Showing papers in "Polymer Journal in 1991"
TL;DR: In this paper, a theory of the application of phase equilibrium was presented as an example for the pore forming mechanism in the solvent casting method, and the growth rate of nucleus by diffusion to the primary particle and the time of attainment of phase equilibria of whole system were determined under the assumption of local equilibrium between nucleus and sorrounding sphere.
Abstract: In order to give better and quantitative understanding of the pore forming mechanism in the solvent casting method, a theory was presented as an example of the application of phase equilibrium. Mechanism of formation of critical nucleus from homogeneous polymer solution in the metastable region of the phase diagram was investigated in accordance with the activation energy of nucleation. The growth rate of nucleus by diffusion to the primary particle and the time of attainment of phase equilibria of whole system were determined under the assumption of local equilibrium between nucleus and sorrounding sphere. Formation of secondary particle by amalgamation was tried to explain by use of the particle Monte–Carlo simulation approach.
637 citations
TL;DR: In this article, a model for chain packing for ordered and disordered modifications of the α-form of syndiotactic polystyrene is suggested, through quantitative comparisons between X-ray diffraction intensities and calculated structure factors.
Abstract: Models for chain packing for ordered and disordered modifications of the α-form of syndiotactic polystyrene are suggested, through quantitative comparisons between X-ray diffraction intensities and calculated structure factors. According to the reported analysis, zig-zag planar chains are packed in the hexagonal unit cell proposed by Greis et al., but with different orientation and relative height of the phenyl groups. In particular, the phenyl groups in both ordered and disordered modifications are packed according to rhombohedral symmetry. The disorder in the α′ modification corresponds to the statistical occurrence of two different, nearly isosteric, orientations of triplets of chains at well defined locations of a threedimensional lattice, which generate a rhombohedral symmetry for the whole unit cell.
157 citations
TL;DR: Amorphous cis-transoidal poly(phenylacetylene) was obtained by [Rh(norbornadiene)Cl] 2 /triethylamine-catalyzed polymerization as discussed by the authors.
Abstract: Amorphous cis-transoidal poly(phenylacetylene) was obtained by [Rh(norbornadiene)Cl] 2 /triethylamine-catalyzed polymerization. The polymer was found to change into crystalline polymer with cis-cisoidal structure when it was poured into toluene or chloroform.
102 citations
TL;DR: In this paper, homopolymerization of non-chiral N-substituted maleimide (RMI) polymers with n-butyllithium (n-BuLi)/(−)-sparteine (Sp) in toluene to obtain chiral homopolymers with considerably high specific rotation was investigated.
Abstract: Homopolymerizations of non-chiral N-substituted maleimide (RMI, N-substituent(R)=N-n-propyl, N-isopropyl, N-n-butyl, N-isobutyl, N-s-butyl, N-t-butyl, N-cyclohexyl (CHMI), N-benzyl, N-phenyl, N-1-naphthyl, and N-2-fluorenyl) were performed with n-butyllithium (n-BuLi)/(−)-sparteine (Sp) in toluene to obtain chiral homopolymers with considerably high specific rotation. The specific rotation [α]D and mean residue ellipticity for CHMI polymer were the largest in the polymers ([α]D=ca. −40°C in CHCl3). The polymerization of CHMI and the chiroptical property of the polymers were investigated in detail. Optical rotation could be attributed to a threo-diisotactic structure of RMI polymer main chains.
81 citations
TL;DR: In this article, N-n-alkylmaleimides (nRMI) with various nalkyl groups (n=4−18) were obtained in the presence of 2,2′-azobisisobutyronitrile in benzene at 60°C.
Abstract: Radical polymerization of N-n-alkylmaleimides (nRMI) with various n-alkyl groups (n=4–18) was carried out in the presence of 2,2′-azobisisobutyronitrile in benzene at 60°C. The high molecular weight polymer (Mn>105) was obtained in a high yield from all nRMIs. The resulting poly(nRMI) were soluble in organic solvents such as benzene, chloroform, and THF, and a thin and tough film was obtained from the solution. It was confirmed that poly(nRMI) showed excellent thermal-stability, i.e., they had a high glass transition temperature and decomposition temperatures. The side-chain crystallization was investigated by differential scanning calorimetry. From the measurement of permeation of oxygen and nitrogen through poly(nRMI), it was revealed that these polymers had a high permeability coefficient of 10−8–10−9 cm3(STP)cm cm−2 s−1 cm Hg−1, which depended intensively on the N-substituents.
