Miscibility and crystallization of poly(ethylene succinate)/poly(vinyl phenol) blends

Miscibility of biodegradable poly(ethylene succinate) (PES)/poly(vinyl phenol) (PVPh) blends has been studied by differential scanning calorimetry (DSC) in this work. PES is found to be miscible with PVPh as shown by the existence of single composition dependent glass transition temperature over the entire composition range. Spherulitic morphology and the growth rates of neat and blended PES were investigated by optical microscopy (OM). Both neat and blended PES show a maximum growth rate value in the crystallization temperature range of 45-65 °C, with the growth rate of neat PES being higher than that of blended PES at the same crystallization temperature. The overall crystallization kinetics of neat and blended PES was also studied by DSC and analyzed by the Avrami equation at 60 and 65 °C. The crystallization rate decreases with increasing the temperature for both neat and blended PES. The crystallization rate of blended PES is lower than that of neat PES at the same crystallization temperature. However, the Avrami exponent n is almost the same despite the blend composition and crystallization temperature, indicating that the addition of PVPh does not change the crystallization mechanism of PES but only lowers the crystallization rate.     

Miscibility and interactions in poly(n-propyl methacrylate)/poly(vinyl alcohol) blends

Poly(n-propyl methacrylate) (PPMA) is miscible with poly(vinyl alcohol) (PVA) over the whole composition range as shown by the existence of a single glass transition temperature in each blend. The interaction between PPMA and PVA was examined by Fourier transform infrared spectroscopy and solid-state nuclear magnetic resonance spectroscopy. The interactions mainly involve the hydroxyl groups of PVA and the carbonyl groups of PPMA. The measurements of proton spin-lattice relaxation time reveal that PPMA and PVA do not mix intimately on a scale of 1-3 nm, but are miscible on a scale of 20-30 nm. A small negative interaction parameter value has been obtained by melting point depression measurement.     

Miscibility and hydrogen bonding in blends of poly(vinyl acetate) with phenolic resin

The miscibility of phenolic resin and poly(vinyl acetate) (PVAc) blends was investigated by differential scanning calorimeter (DSC), Fourier transform infrared spectroscopy (FT-IR) and solid state ¹³C nuclear magnetic resonance (NMR). This blend displays single glass transition temperature (T_g) over entire compositions indicating that this blend system is miscible in the amorphous phase due to the formation of hydrogen bonding between hydroxyl groups of phenolic resin and carbonyl groups of PVAc. Quantitative measurements on fraction of hydrogen-bonded carbonyl group using both ¹³C solid-state NMR and FT-IR analyses result in good agreement between these two spectroscopic techniques. According to the proton spin-lattice relaxation time in the rotating frame (T_1ρ^H), the phenolic/PVAc blend is intimately mixed on a scale less than 2-3 nm. Furthermore, the inter-association equilibrium constant and its related enthalpy of phenolic/PVAc blends were determined as a function of temperatures by infrared spectra based on the Painter-Coleman association model.     

Poly(butylene succinate)/poly(vinyl phenol) blends. Part 1. Miscibility and crystallization

Miscibility has been investigated in blends of poly(butylene succinate) (PBSU) and poly(vinyl phenol) (PVPh) by differential scanning calorimetry in this work. PBSU is miscible with PVPh as shown by the existence of single composition dependent glass transition temperature over the entire composition range. In addition, the polymer–polymer interaction parameter, obtained from the melting depression of PBSU using the Nishi–Wang equation, is composition dependent, and its value is always negative. This indicates that PBSU/PVPh blends are thermodynamically miscible in the melt. Preliminary morphology study of PBSU/PVPh blends was also studied by optical microscopy (OM). OM experiments show the spherulites of PBSU become larger with the PVPh content, indicative of a decrease in the nucleation density, and the coarseness of PBSU spherulites increases too with increasing the PVPh content in the blends.     

