Polymer-polymer Interactions Research Articles

Assessment of polymer-polymer interactions in blends of HPMC and film forming polymers by modulated temperature differential scanning calorimetry.

To assess the miscibility and phase behavior of binary blends of hydroxypropylmethyl cellulose (HPMC) with hydroxypropyl cellulose (HPC), methylcellulose (MC), and polyvinylpyrrolidone (PVP). Polymer-polymer miscibility was assessed by measurement of the glass transition temperature (Tg) and the width of the glass transition temperature (W-Tg), using modulated temperature differential scanning calorimetry (MTDSC). HPMC K4M/PVP and HPMC E5/MC blends were miscible as evidenced by a single, composition dependent, Tg throughout the entire composition range. HPMC/HPC blends were immiscible at all compositions. For the miscible blends, the variation in Tg with blend composition was compared to the values predicted by the Fox and Couchman-Karasz equations. At intermediate blend compositions, HPMC K4M/PVP blends exhibited negative deviations from ideal behavior. The Tg of the HPMC E5/MC blends was found to follow the Fox equation. The W-Tg measurements of the miscible blends gave evidence of phase separation at certain compositions. MTDSC was shown to be a useful technique in characterizing the interactions between some commonly used pharmaceutical polymers.

Estudo da influência das concentrações de monômero principal e de agente reticulante na estrutura do gel poli(N-isopropilacrilamida) através de espectroscopia de aniquilação de pósitrons

Neste trabalho, os géis termossensíveis poli(N-isopropilacrilamida) - IPAA - foram caracterizados através de Espectroscopia de Vida Média de Pósitrons (EVMP) e Análise Térmica como função das concentrações do monômero principal N-isopropilacrilamida e do agente reticulante N,N'-Metilenobisacrilamida. A EVMP foi usada para determinar o raio médio dos volumes livres dos géis. Os géis IPAA foram sintetizados em solução aquosa via radicais livres. Após a síntese, os géis foram cortados em cubos, lavados e secos em estufa. Depois de secos foram moídos e caracterizados através de Análise Termogravimétrica (TGA) e Calorimetria Exploratória Diferencial (DSC). Os géis com composição de monômero principal e agente reticulante variando de 10x1 a 10x6, 10x1 a 16x1 e 10x1 a 16x6 mostraram um raio médio em torno de 2,8Å. O volume livre estimado para os géis não variaram com a variação da composição de monômero principal e agente reticulante. Os resultados foram interpretados em termos da estrutura desses géis.

Determination of Thermodynamic Interactions of the Pvc-Pmma Blend System by Inverse gas Chromatography

In this study, the sorption enthalpy (δHS1), sorption free energy (δG1), sorption entropy (δS1), enthalpy, and free energy at infinite dilution (δH1 and δG1) values were calculated for selected probes such as alcohols, ketones, acetates, cyclic ethers, aromatics, and alkanes in the temperature range 403-433 K for poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC) homopolymers, and the PVC-PMMA blend system. The values of the Flory-Huggins interaction parameters χ1(23) have been calculated in this temperature range and show the importance of specific interactions between the polymers and the solvents. The values of the polymer-polymer interaction parameters χ23(for the temperature range 403–433 K) were found to change from +3.57 to +1.16 for alcohols, from +2.99 to +0.52 for ketones, from + 1.60 to −0.48 for acetates, from +0.96 to −1.46 for cyclic ethers, from +2.66 to +0.12 for aromatics, and from +8.73 to +1.06 for alkanes.

Influence of Polymer-Polymer Interactions on Properties of Ink Jet Coatings

Theoretical and practical aspects of the consequences of polymer-polymer interactions in ink jet receiver coating are discussed. Several examples are presented pertaining to type of modification and charges of polyvinyl alcohol will have an effect on print quality with dye and pigmented inks. It is shown that the introduction of a dye fixative to the coating improves the water fastness but has negative effect on print quality. It was found that the pH adjustments in the ink receiving layers increase the gloss of the media.

