POLYMER
·
2013
·
IF 3.379
Houluo Cong,Lei Li,Sixun Zheng
In this work, we reported the synthesis of poly(N-isopropyl acrylamide)- block - poly(N-vinylpyrrolidone)- block -poly(N-isopropylacrylamide) triblock copolymer (PNIPAAm- b -PVPy- b -PNIPAAm) via reversible addition-fragmentation chain transfer polymerization/macromolecular design via the interchange of xanthate (RAFT/MADIX) process. This approach was further employed to prepare the PNIPAAm- b -PVPy block copolymer networks with N,N′-methylenebisacrylamide as the crosslinker. The results of small angle X-ray scattering (SAXS) indicate that the PNIPAAm- b -PVPy block copolymer networks were microphase-separated, in which PVPy was dispersed into PNIPAAm matrix as the microdomains. The architecture of block copolymer networks allows investigating the effect of the blocked permanently hydrophobic chains ( viz. PVPy) on the deswelling and reswelling behavior of the PNIPAAm hydrogels. It was found that the diffusion of water molecules in PNIPAAm- b -PVPy block copolymer networks was in a non-Fickian and accelerating manner. The swelling ratios of the PNIPAAm- b -PVPy hydrogels were significantly higher than that of control PNIPAAm hydrogel. Compared to control PNIPAAm hydrogel, the PNIPAAm- b -PVPy hydrogels displayed an accelerated response to the external temperature changes in terms of deswelling and reswelling tests. The accelerated thermoresponsive properties is ascribed to the presence of the PVPy blocks in the PNIPAAm- b -PVPy block copolymer networks, which could act as the hydrophilic tunnels to facilitate the diffusion of water molecules in the PNIPAAm networks.
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高影响因子
JOURNAL OF ADHESION SCIENCE AND TECHNOLOGY
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2013
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IF 0.9
Yihang Lv,Hui Ma,Dongdong Gao,Yi Zhong,Hong Xu,Zhiping Mao
Adhesive polymers, which contain an unusual amino acid, 3,4-dihydroxyphenylalanine (DOPA), can bind strongly to all organic or inorganic surfaces. However, due to DOPA’s poor solubility in organic solvents, it is difficult for us to get desired adhesive polymers. In this paper, poly(N-benzyloxycarbonyl-3,4-dihydroxyphenylalanine) (PNBD) was synthesized based on the modified L-DOPA. Gel Permeation Chromatography was used to analyze the molecular weight of PNBD. The structure of PNBD was characterized by Fourier Transform Infrared Spectroscopy and Hydrogen-1 Nuclear Magnetic Resonance. The adhesive properties of PNBD were determined by lap shear tensile strength tests. The results indicated that PNBD was prepared successfully and had formidable adhesive performance on the various substrates.
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高影响因子
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
·
2014
·Vol. 118
·期 3
·1441-1449
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IF 2.206
Qiu Xiaolin,Lu Lixin,Zhang Zhixiong,Tang Guoyi,Song Guolin
This study focused on preparation and thermal properties of poly(stearyl methacrylate) shell (PSMA) microcapsules containing n -octadecane as a phase change material (PCM). Pentaerythritol triacrylate (PETA) and divinylbenzene (DVB) were employed as crosslinking agents. The surface morphologies, particle sizes, and distributions of the microencapsulated phase change material (microPCM) were studied by scanning electron microscopy. The thermal properties, thermal reliabilities, and thermal stabilities of the microPCMs were investigated by differential scanning calorimetry and thermal gravimetric analysis. The microPCM with DVB exhibits higher phase change enthalpies of melting (87.9 J g −1 ) and crystallization (94.8 J g −1 ) and a greater thermal stability in comparison with the microPCM with PETA. The phase change temperatures and enthalpies of the microPCMs varied little after thermal cycles. Thermal images showed that the gypsum board with PSMA/ n -octadecane microPCM possessed temperature-regulated property. Therefore, microencapsulated n -octadecane with PSMA as shell has good thermal energy storage and thermal regulation potential.
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高影响因子
CHEMICAL ENGINEERING SCIENCE
·
2014
·
IF 2.613
Huidong Zheng,Weifeng Ren,Kunxiong Chen,Yao Gu,Zhengshuai Bai,Suying Zhao
An experimental study of the mass transfer rates in single drops with simultaneous Marangoni convection was carried out, using a system in which acetic acid was transferred from water to n -propyl acetate. In all experimental trials, high purity deionized water was employed as the continuous phase while n -propyl acetate served as the dispersed phase. The effects of both the drop diameter and the initial solute concentration in the continuous phase on the mass transfer were examined. The results demonstrated that mass transfer is increased as the drop size decreases and exhibits a maximum at an acetic acid concentration in the aqueous solution of 0.15 g/ml which reveals the competing mechanisms between reduction of velocity and mass transfer enhancement due to Marangoni effects. All current models, including the Newman (1931) model, do not account for the influence of the initial solute concentration, and thus a correction factor, α , was introduced to obtain the factor, R ׳ , by which the effective diffusivity is enhanced, based on Steiner׳s (1986) modified Newman model. This α factor is a function of the initial difference in solute concentration. The mass transfer rates predicted by our modified Newman model were in good agreement with the experimental data obtained in the present study.
