Photochemical degradation of polyepichlorohydrin and its cleavage with n-butyl lithium

The photochemical stability and degradation of polyepichlorohydrin, freed from antioxidant, have been investigated under various conditions, with the polymer in the solid state, in solution, stored in the dark, and exposed to bright sunlight or u.v. light from a medium pressure mercury discharge lamp. The solid polymer maintained in the dark was found to be relatively stable without added antioxidant for at least three months. The polymer in the solid state or in solution exposed to sunlight or u.v. light underwent degradation involving cleavage and possible cross-linking with formation of carbonyl and hydroxyl groups in the degraded polymer. A relatively slow cross-linking reaction occurred with polyepichlorohydrin in solution in the dark. Base cleavage of polyepichlorohydrin with n-butyl lithium has been investigated at room temperature. The polymer underwent a relatively fast cleavage reaction, resulting in a sharp decrease both in molecular weight and limiting viscosity number. Various groups in the degraded polymer such as OH, CCH, α,β-unsaturated carbonyl, for example, were identified by infra-red spectroscopy.     

Aliphatic polyester miscibility with polyepichlorohydrin

Based on the behavior of the glass transition for blends of polyepichlorohydrin with various aliphatic polyesters, miscible amorphous phases are formed in all cases when the ratio of aliphatic carbons to ester groups in the repeat unit is less than 10 but more than 2. This observation includes selected polyesters with branched and saturated cyclic units in their structure. Interaction parameters deduced from polyester melting point depression were all negative and showed a minimum within this range of polyester molecular structures. The composition dependence of the observed glass transitions was found to be severely influenced by the presence of polyester crystallinity in the blend when heated through the transition region.     

Solvent power effect on graessley's time constant in concentrated polystyrene solutions

Results of our measurements of polystyrene solutions and those reported in the literature demonstrate the common dependence of Graessley's relaxation time on the product of concentration and molecular weight, irrespective of the solvent power and its viscosity, and of temperature. Such behavior is in agreement with the conclusions reached in our previous paper, namely, that the shear stress dependence of viscosity of this polymer in solvents differing considerably in viscosity and solvent power may be unified by plotting relative viscosity against the product of velocity gradient and Rouse's relaxation time.     

Camphene as a novel solvent for polypropylene: Comparison study based on viscous behavior of solutions

Polypropylene solutions were prepared using three solvents: paraffin oil, decalin, and a novel solvent—camphene. The effects of these solvents were evaluated based on the activation energy of flow and on their melting‐point depression. Experimental results indicate that the values of the viscosity of the resulting solutions were close to Newtonian behavior in the shear rates below 34 s⁻¹. The Arrhenius–Frenkel–Eyring equation was used to describe the dependence of the viscosity on the temperature. In addition, the viscosity increased with the polymer concentration, which can be described by a power‐law correlation. The activation energy of the flow of the polypropylene/camphene solution was the lowest and that of the paraffin oil solution was the highest. Correspondingly, the melting‐point depression of polypropylene solutions in camphene and decalin were substantially lower than that in paraffin oil (71, 61, and 33°C, respectively). These results indicate that lower activation energies of flow correspond to higher values of melting‐point depression. Moreover, analysis of variance indicated that the primary factor affecting the viscous behavior is the concentration, followed by the solvent and the temperature. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 2068–2074, 2000     

The Viscosity of cottonseed oil,fractionation solvents and their solutions

Cold fractionation of cottonseed oil is made difficult by the high viscosity of the oil. This study was aimed at demonstrating the effect of solvents on the viscosity of mixtures between 0°C and 25°C with a view to facilitating the fractionation of refined cottonseed oil. The solvents used were acetone, methylethylketone, methylisobutylketone, hexane and heptane. Measurements of viscosity were carried out by means of a capillary viscometer. The ratio of the viscosity of cottonseed oil to that of pure solvents is of the order of 300. The viscosities of solutions of various ratios of solvent to oil (1/3, 1/1, 3/1) are between those of cottonseed oil and the pure solvents. The effect of the solvent/oil ratio overrides that of solvent nature. The effect of solvent in reducing the viscosity of cottonseed oil is by descending order: acetone, hexane, methylethylketone, heptane, methylisobutylketone.     

