Dynamics of water sorbed in reverse osmosis polyamide membrane

Dynamical motion of water sorbed in reverse osmosis polyamide membrane (ROPM) material is reported as studied by quasielastic neutron scattering (QENS) technique. The ROPM studied here has pore size of 4.4 Å as determined by positron annihilation lifetime spectroscopy. Analysis of the QENS data showed that diffusion behavior of the water within the membrane is describable by random jump diffusion model. A much longer residence time is found as compared to bulk water. Positive shift of the freezing point as observed in differential scanning calorimetry indicates presence of strong attractive interaction corroborating the slower diffusivity as observed in QENS.     

Evolution of the crosslink structure in the elastomers NR and SBR

An experimental positron annihilation lifetime spectroscopy (PALS), differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) study of the effect of the advance of the crosslinking reaction on the free volume in a copolymer of styrene–butadiene and natural rubbers was carried out. The crosslink density developed in SBR specimens with different sulfur contents and cure temperatures was studied. SAXS technique was applied to study the process of crosslinking in NR as a function of the cure temperature. Finally, a study of different SBR/NR blends is presented using PALS and DSC.     

Network formation studied by temperature scanning Brillouin scattering and differential scanning calorimetry techniques. I. The cure of 1,4-butanediol diglycidyl ether with cis-1,2-cyclohexanedicarboxylic anhydride initiated by triethylamine

The network formation process of the triethylamine-initiated reaction of 1,4-butanediol diglycidyl ether with cis-1,2-cyclohexanedicarboxylic anhydride has been investigated by conventional differential scanning calorimetry and temperature scanning Brillouin light scattering as a new experimental method for the estimation of the reaction's conversion factor. The time-temperature evolution of the observed quantities (reaction enthalpy in the calorimetric measurements and hypersound velocity in the light scattering) reflects in both sets of experimental data, but results in different kinetic parameters obtained by the assumption of an Arrhenius behavior. These differences are ascribed to the relation of the observed properties with respect to the evolution of the reaction. The enthalpy production of the system observed in the calorimetric experiment is shown to be connected directly to the chemical reaction, whereas the change in the hypersound velocity measured by the light scattering method is sensitive to the solidification of the system. © 1995 John Wiley & Sons, Inc.     

Synthesis and phase behavior of liquid crystalline poly(3-n-ALKYL-4-hydroxybenzoates)

A series of 3-n-alkyl substituted poly(4-hydroxybenzoates) were prepared by melt-polycondensation of the corresponding monomers. The length of the alkyl side chains was varied in the range of 3 to 18 carbon atoms. The average degree of polymerisation (DP) was determined by ¹H NMR end-group analysis. The thermal behavior of the polymers was studied by differential scanning calorimetry (DSC) and polarising microscopy (PM). Structural investigations of oriented and not oriented samples were performed by means of wide angle X-ray scattering (WAXS). The density of the polymers was measured by gradient column technique.     

Cellulose-polyamide 66 blends. I. Processing and characterization

Each homopolymer, cellulose and polyamide 66 (PA66), was separately dissolved in a mixture of N-methyl morpholine N-oxide and phenol (80/20 w/w). Then, the two solutions were mixed together. This step leads to the crystallization of PA66 in small aggregates (about 1 μ) regularly dispersed in the cellulose solution. It appeared that this morphology remains independent of further processing such as spinning or casting. Finally, fibers or films were precipitated in methanol. The entire preparation technique used here results mainly in two-phase systems in which PA66 domains are embedded in an amorphous cellulose matrix. The specimens obtained were at first characterized by differential scanning calorimetry, scanning electron microscopy, and wide angle x-ray scattering. © 1994 John Wiley & Sons, Inc.     