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高影响因子
Particuology
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2015
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IF 2.11
Haifeng Jiang,Qianghui Xu,Chao Huang,Lin Shi
Nanofluids were prepared by dispersing Cu nanoparticles (∼20 nm) in n-tetradecane by a two-step method. The effective thermal conductivity was measured for various nanoparticle volume fractions (0.0001–0.02) and temperatures (306.22–452.66 K). The experimental data compares well with the Jang and Choi model. The thermal conductivity enhancement was lower above 391.06 K than for that between 306.22 and 360.77 K. The interfacial thermal resistance increased with increasing temperature. The effective thermal conductivity enhancement was greater than that obtained with a more viscous fluid as the base media at 452.66 K because of nanoconvection induced by nanoparticle Brownian motion at high temperature.
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高影响因子
Energies
·
2015
·Vol. 8
·期 11
·13021-13032
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IF 2.072
Pan Gao,Lu Xue,Qiang Lu,Changqing Dong
To study the effects of inherent and external alkali and alkaline earth metallic species (AAEMs,i.e., K, Ca and Mg) on the behavior of N-containing species release during rice straw (RS) pyrolysis, different pretreatments were applied in numerous experiments. Results indicate that ammonia (NH3) and hydrogen cyanide (HCN) are the major N-containing species and that the yields of isocyanic acid (HNCO) and nitric oxide (NO) are relatively low. The removal of inhert AAEMs shifts N-containing species release to a high-temperature zone according to volatile release behavior because of the increase in activation energy. The formation selectivity of NH3, HNCO, and NO increases by demineralized pretreatment, whereas HCN selectivity decreases. The formation of HNCO is mainly affected by alkaline earth metal. N-containing species release occurs in low temperatures with the addition of external AAEMs. The activation energy of samples impregnated with CaCl2and MgCl2sharply decreases compared to the original RS. The total yields of N-containing species are reduced significantly in the presence of KCl, CaCl2, and MgCl2as additives. The inhibition ability of AAEMs follows the sequence MgCl2> CaCl2> KCl. The inhibition effect of MgCl2can be improved by solution immersion compared with solid powder mixing. The clean biomass pyrolysis and gasification technology with low N-containing species content may be developed according to the results.Keywords:pyrolysis;N-containing species;alkali and alkaline earth metals (AAEMs);formation selectivity;relative yield
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高影响因子
RSC Advances
·
2015
·Vol. 5
·期 120
·99418-99424
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IF 3.84
Jinda Fang,Ke Zhang,Jingwei Jia,Zhengke Wang,Qiaoling Hu
To improve the drug-loading capacity and control the initial release of amphiphilic drug carriers, a series of N-phthaloyl-chitosan-g-(PEO–PLA–PEO) compounds were synthesized with well-defined structures. The self-assembly behavior of copolymers in aqueous solutions was confirmed by various techniques such as fluorescence spectrometry, dynamic light scattering, and transmission electron microscopy. The results demonstrated that the micellization behavior of graft copolymers was different from that of their linear counterparts. The micelle sizes of the graft copolymers could be tuned with chemical composition as well as temperature. Furthermore, when hydrophobic indomethacin was loaded into the micelles, the graft copolymer micelles trapped more indomethacin than PEO–PLA–PEO micelles, facilitating the in vitro control of the initial burst release of the drug. Drug release could be controlled in vitro by simply altering the EO/LA ratio of the grafting chains. The graft copolymer showed low cytotoxicity to 293T cells, indicating its great potential application for drug delivery.