Counterion Condensation Revisited

We review some of the characteristic properties of the structure of polyelectrolyte solutions: the condensed layer of counterions that forms abruptly at a critical threshold charge density on the polymer chain; the more diffuse Debye-Hückel cloud, which is spatially distinct from the condensed layer; and the entropie release of counterions from the condensed layer as a driving force for the binding of oppositely charged ligands. We present a reminder of the basis of our current understanding in a variety of experiments, simulations, and theories; and we attempt as well to clarify some misunderstandings. We present a new analysis of a lattice model that suggests why the limiting laws for polyelectrolyte thermodynamics have proved to be accurate despite the neglect of polymer-polymer interactions in their original derivation. We sketch recent progress in constructing a potential between counterion and polyion. A counterion located in the interface between condensed layer and Debye cloud is repelled from the polyion, creating a sharp boundary between the two counterion populations.

Blends of a thermotropic liquid crystalline polymer and some flexible chain polymers and the determination of the polymer-polymer interaction parameter of the two polymers

Blends of a thermotropic liquid crystalline polymer (LCP) with poly(ether imide) (PEI), poly(ether ether ketone) (PEEK), polysulfone (PSF) and polyarylsulfone (PAS) prepared by screw extrusion have been investigated by differential scanning calorimeter and dynamic mechanical thermal analysis. From the measured glass transition temperature (T g ) and specific heat increment (ΔC p ) at the T g , it appears that the LCP dissolves more in the PEI- and PEEK-rich phases than does the PEI and PEEK in the LCP-rich phase. From the DSC study of PSF-LCP and PAS-LCP blends, the T g (PSF) and T g (PAS) of each blends are almost constant with blend composition. Therefore, it is concluded that PSF and PAS are immiscible with LCP. The polymer-polymer interaction parameter (X 12 ) and the degree of disorder (y/x 1 ) of LCP have been investigated using the Flory lattice theory in which the anisotropy of LCP is considered. The X 12 values have been calculated from the T g data and found to be 0.181±0.004 at 593 K for the PEI-LCP blends and 0.069±0.006 at 623 K for the PEEK-LCP blends. Using the previously presented method, the X 12 and y/x 1 in partially miscible systems have been determined.

Morphology of poly(vinylidene fluoride)/poly(methyl acrylate) blends: influence of chain structure

The morphology of blends of poly(vinylidene fluoride) (PVF 2 ) fractions with poly(methyl acrylate) (PMA), studied by means of polarized light microscopy, exhibits a gradual change in morphology from spherulitic → dendritic → spherulitic both for increasing PMA concentration in the blend and for increasing crystallization temperature. Possible reasons for this change in morphology, viz. the ratio of diffusion constant and growth rate, are discussed. The influence of head to head (H-H) defects of PVF 2 on the morphology of the blends is discussed on the basis of the polymer-polymer interaction parameter.

Morphology of poly(vinylidene fluoride)/poly(methyl acrylate) blends: influence of chain structure

The morphology of blends of poly(vinylidene fluoride) (PVF2) fractions with poly(methyl acrylate) (PMA), studied by means of polarized light microscopy, exhibits a gradual change in morphology from spherulitic → dendritic → spherulitic both for increasing PMA concentration in the blend and for increasing crystallization temperature. Possible reasons for this change in morphology, viz. the ratio of diffusion constant and growth rate, are discussed. The influence of head to head (H-H) defects of PVF2 on the morphology of the blends is discussed on the basis of the polymer-polymer interaction parameter.

Effect of Polymer-Filler and Filler-Filler Interactions on Dynamic Properties of Filled Vulcanizates

Abstract In the past few years, an enormous amount of work has been reported on the progress in the application of conventional fillers and the development of new products to improve the reinforcement of rubber, dynamic properties in particular. While all agree that the filler as one of the main components of the filled-rubber composite, has a very important role in improving the dynamic performances of the rubber products; many new ideas, theories, practices, phenomena, and observations about how and especially why the filler alters the dynamic stress-strain response have been presented. This, of course, suggests that not only is the real world of the filled rubber complex and sophisticated but also multiple mechanisms may be involved. However, it must be admitted that the possibility exists for explaining the effect of all fillers on rubber properties ultimately in similar and relatively nonspecific terms, i.e., the phenomenon related to all filler parameters should follow a general rule or principle. It is the author's belief that, with regard to the effect of filler on the dynamic properties of a given polymer and cure system, filler networking, both its architecture and strength, is the main (although not only) parameter to govern the behavior of the filled rubber. From the thermodynamic and kinetic points of view, filler network formation is especially related to filler-filler, polymer-filler, as well as polymer-polymer interactions. As mentioned in the introduction, this paper is an attempt to review the effect of filler characteristics on dynamic properties in connection with processing conditions and additives. Since the polymer-filler interaction is not only affected by filler, what is also important are the characteristics of polymers such as chemical composition, chain microstructure including molecular weight and molecular weight distribution, configuration, stereoregularity, monomer unit distribution and sequence, and their functionality. All of these have a substantial influence on the physical and/or chemical interactions with other additives and filler surfaces, as well as on the interaction between polymer molecules themselves, which would impact not only the filler network formation but also the viscoelastic response of the polymer matrix. In addition, the polymer network structure which was formed during vulcanization and characterized by crosslink density, crosslink structure, and chain modification, is equally important in contributing to the overall dynamic properties of the filled rubber. In this paper, only some of these aspects have been discussed relative to their effect on filler network formation. Further discussion of these parameters is beyond the subject of the present paper. However, some guidance to these important topics is given in a handbook that was recently published.