Morphology-rheology relationship in hyaluronate/poly(vinyl alcohol)/borax polymer blends

In this work, we have prepared bioartificial polymer blends using hyaluronate (HA) as a biological component and poly(vinyl alcohol)-borax association (PVAs) as a synthetic component, and investigated the rheological properties as well as morphology of the blends. When plotted against the blend composition, the rheological properties showed both positive and negative deviation from the linear additive mixing rule depending on thermal history. The blend showed enhanced viscosity at the composition of 20 wt% of HA and 80 wt% of PVAs, when PVA was dissolved at high temperature. The viscosity enhancement was caused by the network formation of HA aggregates in the micrometer scale. In addition, the network structure of HA aggregates was found to be fractal with the fractal dimension of 1.7. As PVA system also forms a network structure in the nanometer scale between hydroxyl groups of PVA and borate anions, the blend system is unique in that it has network structures in both micrometer and nanometer scales in one material. On the contrary, HA formed aggregates but not any network structure in the blend of the same composition but of the negative deviation. In conclusion, we showed that HA/PVAs blend system may have diverse morphology as well as very broad spectrum of rheological properties, and could suggest that the rheology and morphology of HA/PVAs blends can be designed not only by controlling composition but also by controlling thermal and deformation history of the components.     

Miscibility and interactions in polystyrene and sodium sulfonated polystyrene with poly(vinyl methyl ether) PVME blends. Part II. FTIR

The miscibility and specific interactions of polystyrene (PS) and sodium sulfonated polystyrene (Na-SPS) with poly(vinyl methyl ether) (PVME) blends (ranging from 10 to 90% PS by weight) were examined experimentally by FTIR spectroscopy. The FTIR studies at different temperatures have shown that changes in spectra of polymer blends, as reported in the literature can be explained by temperature changes in pure homopolymers. This indicates that molecular interactions, which are responsible for miscibility, are not detectable by infrared absorptions and are therefore of unspecific strength and location. The FTIR of SPS/PVME blends show that sulfonate groups of PS affect polymer miscibility through changes in configuration of molecules, rather than through direct interaction with the PVME.     

Miscibility of C60-end-capped poly(ethylene oxide) with poly(vinyl chloride)

The miscibility of blends of single [60]fullerene (C₆₀)-end-capped poly(ethylene oxide) (FPEO) or double C₆₀-end-capped poly(ethylene oxide) (FPEOF) with poly(vinyl chloride) (PVC) has been studied. Similar to poly(ethylene oxide) (PEO), both FPEO and FPEOF are also miscible with PVC over the entire composition range. X-ray photoelectron spectroscopy showed the development of a new low-binding-energy Cl2p doublet and a new high-binding-energy O1s peak in FPEO/PVC blends. The results show that the miscibility between FPEO and PVC arises from hydrogen bonding interaction between the α-hydrogen of PVC and the ether oxygen of FPEO. From the melting point depression of PEO, FPEO or FPEOF in the blends, the Flory-Huggins interaction parameters were found to be −0.169, −0.142, −0.093 for PVC/PEO, PVC/FPEO and PVC/FPEOF, respectively, demonstrating that all the three blend systems are miscible in the melt. However, the incorporation of C₆₀ slightly impairs the interaction between PEO and PVC.     

Crystallization behavior and hydrophilicity of poly(vinylidene fluoride)/poly(methyl methacrylate)/poly(vinyl pyrrolidone) ternary blends