76 citations
TL;DR: Temperature-modulated controlled drug release using swelling-shrinking responses of the hydrogels as on-off switches for drug release is reported, and the IPNs demonstrate “on” release at higher temperatures.
Abstract: Interpenetrating polymer networks (IPNs) composed of poly(acrylamide(AAm)-co-butyl methacrylate (BMA)) and poly(acrylic acid) (PAAc) demonstrate positive swelling changes with an abrupt transition as temperature increases. Temperature-modulated controlled drug release using swelling-shrinking responses of the hydrogels as on-off switches for drug release is reported. The IPNs demonstrate “on” release at higher temperatures. When changing from higher to lower temperatures, an immediate pulsatile drug release is observed followed by a nearly complete “off” state of drug release. The drastic increase of drug release rate is due to mechanical squeezing by a shrinking gel surface layer of the IPNs in response to decreasing temperature. The following decrease of drug release is due to a subsequent formation of a dense layer of polymer at the IPN surface.
72 citations
TL;DR: In this article, a composite membrane composed of polyion complexes (PIC) as a separating layer was developed for separating water-ethanol mixtures by the use of the pervaporation technique.
Abstract: For the purpose of separating water-ethanol mixtures by the use of the pervaporation technique, new composite membranes composed of polyion complexes (PIC) as a separating layer were developed. The polyion complex structure, consisting of polyacrylic acid (PAA) and polycation, provided excellent permeation rate and selectivity. To obtain a composite hollow fiber membrane, a new technique was developed instead of coating. That is, the polyacrylonitrile membrane was partially hydrolyzed to introduce a carboxylic group, and then converted to a polyion complex. The alkaline hydrolysis reaction and the formation of the separating layer were analyzed by the use of IR, SEM, and EDX. In this manner, modules with effective membrane area up to 6m2 have been prepared.
56 citations
TL;DR: A method for the prediction of gas permeabilities through polymers from their chemical structure has been developed on the basis of the ratio of molar free volume to molar cohesive energy, V(f)/E(coh).
Abstract: A method for the prediction of gas permeabilities (P) through polymers from their chemical structure has been developed on the basis of the ratio of molar free volume to molar cohesive energy, V(f)/E(coh) The permeation of small gas molecules through polymer membranes is dependent on the chain packing density measured by V(f) and segmental motion of polymer chains measured by E(coh) But no simple relationship between P and V(f) or E(coh) alone was found The permeability data of more than 60 polymers covering 7 orders of magnitude for six gases have been treated with linear regression analysis All plots of log P vs V(f)/E(coh) gave good straight lines It is also found that a linear relationship holds when plotting both the intercepts and slopes of log P vs V(f)/E(coh) lines against square of the diameters of gas molecules Therefore, the permeabilities of all the non-swelling gases through a great variety of polymers can be estimated using two correlations above Moreover, this method is more accurate than others in the literature and may found useful for the selection of gas separation or barrier membrane materials
55 citations
TL;DR: The structural organization and transport properties for various glassy polymers being utilized or having potential to be applied as the materials of separating membranes are discussed in this paper, where free volume of polymers was estimated by sorption of low-molecular-weight probe molecules at various pressures and temperatures, by positron annihilation method, by density technique including calculations by means of group contributions.
