Sorption and Diffusion of Sub/Supercritical Carbon Dioxide in Poly(methyl methacrylate)

Sorption and desorption processes of subcritical and supercritical carbon dioxide in poly(methyl methacrylate) (PMMA) at various temperatures and pressures were investigated systematically. The gravimetric method was used to study the desorption and sorption diffusivities. It was found that there existed a characteristic value of pressure in the sorption isotherm of PMMA, above which saturation was observed to increase more rapidly with pressure. From the measured diffusivities of sorption and desorption under a wide range of operating conditions, the diffusivities of sorption was found to increase with increasing temperature, whereas the diffusivities of desorption showed a contrary trend.     

Monohydric alcohol transport in a rubbery poly(urethan)

Steady-state permeation rates and equilibrium sorption measurements were made as a function of temperature for a series of alcohols in a polybutylene adipate polyurethan. The alcohol series included methanol; ethanol; n-propanol; n-, iso-, sec-, and t-butanol; n-pentanol, n-hexanol, and n-heptanol (all at unit activity). Calculated integral diffusivities of the various penetrants correlated well with effective penetrant size. The solubility coefficients for the various alcohols increased as the difference between the solubility parameters of the polymer and penetrant decreased for the normal alcohol series. The solubility coefficients for the branched alcohol isomers were characterized by values lower than those predicted by the correlation for the normal alcohols; possibly steric hindrance limits sorption on specific polymer sites. A detailed analysis of the system ethanol/poly(butylene adipate-polyurethan) revealed a sigmoidal increase of the diffusion coefficient with increasing penetrant concentration, suggesting a competition between penetrant clustering and polymer plasticization. The diffusion process appears to be time dependent as well as concentration dependent. Anomalies in the diffusion behavior that can reasonably be related to polymer segmental relaxation are present to a much larger degree as temperature is increased. Ethanol sorption was further complicated by positive deviation from Henry's law at activities in excess of 0.2.     

In situ synthesis of cobalt ferrite nanoparticle/polymer hybrid from a mixed Fe–Co methacrylate for magnetic hyperthermia

Hyperthermic CoFe₂O₄ nanoparticle (CFO NP)/polymer hybrids were synthesized by hydrolysis–condensation from a complex of Co and Fe possessing methacrylate ligands. Single-crystal analysis revealed that the complex consisted of two Co and four Fe metal atoms coordinated by methacrylate and 2-methoxyethoxy groups. The complex was copolymerized with 2-hydroxyethyl methacrylate (HEMA) and the resulting copolymer was then hydrolyzed to form a CFO NP/copolymer of poly(methacrylate) and poly(2-hydroxyethyl methacrylate) hybrid. Copolymerization with HEMA enhanced the stability of the hybrid in water. The size and magnetic properties of CFO in the hybrid were controlled by adjusting the hydrolysis conditions. Moreover, the hybrid generated heat under an alternating current magnetic field; its exothermal properties depended on the magnetic properties of the hybrid, the strength of the applied field, and the CFO NP content in the agar phantom matrix.     

The Effect of Cross‐Linking on the Actuation of an Electroactive IPMC Prepared with a Fluorinated Acrylic Copolymer

The hydroxyl group of HEMA was cross‐linked with 1,3‐diethoxy‐1,1,3,3‐tetramethyldisiloxane in order to enhance the actuation force of the ionic polymer‐metal composite (IPMC) made from the acrylic ter‐polymer of fluoroalkyl methacrylate, 2‐acylamido‐2‐methyl‐1‐propanesulfonic acid, and 2‐hydroxyethyl methacrylate (HEMA). The water uptake was reduced and the mechanical strengths of the membrane were improved by the cross‐linkage. The actuation force of the IPMC was generally enhanced, although it was reduced somewhat at high levels of cross‐linking. The current and deformation responses of the IPMC were both decreased by cross‐linking.     