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高影响因子
THERMOCHIMICA ACTA
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2015
·
IF 2.184
Xiaolin Qiu,Lixin Lu,Ju Wang,Guoyi Tang,Guolin Song
Microencapsulation of n -octadecane or paraffin with poly(lauryl methacrylate) (PLMA) shell was performed by a suspension-like polymerization. The polymer shell was crosslinked by pentaerythritol tetraacrylate (PETRA). The surface morphologies of microcapsules were investigated by scanning electron microscopy (SEM). Phase change properties, thermal reliabilities and thermal stabilities of microcapsules were determined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The n -octadecane microcapsule exhibits higher melting enthalpy (118.0 J g −1 ) and crystallization enthalpy (108.3 J g −1 ) compared with the paraffin microcapsule. The thermal resistant temperatures were enhanced by more than 25 °C when n -alkanes were microencapsulated by PLMA. The PCM contents of microcapsules decreased by less than 4 wt% and 6 wt% after 500 and 1000 thermal cycles, respectively. Heat-up experiments indicated that microcapsule-treated foams exhibited upgraded thermal regulation capacities. Consequently, microencapsulated n -octadecane or paraffin with PLMA as shell possesses good potentials for heat storage and thermal regulation.
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高影响因子
COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING
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2015
·
IF 3.071
Wendi Liu,Tingting Chen,Tianshun Xie,Renhui Qiu
Soybean oil-based thermosets from acrylated epoxidized soybean oil (AESO) with a highly reactive vinyl monomer, N -vinyl-2-pyrrolidone (NVP), as crosslinking agent to replace styrene (St) were formulated for the fabrication of hemp fiber composites. The theoretical miscibility of NVP–AESO and St–AESO systems were discussed based on the group contribution method. The AESO resin with 30 wt% NVP exhibited a slightly higher viscosity than the counterpart with St, while the maximum curing temperature of the former was considerably lower than that of the latter. The composites from 20 wt% NVP resin gained comparable mechanical properties and higher glass transition temperature ( T g ) to the composites with 30 wt% St. Further increase in NVP usage to 40 wt% resulted in the composites with higher tensile strength , tensile modulus , flexural strength , flexural modulus, storage modulus, and T g of 29.6%, 22.4%, 22.5%, 20.6%, 21.6%, and 47.2%, respectively, when compared to those of the St-based composites.
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高影响因子
AICHE JOURNAL
·
2015
·Vol. 61
·期 10
·3441-3450
·
IF 2.748
Xiaofei Song,Feng Xin,Hongchao Yan,Xingang Li,Hongri Jia
A method of direct heat removal resulting from the phase change of n-tetradecane was used to intensify the heat transfer during hydrate formation. The growth rates of methane hydrate in aqueous slurries containing 25–45 wt % of solid n-tetradecane were investigated at pressures between 4.70 and 6.46 MPa (gauge) and near the fusion point of solid n-tetradecane. Methane hydrate growth started at a practically constant rate, which became variable after a sudden increase. Two rate laws were established to correlate with the experimental data for the constant and variable rate stages. The methane hydrate growth rates achieved with solid n-tetradecane were significantly enhanced compared with those obtained under indirect heat removal. © 2015 American Institute of Chemical Engineers AIChE J , 61: 3441–3450, 2015
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RSC Advances
·
2013
·Vol. 3
·期 44
·21863-21868
·
IF 2.562
Ningzhao Shang,Shutao Gao,Cheng Feng,Haiyan Zhang,Chun Wang,Zhi Wang
In this paper, an N-heterocyclic carbene–palladium complex (NHC-Pd2+) was immobilized onto the surface of graphene oxide via a chemical bonding method for the first time. The resultant graphene oxide supported NHC–Pd2+ composite (GO supported NHC-Pd2+) was characterized by transmission electron microscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy and infrared spectroscopy. It was demonstrated that the GO supported NHC-Pd2+ can act as an efficient catalyst for Suzuki–Miyaura coupling reactions. The yields of the products were in the range of 83% to 96%. The catalyst can be readily recovered and reused for at least 6 consecutive cycles without any significant loss in catalytic activity.
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高影响因子
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
·
2013
·
IF 1.977
Qingqing Wang,Guoqing Zhan,Chunya Li
Using N -acetyl- l -cysteine (NAC) as a stabilizer, well water-dispersed, high-quality and stable CdHgSe quantum dots were facilely synthesized via a simple aqueous phase method. The as-prepared NAC capped CdHgSe quantum dots were thoroughly characterized by fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. A novel method for the selective determination of hemoglobin (Hb) was developed based on fluorescence quenching of the NAC capped CdHgSe quantum dots. A number of key factors including pH value of phosphate buffer solution, quantum dots concentration, the adding sequence of reagents and reaction time that influence the analytical performance of the NAC capped CdHgSe quantum dots in Hb determination were investigated. Under the optimal experimental conditions, the change of fluorescence intensity (Δ I ) was linearly proportional to the concentration of Hb in the range of 4.0 × 10 −9 –4.4 × 10 −7 mol L −1 with a detection limit of 2.0 × 10 −9 mol L −1 . The developed method has been successfully employed to determine Hb in human urine samples.
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PubMed
高影响因子
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