全氟乙丙烯共聚物的超分子结构与结晶性质

本文用激光小角光散射技术研究了全氟乙丙烯共聚物的超分子结构。发现它的结晶形态主要依赖于熔体温度。当共聚物从315—320℃以下降温结晶时得到无规排列晶片所固有的圆对称散射图象。从315—320℃以上温度冷却时,形成球晶结构。这些结果与DSC测得的结晶性质之间存在对应关系。结晶性质在上述温度区间上下也有突变。这些结果可用熔体中存在有序微区来解释,它在结晶时起晶核的作用,在温度高于315—320℃时消失。     

Crystallinity of ethylene oxide oligomers

Nonaethylene glycol and pentadecaethylene glycol and their dimethyl ethers have been prepared and characterized, with respect to crystallinity by wide- and small-angle X-ray scattering, Raman scattering, i.r. spectroscopy and differential scanning calorimetry. Wide-angle X-ray scattering is similar to that from high molecular weight poly(ethylene oxide). The crystal habit is lamella. The lamellae are highly crystalline and the surface layers are ordered. Comparison with crystalline poly(ethylene oxide) prepared conventionally, and having a distribution of chain lengths, shows that such samples crystallize into lamellae with disordered surface layers.     

Intermolecular interactions in rifabutin–2-hydroxypropyl-β-cyclodextrin–water solutions,according to solubility data

The formulations of rifabutin (RB) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), obtained using different preparation techniques, are studied by means of differential scanning calorimetry and molecular spectroscopy (FTIR, NMR, Raman scattering, and photon correlation light scattering). It is established that molecules of RB do not form inclusion complexes with the molecules of HP-β-CD, and an increase in the solubility of RB determined earlier is caused by the formation of weak intermolecular associates.     

工业用涤纶纤维的熔融行为与某些结构参数关系的研究

用ＤＳＣ法研究了国内外不同厂家生产的工业用ＰＥＴ纤维的熔融行为,其热谱表明,一般呈现熔融双峰．实验证明,双熔融峰是由ＤＳＣ过程中纤维材料中一部分热稳定性差的结构发生重排所致．结合用ＷＡＸＤ法、ＳＡＸＳ法、双折射法、密度法获得的结构参数指出,工业用纤维的熔融行为,除受晶粒尺寸、晶粒完善程度、晶粒尺寸分布等因素的影响之外,连续网的结构也起着重要作用．另外,用ＤＳＣ法测定工业用纤维结晶度的精度还有不如人意之处．     

Synthesis and properties of siloxane(ethylene oxide)urethane block copolymers

A new approach to the synthesis of hydrolytically stable dimethylsiloxane-ethylene oxide polyblock copolymers is described, in which ethylene oxide and siloxane blocks are linked by urethane groups. The molecular-mass parameters of block copolymers of different compositions are determined by capillary viscometry, light scattering, and gel-permeation chromatography. The temperature transitions in copolymers are characterized by differential scanning calorimetry.     

COMPATIBILITY IN POLYMER BLENDS OF POLY (VINYL ACETATE) AND POLY (METHYL METHACRYLATE)STUDIED BY NMR

Compatibility of poly (vinyl acetate) (PVAc) with poly (methyl methacrylate) (PMMA) mixtures has been studied by using nuclear magnetic relaxation, differential scanning calorimeter and small-angle X-ray scattering techniques. The nuclear magnetic relaxation time T_1's were measured as a function of composition in blends of PMMA and PVAc prepared from chloroform solution. The results show that the system is miscible for casting from chloroform solution.     

Discotic liquid crystals Physical parameters of some 2,3,7,8,12,13-hexa(alkanoyloxy)truxenes. Observation of a re-entrant isotropic phase in a pure disc-like mesogen

The synthesis of a new discotic mesogen, 2,3,7,8,12,13-hexa(octadecanoyloxy)-truxene is reported. This new compound has been studied using polarization microscopy, differential scanning calorimetry, small angle X-ray scattering and adiabatic calorimetry. The results are compared with those of two other truxene derivatives from the same series: 2,3,7,8,12,13-hexa(decanoyloxy)truxene and 2,3,7,8,12,13-hexa(tetradecanoyloxy)truxene. Refractive index measurements have been performed on these three truxene derivatives as a function of temperature. A re-entrant isotropic phase has been observed in 2,3,7,8,12,13-hexa(octadecanoyloxy)truxene. This is the first report of such a phase in a pure mesogen. We also report measurements of the ratio of the Frank constants for splay and bend in the nematic regime of this new mesogen as a function of temperature using the magnetic Frederiks transition technique.     

