the surface of alginate beads seemed to be Langmuir isotherm. The beads were coated in the PND solutions (2%, pH 5.0 or pH 7.0) and the amounts of adsorption (g PND/g alginate) were about 1.3 with PND 5 solution (pH 5.0), 1.2 with PND 15 solution (pH 5.0), and 0.75 with PND 15 (pH 7.0). The release from the beads coated with PNDs were observed at 30°C, 37°C, and 45°C using amaranth or FITC-dextran as a dye. The degrees of release were significantly suppressed due to the coating layers of PNDs. However, the coating layers could hardly act as a controller for the temperature-sensitive release.     

Design of Chitosan-5Fu Conjugate Exhibiting Antitumor Activity

In order to provide a macromolecular prodrug of 5-fluorouracil (5FU) reducing the side effects, having an affinity for tumor cells, and exhibiting strong antitumor activity, the covalent attachments of 5FUs to chitosan and chitosamino-oligosaccharide (COS) through hexamethylene spacer groups via urea, urea bonds were carried out. The effect of prolongation of life was tested in vivo against p388 lyrnphocytic leukemia in female CDF, mice by intra-peritoneal (i.p.) transplantation/i.p. injection and the growth-inhibitory effect on Meth-A fibrosarcoma or MH-134Y heputoma was evaluated in vivo in SPF-C3H/He scl male or Balb/c male mice by subcutaneous (s.c.) implantation/intravenous (i.v.) injection. The effects of the degree of polymerization of chitosan and     

噁唑-苯甲酰胺类FtsZ受体抑制剂的3D-QSAR研究

FtsZ蛋白和细菌的繁殖过程有关,是药物设计理想的靶点。本文采用Sybyl分子模拟软件,利用比较分子场方法(CoMFA)及比较分子相似性指数的方法(CoMSIA)对已报道的33个噁唑-苯甲酰胺类FtsZ受体抑制剂进行了分析,建立了三维定量构效关系(3D-Qsar)模型。CoMFA模型的交互验证系数q2为0.619,线性回归系数r2为0.988;CoMSIA模型的q2为0.633,r2为0.936。模型具有较好的预测能力,为今后噁唑-苯甲酰胺类化合物的设计和改造提供了理论依据。     

Magnetically-driven heat transport device using a binary temperature-sensitive magnetic fluid

The magnetic body force in boiling two-phase temperature-sensitive magnetic fluid (TSMF) flow is known to effectively increase the driving force of magnetic fluid in a non-uniform magnetic field. Based on this mechanism, in the present study, a binary TSMF, which is a mixture of the TSMF and a low-boiling-saturation-temperature organic solution, is proposed to be used in a heat transport device to enhance its circulation. In order to see its performance in the heat transport device, the pressure difference at different heated temperatures, magnetic fields and inclination angles of the heating section are investigated experimentally and theoretically. Results showed that the driving force increases remarkably due to more gas phase appearing in the test fluid and the magnetization of it decreasing. At low magnetic field the driving force is enhanced greatly when the inclination angle is close to 60°, while at high magnetic field the driving force is remarkably enhanced due to the effect of the magnetic force in the inclination angle range from 0° to 30° and 60° to 90°.     

光化学合成P(DMAA-co-MMA)/Nano-SiO_2复合水凝胶及其性能研究

以N,N-二甲基丙烯酰胺(DMAA)及甲基丙烯酸甲酯(MMA)为单体,Irgacure 2959为光引发剂,N,N′-二甲基双丙烯酰胺(Bis)为交联剂,利用紫外光引发自由基聚合制备了聚N,N′-二甲基丙烯酰胺(PDMAA)及P(DMAA-co-MMA)水凝胶,并通过加入少量表面改性后的纳米SiO2对该水凝胶进行改性,制得了P(DMAA-co-MMA)/纳米SiO2复合水凝胶,用FT-IR和SEM对产物进行了表征,同时研究该复合凝胶的溶胀动力学、消溶胀动力学、pH值响应性、离子强度等.该方法简便、快捷,大大缩短了聚合时间,合成过程仅需2—3 min.     

Synthesis of temperature-sensitive micron-sized monodispersed composite polymer particles and its application as a carrier for biomolecules

 Temperature-sensitive micron-sized monodispersed composite polymer particles were prepared by seeded copolymerization of dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate with 1.77 μm-sized monodispersed polystyrene seed particles. The change in surface property at temperature above and below 35 °C was examined by differential scanning calorimetry, trypsin activity and the adsorption/ desorption behaviors of low molecular weight cationic emulsifier as well as biomolecules. Received: 6 August 1997 Accepted: 16 January 1998