Ionomer Blend Research Articles

Electrical and dielectric behavior in blends of polyurethane-based ionomers

In the present work, the electrical and dielectric behaviors in ionomer blends of an anion-containing polyurethane (PU 1) and polyaminourethane (PU 2) have been investigated by using ac Dielectric Relaxation Spectroscopy (DRS), Differential Scanning Calorimetry (DSC) and Thermally Stimulated Depolarization Currents (TSDC) methods. The ionomer blends are characterized from microphase separation of soft-rich and hard microregions. Two conductivity mechanisms contribute to the dc conductivity of the ionomer blends. That of the shorter relaxation time is correlated to the soft-rich microregions and the other with the longer relaxation time is correlated to the hard microregions. From the comparison between ionomers of different composition, it is found that a faster conductivity relaxation mechanism of the soft-rich microregions implies a faster conductivity relaxation mechanism of the hard microregions. This behavior can be understood in terms of concept of the dynamic energy barriers. From the comparison between the ionomer blends, a smaller temperature difference, Δ T 1= T MWS− T α, between the temperatures of the current maximum of the Maxwell–Wagner–Sillars (MWS) and α-relaxation mechanisms, corresponds to a greater dc conductivity. The formalisms of the dielectric function ε*, electric modulus M*, and complex impedance Z* of the ac dielectric spectroscopy reveal the existence, with different weights, of the various mechanisms of dipolar and conductivity relaxation. The combined use of these formalisms, and especially their imaginary parts, gives the possibility to extract conclusions about the origin and the characteristics of the various relaxation mechanisms, as well as about their correlation with the physical processes which take place in the bulk of the materials.

Investigation of the Microphase Separation in Blends of Polyurethane-Based Ionomers

Blends of an anion containing polyurethane (PU1) and polyaminourethane (PU2) were investigated. Dielectric relaxation spectroscopy (DRS), differential scanning calorimetry (DSC), and small-angle X-ray scattering (SAXS) were used in a study of the molecular mobility and microphase morphology and their dependence on the composition of these ionomers. Dielectric thermally stimulated depolarization current (TSDC) measurements of the ionomer blends showed four relaxation mechanisms. The subglass secondary γ- and β-relaxations are related to local motions; the α-relaxation is related to the glass transition of the amorphous soft phase of the ionomers, and the Maxwell-Wagner-Sillars (MWS) relaxation is related to interfacial polarization caused by the motion of ions released during the glass transition. The α- and MWS TSDC relaxations are strongly affected by the degree of microphase segregation (DMS) of the ionomer blends. Based on TSDC measurements, the parameter m TSDC, a criterion expressing a relative degree of phase mixing, is introduced. According to this parameter, the classification of the investigated ionomer blends, in order of decreasing phase mixing (PU1/PU2 in %) is 50/50 (mixed) > 0/100 > 5/95 > 10/90 > 100/0 > 30/70 (high separation). It appears that, as a result of the complexity of the systems, their structures and their properties are not simple functions of their composition. SAXS measurements show that pure PU1 ionomer has a high degree of microphase separation. The introduction of PU2 in the blend causes defects in the hard domains and leads to a structure with mixing of the soft and hard microphases. SAXS measurements concerning DMS are in good agreement with the TSDC results and support the introduced criterion of the relative degree of phase mixing.

Development of new ionomer blend membranes, their characterization, and their application in the perstractive separation of alkenes from alkene–alkane mixtures. I. Polymer modification, ionomer blend membrane preparation, and characterization

Development of new ionomer blend membranes, their characterization, and their application in the perstractive separation of alkenes from alkene–alkane mixtures. I. Polymer modification, ionomer blend membrane preparation, and characterization

Infrared Spectroscopic Study of the Binary Blends of Sodium and Zinc Salt Ionomers Produced from Poly(ethylene-co-methacrylic acid)

Infrared (IR) and far-infrared studies were performed for the binary blends of sodium and zinc salt ionomers of poly(ethylene-co-methacrylic acid) (EMAA), which are known to show a dramatic improvement of small strain moduli (e.g., stiffness) compared with the two component salts. The IR spectra of the blends showed a new asymmetric carboxylate stretching band at 1569 cm-1, which is assigned to carboxylate groups bridging sodium and zinc cations. When temperature was raised, the bandwidth began to increase at around 310 K, just below a transition temperature (Ti = ca. 325 K) observed by DSC and far below the melting of polyethylene crystalline region (Tm = ca. 360 K); this increase was almost linear with temperature and continued to 403 K above Tm, reflecting the increased distribution of the states of the bridging mode with temperature. These results are explained by a structural transition of ionic aggregates at Ti in EMAA ionomers, which was proposed in our previous publications.