Ternary blends composed of matrix polymer poly(vinylidene fluoride) (PVDF) with different proportions of poly(methyl methacrylate) (PMMA)/poly(vinyl pyrrolidone) (PVP) blends were prepared by melt mixing. The miscibility, crystallization behavior, mechanical properties and hydrophilicity of the ternary blends have been investigated. The high compatibility of PVDF/PMMA/PVP ternary blends is induced by strong interactions between the carbonyl groups of the PMMA/PVP blend and the CF₂ or CH₂ group of PVDF. According to the Fourier transform infrared and wide‐angle X‐ray difffraction analyses, the introduction of PMMA does not change the crystalline state (i.e. α phase) of PVDF. By contrast, the addition of PVP in the blends favors the transformation of the crystalline state of PVDF from non‐polar α to polar β phase. Moreover, the crystallinity of the PVDF/PMMA/PVP ternary blends also decreases compared with neat PVDF. Through mechanical analysis, the elongation at break of the blends significantly increases to more than six times that of neat PVDF. This confirms that the addition of the PMMA/PVP blend enhances the toughness of PVDF. Besides, the hydrophilicity of PVDF is remarkably improved by blending with PMMA/PVP; in particular when the content of PVP reaches 30 wt%, the water contact angle displays its lowest value which decreased from 91.4° to 51.0°. Copyright © 2011 Society of Chemical Industry     

Tacticity effects on the miscibility behavior of poly(methyl methacrylate)/poly(ethylene oxide-b-dimethylsiloxane-b-ethylene oxide) blends

The miscibility of a triblock copolymer poly(ethylene oxide)-poly(dimethylsiloxane)-poly(ethylene oxide) with syndiotactic and isotactic poly(methylmethacrylate) wasstudied. Although isotactic poly(methyl methacrylate) (PMMA) was miscible with poly(ethylene oxide) (PEO) in the pure state, it was immiscible with the PEO end blocks in the copolymer. In comparison, the syndiotactic poly(methyl methacrylate) (sPMMA) was miscible with the PEO blocks as indicated by melting point depression, decrease in crystallinity, and slower rate of spherulite growth of PEO. When blends of the triblock copolymer were cooled to low temperatures, the poly(dimethylsiloxane) (PDMS) middle block which resided in the interlamellar region of PEO spherulites also crystallized; the development of PDMS crystals was clearly suppressed at high sPMMA contents.On leave from Union Chemical Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan     

Studies on the miscibility and phase structure in blends of poly(epichlorohydrin) and poly(vinyl acetate)

The miscibility of atactic poly(epichlorohydrin) (aPECH) with poly(vinyl acetate) (PVAc) was examined under two different conditions: (i) in dilute solution, using vicometeric measurements and (ii) as cast films, using differential scanning calorimetric (DSC) and FT-infrared spectroscopy. Phase separation on heating, i.e. lower critical solution temperature (LCST) behavior of the aPECH/PVAc blends was examined by the measurement of transmitted light intensity against temperature. From viscosity measurements, the Krigbaum-Wall polymer-polymer interaction (ΔB) was evaluated. The DSC results show that the aPECH/PVAc blends are miscible as evidenced by the observation of a single composition-dependent glass-transition temperature (T_g) which is well described by the Couchman and Gordon Taylor models. The Flory-Huggins interaction parameter (χ₁₂) calculated from the T_g-method was negative and equal to −0.01, indicating a relatively low interaction strength. The FT-IR results match very well with those of DSC. The cloud point phenomenon is thermodynamically driven but phase separation, once taken place, is diffusion controlled in normal accessible time.     

Miscibility of poly(vinyl alcohol)/polyacrylamide blends before and after gamma irradiation

Films of polymer blends having various contents of poly(vinyl alcohol) (PVA) and polyacrylamide (PAM) were prepared by the solution casting technique using water as a common solvent. The thermal, mechanical and morphological properties of these blends before and after exposure to various doses of gamma radiation, up to 100 kGy, have been investigated. The visual observation and reflectance measurements show that PVA/PAM blends are miscible over a wide range of composition. Moreover, the differential scanning calorimetry (DSC) thermograms show only a single glass transition temperature (T_g), but not those of PVA or PAM homopolymers, giving further support to the complete compatibility of such blends. The T_g of PVA/PAM blends decreases with increasing content of PAM but increases after exposure to gamma irradiation, indicating the occurrence of crosslinking. These findings were demonstrated by the scanning electron micrographs of the fracture surfaces and the tensile mechanical properties. The TGA thermograms and percentage mass loss at different decomposition temperatures show that unirradiated PVA homopolymer possesses higher thermal stability than PAM homopolymer and their blends within the heating temperature range investigated, up to 250 °C. An opposite trend is observed within the temperature range 300–500 °C. In general, the thermal stability of homopolymers or their blends improves slighly after exposure to an irradiation dose of 100 kGy. These findings are clearly confirmed by the calculated activation energies of the thermal decomposition reaction of the homopolymers and the blends. © 2003 Society of Chemical Industry     

