Polyether Segments Research Articles

Pervaporation, a novel technique for the measurement of vapor transmission rate of highly permeable films

The moisture vapor transmission rate (MVTR) of poly(ether-block-amide) breathable films were measured with a set-up based on the ASTM E96 E and BW methods. These methods led to reliable MVTR for films of low breathability, but not for films of high breathability. The latter shows MVTR values varying over a large range when the operating conditions are changed. An analysis of the mass and the heat transfers pointed out the crucial role of the transfer resistances in the external phases adjacent to the film. The pervaporation technique was designed to minimize these mass and heat transfer resistances using a powerful stirring of the upstream chamber and a good vacuum applied on the downstream chamber. The MVTR was determined from the weight of vapor condensed in a cool trap. The MVTR of films of high breathability were reliably determined by this method; their value was much higher than those obtained with the ASTM E96 BW method for the same films. The obtained intrinsic MVTR data suggest that (i) the film structure is more ordered at lower thickness, and (ii) the activation energy for water permeation is low, probably due to the high flexibility of polyether segments. The technique was successfully used for the measurement of a very high MVTR film made of poly(vinylalcohol), ca. 120 kg day −1 m −2, and for the measurement of the permeation rate of ethylacetate through a silicone rubber film.

Morphology, dielectric relaxation and conductivity of the novel polyurethanes with acid and ionic groups in the polyether segments

The thermal transitions, microphase structure, local segmental and conductivity relaxation of the novel polyurethanes (PUs) based on the poly(tetramethylene glycol) as soft segments (SSs) and 4,4′-diphenylmethane diisocyanate-1,4-butane diol sequences of various length as hard segments (HSs) containing acid or ionic groups in SSs are studied by calorimetry, X-ray scattering and dielectric relaxation spectroscopy. The techniques used include differential scanning calorimetry, 173–473 K, wide-angle X-ray scattering, (WAXS) small-angle X-ray scattering (SAXS), broad band dielectric relaxation spectroscopy (DRS), 10 −2–10 6 Hz, and thermally stimulated depolarization currents (TSDC) techniques, 100–300 K. The peculiarities of microphase-separated structure (MSS) of the PUs such as composition of the microphases, periodicity of non-ionic PU MSS (about 17 nm), size of ionic aggregates in the ionomer (about 7 nm) and their distribution in the SS matrix were determined. The features of α-relaxation, conductivity relaxation and dc conductivity of the proton-conducting PU with acid groups and ion-conducting PU with ionic ones are found and discussed in connection with MSS of the PUs. The level of protonic dc conductivity increases with temperature up to 10 −5 S/m (323 K), whereas the ionic PU exhibits by about two decades lower conductivities, evidently due to ionic aggregation. Accordingly for the latter, apparent activation energy of the conductivity relaxation is considerably more than for the former.

Synthesis of conducting block and graft copolymers with polyether segments

Synthesis of block and graft copolymers containing polyether and conducting polypyrrole sequences were described. Pyrrole moieties were incorporated at the chain ends of polytetrahydrofuran and polysiloxane and at the side chains of polyethyl vinylether by ionic polymerization and appropriate chemical reactions. Subsequent electropolymerization with pyrrole through these moities yielded free standing films of the corresponding block and graft copolymers. The formation copolymers was evidenced by FTIR spectroscopy and extraction with solvent of the precursor homopolymers. The thermal and morphological properties were also characterized. The two surface of the copolymer films generally differ in appearance, the surface at the solution side being cauliflowerlike or wrinkled, whereas the surface at the electrode side smooth. Conductivies of the copolymers were comparable with that of the pure polypyrrole.

Interactions among Hydrophobically Modified Polyelectrolytes and Surfactants of the Same Charge

Effects of sodium dodecyl sulfate (SDS) on surface tension and rheology of aqueous solutions of an associative polymer, poly(ethylene oxide)−b-poly(propylene oxide)−b-(poly(ethylene oxide))−g-poly(acrylic acid) (Pluronic-PAA) have been studied. SDS starts to bind to the Pluronic-PAA copolymer at a concentration that is 25-fold lower than the critical micellization concentration (CMC) of the surfactant. The data indicate predominant binding between SDS and polyether segments of Pluronic-PAA. Incorporation of SDS into the Pluronic micelles makes the polymer less surface-active, as the surface tension increases. The Pluronic-PAA chains collapse when SDS binds, because the surfactant enhances hydrophobic intramolecular associations.