含丙磺舒高分子药物纳米微球的制备

非甾体抗炎药丙磺舒与甲基丙烯酸 2 羟乙酯 (HEMA)反应制得含丙磺舒单体HP ,此单体在乙醇 /水体系中与甲基丙烯酸甲酯 (MMA)共聚得到含丙磺舒高分子药物纳米微球 ,聚合产物用1H NMR ,FTIR ,GPC和TEM进行了表征。结果表明HP中丙磺舒以酯键连接到甲基丙烯酸 2 羟乙酯上 ,微球由HP和MMA的共聚物构成 ,平均直径为 ( 90± 5 )nm ,含丙磺舒 4 7 4 % ,含药量较高。     

Permeability,Solubility, and Diffusivity of Methane and Butane in Diphenylsiloxane-Dimethylsiloxane Copolymer Membranes

Permeation and sorption of methane and n-butane gases in polydimethylsiloxane (PDMS) and diphenylsiloxane-dimethylsiloxane (DPh-DM) block copolymer membranes were studied at room temperature and different upstream pressures. The membranes were prepared via room temperature vulcanization of vinyl terminated siloxanes through platinum catalyzed hydrosilylation reactions by mixing stoichiometric amounts of polymer, crosslinker, and catalyst, and casting of the mixture solutions with hexane. Composite membranes of polysiloxanes on a polyacrylonitrile microporous support were synthesized for permeation experiments and single layer dense films were used in sorption experiments. The effect of upstream pressure on permeability, solubility, and diffusivity of these membranes was evaluated. It was found that selectivity of the DPh-DM copolymer membrane for n-C₄H₁₀ relative to CH₄ was up to 19% higher than that in PDMS membrane. Both solubility and diffusivity selectivities had positive contributions in permselectivity improvement. The improvement in selectivity was attained with less than a 6% decrease in permeability of n-C₄H_10. Up to 11% improvement in selectivity was also obtained in mixed gas experiment.     

Time-resolved thermal lens study on the heat dissipation effects in solid polymeric matrices used as laser dyes

A dual-beam pulsed-laser time-resolved thermal lens (TRTL) has been used to study the heat dissipation effects in solid polymers employed as laser dyes. The laser-dye samples studied are polymer solutions of rhodamine 6G (Rh6G), namely homopolymers of methyl methacrylate (MMA) and copolymers of methyl methacrylate and 2-hydroxyethyl methacrylate (HEMA) with MMA:HEMA compositions 1:1 and 7:3 vol./vol., where the dye is either dissolved or modified and copolymerized with methacrylate monomers. The long-term stability of the laser material is independent of the thermal diffusivity of the samples, as determined by the TRTL technique. This suggests that the rate of heat dissipation does not play a major role in the photostability of the samples. In contrast, the TRTL experiments have revealed permanent changes in the optical properties of the polymers when subjected to a large number of laser pulses. This is explained in terms of permanent plastic deformation of the matrices. Received: 19 June 2002 / Revised version: 1 August 2002 / Published online: 15 November 2002 RID="*" ID="*"Dedicated to Prof. S.E. Braslavsky on the occasion of her 60th birthday. This work was presented at the V Congreso de Fotoquímica, Torremolinos, Spain, 2001 RID="**" ID="**"Corresponding author. Fax: +34-93/205-6266, E-mail: s.nonell@iqs.es     

Influence of water states in hydrogels on the transmissibility and permeability of oxygen in contact lens materials

The properties of water in soft contact lenses such as the water content, free-to-bound water ratio were key determinants of their oxygen transmissibility characteristics. Differential scanning calorimetry (DSC) was used for measuring the different states of water in hydrogel materials. The convenient apparatus was devised for testing the oxygen permeability coefficient of hydrogel membranes. DSC data showed that the content of freezing water in hydrogel increased with growth of N-vinyl pyrrolidone (NVP) percentage, and the non-freezing water in hydrogel increased with growth of 2-hydroxyethylmethacrylate (HEMA) percentages. It was found that the transmissibility and permeability of oxygen in hydrogel could be described according to the solution-diffusion model. The systematic variations in chemical structure and volume fraction of water in polymer bring about significant changes in oxygen permeability coefficients. The permeability of the material was affected by the freezing water in hydrogel rather than by the non-freezing water.     

