Butanol isomer separation using polyamide-imide/CD mixed matrix membranes via pervaporation

Mixed matrix membranes (MMMs) comprising polyamide-imide (PAI) and α-, β- or γ-cyclodextrin (CD) have been investigated experimentally and computationally for isomeric n-butanol/tert-butanol (n-BuOH/t-BuOH) separation via pervaporation. Consistent with molecular simulation, experimental results show that the CD inclusion ability and butanol discrimination ability are dependent on both CD cavity size and butanol molecular size. The PAI membrane incorporated with α-CD has the smallest cavity and has the highest discrimination ability for the n-BuOH/t-BuOH pair but with a low butanol flux. The mixed matrix membrane embedded with γ-CD has the lowest selectivity and the highest flux. The PAI/β-CD membrane has a comparable selectivity and flux, and exhibits preferential sorption and diffusion selectivity toward n-BuOH. A maximum separation factor of 1.53 with a corresponding flux of 4.4 g/m² h are obtained at an optimal β-CD loading of 15 wt%. Further increments in the CD content eventually lead to a decrease in separation performance because of CD agglomeration and severe phase separation. To better understand the influence of CD on the separation performance of mixed matrix membranes, SEM, FTIR and XRD have been employed for membrane characterizations. The effect of n-butanol/t-butanol ratio in the feed composition has also been studied. It is found that both flux and separation factor decrease with increasing n-butanol content in the feed. The decline is attributed to the change in total vapor pressure at the upstream and the mutual drag effect of isomeric butanol molecules.     

Poly(vinyl pyrrolidone‐co‐octavinyl polyhedral oligomeric silsesquioxane) hybrid nanocomposites: Preparation,thermal properties,and Tg improvement mechanism

A series of poly(vinyl pyrrolidone‐co‐octavinyl polyhedral oligomeric silsesquioxanes) (PVP‐POSS) organic–inorganic hybrid nanocomposites containing different percentages of POSS were prepared via free radical polymerization and characterized by FTIR, high‐resolution ¹H‐NMR, solid‐state ²⁹Si‐NMR, GPC, DSC, and TGA. POSS contents in these nanocomposites can be effectively controlled by varying the POSS feed ratios which can be accurately quantified by FTIR curve calibration. On the basis of ²⁹Si‐NMR spectra, average numbers of reacted vinyl groups of each octavinyl‐POSS macromer are calculated to be 5–7, which depends on POSS feed ratios. Both GPC and DSC results indicate that these nanocomposites display network structure and the degree of crosslinking increases with the increase of the POSS content. The incorporation of POSS into PVP significantly improves their thermal properties (T_g and T_dec) primarily due to crosslinking structure and dipole–dipole interaction between POSS cores and PVP carbonyl groups. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Performance and characterization of irradiated poly(vinyl alcohol)/polyvinylpyrrolidone composite hydrogels used as cartilages replacement

In this article, hydrogels were prepared by compounding polyvinylpyrrolidone (PVP) with poly(vinyl alcohol) (PVA), which is used as artificial cartilages, by means of repeating freezing and thawing and irradiation, for improving their mechanical and surface lubricative properties. The structures and properties, including gel content, crystallized degree, elastic modulus, and frictional coefficients of the compound hydrogels with different PVP contents and irradiative conditions, were examined and compared. The existence of PVP macromolecules interfered with the crystallization of PVA hydrogels resulted in the decrease of gel contents and elastic modulus, as well as the unstable external frictional coefficient in water. After irradiation treatment, these performances increased with irradiation intensity in lower dose ranges. The solubility and exudation of PVP in water were prevented and reduced because of the chemical crosslink of PVA and PVP, and the lubricative properties of PVA/PVP hydrogels in water were improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and functionalization of nanoengineered materials using click chemistry

The synthesis of nanoengineered materials with precise control over material composition, architecture and functionality is integral to advances in diverse fields, including biomedicine. Over the last 10 years, click chemistry has emerged as a prominent and versatile approach to engineer materials with specific properties. Herein, we highlight the application of click chemistry for the synthesis of nanoengineered materials, ranging from ultrathin films to delivery systems such as polymersomes, dendrimers and capsules. In addition, we discuss the use of click chemistry for functionalizing such materials, focusing on modifications aimed at biomedical applications.     