Measurement of anisotropic ion conduction in liquid crystalline states having polyether segments

Measurement of anisotropic ion conduction in liquid crystalline states having polyether segments

Effect of the diisocyanate on the structure and properties of polyurethane acrylate prepolymers

In this study, we investigated the role of diisocyanate on the properties of polyurethane acrylate (PUA) prepolymers based on polypropylene oxide (Mn = 2000 g · mol−1). The diisocyanates studied were isophorone diisocyanate, 4-4′dicyclohexylmethane diisocyanate, and toluene diisocyanate (pure 2,4-TDI, pure 2,6-TDI, and a TDI mixture, TDItech). The molecular structure of the diisocyanate had a major role on the course of the polycondensation and, more precisely, on the sequence length distribution of the final prepolymer. Moreover, the structural organization of the prepolymer also strongly depended on the nature of the diisocyanate. Two types of behaviors were particularly emphasized. On the one hand, the PUA synthesized from 2,4-TDI displayed an enhanced intermixing between soft polyether segments and hard urethane groups, as revealed by the analysis of hydrogen bonding in Fourier transform infrared. Consecutively, the glass transition shifted to higher temperatures for these polymers. On the other hand, strong hard–hard inter-urethane associations were observed in 2,6-TDI-based prepolymers; these led to microphase segregation between polyether chains and urethane groups, as revealed by optical microscopy. This inhomogeneous structure was thought to be responsible for the unusual rheological behavior of these PUA prepolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2750–2768, 2000

Synthesis and electrochemical properties of redox active polyurethanes with ferrocene units in polyether soft segments

Electrochemical active segmented polyurethane with ferrocene units in polyether soft segments (PU-S-Fc) has been originally synthesized and identified by 1H-NMR spectra. Electrochemical behaviors of PU-S-Fc blending with lithium perchlorates were investigated by cyclic voltammetry. In N,N′-dimethyl formide solution, PU-S-Fc exhibited normal cathodic and anodic peaks of the ferrocene/ferricinium (Fc/Fc+) couple. Compared with that of ferrocene molecules blended in ordinary polyurethane (PU-B-Fc), redox peaks of ferrocene units in PU-S-Fc were found to be broader, which may be ascribed to the weak adsorption of the polyurethane on the electrode surface. The influence of lithium perchlorate concentration on peak potentials indicated that supporting electrolytes played an important role in electrochemical redox of PU-S-Fc. In the solid state, PU-S-Fc/Li+ showed discernible redox peaks at temperatures higher than 60°C, and an exponential increase curve of electrochemical response with an increase of temperature was found. Temperature variations of the solid-state ionic conductivity for PU-S-Fc/Li+ can be interpreted by the Arrhenius equation. The similarity between the temperature dependence of ionic conductivity and electrochemical response revealed that transport mechanism of ionic and redox species in the polyurethane matrix was controlled by the mobility of polyether chains. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2674–2680, 1999

Polymer Electrolytes Based on Unsaturated Ethylene Oxide-Segmented Polymers

Polymer electrolytes were prepared from LiClO{sub 4} and high molecular weight unsaturated ethylene oxide-segmented polymers with the generic formula {minus}[(CH{sub 2}){sub x}CH{double{underscore}bond}CH(CH{sub 2}){sub x}O(CH{sub 2}CH{sub 2}O){sub y}]{sub n}--([C{sub x}{pi}C{sub x}EO{sub y}]{sub n}). Synthesized by metathesis polymerization of {alpha}, {omega}-dienes that contain oligomeric poly(ethylene oxide) cores, these polymers are tacky, adhere well to glass and metal surfaces, and have glass transition temperatures between {minus}70 and {minus}80 C. Polymers that contain relatively long alkyl or polyether segments are crystalline below room temperature, but adding LiClO{sub 4} to the polymers converts them to amorphous polymer electrolytes with room-temperature conductivities (20 C) of {approx}2 x 10{sup {minus}5} S/cm. The T{sub g}s of the materials can be fit by a simple model based on the Fox equation, and an analysis of the results indicates that the Li{sup +}:monomer repeat unit stoichiometry is 1:1 for polymers with long block lengths, and decreases to 1:2 for polymers with poly(ethylene oxide) segments with less than 4 repeat units.