Solid electrolyte membranes from semi-interpenetrating polymer networks of PEG-grafted polymethacrylates and poly(methyl methacrylate)

Solid polymer electrolyte membranes were prepared as semi-interpenetrating networks by photo-induced polymerization of mixtures of poly(ethylene glycol) (PEG) methacrylate macromonomers in the presence of poly(methyl methacrylate) (PMMA) and lithium bis(trifluoromethanesulfonyl)imide salt. The composition of the membranes was varied with respect to the PMMA content, the degree of cross-linking, and the salt concentration. Infrared analysis of the membranes indicated that the lithium ions were coordinated by the PEG side chains. Calorimetry results showed a single glass transition for the blend membranes. However, dynamic mechanical measurements, as well as a closer analysis of the calorimetry data, revealed that the blends were heterogeneous systems. The ionic conductivity of the membranes increased with the content of PEG-grafted polymethacrylate, and was found to exceed 10^− 5 S cm^− 1 at 30 °C for membranes containing more than 85 wt.% of this component in the polymer blend.     

Equivalent cross-relaxation rate imaging in the synthetic copolymer gels and invasive ductal carcinomas of the breast

The values of equivalent cross-relaxation rate (ECR) correlated well with [i] water conditions in various copolymer gels and [ii] nature of malignant cells with regard to nuclear dysplasia and mitotic potential in breast carcinomas. The synthetic copolymer gels composed of any two or three monomers among 2-hydroxyethyl methacrylate (HEMA), glycidyl methacrylate (GMA), N-vinyl-2-pyrrolidinone (N-VP), methyl methacrylate (MMA) and benzyl methacrylate (BMA). The ECR measurement was performed by using an off-resonance saturation pulse under conventional field-echo imaging at frequency within +/- 75 ppm apart from the water resonance frequency. The ECR values were readily to determine and non-time consuming parameter for cross relaxation rate. The ECR values at the frequency offset by 7-ppm (ECR-7) were divided the sample gels two classes, which must correspond to hydrophilic or hydrophobic ones.The sensitivity in the gels was nearly equivalent to the cross-relaxation rate itself. In the breast carcinomas, the ECR-7 correlates with the nature of malignant cells with regard to nuclear dysplasia and mitotic potential. The ECR-7 is better or more accurate than the STR-7 because the SDNRs between carcinoma and glandular tissue increased by approximately 50% on the ECR-7 compared with the STR-7. Thus the ECR values could be a new parameter for malignancy and cell proliferative activity of the breast carcinomas with non-invasive modalities by magnetic resonance imaging.     

Permeability of cellulose acetate membranes to selected solutes

The permeability of cellulose 2.5-acetate films to several electrolytes and nonelectrolytes was measured. Permeabilities were determined by a desorption-rate method in which diffusion and distribution coefficients were measured. The rejection of the same solutes by modified cellulose acetate membranes in reverse osmosis experiments was also measured. A comparison was made between intrinsic water and solute permeabilities and the reverse osmosis semipermeability data using a noncoupled flow model of solute and water transport. The results were in reasonable agreement, indicating that flow coupling is not generally important in these films. Some of the factors, such as thermal history and casting environment, affecting the transport properties of acetone-cast cellulose acetate films were examined.     

Diffusivity control in nanoporous membrane through organic-inorganic hybridization

Nanoporous inorganic materials have attracted great interest due to their potential application as nanofilters, drug delivery carriers and adsorbents. In order to control the molecular passage through nanopores, we have modified the pore channel of inorganic materials with organic moieties and investigated the diffusion pattern of small molecules. The surface was modified by octyltriethoxysilane (OTS) by refluxing in toluene for 12 h. The water contact angle of OTS modified zirconia membrane was observed ∼110° showing hydrophobic surface. Contact angles to various solvents were also examined to verify the self-assembled monolayer of octyl chains on the inorganic membrane. The molecular passage patterns of both pristine and modified nanoporous membrane were evaluated by means of the diffusivity of small dye molecule, azobenzene. The diffusion coefficients of azobenzene on both membranes were measured in various solvents on the basis of Fick’s diffusion law. The diffusivities in various solvents for pristine and its modified zirconia membrane were determined. The diffusivity was observed to be influenced by surface energy of both membrane and solvent as well as the polarity of solvents.     