Studies on Bi-Cyclic Aromatics Extraction using Furfural and N-Methyl Pyrrolidone (NMP) as Solvent

In this work, the separation of naphthalene, a bicyclic aromatic component, by the solvent extraction method from a model oil (p-xylene, iso-octane, and naphthalene) using furfural and n-methyl pyrrolidone (NMP) as solvent has been investigated. A four factor Box-Behnken design was used to study the individual and interactive effects of four main parameters namely paraffinic content in model oil (P/F): 0.7–0.8; solvent to feed ratio (S/F): 0.5–1.0; temperature (T): 20–40°C; time (t): 1–3 h for furfural and 1–7 h for NMP on the yield and selectivity of naphthalene. Gas chromatography was carried out to analyze the composition of raffinate and extract phases. Various polynomial models were fitted to find out the best model for the system. Pareto analysis of variance (ANOVA) and other statistical tests were performed to check the significance of the model. Furfural was found to be a better solvent as compared to NMP, both in terms of yield and selectivity. The operating conditions leading to maximum aromatic recovery have been optimized. The optimum conditions for furfural was found to be P/F = 0.7, S/F = 0.5, temperature = 24°C and time = 3 h whereas the optimum conditions for NMP were: P/F = 0.76, S/F = 0.76, temperature = 22°C, and time = 4.1 h.     

Miscibility studies of hydroxypropyl cellulose/poly(vinyl pyrrolidone) in dilute solutions and solid state

The miscibility of hydroxypropyl cellulose (HPC) and poly(vinyl pyrrolidone) (PVP) blends in aqueous solutions was studied using viscosity, ultrasonic velocity, and refractive index techniques at 30°C. The interaction parameters ΔB, μ, and α calculated from viscosity using Sun and Chee methods indicated the miscibility of this blend. This was further confirmed by ultrasonic and refractive index results. The HPC/PVP blend films are prepared by solution casting method and are analyzed by differential scanning calorimetry, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopic techniques that confirmed the complete miscibility. This miscibility is due to the strong intermolecular H-bonding interactions between  OH groups of HPC and CO groups of PVP. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Characterization of macroporous 1‐vinyl‐2‐pyrrolidone copolymers obtained by suspension polymerization

Radical suspension copolymerization of 1‐vinyl‐2‐pyrrolidone (VP) with three different cross‐linkers: divinylbenzene (DVB), trimethylolpropane trimethacrylate (TRIM), and di(methacryloxymethyl) naphthalene (DMN) was used to prepare macroporous microspheres. During the copolymerization, the mixture of toluene and n‐dodecane as a pore‐forming diluent was used. All samples were characterized in terms of particle size and distribution, nitrogen content, specific surface area total pore volume, and pore size distribution. It was found that specific surface area of the obtained beads is strongly dependent on the diluent system and the type of cross‐linker and achieves value from 27 to 845 m²/g. To determine the influence of chemical structure of cross‐linkers on the selectivity and polarity of the copolymers, inverse gas chromatography was applied. In addition, VP–DVB and VP–DMN copolymers were modified by sulfonation into cation‐exchangers with cation exchange capacity equal 1.98 and 2.31 mmol/g, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

奈非西坦的合成研究

奈非西坦是新研制的一种对阿尔茨海默氏病和脑血管后遗症有良好的临床治疗价值的药物。对奈非西坦的各种合成方法进行了总结,分析了各路线的优缺点,并对奈非西坦的药理学内容做了概述。     

共聚物水凝胶温度及pH敏感行为的研究

用自由基聚合法合成了NVP／HEMA和NVP／HEMA／AAm共聚物水凝胶材料,研究了温度、pH值、离子强度等因素对凝胶溶胀性能的影响。结果表明水凝胶的溶胀度随着温度的升高而减少;水凝胶在酸性溶液中溶胀,在碱性溶液中收缩,显现出良好的pH值敏感性;水凝胶的溶胀度随着离子强度的增加而减少。     

萃取精馏分离乙腈-正丙醇的研究

采用萃取精馏的方法分离乙腈-正丙醇的共沸物系。首先利用溶剂选择原理和UNIFAC基团贡献法选出N-甲基吡咯烷酮作为萃取精馏的萃取剂,同时采用NRTL模型对常压下乙腈-正丙醇物系和加入萃取剂N-甲基吡咯烷酮后的汽液平衡进行模拟和实验验证,模拟结果与实验数据吻合较好。然后通过间歇萃取精馏实验进一步考察所选萃取剂的分离效果。结果表明,N-甲基吡咯烷酮能够打破共沸,有效分离乙腈-正丙醇共沸物系。采用有28块理论板的填料塔,萃取剂进料位置为第4块板,溶剂比为1.0,回流比为3,可以从塔顶得到质量分数为98.6%的乙腈产品。最后,用Aspen Plus软件对乙腈-正丙醇物系的连续萃取精馏流程进行了模拟,得出的参数为进一步的工业应用奠定基础。