Abstract: The structural organization and transport properties for various glassy polymers being utilized or having potential to be applied as the materials of separating membranes are discussed. Among them are poly(vinyltrimethylsilane) (PVTMS), poly(trimethylsilyl-1-propyne) (PTMSP), and poly(phenylene oxide) (PPO). In addition, the data for other glassy and rubbery polymers are included into consideration for the comparison. Free volume of polymers was estimated by sorption of low-molecular-weight probe molecules at various pressures and temperatures, by positron annihilation method, by density technique including calculations by means of group contributions. Transport characteristics of polymers investigated were studied by sorption-desorption and permeation techniques. It was shown that highly permeable glassy polymers may posses free volume fraction on the level of that for highly permeable rubbers. This free volume has non-equilibrium nature and exist in the glassy polymer as a interconnected microporous network. Glassy polymers have heterogeneous structure consisting of the regions with ordered and disordered structures. The regularities of gas sorption in and transport through the glassy polymers and rubbery ones are different. The following sequence of changing in gas sorption and diffusion mechanism can be proposed: liquids, rubbery polymers, glassy polymers, highly permeable glassy polymers, microporous sorbents. sorbents.
55 citations
TL;DR: In this paper, it was shown that if the particles repel each other (e.g., by virtue of their electrical charge) they may not approach closely enough for bridging to occur, there is the possibility of floc formation.
Abstract: When (homo-) polymers adsorb from solution onto a surface, forming reversible, physical bonds with the surface, a diffuse structure results which can be characterized in several ways. On the level of individual molecules one may distinguish between sequences of monomer units attached to the surface (‘trains’), parts which start from the surface and return there (‘loops’) and parts where one end dangles freely in solution (‘tails’). On the level of the adsorbed layer as a whole one is interested in the density of monomer units as a function of distance from the surface (the so-called profile), the (total) adsorbed mass, and the thickness of the layer. Of course all these properties depend on the molar mass of the polymer, its structure and its interaction with the surface and with the solvent. The static (equilibrium) situation has been studied in depth over the past 20 years, both experimentally and theoretically. A particularly important step forwards was the theoretical work of Scheutjens et al. who developed an elegant and exact method to calculate adsorbed polymer properties on the basis of a lattice model. Together with results from modern experimental techniques (e.g., small angle neutron scattering, photo-correlation spectroscopy) a fairly consistent picture is now established and work is directed towards more complicated systems such as copolymers and polyelectrolytes. The kinetics of the adsorption process however, is much less understood and the same holds for the dynamics of adsorbed chains. Although it was long suspected that slow rearrangement processes occur in adsorbed layers, it was shown only recently that a freshly prepared polymer layer thins in the course of time as long as the surface is unsaturated. This has important consequences for the process of flocculation (aggregation) of colloidal particles by adsorbed polymer. Such aggregation will namely occur only if the polymer molecules can bridge the gap between two particles in close proximity (so-called ‘bridging’ flocculation). If the particles repel each other (e.g., by virtue of their electrical charge) they may not approach closely enough for bridging to occur. Big polymer molecules can however bridge a gap of 100 A or more, provided they have not yet had time to rearrange into a flat conformation. Hence, only if adsorption occurs rapidly enough to compete successfully with the rearrangement process, there is the possibility of floc formation. Recent attempts to get more direct information on the kinetics of adsorption, desorption and exchange will be reviewed.
51 citations
TL;DR: In this article, the authors give new evidence for the Fujita-Kishimoto approximation to the composition dependence of the fractional free volume, and show that the former is contained as a special case of the latter.
Abstract: There are two typical formulations for the mobilities of jumping units in concentrated polymer solutions on the basis of free volume concept. One is due to Fujita and the other to Vrentas and Duda. The prevailing notion that the former is contained as a special case of the latter is not correct, because the two theories are built on significantly different assumptions. The present paper clarifies this point and gives new evidence for the Fujita-Kishimoto approximation to the composition dependence of the fractional free volume.