真空热处理人工林落叶松木材吸湿性变化机理研究

热处理是一种环境友好型的木材改性方法,可提高木材的耐腐性和尺寸稳定性。研究以落叶松木材为试验材料,在处理温度200 ℃的条件下,对其进行了不同时间的真空热处理。利用动态水蒸气吸附(DVS)对热处理前后木材吸湿性的变化进行了表征,通过傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)和X射线衍射(XRD)分析了热处理前后木材化学组分和结构变化,通过化学变化分析阐明了热处理木材吸湿性变化的作用机制。结果表明：真空热处理落叶松木材的平衡含水率降低,热处理木材的平衡含水率随热处理时间的延长呈逐渐下降的趋势。结合红外光谱和光电子能谱发现,热处理后木材纤维素和半纤维素等化学成分发生降解,木质素发生交联缩合反应,使得吸湿性基团含量减少,碳元素与氧元素含量发生变化,氧碳比降低,从C原子的结合形式来看,热处理材的C1含量增加,C2和C3含量降低,这些化学变化使得热处理材的吸湿性降低。此外,真空热处理未破坏木材的结晶结构,木材的相对结晶度随真空热处理时间的延长而增大,结晶度的增大减少了纤维素分子链上吸水性基团的数量,从而降低了木材的吸湿性。     

Opto-acoustic study of tinuvin-P and rhodamine 6G in solid polymeric matrices

Laser-induced opto-acoustic calorimetry has been used to examine the thermo-elastic properties of two polymer matrices doped with tinuvin-P and the radiation-less decay processes of rhodamine 6G (Rh6G) in them. The matrices assayed were methyl methacrylate (MMA) homopolymers P(MMA), and methyl methacrylate and 2-hydroxyethyl methacrylate (HEMA) copolymers P(MMA:HEMA). A slight difference in the thermo-elastic properties of the polymers, namely their adiabatic expansion coefficients, has been detected and found to correlate with the long-term stability of the laser material. This suggests a key role of the heat-dissipation processes in the photostability of these polymeric materials. On the other hand, the fluorescence quantum yield of Rh6G is shown to vary with the polymer-matrix composition in a way consistent with its lasing efficiency. The Rh6G absorption and fluorescence quantum yield also change dramatically upon increasing its concentration, which suggests the co-existence of different Rh6G forms with different photophysical properties. Received: 10 February 2000 / Revised version: 12 June 2000 / Published online: 10 January 2001     

Chemically induced graft copolymerization of 2-hydroxyethyl methacrylate onto polyurethane surface for improving blood compatibility

To improve hydrophilicity and blood compatibility properties of polyurethane (PU) film, we chemically induced graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto the surface of polyurethane film using benzoyl peroxide as an initiator. The effects of grafting temperature, grafting time, monomer and initiator concentrations on the grafting yields were studied. The maximum grafting yield value was obtained 0.0275 g/cm² for HEMA. Characterization of the films was carried out by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements. ATR-FTIR data showed that HEMA was successfully grafted onto the PU films surface. Water contact angle measurement demonstrated the grafted films possessed a relatively hydrophilic surface. The blood compatibility of the grafted films was preliminarily evaluated by a platelet-rich plasma adhesion test and hemolysis test. The results of platelet adhesion experiment showed that polyurethane grafted polymerization with monomer of 2-hydroxyethyl methacrylate had good blood compatibility featured by the low platelet adhesion. Hemolysis rate of the PU-g-PHEMA films was dramatically decreased than the ungrafted PU films. This kind of new biomaterials grafted with HEMA monomers might have a potential usage for biomedical applications.     

Dual-Mode Sorption of Inorganic Acids in Polybenzimidazole (PBI) Membrane

The sorption behaviors of sulfuric, perchloric, and phosphoric acids in polybenzimidazole membranes have been investigated. The results of sorption isotherms are consistent with the general form of a dual-mode sorption isotherm. The dual-mode sorption parameters were found using a least-squares program by fitting experimental data to a dual-mode equation. Results indicate a correlation between permeant properties like acidity, size, and the affinity constant in Langmuir-mode sorption species. Moreover, the results show that the size of the permeants has the dominant effect on Henry's constant. The obtained results for , site saturation constant, in Langmuir-mode sorption in the case of perchloric and phosphoric acids, reveals that the two acid molecules interact with two N?H basic groups in the polybenzimidazole repeat units. But in the case of sulfuric acid, it is shown that sulfuric acid neutralizes some of the basic groups in the polymer by its strong second hydrogen and the obtained value for was 1.25.     