Effect of thermal history on properties ofblock-copolyetheresters with poly(tetramethylene 2,6-naphthalenedicarboxylate) segments

The effect of compression molding on the thermal transitions and crystalline properties of block-copolyetheresters with hard segments of poly(tetramethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were investigated by differential scanning calorimetry (DSC), X-ray diffraction, thermal stimulated current (TSC), and dynamic mechanical analysis (DMA). The X-ray diffraction patterns of compression molded samples of the block-copolymers were considerably different from those of the corresponding samples with slow-cooling history. After compression molding, the diffraction peaks were changed completely indicating a different crystalline structure for the polyester segments, and the diffraction peaks became sharper indicating a higher crystallinity. The DSC results also showed that the melting point and crystallinity of the polyester segments were increased after compression molding. The glass transition temperatures of the polyether soft phase and polyester hard phase also were determined by DSC, TSC, and DMA separately with consistent data and were found to be dependent on the content of polyether segments and the molecular weight of the poly(tetramethylene ether)glycol (PTMEG) used. A γ-transition was observed by TSC and DMA and seemed to be independent of the composition and the thermal history. The glass transition temperatures of the polyether soft phase and the polyester hard phase of the block-copolymers derived from PTMEG 650 and PTMEG 1000 shifted to a lower temperature after compression molding possibly because of the partial miscibility between the comprising segments in these two series. The abrupt drop in log G′ in the temperature range of −10–15°C for the block-copolymers derived from PTMEG 2000 was caused by the melting of the polyether segments and indicated that the crystalline properties of the polyether segments could affect their mechanical properties. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1441–1449, 1999

MOLECULAR INTERACTIONS OF CARBOXYLATED URETHANE ACRYLATE IONOMERS IN LOW-POLARITY AND POLAR SOLVENTS

Carboxylated urethane acrylate ionomers that have a small number of ionic groups per chain were synthesized with varying the molecular weight of soft segment, the degree of ionization, and the sort of diisocyanate. The effect of intra-and intermolecular interactions on solution properties was studied by viscosity measurements in low-polarity and polar solvents. In a low-polarity solvent (1,4-dioxane), ionomers showed almost no intramolecular interaction at dilute concentration and a small degree of intermolecular interaction at high concentrations, resulting from a small number of ionic groups per chain. In a polar solvent (dimethylacetamide, DMAc), ionomers showed typical polyelectrolyte behavior, even though ionomers have a small number of ionic groups per chain. Intermolecular interaction caused by polyether soft segment, phenyl group, and hydrogen bond between urethane acrylate ionomer chains contributed to the increase of reduced viscosity at low concentration.

Organic–inorganic membranes prepared from polyether diamine and epoxy silane

Organic–inorganic polymer membranes were prepared by reacting 3-glycidoxypropyl trimethoxysilane with diamines containing polyether segments, followed by hydrolysis and condensation with acid catalysis. The films were characterized by nuclear magnetic resonance and by dynamic mechanical analysis. The rigidity of the films increased with increasing epoxy content and also with addition of tetraethoxy silane (TEOS) to the reacting medium. Water absorption experiments showed that the diffusivity is decreased with increasing TEOS content. Membranes were evaluated for nanofiltration giving cut offs down to 860 g/mol (with a water flux of 2.5 l/h m 2 bar). For gas separation, CO 2/N 2 selectivity values up to 89 were obtained with CO 2 permeability of 125 Barrer.

Polyurethane-maleamides for cardiovascular applications: synthesis and properties.

Several polyurethane-maleamides (PUMAs) containing polyether or polycarbonate soft segments, and aromatic or aliphatic hard segments were synthesized by solution or bulk polymerization, using maleic acid (MA) or a mixture of MA and butanediol as chain extenders. Using this process, activated double bonds are introduced into the polymer chains and the base polyurethanes may undergo further modification via specific grafting, thus improving their tissue compatibility. PUMAs chemicophysical properties were evaluated by gel permeation chromatography (GPC), intrinsic viscosity analyses, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR) and tensile mechanical tests. Polycarbonate diol (PCU)-based PUMAs showed higher molecular weights than polyether diol (PEU)-based ones. The use of butanediol in mixture with maleic acid led to an increase of molecular weights. FT-IR confirmed the presence of the bands related to the amide groups and to the conjugated double bond, yet more evident for the polymer obtained in solution. The higher crystallinity shown by this polymer was also indicative of a better phase separation. All the PCU-PUMAs exhibited similar tensile properties with a higher stiffness than PEU-PUMAs. Among the PEU-PUMAs, the highest tensile properties were shown by the polymer obtained in solution, and by the one derived from a mixture of maleic acid and butanediol.