The influence of solvent type on the viscosity of concentrated polymer solutions

The viscosity of concentrated (17.5 g/dl) solutions of cellulose acetate in 11 single solvents and in four binary solvent mixtures was related to a thermodynamic measure of solvent power. In single solvents, the specific viscosity varied from 4600 in dimethyl sulfoxide to 78,000 in diacetone alcohol, with the specific viscosity increasing with decreasing abolute value of the partial molar free energy of dilution. This behavior can be accounted for by the hypothesis that the number of chain entanglements increases with decreasing solvent power. In solvent mixtures, the specific viscosity often attains a minimum value at a composition where the average solubility parameter locus is near the center of the solubility region of the polymer.     

Eigenschaften von gelösten und gequollenen Polymethylmethacrylaten in Abhängigkeit von der Struktur

The stereocomplex formation, which is observed after mixing of stereoregular samples of polymethylmethacrylate (PMMA) in various solvents was studied by dielectric and viscosimetric measurements. By means of X-ray wide angle diffraction measurements of mixtures of stereoregular polymers freed from solvent it was found that the stereocomplex consists of crystalline regions. From viscosity measurements of solutions of various tacticity in comparison with swelling properties of crosslinked PMMA it is concluded that the association of isotactic and syndiotactic sequences, which is considered to be the reason for stereocomplex formation, also exists in solutions and gels of atactic PMMA. From the temperature dependence of the reduced specific viscosity, the complex dielectric constant, and the swelling we deduce that the association in microcrystalline regions leads to formation of physical crosslinks, which melt in a certain temperature range. The properties of dilute solutions prepared from mixtures of isotactic and syndiotactic PMMA and toluene can be interpreted by intermolecular association mainly. The anomalies observed in very dilute solutions are explained by intramolecular association. The properties of solutions in which association occurs are dependent on their preliminary thermal treatment and their previous history.     

Synthetic hydrogels. 1. Effects of solvent on poly(acrylamide) networks

Acrylamide hydrogels were synthesized in a series of hydro-organic solvents to examine how solvent affects the network structure by influencing properties of the first formed polymer in the reaction mixture. The looser and more heterogeneous network structure of gels formed in aqueous solutions of ethylene glycol or propylene glycol was found to be largely due to the reduced chain lengths of the primary polymer molecules. Results from NMR analysis of the monomer, and intrinsic viscosity measurements of the polymer in various solvents indicate that solvent effects on the reactivity of the monomer and the propagating radical impose an overriding control over properties of the resultant networks.     

Flow behavior of concentrated solutions of an SBS block copolymer

The non-Newtonian viscosity of concentrated solutions of a styrene-butadiene-styrene, SBS, block copolymer was measured with a novel capillary viscometer. Polymer concentrations ranged from 0.165 to 0.306 g/cc. Apparent shear rates ranged from 1 to 10⁵ sec^?1. Five different solvents were employed. All of the flow curves can be reduced to a single master curve with the same shape exhibited by monodisperse polystyrenes and the Graessley theory. The shift factor for the shear rate axis, τ₀, approximately parallels the Rouse relaxation time, τ_R, but shows a residual concentration and solvent dependence not predicted by the Rouse form. For different solvents at the same concentration, better solvents show a minimum relative zero shear viscosity, η₀/η_s, and a maximum ratio τ_R/τ₀. It is concluded that all solvent effects are not adequately incorporated into the zero shear viscosity for the purposes of constructing master plots; however, the shape of the master plot is not affected by the solvent or the polymer block structure.     

非良溶剂存在下静电纺PVDF和P(VDF-HFP)纤维的可纺性研究

将聚偏氟乙烯(PVDF)和聚偏氢氟乙烯-六氟丙烯共聚物[P(VDF-HFP)]分别溶解于良溶剂N,N-二甲基乙酰胺(DMAc)和非良溶剂丙酮(Act)的混合体系中(DMAc:Act体积比为3:7),用静电纺丝法制备两种超细纤维。考察了在非良溶剂存在的情况下两种溶液浓度和增比粘度(η8p)的依赖关系,测定了两种溶液中的缠结浓度(Ce)。结果表明,PVDF和[P(VDF-HFP)]两种溶液的浓度的对数和8p的对数在一定的浓度范围内存在线性关系,其Ce的质量分数分别为6．8％和4．8％;静电纺纤维经扫描显微镜观察表明,在缠结数评估失效情况下,Ce对两种含非良溶剂的高聚物溶液可纺性也具有半定量的评估作用。两种溶液浓度低于Ce时无法纺出纤维,主要形成聚合物液滴;Ce是电纺出珠状纤维的最小浓度,而纺出均一的无珠纤维溶液浓度为(2-2．5)Ce。     

Sulfonated polyisobutylene telechelic ionomers. XIII. Viscosity behavior in nonpolar solvents and nonpolar–polar solvent mixtures