TL;DR: In this paper, a method for the synthesis of sequential polyamide (head-to-head, or tail-totail) has been developed, which was prepared by the direct polycondensation of symmetric monomer (YccY), isophthalic acid (2b), XabX, 2,6-dimethyl-p-phenylenediamine (4) using the activating agent, diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphate (1
Abstract: A convenient method for the synthesis of sequential polyamide (head-to-head, or tail-to-tail) has been developed. This polymer was prepared by the direct polycondensation of symmetric monomer (YccY), isophthalic acid (2b) with nonsymmetric monomer (XabX), 2,6-dimethyl-p-phenylenediamine (4) using the activating agent, diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphate (1). The polycondensation was carried out by slow addition of 2b to 4, and gave the sequential (head-to-head, or tail-to-tail) polyamide (14) with inherent viscosity of 0.2 dlg−1. The authentic polyamides with different values of s (probability of –accb– placement) were prepared to verify the structure of polyamide 14. Furthermore, the model reaction was studied in detail to demonstrate the feasibility of the sequential polyamidation.
TL;DR: Poly(ethylene oxide) Macromonomers IX. Synthesis and Polymerization of Macromonomic Carrying Styryl End Groups with Enhanced Hydrophobicity.
Abstract: Poly(ethylene oxide) Macromonomers IX. Synthesis and Polymerization of Macromonomers Carrying Styryl End Groups with Enhanced Hydrophobicity
TL;DR: In this paper, copolymerization of AAm and MB with a certain amount of methacrylic acid (MAc) resulted in the formation of fine monodisperse hydrogel microspheres.
Abstract: Precipitation polymerization of acrylamide (AAm) and methylene-bisacrylamide (MB) was carried out in alcohols. Large, bulky and porous particles were formed by the polymerization. On the contrary, copolymerization of AAm and MB with a certain amount of methacrylic acid (MAc) resulted in the formation of fine monodisperse hydrogel microspheres. This was attributed to the contribution of MAc units to the stabilization of the particles formed at the initial stage of polymerization and the enhancement of swelling of the particles by monomer and alcohol.
TL;DR: In this article, a new organic vapor separation membrane has been developed, which is a composite membrane consisting of a thin skin layer and a porous support layer and nonwoven polyester backing.
Abstract: New organic vapor separation membrane has been developed. Air containing a relatively high organic vapor concentration is fed to the membrane and the organic vapor is selectively extracted. The organic vapor separation membrane is a composite membrane. It consists of a thin skin layer and a porous support layer and nonwoven polyester backing. The skin layer is the selective barrier layer composed of three dimensionally crosslinked elastomeric polymer. Polyimide which has a high resistance to solvents is used for the porous support layer. The composite membrane has an organic vapor permeation rate of 5–20 Nm3/m2hratm, depending on the types of the organic vapors. The permeation rate shows good correlation with the boiling point of the organic vapors. Spiral module type is used for actual application. Vapor concentration after treatment of the module is changed significantly depend on the vapor pressure ratio and flow rate difference between feed side and permeate side of the module.
TL;DR: In this paper, two kinds of alkali metal salts of poly(sulfoalkyl methacrylate)s (PSAMM) were prepared, with which the blend complexes of poly[oligo(oxyethylene) methACrylate] (PMEOn) were formed.
Abstract: Two kinds of alkali metal salts of poly(sulfoalkyl methacrylate)s (PSAMM) were prepared, with which the blend complexes of poly[oligo(oxyethylene) methacrylate] (PMEOn) were formed. These blend complexes contain neither organic plasticizer nor low molecular weight Li-salt and are considered to be single-cationic conductors which are characterized by stable dc ionic conductivity. Cationic conductivity is deeply influenced by the glass transition temperature, cation species, polar group (acrylonitrile), the concentration of polymeric salts, and the size of side-group in PSAMM. An optimum Li+-ionic conductivity of 1.1×10−6 S cm−1 at 25°C is obtained for the blend complex P(0.6MEO18−0.4AN)/P(0.5SHMLi−0.5AN) (AN, acrylonitrile; SHMLi, lithium sulfohexyl methacrylate) with O/Li=72.
TL;DR: Gas Separation Membrane Material Selection Criteria: Weakly and Strongly Interacting Feed Component Situations as discussed by the authors, which is based on a combination of weakly and strongly interacting feed component situations.
Abstract: Gas Separation Membrane Material Selection Criteria: Weakly and Strongly Interacting Feed Component Situations
TL;DR: In this article, the authors present conductivity measurements of solutions, gels and bulk membranes, which measurements are of primary interest for potential applications in electrochemical devices, such as sensors, batteries, fuel cells, electrochromic displays, etc.
