Infrared and conductivity studies on blends of PMMA/PEO based polymer electrolytes

Poly(methylmetacrylate)/poly(ethylene oxide) (PMMA/PEO) based polymer electrolytes were synthesized using the solution cast technique. Four systems of PMMA/PEO blends based polymer electrolytes films were investigated:

1. PMMA/PEO system,
2. PMMA/PEO + ethylene carbonate (EC) system,
3. PMMA/PEO + lithium hexafluorophosphate (LiPF₆) system and
4. PMMA/PEO + EC + LiPF₆ system.

The polymer electrolytes films were characterized by Impedance Spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). The FTIR spectra show the complexation occurring between the polymers, plasticizer and lithium salt. The FTIR results give further insight in the conductivity enhancement of PMMA/PEO blends based polymer electrolytes.     

Monte carlo studies of phase transitions in polymer blends and block copolymer melts

Summary The unmixing transition of both symmetrical polymer blends AB (i.e. chain lengthsN _A=N _B=N) and asymmetrical ones (N _B/N _A=2,3) is studied by large-scale Monte Carlo simulations of the bond fluctuation model. Combination of semi-grand-canonical simulation techniques, ?histogram reweighting? and finitesize scaling allows an accurate location of the coexistence curve in the critical region. The variation of the critical temperature with chain length (N) is studied and compared to theoretical predictions. For the symmetrical case, use of chain lengths up toN=512 allows a rough estimation of crossover scaling functions for the crossover from Ising to mean-field exponents. The order-disorder transitions in melts of both symmetric (compositionf=N _A/(N _A+N _B)=1/2) and asymmetric (f=3/4) block copolymers is studied for very short chains (16≤N≤60). The interplay between structure and chain configuration is emphasized. Qualitative evidence for ?dumbell formation? of chains and vacancy enrichment in A-B-interfaces and near hard walls is presented. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Infrared studies on the molecular interactions of polymer blends: polystyrenes and polycarbonates systems

Fourier—transform infrared (FT-IR) with digital subtraction method has been applied to investigate the molecular interactions of immiscible polystyrene (PS)/bisphenol A polycarbonate (PC) blends and miscible PS/tetra-methyl PC (TMPC) blends. The FT-IR results show that there are no interactions for PS/PC, and the miscibility of PS/TMPC blends is mainly due to the intermolecular interaction between the phenyl ring of PS and the carbonate group of TMPC. The phenyl ring band of PS is linearly shifted to higher wave number with increasing concentration of TMPC, and the bandwidth at half maximum intensity of the carbonyl band of TMPC is linearly decreased with increasing concentration of PS. The amplitude of the interactional bands is decreased with increasing temperature consistent with LCST behavior of the blend. The miscibility of PS/TMPC and immiscibility of PS/PC has also been discussed in terms of local free-volume, self-interactions, and intermolecular interactions based on the chemical structures of PC and TMPC. Furthermore, the immiscibility behavior for blends of methyl-substituted PS and TMPC, and blends of PS and halogen-substituted PC has been explained in terms of intra and intermolecular interactions caused by steric and/or induction effects.     

Viscoelastic phase separation in polymer blends

In this paper, the dynamics and morphology of viscoelastic phase separation in polymer blends is investigated based on the two-fluid model in two dimensions. At critical composition, we have carefully checked the role of shear modulus, without taking account of bulk modulus. The results show that the higher shear modulus component tends to form a dispersed phase in the intermediate stage of phase separation, if the difference between the shear moduli of the components is large enough. This is opposite to the role of bulk modulus, that the higher bulk modulus component forms a networklike pattern without taking account of the shear modulus even if it is the minority phase. The morphological formation is determined by the competition of opposite effects of shear modulus and bulk modulus. For polymer blends at critical composition, the bulk modulus difference leads to a networklike pattern formed by the higher modulus component in the intermediate stage of phase separation. But if the difference between the shear moduli of the components is large enough, a co-continuous structure is observed, resulting from the competition between shear and bulk moduli. For off-critical composition, difference in bulk modulus also leads to a networklike pattern of the component with higher bulk modulus in the intermediate stage of phase separation, but phase inversion is observed rapidly. A small difference between the shear moduli of the components can support the networklike pattern to continue for longer time. But the networklike pattern does not occur for large difference between shear moduli.Received: 9 September 2004, Published online: 10 November 2004PACS: 64.75. + g Solubility, segregation, and mixing; phase separation - 83.80.Tc Polymer blends     