Data Reduction in Multidetector Size Exclusion Chromatography

A comprehensive analysis of multidetector size exclusion chromatography (SEC) is presented. The system examined consists of differential refractometer, capillary viscometer, and light-scattering detector combination. New approaches for interpreting multidetector data have been developed. The first one consists in eliminating the concentration chromatogram from the data reduction process. The traces of two molecular-weight-sensitive detectors alone allow calculating molecular weight and intrinsic viscosity distributions of an unknown polymer, assuming the validity of the universal calibration concept for this polymer. This approach can dramatically improve the characterization of polymers with long high-molecular-weight tails, when small amounts of high-molecular-weight fractions are detected by the light-scattering and viscometer detectors, but the concentration is too low to be registered by the refractometer. Another opportunity discovered is the calculation of the hydrodynamic volume of each fraction of a chromatographed polymer across its distribution, using measured signals from three on-line detectors. This calculation can be performed for any complex polymers, e.g., copolymers or oligomers, even in situations when refractive index increments of molecules depend on retention volume, or columns do not provide full recovery of injected polymer mass. The verification of the universal calibration hypothesis for any unknown polymer is accomplished now by the routine single chromatographic run. The method developed helps to analyze different reasons responsible for the deviation from universal calibration, such as polymer-polymer interactions in solution, band-broadening phenomena, non-steric interactions with a stationary phase or the structural or chemical heterogeneity of a solute. Using triple detection with multiangle light-scattering detector allows, also, to calculate the Flory's viscosity factor across the distribution for polymers with different configurational and conformational structure. The experimental data supporting the theoretical predictions are presented.

1H NMR study of thermoreversible gels of chemically modified poly(vinyl chloride) in diester solvents

The temperature dependences of the associated fraction of PVC units were determined from measurements of integrated intensities of high-resolution 1H NMR spectra in thermoreversible gels of PVC and chemically modified PVC in diethyl oxalate (DEO) and dibutyl oxalate (DBO). The existence of two types of associates of different thermal stability, completely melting at 55°C and 90–130°C, was indicated by these measurements. While the associated fraction and the thermal stability of the associates increase with increasing polymer concentration, a significant reduction in the associated fraction is observed in samples where ≈5% of chlorine atoms are replaced by phenylthio groups or hydrogen. Because the chemical modification takes places only on isotactic and heterotactic triads, this result confirms the important role of these sequences in interactions associated with the gel formation. In DBO gels, the values of the associated fraction are lower than in DEO gels. A complete parallelism was found for temperature dependences of the associated fraction and viscoelastic storage modulus. From measurements of selective and nonselective 1H spin-lattice relaxation times of the solvent, the existence of PVC/DEO complex was confirmed. The life-time of bound solvent molecules which could bridge different chains is shorter than 1 s. Both polymer/solvent complex and polymer-polymer interactions seem to act as physical crosslinks.