Development of new ionomer blend membranes, their characterization, and their application in the perstractive separation of alkenes from alkene-alkane mixtures. II. Electrical and facilitated transport properties

In this contribution, the synthesis and characterization of novel ion-exchange blend membranes which contain the SO 3 Ag group for the application in the perstractive separation of alkene-alkane mixtures, where the Ag + ion serves as facilitated transport site for the alkene via formation of a pi complex with the alkene double bond, is presented. In this part of the article, the transport properties of the following blend membrane types are described: (1) acid-base blend membranes of ortho-sulfone-sulfonated polysulfone (PSU) with ortho-sulfone-diaminated PSU; (2) blend membranes of ortho-sulfone-sulfonated PSU with unmodified PSU; (3) blend membranes of ortho-sulfone-sulfonated PSU with ortho-sulfone disilylated PSU.

Development of new ionomer blend membranes, their characterization, and their application in the perstractive separation of alkenes from alkene-alkane mixtures. I. Polymer modification, ionomer blend membrane preparation, and characterization

In this contribution, the synthesis and characterization of novel ion-exchange blend membranes which contain the SO3Ag group for the application in the perstractive separation of alkene–alkane mixtures, where the Ag+ ion serves as facilitated transport site for the alkene via formation of a pi complex with the alkene double bond, is presented. In this part of the article, the synthesis and characterization of following blend membrane types are described: (1) acid–base blend membranes of ortho-sulfone-sulfonated polysulfone (PSU) with ortho-sulfone-diaminated PSU; (2) blend membranes of ortho-sulfone-sulfonated PSU with unmodified PSU; (3) blend membranes of ortho-sulfone-sulfonated PSU with ortho-sulfone disilylated PSU. The differently modified PSU types were characterized via 1H nuclear magnetic resonance (1H-NMR). The acid–base blend membranes were characterized via Fourier transfer infrared (FTIR) spectroscopy. It could be indirectly proved that formation of PSU–SO3+H3N–PSU ionic crosslinks takes place. Transmission electron microscopy (TEM) investigations of (1) and (2) yielded the results that these blends are inhomogeneous at the microscopic scale. Mechanical stabilization of these blends is accomplished by physical entanglement of the different macromolecules. The blends (3) were macroscopically inhomogeneous due to the strong difference in hydrophilicity of the blend components. Only the blend 90% PSU–SO3H10% PSU[Si(CH3)3]2 formed a blended membrane. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 428–438, 1999