Microphase separation in cross-linked polymer blends

We investigate the behaviour of randomly cross-linked (co)polymer blends using a combination of replica theory and large-scale molecular dynamics simulations. In particular, we derive the analogue of the random phase approximation for systems with quenched disorder and show how the required correlation functions can be calculated efficiently. By post-processing simulation data for homopolymer networks we are able to describe neutron scattering measurements in heterogeneous systems without resorting to microscopic detail and otherwise unphysical assumptions. We obtain structure function data which illustrate the expected microphase separation and contain system-specific information relating to the intrinsic length scales of our networks.     

Morphology of ternary immiscible polymer blends

Ternary blends consisting of thermoplastic and thermotropic immiscible polymers were studied. Both thermodynamic and kinetic considerations were found to affect their multiphase structure. Thermodynamics is expressed by means of spreading coefficients, whereas the kinetic effect is driven by the dispersed phase viscosity ratio. Some morphologies could be predicted, when both effects acted cooperatively. However, in cases where the effects were opposing, kinetics hindered the development of the expected structure; interpenetration between the two minor phases, rather than engulfing or separately dispersed morphology, took place. In cases where two relatively polar phases were dispersed in a nonpolar matrix (e.g., nylon and polycarbonate in polypropylene), the interaction between the two dispersed minor phases always existed due to their low interfacial tension. Spreading of one minor phase over another, rather than penetration, is the dominating mechanism of encapsulation in polymer blends, contrary to low molecular weight liquids where both spreading and penetration play an important role in the structurization.     

Rheology of ring polymer melts: from linear contaminants to ring-linear blends

Ring polymers remain a challenge to our understanding of polymer dynamics. Experiments are difficult to interpret because of the uncertainty in the purity and dispersity of the sample. Using both equilibrium and nonequilibrium molecular dynamics simulations we have investigated the structure, dynamics, and rheology of perfectly controlled ring-linear polymer blends of chains of up to about 14 entanglements per chain, comparable to experimental systems. Linear contaminants increase the zero-shear viscosity of a ring polymer melt by about 10% around one-fifth of their overlap concentration. For equal concentrations of linear and ring polymers, the blend viscosity is about twice that of the pure linear melt. The diffusion coefficient of the rings decreases dramatically, while the linear polymers are mostly unaffected. Our results are supported by a primitive path analysis.     

Shear-induced phase transitions in ternary polymer blends

We present a study of flow-induced phase transitions in microemulsion phases of ternary polymer blends. The results match qualitatively with the recent experimental observations on such systems but differ from the behavior expected and observed in the analogous system of surfactants. We rationalize this contrast from a molecular viewpoint suggesting that the interplay between polymer chain conformations and their flow deformations can lead to novel flow effects upon the phase, structural, and rheological behavior of multicomponent polymer systems.     

Ultrasonic studies on polystyrene/styrene butadiene rubber polymer blends filled with glass fiber and talc

The compatibility of solid blends: PS/SBR, PS/SBR filled with glass fiber and PS/SBR filled with talc were studied using ultrasonic pulse echo technique. Measurements were carried out at room temperature (298 K) and a frequency of 3 MHz. The ultrasonic velocity for the compressional wave and that for shear wave have been measured to obtain the elastic moduli data by knowing of density. The variation of ultrasonic wave velocities and elastic moduli with weight percent of the blend was found to be linear in PS/SBR blend, indicating some degree of compatibility but the drawback of elastic moduli indicate incompatibility of the system blend, while it deviates from linearity in blends of PS/SBR filled with glass fiber and talc but the increase in elastic moduli indicates that there is an increase in degree of compatibility between PS and SBR due to adding of glass fiber or talc. The ultrasonic absorptions for longitudinal wave in the temperature range from 298 to 423 K in the studied system were measured using ultrasonic pulse echo technique. Typical results showing the temperature dependence of the ultrasonic absorption at frequencies of 1, 2, 3 and 5 MHz are illustrated for all samples of the different compositions. The study of compositional and temperature dependence of the ultrasonic absorption in the present studied blends reveals the same behavior of the compatibility degree of the blends. Density data of the blends confirmed the ultrasonic results. Also the correlation between hardness and elastic moduli for the present blend systems has been studied.     