Investigation on crystallization behavior and hydrophilicity of poly(vinylidene fluoride)/poly(methyl methacrylate)/poly(vinyl pyrrolidone) ternary blends by solution casting

Ternary blends composed of matrix polymer poly(vinylidene fluoride) (PVDF) with different proportions of poly(methyl methacrylate) (PMMA)/poly(vinyl pyrrolidone) (PVP) blends were prepared by solution casting. The crystallization behavior and hydrophilicity of ternary blends were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), wide angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and contact angle test. According to morphological analysis, the surface was full of typical spherulitic structure of PVDF and the average diameter was in the order of 3 μm. The samples presented predominantly β phase of PVDF by solution casting. It indicated that the size of surface spherulites and crystalline phase had little change with the PMMA or PVP addition. Moreover, FTIR demonstrated special interactions among the ternary polymers, which led to the shift of the carbonyl stretching absorption band of PVP. On the other hand, the melting, crystallization temperature, and crystallinity of the blends had a little change compared with the neat PVDF in the first heating process. Except for the content of PVP containing 30 wt %, the crystallinity of PVDF decreased remarkably from 64% to 33% and the value of t_1/2 was not obtained. Besides, the hydrophilicity of PVDF was remarkably improved by blending with PMMA/PVP, especially when the content of PVP reached 30 wt %, the water contact angle displayed the lowest value which decreased from 98.8° to 51.0°. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Miscibility and intermolecular specific interactions in blends of poly(hydroxyether of bisphenol A) and poly(4-vinyl pyridine)

The blends of poly(hydroxyether of bisphenol A) (phenoxy) with poly(4-vinyl pyridine) (P4VPy) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy. The single, composition-dependent glass transition temperature (T_g) was observed for each blend, indicating that the system is completely miscible. The sigmoid T_g-composition relationship is characteristic of the presence of the strong intermolecular specific interactions in the blend system. FTIR studies revealed that there was intermolecular hydrogen bonding in the blends and the intermolecular hydrogen bonding between the pendant hydroxyl groups of phenoxy and nitrogen atoms of pyridine ring is much stronger than that of self-association in phenoxy. To examine the miscibility of the system at the molecular level, the high resolution ¹³C cross-polarization (CP)/magic angle spinning (MAS) together with the high-power dipolar decoupling (DD) NMR technique was employed. Upon adding P4VPy to the system, the chemical shift of the hydroxyl-substituted methylene carbon resonance of phenoxy was observed to shift downfield in the ¹³C CP/MAS spectra. The proton spin-lattice relaxation time T₁(H) and the proton spin-lattice relaxation time in the rotating frame T_1ρ(H) were measured as a function of the blend composition. In light of the proton spin-lattice relaxation parameters, it is concluded that the phenoxy and P4VPy chains are intimately mixed on the scale of 20-30 Å.     

Synthesis and Characterization of Poly(vinyl alcohol)/Poly(vinyl pyrrolidone)-Iodine Nanofibers with Poloxamer 188 and Chitosan

This study focuses on the fabrication of poly(vinyl alcohol)/ poly(vinyl pyrrolidone)-Iodine nanofibers via electrospinning. Electrospun fibers were characterized by FT-IR, DSC and SEM techniques. DSC results indicated that the thermal stability of nanofibers were improved after the addition of chitosan and poloxamer 188. SEM images showed that the spongiform structure is much more compact and fibrous in the case of added chitosan, with an average fiber diameter of 374 nm, whereas the addition of poloxamer 188 resulted in a more porous and beaded composition, with average fiber diameter of 489 nm.     