The effect of molecular variables upon the dilute solution viscosity of sulfonated polyisobutylene telechelic ionomers has been studied in both nonpolar solvents and nonpolar–polar solvent mixtures. In nonpolar solvents, association of the terminal salt groups results in an increase in viscosity and gelation at very low concentrations. The concentration at which gelation occurs was found to be dependent upon molecular variables such as architecture, molecular weight, neutralizing cation, extent of neutralization, and the type of solvent. Addition of a small amount of a more polar cosolvent tends to break up ionic associations between polymer chains and thus reduces viscosity. Finally, such solutions with a small amount of polar cosolvent may display dramatic increases in viscosity with increasing temperature due to a dynamic equilibrium between the ionic groups on the polymer chain, the nonpolar solvent, and the polar cosolvent. The results of this work suggest that these ionomers may potentially be useful as viscosity modifiers or “thermal thickeners” in some applications.     

Determination of the diffusion coefficients of organic solvents in polyepichlorohydrin: A comparative study of inverse gas chromatography and sorption methods

The diffusivity of organic solvents in polyepichlorohydrin was studied with two different experimental setups: inverse gas chromatography (IGC) with packed columns and sorption measurements in gravimetric experiments monitored in a Cahn electrobalance. The aim of this work was to test the possibility of solving an inherent problem in the data reduction of IGC measurements, that is, the necessity of characterizing the morphology of the polymer coated on the support (usually given in the so‐called geometric factor of the column). Temperatures between 35 and 65°C were used in the IGC experiments, whereas the sorption measurements were performed between 30 and 40°C. Glass beads were used as supports in IGC for obtaining data concerning the variation of the plate height with the average gas velocity, with which the use of the Van Deemter equation allowed the determination of the diffusion coefficient if the geometric factor was known. In the sorption experiments, the diffusion coefficients at different penetrant activities were directly measured. For their extrapolation within the same concentration range used for IGC (infinite dilution of the penetrant), the theoretical model of Vrentas and Duda was used. By a combination of sorption and IGC experiments, the geometric factor of an IGC column could be adjusted, and this allowed the determination of the diffusion parameters of any other solvent in the same column. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2216–2223, 2003     

Synthetic hydrogels 3. Solvent effects on poly(2-hydroxyethyl methacrylate) networks

Poly(2-hydroxyethyl methacrylate) networks were synthesized in aqueous solutions of propylene glycol, ethylene glycol, ethylene glycol monomethyl ether, or ethylene glycol dimethyl ether and the influences of solvent on phase separation during the polymerization process studied. Results from conversion-phase diagrams, turbidity measurements, swelling studies, and viscosity measurements show that the phase separation process is dependent upon the solubility parameter of the organic solvent, the instantaneous monomer concentration at each stage of the gel formation process, and the crosslinker content of the reaction mixture.     

13C-NMR determination of the tacticity of polyepichlorohydrin

The microstructure of polyepichlorohydrin was directly studied by high-field ¹³C-NMR. Spectral features were found that correspond to different tacticities. By using curve deconvolution techniques, the different tacticities were assigned and quantified.     

聚环氧氯丙烷胺的合成及其在荷电镶嵌膜中的应用

以环氧氯丙烷、二甲胺、乙二胺为原料制备荷正电的高分子材料聚环氧氯丙烷胺.红外光谱分析表明聚环氧氯丙烷胺含有季铵盐基团,可以作为荷正电剂使用.实验以聚环氧氯丙烷胺及2,5-二胺基苯磺酸的混合水溶液为无机相,三酰氯的正己烷溶液为有机相,在聚醚砜超滤基膜上,通过界面聚合制备了一种新型复合荷电镶嵌膜.由图谱可以确定,2,5-二胺基苯磺酸与三酰氯的界面聚合产物是一种带有阳离子交换基团磺酸基团的芳香族聚酰胺类物质;同时由于膜制备过程中荷正电材料聚环氧氯丙烷胺的加入,使得膜的表层带有阴离子交换基团.复合膜由于带有阴阳离子交换基团而具有荷电镶嵌膜的特征.     

Investigations in modified alkaline iron-tartrate complex solvent for cellulose

A simple method of preparing a stable alkaline iron-tartrate complex solvent (FeTNa (NaCl)) solvent starting from anhydrous ferric chloride was developed. The solvent having the composition: 300 g/l complex, 2N free alkali and 37.5 g/l sodium tartrate as stabiliser, dissolves cotton samples of a high degree of polymerization under higher ambient temperature conditions like those in India. In contrast to solutions in other solvents, cellulose solutions in FeTNa (NaCl) solvents are practically non-sensitive to air exposure. Intrinsic viscosity values were determined for a large number of cellulosic samples. The influence of the viscosity gradient on several viscosity functions was found to be of the same order as in other FeTNa solvents of similar compositions. Fractional precipitation of cellulose dissolved in this solvent was investigated by adding different quantities of aqueous solutions of mannitol.     