Self-confined polymer dynamics in miscible binary blends

Near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy was used to measure simultaneously the relaxation rates of polystyrene (PS) molecules at the free surface and in the bulk. The samples were uniaxially stretched and annealed at temperatures below the bulk glass transition temperature of PS. The surface and bulk chain relaxation was monitored by measuring the partial-electron and the fluorescence NEXAFS yields, respectively, both parallel and perpendicular to the stretching direction. The decay of the optical birefringence was also measured to provide an independent measure of the bulk relaxation. Relaxation of PS chains was found to occur faster on the surface relative to the bulk. The magnitude of the surface glass transition temperature suppression over the bulk was estimated based on the information on the temperature dependence of the rates.Received: 1 January 2003, Published online: 14 October 2003PACS: 68.35.Ja Surface and interface dynamics and vibrations - 68.47.Mn Polymer surfaces     

Self-confined polymer dynamics in miscible binary blends

The segmental dynamics of PVME within the single-phase state of poly(styrene)/poly(vinyl methyl ether) blends (PS/PVME) was examined by dielectric spectroscopy. A particular attention has been given to the high PS concentration regime. In this latter, rather localized, weakly cooperative motions of the PVME segments are detected at low temperatures, in addition of the secondary relaxation processes. This feature is attributed to confinement effects induced by the PS chains on the PVME.     

Application of129Xe NMR to polymer blends

¹²⁹Xe NMR experiments on two different polymer blends are described. The first system, a blend of polypropylene (PP) and the copolymer of polypropylene and polyethylene (EP), shows separate domains of polypropylene and of the copolymer. The latter phase forms rubbery domains in the polypropylene matrix. The second system is the compatible blend of polyvinylidenefluoride and polymethylmethacrylate. For the incompatible blend two Xe resonances are found, one for Xe absorbed in the matrix and one for Xe in the rubbery EP phase. The chemical shift of the Xe absorbed in the rubbery phase can be related to the polyethylene content of the copolymer. The line widths and chemical shifts are affected by the polymer motions as a function of the temperature. Although the system has two very different glass transition temperatures, it is striking to see that upon approaching the polypropylene glass transition temperature the Xe resonance of Xe in the rubbery phase is also affected. Due to the dipolar interaction between Xe spins and polymer proton spins, cross-polarization experiments can be performed. This allows the measurement of correlated NMR spectra. The compatible blend shows only one line with a chemical shift proportional to the composition.     

Drop deformation in polymer blends during elongational flow

An original method for measuring droplet deformation in polymer melts during uniaxial elongational flow has been developed. It is based on the observation of a limited number of drops, before and after elongation in the melt. The shape of the elongated drops was frozen by fast quenching. Two PS samples for the continuous phase, plus two HDPE, and one PMMA for the drops, allowed a wide range of viscosity ratios (0.0046 < p < 13). Experiments at high capillary number (Ca) values were in good agreement with Taylor's linear newtonian theory up to deformations of about λ = 4: viscous drops (p > 1) deform less than the surrounding matrix, whereas the opposite is observed for low viscosity drops (p < 1) with a limiting ratio of drop vs. matrix deformation of 5/3 at vanishing drop viscosity. Experiments carried out at Ca values of the order of unity showed that the drop deformation increases linearly with their initial radius in agreement with the linear theory. In some cases, the agreement with the data could be improved by using Palierne's theory for viscoelastic systems. Analytical expressions could be obtained for maxwellian fluids and high capillary numbers.     

Thermodynamics of ion-containing polymer blends and block copolymers

We develop a theory for the thermodynamics of ion-containing polymer blends and diblock copolymers, taking polyethylene oxide (PEO), polystyrene and lithium salts as an example. We account for the tight binding of Li^{+} ions to the PEO, the preferential solvation energy of anions in the PEO domain, the translational entropy of anions, and the ion-pair equilibrium between EO-complexed Li^{+} and anion. Our theory is able to predict many features observed in experiments, particularly the systematic dependence in the effective χ parameter on the size of the anions. Furthermore, comparison with the observed linear dependence in the effective χ on salt concentration yields an upper limit for the binding constant of the ion pair.