Comparison of the phase behaviour of the liquid-crystalline polymer/poly(methyl methacrylate) and poly(vinyl acetate)/poly(methyl methacrylate) blends

The phase behaviour of blends of a liquid-crystalline polymer (LCP) and poly(methyl methacrylate) (PMMA), as well as the phase state of blends of PMMA and poly(vinyl acetate) (PVA) has been investigated using light scattering and phase-contrast optical microscopy. The blends of LCP and PMMA have been obtained by coagulation from ternary solutions. The cloud point curves were determined. It was established that both pairs demix upon heating, ie have an LCST. In the region of intermediate composition, the phase separation proceeds according to a spinodal mechanism; however for LCP/PMMA blends, the decomposition proceeds according to a non-linear regime from the very onset. In the region of small amounts of LCP, the phase separation follows a mechanism of nucleation and growth. For PMMA/PVA blends, the spinodal decomposition proceeds according to a linear regime, in spite of the molecular mobility that PVA chains develop at lower temperatures. Only after prolonged heat treatment does the process transit to a non-linear regime. The data show a similarity between the phase behaviour of blends of liquid-crystalline and of flexible amorphous polymers. The distinction consists of the absence of a linear regime of decomposition for LCP-PMMA blends. © 1999 Society of Chemical Industry     

Miscibility and crystallization in crystalline/crystalline blends of poly(butylene succinate)/poly(ethylene oxide)

Miscibility and crystallization behavior have been investigated in blends of poly(butylene succinate) (PBSU) and poly(ethylene oxide) (PEO), both semicrystalline polymers, by differential scanning calorimetry and optical microscopy. Experimental results indicate that PBSU is miscible with PEO as shown by the existence of single composition dependent glass transition temperature over the entire composition range. In addition, the polymer-polymer interaction parameter, obtained from the melting depression of the high-T_m component PBSU using the Flory-Huggins equation, is composition dependent, and its value is always negative. This indicates that PBSU/PEO blends are thermodynamically miscible in the melt. The morphological study of the isothermal crystallization at 95 °C (where only PBSU crystallized) showed the similar crystallization behavior as in amorphous/crystalline blends. Much more attention has been paid to the crystallization and morphology of the low-T_m component PEO, which was studied through both one-step and two-step crystallization. It was found that the crystallization of PEO was affected clearly by the presence of the crystals of PBSU formed through different crystallization processes. The two components crystallized sequentially not simultaneously when the blends were quenched from the melt directly to 50 °C (one-step crystallization), and the PEO spherulites crystallized within the matrix of the crystals of the preexisted PBSU phase. Crystallization at 95 °C followed by quenching to 50 °C (two-step crystallization) also showed the similar crystallization behavior as in one-step crystallization. However, the radial growth rate of the PEO spherulites was reduced significantly in two-step crystallization than in one-step crystallization.     

Water sorption in cross-linked poly(vinyl alcohol) networks

Poly(vinyl alcohol) (PVA) networks of different cross-linking densities were prepared by reaction with hexamethylene diisocyanate in solution and casting. The dynamic-mechanical properties of PVA films have been investigated in the temperature range of −150 to +150 °C. Two relaxations processes labeled α and β in order of decreasing temperature were observed. The α-relaxation shifts to lower temperature and the average molecular weight between cross-links decreases with increasing cross-linking density. Isothermal sorption from vapor and liquid water allowed determination of the Flory-Huggins interaction parameter between water and the polymer chain segments, which decreased with the water activity in the hydrogel and increased with the cross-linking density as a consequence of the hydrophobic character of the cross-linking agent. The water diffusion coefficients, D, in the networks obtained by means of dynamic sorption experiments increased with increasing water activity. This behavior is interpreted in terms of plasticization of the polymer by water molecules.     