Abstract: Perfluorinated ionomer membranes either sulfonated or carboxylated have been extensively studied in order to understand the relations between their structure and properties. In addition to their uses as separator in the Cl2/NaOH industry large potential applications exist in different fields like sensors, batteries, fuel cells, electrochromic displays, etc. Some of these applications are due to the possibility of getting solutions, gels from these materials in different solvents and of reconstructing membranes of different thicknesses. The aim of this presentation is to present conductivity measurements of solutions, gels and bulk membranes, which measurements are of primary interest for potential applications in electrochemical devices. Room temperature measurements of conductivity of solutions/gels: First of all we recall the results already published which show the high conductivity of these gels associated with a transport number t+=1 since the COO− or SO3− anions are covalently bound to the rigid perfluorinated rod like structure. Low temperature measurements: Polymers having ionic conductivity usually show drastic changes upon temperature associated to transition (Tg, Tm or sub Tg relaxations). Measurements of conductivity of NAFION® 1100 solutions in propylene carbonate or dimethoxyethane over a temperature range between +20°C and −40°C have shown only small changes mainly due to viscosity modifications of the solvent as evidenced from the calculated activation energies. Conductivity/swelling measurements: We have recently developed an experiment which permits to obtain both the conductivity and the swelling of ion exchange membranes. Equilibrium experiments with solvent mixtures permit to check the conductivity and swelling changes versus different parameters (dielectric constant of solvent, ionic radius of the counterion, etc.). Diffusion coefficients are also obtained from the time lag when immersing the membrane in the solvent.
TL;DR: In this paper, the initial rate of polymerization was Rp=k[AIBN]0.4, where k is an over-all rate constant, and the monomer reactivity ratios (r1, r2) in the polymerization of N-(4-carboxyphenyl)maleimide (CPMI) with styrene (ST, M2), or with methyl methacrylate (MMA, M 2) and Alfrey-Price Q, e values were determined as r1=0.23, Q1=
Abstract: Homopolymerization and copolymerization of N-(4-carboxyphenyl)maleimide (CPMI) were performed at 70°C in the presence of azobisisobutyronitrile (AIBN) as an initiator in tetrahydrofuran. The initial rate of polymerization was Rp=k[AIBN]0.65 [CPMI]2.4, where k is an over-all rate constant. The monomer reactivity ratios (r1, r2) in the polymerization of CPMI (M1) with styrene (ST, M2), or with methyl methacrylate (MMA, M2) and Alfrey-Price Q, e values were determined as r1=0.019, r2=0.23, Q1=0.67, e1=1.53 for the CPMI-ST system; r1=0.24, r2=1.08, Q1=1.09, e1=1.56 for the CPMI-MMA system.
TL;DR: The phase transition of water-sodium alginate with water content (Wc) from 0 to 2.5 was studied using differential scanning calorimetry (DSC) as mentioned in this paper.
Abstract: The phase transition of water–sodium alginate with water content (Wc) (grams of water/gram of dry sample) from 0 to 2.5 was studied using differential scanning calorimetry (DSC). Upon heating, glass transition (Tg), cold crystallization and melting were observed in the Wc range from 0.49 to 2.5. At a Wc less than 0.49, only Tg was observed. During cooling, the crystallization of water in the system was observed from the Wc=0.77. The above difference suggests the presence of glassy water which crystallizes during the heating process. The contribution of non-freezing water and glassy water to Tg and Cp of the system was estimated.
TL;DR: In this article, a zero-order drug release model for hydrophilic polymeric matrices is proposed, which is based on a new model for zero-Order drug release.
Abstract: A New Model for Zero-Order Drug Release I. Hydrophobic Drug Release from Hydrophilic Polymeric Matrices
TL;DR: In this paper, high-isotropic poly(methyl methacrylate) (PMMA) macromonomers having styrene end group were prepared by the reaction of the corresponding PMMA living anions with p-vinylbenzyl bromide and their polymerizations were studied in toluene using 2,2′-azobisisobutyronitrile as an initiator.