Development and characterization of ion-exchange polymer blend membranes

In the presented paper, the preparation and characterization of new ionomer blend membranes containing sulfonated poly(etheretherketone) PEEK Victrex® is described. The second blend components were Polysulfone Udel®-ortho-sulfone-diamine, polymide PA Trogamid P (producer: Huls) and poly(etherimide) PEI Ultem (producer: General Electric). In the blend membranes swelling was reduced by specific interaction, in the case of the blend components PA and PEI hydrogen bonds, and in the case of the blend component PSU–NH2 (partial) polysalt formation, leading to electrostatic interaction between the blend component macromolecules, and hydrogen bonds. The acid–base interactions also led to decrease of ionic conductivity by partial blocking of SO−3 groups for cation transport, compared with the ionic conductivity of the hydrogen bond blends. The acid–base blends showed better ion permselectivities than the hydrogen bond blends, even at high electrolyte concentrations, and thus better performance in electrodialysis. The thermal stability of the investigated blends was very good and in the case of the acid–base blends even better than the thermal stability of pure PEEK–SO3H. DSC traces of the blend membranes showed only one Tg. In addition, the membranes are transparent to visible light. But therefrom it cannot be concluded that the blend components are miscible to the molecular level: at the acid–base blend blends, the Tg of PEEK–SO3H is very similar to the Tg of PSU–NH2, and in the investigated hydrogen bond blends, the portion of PA or PEI, respectively, might be too low to be detected by DSC. The investigated blend membranes showed similar performance as the commercial cation-exchange membrane CMX in electrodialysis (ED) application. The performance of the acid–base blend membrane is better than the performance of the hydrogen bonded PEEK–PA blend, especially in the ED experiment applying the higher NaCl concentration. This is mainly due to the lower swelling and thus better ion permselectivity of the acid–base blend membrane, compared with the PEEK–PA blend. To get a deeper insight into the microphase structure of the investigated blends, dynamic mechanical analyses and TEM investigations of the prepared blend membranes are planned. In addition, due to their promising properties, the preparation of arylene main-chain acid–base blends with other polymeric acidic and basic components is planned. Furthermore, the acid–base blend membranes will be tested in H2 polymer electrolyte fuel cells and direct methanol fuel cells, because preliminary tests have shown that they have a good perspective in this application.

Dynamics and Nanolevel Structure in an Ionomer Blend of Two Polymers with Widely Separated Glass Transitions

A new ionomer blend of zinc-neutralized sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) and an amino silicone copolymer was prepared. The blend precipitates as a gel from dilute solution and forms a coherent film. Magic angle spinning carbon-13 spectra indicated coordination of the amine of the amino silicone copolymer by the zinc ion. Differential scanning calorimetry and dynamic mechanical spectra show a smearing out of the glass transition over the more than 300 deg temperature separation of the glass transitions of the component polymers. Solid-state proton NMR line shapes indicate narrowing commences at −115 °C, but then the line remains a composite of a narrow Lorentzian line and a broad Gaussian line for at least the next 200 deg, in agreement with the dynamic mechanical data. Goldman−Shen proton spin diffusion measurements give a domain size of the order of 30 Å, corresponding to the more mobile protons contributing to the Lorentzian line shape component. Silicon-29 chemical shift anisotropy line shapes demonstrate the onset of mobility for some of the siloxane units beginning at −115 °C, but complete line shape collapse does not occur even after a 200 deg temperature rise. This again indicates an extended glass transition process even when considering just one component of the blend.

Contact Electrification of Materials: The Chemistry of Ions on Polymer Surfaces

This report summarizes some recent studies aimed at determining the role of ion transfer in contact charging in polymers. The studies were carried out using blends of polymers and ionomers or polymers and organic salts. These blends were charged by contacting with a metal surface and the contact charge which developed was related to the amount and structure of the ions in the polymer blend. A Kelvin Probe and an atomic Force Microbalance were used to determine the charge. A ion transfer model for contact charging was developed which relates the charge to the ions which are on the surface and are mobile, i.e. not covalently bonded or ion pair associated.

Ionomeric Blends of Poly(ethyl acrylate-co-4-vinylpyridine) with Metal-Neutralized Sulfonated Poly(ethylene terephthalate). 4. Effects of Counterions

This is the fourth part in a series of studies on the ionomer blend system of poly(ethyl acrylate-co-4-vinylpyridine) with metal-neutralized sulfonated poly(ethylene terephthalate). The focus of this work was to investigate the influence of counterions of the ionomers on the phase behavior and the ultimate mechanical properties of the blend system. The counterions examined included the group I and II metals Li+, Na+, and Ca2+ and the transition metals Co2+, Ni2+, Cu2+, and Zn2+. Specific interactions between the different metal-neutralized sulfonate groups and the vinylpyridine groups were proven by FTIR spectroscopy to exist for the transition metal counterions. As a result of these specific intermolecular interactions, compatible blends were achieved with the transition metal counterions whereas the group I and II counterions showed total immiscibility as evidenced by the glass transition behavior probed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). In addition, the mechanical properties of the compatible blends were significantly better than those of the immiscible blends, probably due to the lack of interfacial adhesion in the latter. The modulus and tensile strength of the Ca2+-containing blend showed some enhancement compared to the group I metal-containing blends, and this could arise from the presence of some interfacial interactions in it. The degree of property enhancement was found to be a complex function of the nature, strength, and extent of the transition metal complexation between the polymeric components. The crystalline phase in terms of the crystallization kinetics and crystalline morphology of the PET ionomers was strongly influenced by the presence of different counterions and their interactions with the vinylpyridine-containing polymer. The observed modifications provide indirect evidence for the compatibility of the blend system.