1H NMR study of thermoreversible gels of chemically modified poly(vinyl chloride) in diester solvents

The temperature dependences of the associated fraction of PVC units were determined from measurements of integrated intensities of high-resolution 1H NMR spectra in thermoreversible gels of PVC and chemically modified PVC in diethyl oxalate (DEO) and dibutyl oxalate (DBO). The existence of two types of associates of different thermal stability, completely melting at 55°C and 90–130°C, was indicated by these measurements. While the associated fraction and the thermal stability of the associates increase with increasing polymer concentration, a significant reduction in the associated fraction is observed in samples where ≈5% of chlorine atoms are replaced by phenylthio groups or hydrogen. Because the chemical modification takes places only on isotactic and heterotactic triads, this result confirms the important role of these sequences in interactions associated with the gel formation. In DBO gels, the values of the associated fraction are lower than in DEO gels. A complete parallelism was found for temperature dependences of the associated fraction and viscoelastic storage modulus. From measurements of selective and nonselective 1H spin-lattice relaxation times of the solvent, the existence of PVC/DEO complex was confirmed. The life-time of bound solvent molecules which could bridge different chains is shorter than 1 s. Both polymer/solvent complex and polymer-polymer interactions seem to act as physical crosslinks.

Swelling of polyacrylamide gels in polyacrylamide solutions

Swelling behavior of polyacrylamide (PAAm) and polyacrylamide-co-poly- acrylic acid (PAAm-co-PAAc) gels was investigated in aqueous solutions of monodis- perse PAAms with molecular weights (M V w) ranging from 1.5 1 10 3 to 5 1 10 6 g/mol. The volume of the gels decreases as the PAAm concentration in the external solution increases. This decrease becomes more pronounced as the molecular weight of PAAm increases. The classical Flory-Huggins (FH) theory correctly predicts the swelling behavior of nonionic PAAm gels in PAAm solutions. The polymer-polymer interaction parameter x23 was found to decrease as the molecular weight of PAAm increases. The swelling behavior of PAAm-co-PAAc gels in PAAm solutions deviates from the predictions of the FH theory. This is probably due to the change of the ionization degree of AAc units depending on the polymer concentration in the external solution. q 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1313-1320, 1998

Miscibility and interactions in a mixture of poly(ethylene oxide) and an aromatic poly(ether amide)

Results concerning a mixture of an experimental aromatic poly(ether amide) and poly(ethylene oxide) are reported. The presence of other groups in both polymers, and the possibility of a great number of intermolecular hydrogen bonds, give rise to polymer-polymer interactions that result in partial miscibility, as it has been demonstrated by FT-i.r., differential scanning calorimetry and optical microscopy. These results are qualitatively consistent with theoretical phase diagrams calculated from an association model which emphasizes the role of hydrogen bond interactions in this type of blend.

Glass transition and thermal stability of poly(N-isopropylacrylamide) gels and some of their copolymers with acrylamide

Poly(N-isopropylacrylamide) (NIPAAm) and poly(N-isopropylacrylamide)-coacrylamide (NIPAAm/AAm) gels were characterized by thermal analysis. Differential scanning calorimetry (DSC) was used to determine the glass transition temperatures ( T g ) of NIPAAm and NIPAAm/AAm gels, as well as to study their thermal stability, by measuring the endothermic heats and the degradation temperatures ( T d ). The thermal stability of the gels was also studied by thermogravimetric analysis (TGA), with the weight losses and the T d 's being determined. NIPAAm gel 10 × 1 showed a T g of 135.0 ± 0.2 °C. The copolymers with acrylamide (NIPAAm/AAm 10 × 1), with the acrylamide composition varying from 2 to 70 wt%, showed an increasing T g up to 179.0 ± 0.5 °C. The T d s decreased with increasing acrylamide concentration. The results are discussed in terms of the changes in the gels' structure due to different polymer-polymer interactions.

Predicting EHD Film Thickness of Lubricant Polymer Solutions

It is well-known that the elastohydrodynamic (EHD) film thicknesses formed by solutions of medium to high molecular weight polymers in lubricating oils are less than those predicted from EHD theory based on the low shear rate viscosities of the polymer solutions. This is usually ascribed to shear thinning of polymer solutions in the high shear stress conditions in the inlet of the EHD contact. This paper describes a systematic study of the EHD film-forming properties of polymer solutions in which a range of well-characterized, low dispersivity polymers is employed to investigate the influence of polymer type, molecular weight and concentration in base oil on EHD film thickness. It is shown that the disparity between measured film thickness and that predicted from EHD theory using low shear rate viscosity increases progressively as both polymer concentration and polymer molecular weight are raised. Analysis of the results suggests, however, that conventional EHD film thickness equations can be employed to predict the film-forming behavior of polymer solutions if viscosity values are used which are derived from intrinsic viscosities on the assumption of dilute polymer solution behavior, i.e., negligible polymer-polymer molecular interaction in solution. Presented as a Society of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, United Kingdom, September 8–12, 1997