Photooxidation of functionalized perfluorinated polyethers—II

Three functionalized perfluorinated polyethers (PFPE) were exposed to UV light ( λ >300 nm) in air, and chemical changes recorded by FTIR and 1H, 13C, 19F NMR spectrometry. One of the derivatives (ZTET), end-capped by an hydrogenated ether segment and containing four hydroxyl groups per molecule, was found to readily undergo photooxidation as shown by rapid development of carbonyl oxidation species and a corresponding decrease in C–H character. The carbonyl products were assigned to formate and ester groups respectively, which formation can be described by hydroperoxidation of the functionalized chain ends followed by their photolysis. The formate group is produced as a result of beta-scission of the secondary hydroperoxide γ to the perfluorinated chain and is further transformed to a hydroxymethyl chain end group (ZDOL) stabilised by the shielding effect of the adjacent perfluoromethylene group. The ester formation can be accounted for by oxidation of the methylene group α to the perfluorinated chain giving α carboxylic group which then reacts with ZDOL. The final oxidation product of ZTET is thus a polymer made of fluorinated polyether segments linked by an ester bond. The modification of ZTET by urethane or ester end-caps, in order to simulate crosslinks that are present in an eventual isocyanate-cured polyurethane or polyester coating, strongly increased the photostability of the compound. This marked increase in stability was attributed to both chemical and physical modification of the structure.

Infrared analysis of the photochemical behaviour of segmented polyurethanes: aliphatic poly(ether-urethane)s

The photooxidative degradation of a polyether/aliphatic diisocyanate based polyurethane, ETHDI, was studied using FTi.r. spectroscopy. It was confirmed that the oxidation of this type of polyurethane results from the important sensitivity of the polyether soft segments to oxidative degradation. The photooxidation mechanism of the polyether segment was studied using the photodecomposition of polytetramethylene glycol, PTMG, as a model for that of the soft segments of ETHDI. The photooxidation of PTMG was studied until the ultimate degradation of the polymer and the different photoproducts were identified by analysis of both the solid polymeric matrix and the gas phase. Oxidation of the ether groups produced formates, which further decomposed to give ethylene and methyl formate, and regenerated the formates. For irradiation of the ETHDI polymer until the total disappearance of the ether groups, the decomposition of the urethane functions was observed and the corresponding photoproducts characterized.

Polyether‐segmented nylon hemodialysis membrane. VI. Effect of polyether segment on morphology and surface structure of membrane

Polyether‐segmented nylon hemodialysis membrane. VI. Effect of polyether segment on morphology and surface structure of membrane

Polyether-segmented nylon hemodialysis membrane. VI. Effect of polyether segment on morphology and surface structure of membrane

Amorphous nylon, poly(iminoisophthaloyliminomethylene-1,3-cyclohexylenemethylene) (NyBI) and poly(ethylene oxide) (PEO)-segmented NyBI (PEO–NyBI) membranes were prepared by a phase-inversion method using water/dimethyl sulfoxide (DMSO) mixtures as coagulants. The influence of the PEO segment and coagulant compositions on the morphology of the membranes was investigated. The cloud-point curves in the polymer/DMSO/water ternary system showed that PEO–NyBI and NyBI had the same coagulation processes, that is, instantaneous liquid–liquid phase separation occurred, resulting in a fingerlike structure in the cross section of the membranes. The membrane morphologies observed under a scanning electron microscope (SEM) agreed with the prediction. The PEO segment had little or no effect on the membrane morphologies which were prepared in the coagulants with a low DMSO concentration, and it promoted the change of the phase-separation style from the instantaneous to the delayed one in the case of the DMSO-rich coagulant. The PEO segment, however, significantly influenced the ultrafiltration rate. Additionally, the relationship between the surface composition of the PEO–NyBI membrane and the coagulation condition was also investigated by use of electron spectroscopy for chemical analysis (ESCA) and static secondary ion mass spectrometry (SSIMS). A small enrichment of the PEO segment at the top surface of the membranes was observed with the increase of the DMSO concentration in the coagulant. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1645–1659, 1998

Block copolyetheresters with poly(trimethylene 2,6-naphthalenedicarboxylate) segments: Effect of composition on thermal properties

Block copolyetheresters with hard segments of poly(trimethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were prepared by melt polycondensation of dimethyl 2,6-naphthalenedicarboxylate, 1,3-propanediol and poly(tetramethylene ether)glycol (PTMEG) of molecular weights of 650, 1000 and 2000. The block copolyetheresters were characterized by FTIR, 1H NMR, DSC, X-ray diffraction, TSC (thermal stimulated current), DMA and TGA. It was found that the thermal transitions were dependent on the composition. As the charge molar ratio of PTMEG to dimethyl 2,6-naphthalenedicarboxylate, x, increased, the Tm and ΔHm of the polyester segments decreased, which has been also confirmed by the X-ray diffraction data. The polyether segments of the block copolyetheresters derived from PTMEG2000 could crystallize after cooling, but those of the block copolyetheresters derived from PTMEG1000 and PTMEG650 could not crystallize. The DSC, TSC and DMA results show consistent Tg data of the polyether segments. Based on the shift in Tg of the polyether segments, the amorphous parts of the polyether segments and the amorphous parts of the polyester segments were immiscible for the block copolyetheresters derived from PTMEG2000, but became partially miscible for the block copolyetheresters derived from PTMEG1000 and PTMEG650. The TGA results indicated that composition had little effect on thermal degradation under nitrogen.