The influence of the solvent upon the low shear viscosity of styrene–acrylonitrile copolymer solutions

This paper describes the results of an experimental investigation concerning the effect of polymer–solvent thermodynamics on low-shear viscosity of copolymer soltions. Thermodynamic parameters and low-shear solution viscosities were measured for solutions of polystyrene homopolymer and styrene–acrylonitrile copolymers in four solvents: benzene, dioxane, methyl ethyl ketone, and dimethylformamide. The thermodynamic quality of a solvent for a polymer is characterized by free-energy-of-mixing parameters. These quantities are: the Flory-Huggins thermodynamic interaction parameter χ, the second virial coefficient (from light scattering), the intrinsic viscosity, and the polymer expansion factor. The thermodynamic interaction between a solvent and a polymer in solution influences the rheological behavior of the system. At low concentrations of polymer in solvent, the low-shear solution viscosity is larger in a good solvent than in a poor solvent. In solutions of higher concentration, the reverse may be true and the viscosity is often significantly larger in a poor solvent than in a good one. These results are not predicted quantitatively by existing theory. The parameters in existing viscosity correlation techniques are found to be solvent dependent. The so-called entanglement concentrations for polymer solutions are not unique for a particular polymer but are related to the free energy of mixing polymer with solvent.     

高分子稀溶液中溶剂对分子特性与流变性能的影响

本文研究了不同溶剂对离子性和非离子性高分子稀溶液的分子构型和流变性能的影响.在部分水解的聚丙烯酰胺水溶液中加入无机盐,测量并计算了分子扩张因数,特征粘度与盐浓度、盐离子价数、溶液pH值的关系.同时使用不同的有机溶剂测量聚丁烯溶液的Maxwell模型松弛时间和分子扩张因数.研究表明,高分子稀溶液可藉调整溶剂性质的方法以达到期望的流变特性.     

Electrospun poly lactic acid (PLA) fibres: Effect of different solvent systems on fibre morphology and diameter

The selection of an appropriate non-hazardous solvent or solvent system is essential to determine the rheological properties and electrospinnability of the solution, the productivity, and the morphology of nanofibres. In this study, poly lactic acid (PLA) solutions were prepared in various pure solvents and binary-solvent systems to investigate the effect of different solution properties on nanofibre morphology and diameter. Viscosity, conductivity and surface tension of each solution were measured. Nanofibre morphology was observed by scanning electron microscopy (SEM). Of all the solvent systems used acetone/dimethylformamide gave the highest fibre productivity and finest defect-free nanofibres. Therefore this solvent system was studied in more detail, varying the solvent ratio. Also the polymer concentration in this solvent system was varied to investigate the effect on nanofibre morphology and solution properties. Morphological investigations were done in correlation with rheological measurements: beaded nanofibrous structures were collected from solutions with concentration around the critical chain entanglement concentration (C_e), while defect-free nanofibres were produced when the concentration was increased to about twice the entanglement concentration. Further investigation of the effect of the PLA concentration on the elastic (G′) and the plastic (G″) moduli showed a sudden increase of the elastic moduli (G′) at the critical chain entanglement concentration. The results showed that the solvent properties, boiling point, viscosity, conductivity and surface tension, have a significant effect on process productivity, morphology and diameter distribution of the PLA nanofibres.     

Photoactive epichlorohydrin, 2. Photoinitiated free-radical and promoted cationic polymerization by using polyepichlorohydrin with benzoin terminal groups

The photoinitiated free-radical polymerization of methyl methacrylate (MMA) and the radical-promoted cationic polymerization of cyclohexene oxide (CHO) in the presence of low-molecular-weight polyepichlorohydrin terminated with groups containing benzoin derivatives were studied. Benzoin-terminated polyepichlorohydrin was prepared by Activated Monomer (AM) polymerization. Upon photolysis. polymer-bound alkoxy benzyl radicals were generated, initiating the radical polymerization of MMA. In the case of radical-promoted cationic polymerization of CHO, the cationic initiating species were formed by the oxidation of photochemically generated polymeric radicals by N-ethoxy-2-methylpyridinium hexafluorophosphate.