Blends of Biphasic Ionomers with Chemically Identical Mono- and Bifunctional Oligomers

Biphasic Cs and Ba carboxylated polystyrene ionomers were blended with chemically identical mono- and bifunctional oligomers whose chain lengths are significantly greater than the average segmental length between ionic groups in the ionomer. The ionomers were chosen to have two ion contents such that, in one case, the matrix phase is dominant and, in the other, the cluster phase is dominant. From dynamic mechanical thermal analysis, it was observed that the biphasic morphology of the ionomers is preserved in all blends (containing up to 60 wt % oligomer). The monofunctional oligomers tend to have a mild plasticizing action on the two phases. In the matrix-dominated ionomer, the bifunctional oligomer has an antiplasticization effect at lower oligomer contents ; this is attributed to a greater dispersion of ionic aggregates in the matrix phase, accompanied by pinning of the oligomer extremities in multiplets, which prevents plasticizing action. In the cluster-dominated ionomer, the oligomer forms a separate phase, which is related to insufficiently large ion-poor styrene regions in the ionomer to accommodate the long nonionic portion of the oligomer chains.

Plasticization of Biphasic Ionomers by Chemically Identical, Short, Monofunctional Oligomers

Blends of carboxylated polystyrene ionomers containing 7 mol % of ionic units and carboxylate-terminated, monofunctional, monodisperse styrene oligomers of MW 800 were investigated by dynamic mechanical analysis and small angle X-ray scattering (SAXS). Both Cs and Ba carboxylate salts were studied, as well as blends of the Cs oligomer with homopolystyrene. The cluster phase is preferentially plasticized by the oligomers for both salts. However, whereas the nonclustered phase of the Cs system is only a little more plasticized than that of the Ba system, the cluster phase in the Cs system undergoes dramatic plasticization, the cluster transition disappearing at 5 wt % oligomer content. Simultaneously, the SAXS ionomer peak disappears. A peak reappears at 20 wt % oligomer content, suggesting the development of a new morphology, proposed to be micelles or inverted multiplets. The difference between the two systems is attributed to the much stronger electrostatic interactions in the Ba system ; this is analyzed in terms of elementary ion units. It is concluded that, whereas the nature of the nonpolar tail is relatively unimportant, the nature and strength of the electrostatic interactions involved can be of critical importance to the plasticization effects in blends of ionomers with short, monofunctional oligomers.

Blends from redox active liquid crystal ionomers and amorphous ionomers

Abstract Biphasic blends (mixtures) of liquid crystal ionomers (prepared from ferrocene containing liquid crystal polymers by a redox reaction) and partially sulfonated polystyrene combine the constituent properties in a way, which is dependent on the measuring method. Polarizing microscopy shows homogenous textures similar to the pure liquid crystal polymer. Mechanical measurements show however the elastomeric behaviour of sulfonated polystyrene. The phase separated structure of these blends is proved by differential scanning calorimetry measurements.

Miscibility of carboxylated and sulfonated polystyrene ionomers with polyamides-66, -610 and -11

Differential scanning calorimetry (d.s.c.) of blends of polystyrene ionomers and polyamide-66 shows that lithium sulfonate groups are more effective than lithium or sodium carboxylate groups in enhancing the miscibility between this polyamide and polystyrene. The miscibility between aliphatic polyamides and the polystyrene ionomer containing 9.8 mol% lithium sulfonate groups decreases as the amide content of the polyamide decreases. Thus, while blends of this ionomer with polyamide-66 and polyamide-610 (PA-610) appear miscible by d.s.c., the blends with polyamide-11 (PA-11) show evidence of some phase separation. Dynamic mechanical measurements of the 50:50 blends of this ionomer with PA-610 and PA-11 confirm the one-phase and two-phase behaviour of these blends, respectively.