Preparation and characterization of modified nano-porous PVDF membrane with high antifouling property using UV photo-grafting

In this study, the poly(vinylidene fluoride) (PVDF) membrane was prepared via immersion precipitation technique and modified by UV photo-grafting of hydrophilic monomers on the top membrane surface. Acrylic acid (AA) and 2-hydroxyethylmethacrylate (HEMA) as acrylic monomers and 2,4-phenylenediamine (PDA) and ethylene diamine (EDA) as amino monomers were used at different concentrations to modify the membrane and improve the hydrophilicity with less fouling tendency. Moreover the presence of benzophenon as photo-initiator for grafting the hydrophilic monomers onto PVDF membrane surface was elucidated. The virgin and modified PVDF membranes were characterized by contact angle, ATR-FTIR, SEM and cross-flow filtration. The contact angle measurements demonstrated that the hydrophilicities of the membranes were significantly enhanced by UV photo-grafting of hydrophilic monomers onto the membrane surface. The ATR-FTIR confirmed the occurrence of modification on PVDF membrane by UV photo-grafting. The pure water flux of membranes was declined by UV photo-grafting but the milk water permeation and protein rejection were slightly improved. Moreover the antifouling properties and flux recovery of PVDF membrane were improved by UV photo-grafting of hydrophilic monomers.     

Microstructure,Rheology, and Potential Oil Absorbency of Poly(Butyl Methacrylate) and Poly(Hydroxyethyl Methacrylate) Blends

To prepare oil-absorptive polymers with moderate cross-linking structure, poly(butyl methacrylate) (PBMA) was synthesized as a linear hydrophobic polymer by suspension polymerization. In addition, hydroxyethyl methacrylate (HEMA), as a monomer, which could construct a network structure among the macromolecules via hydrogen bond interactions, was solution polymerized in dimethylacetamide (DMAc) with PBMA, yielding a polymer blend of PBMA and PHEMA. The solution of the polymer blend was investigated by rotational viscometry and extended rheometry. The results showed that the viscosity varied greatly with the temperature and shear rate for three different compositions. Fourier transform infrared (FTIR) spectra indicated that an entanglement or interlocking cross-linking structure of molecular chains was constructed by hydrogen bonds. The results from nuclear magnetic resonance (NMR) spectra exhibited a downfield movement of the proton peak as influenced by end groups or hydroxyls in the polymer chains. The rheological measurements demonstrated that the cross-linking structure greatly affected the rheological behavior of the blend solution. In addition, the cross-linking structure was also evaluated by oil absorbency of films.     

Preparation of poly(vinyl alcohol)–silicone based hybrid membranes for the pervaporation separation of water–acetic acid mixtures

Hybrid membranes were prepared using poly(vinyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) via hydrolysis followed by condensation. The obtained membranes were characterized by Fourier transform infrared spectroscopy, wide-angle x-ray diffraction and differential scanning calorimetry. A remarkable decrease in degree of swelling was observed with increasing TEOS content in membranes and is attributed to the formation of hydrogen bonding and covalent bonds in the membrane matrix. The pervaporation performance of these membranes for the separation of water–acetic acid mixtures was investigated in terms of feed concentration and the content of TEOS used as cross-linking agent. The membrane containing 1 : 2 mass ratio of PVA and TEOS gave the highest separation selectivity of 1116 with a flux of 3.33 × 10^?2kg/m²h at 30°C for 10 mass% of water in the feed. Except for membrane M-1, the observed values of water flux are close to the values of total flux in the investigated composition range, signifying that the developed membranes are highly water selective. From the temperature dependence of diffusion and permeation values, the Arrhenius apparent activation parameters have been estimated. The resulting activation energy values obtained, showing that water permeation is lower than that of acetic acid, suggest that the membranes have higher separation efficiency. The activation energy values calculated for total permeation and water permeation are close to each other for all the membranes except membrane M-1, signifying that coupled-transport is minimal because of the higher selective nature of membranes. The negative heat of sorption values (ΔH _s) for water in all the membranes suggests a Langmuir mode of sorption.     

扩散系数的分子动力学模拟

本文选用平衡分子动力学模拟方法,应用不同的势能模型对强极性分子水的扩散系数进行了模拟计算．结果表明,用分子动力学模拟方法计算水的扩散系数时,模拟结果对模型的选取极为敏感。在目前应用较为广泛的几种模型中以 SPCE模型较为适用,所得的扩散系数与实验值较为接近。