Synthesis and properties of polyoxyethylated amine polyurethane ionomers

Based on polyoxyethylated amines (Mn = 600, 1,200) derived from n-butyl amine and ethylene oxide, 4,4′-diphenylmethane diisocyanate, and different chain extenders, two series of polyether–polyurethane (PU) ionomers with reasonable mechanical properties were synthesized. Chain-extended by 1,4-butanediol and subsequently reacted with 1,3-propane sultone, PU elastomers can be conveniently converted to PU zwitterionomers whose ions are located in polyether soft segments. Chain-extended by N-methyl diethanolamine or sodium-S-1,2-dihydroxypropyl sulfonate along with ionization by 1,3-propane sultone, PU ionomers with ions incorporated into both hard and soft domains can be prepared. Physical properties were studied by means of Fourier transform infrared spectra, differential scanning calorimetry, and uniaxial stress–strain testing. Complex impedance spectra were also measured to estimate solid-state ionic conductivity. The results show that ionization of both hard and soft segments induced a much decreased glass transition temperature and brought higher ionic conductivity at room temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2179–2185, 1998

Synthesis and characterization of block copolyetheresters with poly(tetramethylene 2,6-naphthalenedicarboxylate) segments

The block copolyetheresters with hard segments of poly(tetramethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were prepared by melt polycondensation of dimethyl 2,6-naphthalenedicarboxylate, 1,4-butanediol, and poly(tetramethylene ether) glycol (PTMEG) with molecular weights of 650, 1000, and 2000. The block copolymers were characterized by Fourier transform infrared and 1H-NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis (TGA), and X-ray diffraction. The block copolymer compositions were governed by the charge molar ratio (x) of PTMEG to dimethyl 2,6-naphthalenedicarboxylate. It was found that the thermal transitions were dependent on the compositions. As x increases, Tm and ΔHm of the polyester segments decrease due to the decrease in the sequence length. The X-ray diffraction data also indicate that the crystallinity of the polyester segments decreased as x increased. The molecular weight of the PTMEG used has a significant influence on the glass transition temperature (Tg) and the crystallizability of the polyether segments. The polyether segments of block copolymers derived from PTMEG 2000 could crystallize after cooling and showed a Tg of about −67°C, independent of x. However, the polyether segments of copolymers derived from PTMEG 1000 and PTMEG 650 could not crystallize, and the Tg of the polyether segments decreased as x increased. This is described as the difference in the miscibility between amorphous parts of the polyether segments and those of the polyester segments. The TGA results indicate that the composition had little effect on the nonisothermal thermal degradation under nitrogen. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1411–1418, 1997

Photooxidation of functionalized perfluorinated polyethers—I

The photooxidation of a series of functionalized perfluorinated polyethers (PFPEs) was studied by FTIR, 1H- and 19F-NMR with progressive exposure to UV light (λ > 300nm). The objective of this work is to build an understanding of the UV stability of new fluorinated oligomers containing hydrogenated end-cap segments having potentially labile groups such as urethane and ether bonds, these groups being both close to and removed from the fluorinated backbone. These selected structures are representative of a new family of fluorinated resins or model compounds that, simulating the bond in the crosslinked network, allow us to establish the stability of urethane bonds in a cured PFPE-based coating. These last model compounds were synthesized by reacting perfluorinated oligomeric diols with an isocyanate. The results show that dimethylene-diol derivative (ZDOL) is intrinsically stable to UV irradiation. In contrast, the addition of a polyether segment based on CH 2O(CH 2CH 2O) n to the PFPE chain (ZDOLTX) markedly increases the reactivity of the molecules towards photooxidation; the ultimate breakdown product is ZDOL. The addition of a urethane end-cap to the ethoxylated PFPE sample leads to a substantial improvement in its photooxidative stability; accordingly, the corresponding ZDOL-based derivative also shows a high stability with only minor degradation.