Miscibility behavior of Poly(vinyl alcohol)/Nylon 6 blends and their reactive blending with Poly(ethylene-co-ethyl acrylate)

Melt-mixed blends of Poly(vinyl alcohol) (PVOH) with Nylon 6 were found to have good mechanical properties in the entire composition range. Determination of the glass transition temperature by dynamic mechanical analysis showed one broad Tg for the compositions rich in Nylon 6. In the case of the blends rich in PVOH, two Tg's were obtained, one close to that of the pure PVOH and another one in the region between the Tg's of the pure components. Characterizing blends with differential scanning calorimetry indicated a depression of the equilibrium melting point of Nylon 6. From the melting point data of the high Tm component, a value for the polymer-polymer interaction of x12 = − 0.05 was derived using the simplified Nishi—Wang equation. Ternary blends composed of PVOH/Nylon 6/Poly(ethylene-co-ethyl acrylate) (PEEA) were prepared under reactive conditions in order to examine the possibility of using them as oxygen barrier material. The bonding of the ethylenic copolymer through reactive processing to the PVOH/Nylon 6 binary is expected to facilitate dispersion as well as interfacial adhesion in the case of mixing the above ternary in a polyethylene matrix.

Amorphous phenolphthalein-basedpoly(arylene ether) modified cyanate ester networks: 1. Effect of molecular weight and backbone chemistry on morphology and toughenability

Low toughness is a major drawback with most cross-linked thermosetting materials, including the cyanate ester networks. Reactive functional thermoplastic toughness modifiers not only enhance toughness but also permit highly desirable stability to solvent stress racking without seriously affecting the moderately high modulus. Careful control of the heterophase morphological structure is necessary to achieve significant toughening. In the present work, hydroxyl functional phenolphthalein-based amorphous poly(arylene ether ketone)s, poly(arylene ether sulfone)s and poly(arylene ether phosphine oxide)s were investigated as potential toughness modifiers for the bisphenol-A based cyanate ester networks. In particular, the use of poly(arylene ether sulfone)s resulted in remarkable improvements in toughness. Multiphase networks were generated without compromising either T g or the moderately high modulus of the unmodified cyanate ester networks. It was demonstrated that the toughenability of these systems is governed by microphase-separated morphologies and the sizes of the phase-separated domains. The formation of these heterophase morphological structures is strongly influenced by the backbone chemistry and the molecular weight of the thermoplastic modifier, probably via control of the polymer-polymer interaction parameter.

Polymer-polymer interaction and modeling

The nature of intermolecular interaction in PVC/EVA system was investigated. Bathochromic shifts in infrared region revealed that not only EVA carbonyl but the ester group participates on interaction with PVC chain. These shifts were proportional to acetate content in the copolymer and the composition of EVA in the blend. The PVC group that effectively participates on interaction was not elucidated by infrared spectrometry, but molecular modeling of low molecular weight analogues indicated that hydrogen bonding is the most probable kind of intermolecular interaction present in this system.

Acoustic properties of poly(4,4′-cyclohexylidene-R-R′-diphenylene-3-3′-benzophenone disulfonates) at 30 °C

Several acoustic parameters of poly(4,4′-cyclohexylidene-R-R′-diphenylene-3,3′-benzophenone disulfonates (R = R′ = Cl, and R = CH 3 and R′ = Cl) in chlorinated and aprotic solvents: chloroform (CF), 1,2-dichloroethane (DCE), chlorobenzene (CB), tetrahydrofuran (THF) and 1,4-dioxane (DO) at 30 °C have been evaluated at 3 MHz in order to understand the structures, polymer-solvent and polymer-polymer interactions. The parameters are correlated with concentration and excellent correlations are observed except the viscosity and the relaxation time where curvature is observed after about 1.0% concentration (except the DO system) which is attributed to structural changes (chain entanglements). The trend in velocity is CF < DCE < CB < THF < DO. The increase of U, Z, R, b, π and decrease of K s , r and L f with C indicated strong polymer-solvent interaction and is further supported by positive values of S n . The structure of the solutes in solutions are dependent on the types of substituents in the main chain, concentration and dielectric constant of the medium at constant temperature.