Abstract: Highly isotactic (iso-) and syndiotactic (syn-) poly(methyl methacrylate) (PMMA) macromonomers having styrene end group were prepared by the reaction of the corresponding PMMA living anions with p-vinylbenzyl bromide and their polymerizations were studied in toluene using 2,2′-azobisisobutyronitrile as an initiator. The rate of polymerization (Rp) of iso-PMMA macromonomer was slightly higher than that of syn-macromonomer. A similar tacticity dependence of the reactivity was also observed in the radical copolymerization of the macromonomers with styrene. Propagation rate constant (kp) for the homopolymerization of macromonomers was estimated from Rp, termination rate constant (kt) determined by ESR spectroscopy [K. Hatada et al., Makromol. Chem., Rapid Commun., 11, 101 (1990)] and initiator efficiency (f) determined from end group analysis of polymacromonomer by means of NMR spectroscopy [T. Kitayama et al., Polym. Bull., 25, 205 (1991)]. Both the kt and kp values were much smaller than those for styrene polymerization, and the decrease of kt of the macromonomer was much more evident than the decrease of kp. The kp and kt values for iso-macromonomer were much larger than the corresponding values for the syn- one. The results suggest that the higher segmental mobility of iso-PMMA chain than that of syn-PMMA chain brings about the larger rate constants for propagation and termination reactions.
TL;DR: Ringed spherulite in Binary Blends of Poly(e-caprolactone) and e-CaprolACTone-Butadiene Diblock Copolymer.
Abstract: Ringed Spherulite in Binary Blends of Poly(e-caprolactone) and e-Caprolactone-Butadiene Diblock Copolymer
TL;DR: In this paper, surface modifications were carried out by using maleic anhydride (MA) as a coupling agent, which provided a positive response with regard to the mechanical properties of composites.
Abstract: This paper deals with the mechanical properties of surface modified cellulose fiber-filled thermoplastic composites. The surface modifications were carried out by using maleic anhydride (MA) as a coupling agent. MA-coated fibers provided a positive response with regard to the mechanical properties of composites. On the whole, these properties improved compared to those of virgin polymers. The influence of two organic peroxides, e.g., benzoyl peroxide (BPO) and dicumyl peroxide (DCP), on the properties of composites was also studied. The concentration of MA, initiators and wood fibers plays an important role on the mechanical properties of the composites, e.g., properties improved along with the rise in concentration of each of the above, up to a certain limit, and then decreased at higher concentrations. Moreover, properties varied with the change in type of cellulose fiber, e.g., CTMP aspen, sawdust aspen and nutshell, and nature of thermolastic, e.g., polyethylene and polystyrene. As far as the mechanical properties of the composites were concerned, DCP was believed to be a better initiator.
TL;DR: In this paper, the effect of addition of free polymer to sterically stabilised dispersions, i.e. depletion flocculation, was investigated using rheological measurements, and the latter was applied to calculate the energy of separation Esep between the particles in a flocculated structure.
Abstract: The theories of steric stabilisation and the main parameters that control stability are briefly reviewed. This followed by description of the methods that can be applied for studying steric interactions. Of these viscoelastic measurements offer an indirect, but simple method, for studying interparticle interaction. The storage modulus (G′) volume fraction (φ) results could be compared with the force-distance curves obtained from direct measurements. The effect of addition of free polymer to sterically stabilised dispersions, i.e. depletion flocculation, was investigated using rheological measurements. The latter was applied to calculate the energy of separation Esep between the particles in a flocculated structure. Esep was compared with the free energy of depletion Gdep that was calculated using Asakura and Oosawa as well as Fleer, Scheutjens and Vincent’s theories.
TL;DR: In this article, the authors investigated the properties of poly(vinyl alcohol)/poly(methacrylic acid) complexes and polyvinyl alkaline/poly(acrylic) blends using high-resolution 13C solid-state NMR method.