Compatibilization in ionomer blends

Two kinds of copolymers, i.e. poly(styrene-co-methacrylic acid) (SMaa) and poly(butyl methacrylate-co-methacrylic acid) (BmaMaa) containing a common but minor (10–20%) component of methacrylic acid, were synthesized. The blends of the corresponding ionomers of SMaa and BmaMaa neutralized with a series of metal-ions produced by solvent casting and moulding were examined by DSC and TEM. It has been shown that introducing metal-ions to the blends of copolymers apparently improves the miscibility. This miscibility enhancement depends on the nature and amount of the counter ions. In the case of SMaa-Na+/BmaMaa-Na+ even a singlephase blend can be produced. The results confirm compatibilization in the blends of similar-charged ionomers.

Compatibilization in ionomer blends

Copolymers of poly(styrene-co-4-vinylpyridine) (SV p ) and poly(butyl methacrylate-co-4-vinylpyridine) (BmaV p ) containing common minor units of pyridine were prepared. The blends of BmaV p /SV p were reacted with a series of metal acetates and carboxylic acids respectively. Due to coordination complexation between the V p units and metal-ions and proton-transfer from the acids to V p units, in both cases the two component ionomers carry positive charge. DSC examination of the two kinds of blends show an apparent miscibility enhancement by introducing the ion groups although there is no favorable columbic interaction between the component ionomers. These results provide a new evidence of compatibilization in the blends of the ionomers with an identical charge

Blends from redox active liquid crystal ionomers and amorphous ionomers

Abstract Biphasic blends (mixtures) of liquid crystal ionomers (prepared from ferrocene containing liquid crystal polymers by a redox reaction) and partially sulfonated polystyrene combine the constituent properties in a way, which is dependent on the measuring method. Polarizing microscopy shows homogenous textures similar to the pure liquid crystal polymer. Mechanical measurements show however the elastomeric behaviour of sulfonated polystyrene. The phase separated structure of these blends is proved by differential scanning calorimetry measurements.

Physically interpenetrating networks in polyurethane ionomers/poly(vinyl alcohol) blends

AbstractThree series of blends of polyurethane ionomers (PUI) with poly(vinyl alcohol) (PVA) were prepared by mixing aqueous PUI emulsions with aqueous PVA solutions and then allowing them to dry. The characterization of the blends of various compositions was carried out using infrared spectroscopy, dynamic mechanical analysis, differential scanning calorimetry and tensile‐elongation testing. It was found that poly(ether‐urethane) cationomer (Cat‐Et)/PVA‐1 and poly(ether‐urethane) anionomer (An‐Et)/PVA‐2 blends exhibit a positive synergistic effect with respect to the tensile strength and that the amorphous phase of PVA is at least partially compatible with both the disordered hard domains and the soft domains of the ionomers. For the former blends, this behaviour is due to the formation of hydrogen bonding with the glycolate anions and ether groups, and for the latter blends to the formation of hydrogen bonds with the ether groups. For poly(ester‐urethane) cationomer (Cat‐Es)/PVA‐3 blends, there is no hydrogen bonding between these two components and no synergistic effect in the tensile strength after blending. Physically interpenetrating polymer networks (IPNs) are expected to occur in the former two blends, but not in the latter one.

A review of miscibility enhancement via ion‐dipole interactions

AbstractIt is shown that ion‐dipole interactions induce considerable miscibility enhancement in blends of styrene ionomers with poly(alkylene oxides). Dynamic mechanical studies, in conjunction with transparency and brittleness of the samples, are used to evaluate miscibility. The effect is clearly thermodynamics in that phase separation can be induced in miscible samples by raising the temperature, with miscibility reestablished ons cooling. The miscibility enhancement in these systems is compared with that resulting from hydrogen bonding. In addition to the styrene/alkylene oxide system, ion‐dipole interactions are found to be effective in enhancing the miscibility of many ionic polymer/polar polymer pairs. The ionomers used in this study were styrene lithium methacrylate and ethyl acrylate lithium acrylate copolymers, while polyethers, polysulfides, polyesters, polyimines, and substituted polyethylenses served as polar polymers.