Miscibility and phase structure of binary blends of poly(L‐lactide) and poly(vinyl alcohol)

Blend films of poly(L ‐lactide) (PLLA) and poly(vinyl alcohol) (PVA) were obtained by evaporation of hexafluoroisopropanol solutions of both components. The component interaction, crystallization behavior, and miscibility of these blends were studied by solid‐state NMR and other conventional methods, such as Fourier transform infrared (FTIR) spectra, differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction (WAXD). The existence of two series of isolated and constant glass‐transition temperatures (T_g's) independent of the blend composition indicates that PLLA and PVA are immiscible in the amorphous region. However, the DSC data still demonstrates that some degree of compatibility related to blend composition exists in both PLLA/atactic‐PVA (a‐PVA) and PLLA/syndiotactic‐PVA (s‐PVA) blend systems. Furthermore, the formation of interpolymer hydrogen bonding in the amorphous region, which is regarded as the driving force leading to some degree of component compatibility in these immiscible systems, is confirmed by FTIR and further analyzed by ¹³C solid‐state NMR analyses, especially for the blends with low PLLA contents. Although the crystallization kinetics of one component (especially PVA) were affected by another component, WAXD measurement shows that these blends still possess two isolated crystalline PLLA and PVA phases other than the so‐called cocrystalline phase. ¹³C solid‐state NMR analysis excludes the interpolymer hydrogen bonding in the crystalline region. The mechanical properties (tensile strength and elongation at break) of blend films are consistent with the immiscible but somewhat compatible nature of these blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 762–772, 2001     

Phase behavior and properties of poly(methyl methacrylate)/poly(vinyl acetate) blends prepared via in situ polymerization

Polymer blends composed of poly(methyl methacrylate) (PMMA) and poly(vinyl acetate) (PVAc) were prepared via radical-initiated polymerization of methyl methacrylate (MMA) in the presence of PVAc. Differential scanning calorimetry and dynamic mechanical analysis were employed to investigate the miscibility and phase behavior of the blends. The PMMA/PVAc blends of in situ polymerization were found to be phase separated and exhibited a two-phase structure, although some chain transferring reaction between the components occurred. The phase separation resulted from the solvent effect of MMA during the in situ polymerization, which was confirmed by the investigation of phase behavior based on solution cast blending. Solubility analysis of the polymerized blends indicated that some chain transferring reaction between the components occurred during the polymerization. An abrupt increase in gel content from 21.2 to 72.4 wt % was observed when the inclusion of PVAc increased from 30 to 40 wt %, and the gel component consisted of the component polymers as shown by infrared spectroscopy studies. The thermogravimetric analysis study indicated that the inclusion of a small amount of PVAc gives rise to a marked stabilization effect on the thermal stability. The PMMA/PVAc blends exhibited increased notched impact properties with the inclusion of 5 wt % PVAc. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 675–684, 1998     

Facile fabrication of poly(vinyl alcohol) gels and derivative aerogels

A facile preparation of poly(vinyl alcohol) (PVOH) hydrogels and their derivative PVOH/montmorillonite clay aerogels is reported, using water as solvent and divinylsulfone as crosslinking agent, making use of an environmentally friendly freeze drying process. The materials exhibit significantly increased mechanical properties after crosslinking. The compressive modulus of an aerogel prepared from an aqueous suspension containing 2 wt% PVOH/8 wt% clay increased 29-fold upon crosslinking, for example. Crosslinking of the polymer/clay aerogels decreased the onset decomposition temperature as measured by thermogravimetric analysis, and generated a more continuous structure at higher clay contents. Such polymer/clay aerogels are promising materials for low flammability applications.