Abstract: Miscibility of poly(vinyl alcohol)/poly(methacrylic acid) complexes and poly(vinyl alcohol)/poly(acrylic acid) blends is investigated by high-resolution 13C solid-state NMR method. Observed 13C spectra are discussed in terms of hydrogen-bonding effects on chemical shift. The results indicate that poly(vinyl alcohol) and poly(methacrylic acid) are intimately mixed on a scale of 20–30 A due to intermolecular hydrogen bonding to form equimolar-ratio complexes. For the poly(vinyl alcohol)/poly(acrylic acid)=1/1 blend, the two polymers are also miscible, the crystalline phase of PVA is destroyed completely and no detectable domain can be observed for the blend on a scale of 20–30 A. Poly(vinyl alcohol)/poly(acrylic acid)=2/1 and 1/2 blends are homogenous on a scale of 200–300 A, but heterogeneous on a smaller scale.
TL;DR: In this paper, the current status of reverse osmosis and ultrafiltration membranes is reviewed with the view for the future, and new crosslinked aromatic polyamide membranes exhibited the superior separation performance with the sufficient water permeability, the high tolerance for oxidizing agents and chemicals.
Abstract: The current status of reverse osmosis and ultrafiltration membranes are reviewed with the view for the future. In the case of reverse osmosis (RO) membranes, as examples, new crosslinked aromatic polyamide membranes exhibited the superior separation performance with the sufficient water permeability, the high tolerance for oxidizing agents and chemicals. Ultrafiltration (UF) membrane based on poly(phenylene sulfide sulfone)(PPSS) also exibited the superior separation performance with the high solvent, heat and fouling resistance.
TL;DR: The tensile strength and modulus of as-spun polysulfone/TLCP fibers were increased as the TLCP content and spin draw ratio were increased as mentioned in this paper.
Abstract: Blending Amoco polysulfone Udel P-1700 and Hoechst Celanese thermotropic liquid-crystalline polymer (TLCP) Vectra A-950 in a twin-screw extruder produced in-situ composites. An inclusion of TLCP did not notably change the thermal properties of polysulfone but the rheological properties were notably changed depending on the measured temperature and blend composition. In the vicinity of crystal-nematic transition temperature, an incorporation of TLCP into polysulfone increased the melt viscosity and gave rise to a large yield stress. Above the crystal-nematic transition temperature, however, TLCP dramatically decreased the melt viscosity and the resultant yield stress was very small. The tensile strength and modulus of as-spun polysulfone/TLCP fibers were increased as the TLCP content and spin draw ratio were increased. The increase in tensile strength with spin draw ratio was more noticed with the polysulfone/TLCP fiber containing higher TLCP content. Wide angle X-ray diffraction patterns suggested that the increase in tensile strength is ascribable to the enhanced molecular orientation and resultant fibrillation of TLCP. The compositional moduli of as-spun blend fibers were well fitted to the additivity rule of mixtures, viz., the Tsai-Halpin equation for the reinforcement of infinite aspect ratio.
TL;DR: In this article, the propagation process in radical polymerization of dialkyl fumarates (DRF) was investigated and the propagation rate constants (kp) for some DRFs were determined by ESR spectroscopy.
Abstract: The propagation process in radical polymerization of dialkyl fumarates (DRF) was investigated. The propagation rate constants (kp) for some DRFs were determined by ESR spectroscopy. It was revealed that kp increased with the introduction of a bulky tert-butyl ester group in the following order: di-tert-butyl fumarate>methyl tert-butyl fumarate>dimethyl fumarate. The absolute rate constants for meso and racemo additions were elucidated by the combination of the kp and the probability of meso addition, which was determined by 13C NMR spectroscopy.
TL;DR: Miscibility of polyvinyl alcohol/poly(methacrylic acid) and poly(vinyl acid)/poly(acrylic acids) systems: I. High-Resolution NMR Studies in Solution as mentioned in this paper
Abstract: Miscibility of Poly(vinyl alcohol)/Poly(methacrylic acid) and Poly(vinyl alcohol)/Poly(acrylic acid) Systems: I. High-Resolution NMR Studies in Solution