Fractional crystallization of oil droplets in O/W emulsions dispersed by Synperonic F127

The aim of this works is to study an oil-in-water emulsion stabilized with a triblock copolymer Synperonic F127 which presents a double size distribution of oil droplets. The emulsions were studied experimentally by means of differential scanning calorimetry (DSC) and dynamic light scattering (DLS). The DSC analysis was carried out focusing on the cooling behavior of the emulsion. The cooling thermograms of the oil-in-water emulsion revealed two crystallization peaks with Gaussian profile; the interesting characteristic is that both peaks are separated in temperature. In accordance to previous works for a single oil dispersed within an aqueous phase, the DSC technique must show a single Gaussian peak of crystallization attributable to a size distribution of droplets. In the present case of emulsions stabilized with 1 g/L of Synperonic F127, the aggregation behavior of triblock as a function of temperature allows to produce an emulsion with a double size droplet distribution. Comparison with emulsions stabilized with 2 and 4 wt% of non-ionic Tween 20 are also presented.     

纳米催化共振散射光谱分析

共振散射光谱技术是利用荧光分光光度计的同步扫描技术建立起来的一项光谱分析新技术,具有简便、快速、灵敏度高等优点,在蛋白质、核酸、无机离子等痕量分析中得到应用.结合本课题组近年来的研究工作,本文综述了共振散射光谱技术在免疫纳米催化、核酸适配体纳米催化分析中的应用.     

The surface properties of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane after partial solution in nitro esters

The thermophysical properties and surface structure of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (TNCO) particles before and after their contact with liquid nitro esters were studied by differential scanning calorimetry and small-angle X-ray scattering. The thermophysical properties of TNCO changed after contact with nitro esters, and the temperature range of the transition from the β to δ polymorph broadened. This peculiarity was explained in terms of the fracton theory by changes in the heat capacity of particles related to the formation of nanoscale roughness with a fractal (scale-invariant) organization as a result of surface etching by solvents such as nitro esters, which are thermodynamically “bad” with respect to TNCO. The volume properties of particles did not change. The possibility of determining the fractal dimension of the surface of TNCO particles by differential scanning calorimetry was demonstrated. The rate of heating was then used as a “scale ruler” (“yardstick”), and the temperature range of the transition from the β to δ polymorph, as a measured parameter. The dimension of the surface fractal was also determined by an independent method (small-angle X-ray scattering). The results obtained by the two methods were closely similar.     

Anionic polymerization of cyclic ester and amide in miniemulsion: Synthesis and characterization of poly(ε‐caprolactone) and poly(ε‐caprolactone‐co‐ε‐caprolactam) nanoparticles

For the first time, poly(ε‐caprolactone) and poly(ε‐caprolactone‐co‐ε‐caprolactam) nanoparticles were successfully obtained by anionic polymerization of ε‐caprolactone and anionic copolymerization of ε‐caprolactone with ε‐caprolactam, respectively, in heterophase by the miniemulsion technique. After polymerization the resulting dispersions are stable for hours in case of the pure polyester and days for the copolymer. The syntheses were carried out with different continuous phases, amounts of surfactant, initiator, and monomers. The influence of the reaction parameters on the molecular weight of the polymers and on colloidal characteristics like size and morphology of the nanoparticles were studied by dynamic light scattering, gel permeation chromatography, differential scanning calorimetry, nuclear magnetic resonance, and Fourier transform infrared spectroscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

PBT-PA6嵌段共聚物中嵌段间的相容性

用热分析、动态粘弹谱、红外光谱和小角X光散射的实验结果,证实了在聚对苯二甲酸丁二酯-聚己内酰胺嵌段共聚物(简称PBT-PA_6)的无定形区中,两嵌段间具有良好的相容性,两嵌段间有氢键生成。     

Calorimetric and diffractometric study of the lowest room-temperature transition of polytetrafluoroethylene

Through differential scanning calorimetry and wide angle x-ray scattering, the room-temperature transitions of native (never melted) polytetrafluoroethylene have been investigated. The independence of the transitions, and in particular of the lowest one, on the heating kinetics, seems to suggest that also this transition is a true crystal-crystal transition.     

Mesoscale chiroptics of rhythmic precipitates

Rhythmic precipitates of centrosymmetric phthalic acid were analyzed by a square-wave mechanically modulated circular extinction imaging microscope. Spherulites were bisected into square-millimeter sized heterochiral domains that are a consequence of circular intensity differential scattering of left and right circularly polarized light. The dissymmetry and chiral amplification indicated optically was confirmed in the microtexture established by atomic force and scanning electron microscopies.