Thermal properties and structure of electrospun blends of PVDF with a fluorinated copolymer

We report the structure and thermal properties of blends comprising poly(vinylidene fluoride) (PVDF) and a random fluorinated copolymer (FCP) of poly(methyl methacrylate)‐random‐1H,1H,2H,2H‐perfluorodecyl methacrylate, promising membrane materials for oil–water separation. The roles of processing method and copolymer content on structure and properties were studied for fibrous membranes and films with varying compositions. Bead‐free, nonwoven fibrous membranes were obtained by electrospinning. Fiber diameters ranged from 0.4 to 1.9 μm, and thinner fibers were obtained for PVDF content >80%. As copolymer content increased, degree of crystallinity and onset of degradation for each blend decreased. Processing conditions have a greater impact on the crystallographic phase of PVDF than copolymer content. Fibers have polar beta phase; solution‐cast films contain gamma and beta phase; and melt crystallized films form alpha phase. Kwei's model was used to model the glass transition temperatures of the blends. Addition of FCP increases hydrophobicity of the electrospun membranes. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 312–322     

Crystallization and morphology of poly(vinylidene fluoride)/poly(3‐hydroxybutyrate) blends. III. Crystallization and phase diagram by differential scanning calorimetry

The crystallization of poly(vinylidene fluoride) (PVDF)/poly(3‐hydroxybutyrate) (PHB) blends was studied with differential scanning calorimetry, from which the phase diagram was derived. Strong miscibility was underlined by the large negative Flory–Huggins interaction parameter (?0.25). The crystallization of the blend components differed remarkably. Whereas PVDF always crystallized in the surroundings of a homogeneous melt, PHB crystallized in a volume that was confined by the already existing PVDF spherulites, partly in their surroundings and partly inside. Under isothermal conditions, PVDF usually crystallized regularly in three dimensions with predominant quench‐induced athermal nucleation. The Avrami exponent for PVDF dendritic spherulitic growth was, however, distinctly smaller than that for compact growth, and this revealed the two‐dimensional lamellar growth inside. This deviation from ideal Avrami behavior was caused by the development of compositional inhomogeneities as PVDF crystallization proceeded, and this decelerated the kinetics. PHB crystallized three‐dimensionally with mixed thermal and athermal nucleation outside the PVDF spherulites. Inside the PVDF spherulites, PHB crystallization proceeded in a fibrillar fashion with thermal nucleation; the growth front followed the amorphous paths inside the dendritic PVDF spherulites. The crystallization was faster than that in the melt of uncrystallized PVDF. Solid PVDF acts possibly heterogeneously nucleating, accelerating PHB crystallization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 287–295, 2005     

Crystallization kinetics of poly(ethylene oxide) confined in semicrystalline poly(vinylidene) fluoride

Polymer blends based on poly(vinylidene fluoride) (PVDF) and poly(ethylene oxide) (PEO) have been prepared to analyze the crystallization kinetics of poly(ethylene oxide) confined in semicrystalline PVDF with different ratios of both polymers. Both blend components were dissolved in a common solvent, dimethyl formamide. Blend films were obtained by casting from the solution at 70 °C. Thus, PVDF crystals are formed by crystallization from the solution while PEO (which is in the liquid state during the whole process) is confined between PVDF crystallites. The kinetics of crystallization of the confined PEO phase was studied by isothermal and nonisothermal experiments. Fitting of Avrami model to the experimental DSC traces allows a quantitative comparison of the influence of the PVDF/PEO ratio in the blend on the crystallization behavior. The effect of melting and further recrystallization of the PVDF matrix on PEO confinement is also studied. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 588–597     

The effects of dopant acids on structure and properties of poly(o‐methoxyaniline)

Poly(o‐methoxyaniline) (POMA) was chemically synthesized using ammonium persulfate (APS) as oxidant. Methane sulfonic acid (MSA), hydrochloric acid (HCl), and p‐toluene sulfonic acid (pTSA) were used as dopants, under the same reaction conditions. For comparison, undoped POMA was also synthesized. The polymer samples were characterized by Fourier transform infrared spectroscopy (FTIR), four‐probe conductivity measurement, scanning electron microscopy (SEM), electron spin resonance (ESR), gel permeation chromatography (GPC), and determination of specific surface area. The antioxidant activities of POMA were assessed via reaction with 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) free radical, and the anti‐microbial activities were determined as minimum bactericidal concentrations against E. coli 25422 and S. aureus 6838. When doped with relatively strong acids, high yield (above 84%) was achieved, compared to the relatively low yield (45%) when no dopant was present. The conductivity decreased in the order POMA‐pTSA > POMA‐HCl > POMA‐MSA > undoped POMA. A polaron conduction mechanism was supported by FTIR and ESR spectra. The morphology of the polymers was found to be effectively controlled by dopants. All POMA polymers showed strong free radical scavenging ability, which was highly correlated with the specific surface areas of the polymer particles. All the tested samples showed activity against S. aureus 6838, but not at the concentrations tested against E. coli 25422. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Miscibility and crystallization behavior in blends of poly(methyl methacrylate) and poly(vinylidene fluoride): Effect of star‐like topology of poly(methyl methacrylate) chain

A tetraarmed star‐shaped poly(methyl methacrylate) (s‐PMMA) was synthesized via atom transfer radical polymerization with 2‐bromoisobutyryl pentaerythritol as the initiator. For comparison, a linear PMMA with the identical molecular weight (l‐PMMA) was also prepared. The blends of the two PMMA samples with poly (vinylidene fluoride) (PVDF) were prepared to investigate the effect of macromolecular topological structure on miscibility and crystallization behavior of the binary blends. The behavior of single and composition‐dependent glass transition temperatures was found for the blends of s‐PMMA with PVDF, indicating that the s‐PMMA is miscible with PVDF in the amorphous state just like l‐PMMA. The miscibility was further evidenced by the depression of equilibrium melting points. It is found that the blends of s‐PMMA and PVDF displayed the larger k value of Gordon–Taylor equation than the blends of l‐PMMA and PVDF blends. According to the depression of equilibrium melting points, the intermolecular parameters for the two blends were estimated. It is noted that the s‐PMMA/PVDF blends displayed the lower interaction parameter than l‐PMMA/PVDF blends. The isothermal crystallization kinetics shows that the crystallization of PVDF in the blends containing s‐PMMA is faster than that in the blends containing the linear PMMA. The surface‐folding free energy of PVDF chains in the blends containing s‐PMMA is significantly lower than those in the blends containing l‐PMMA. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2580–2593, 2007     

Molecular dynamics in PVDF/PVA blends as revealed by dielectric loss spectroscopy

The relaxation behavior of a series of compatible poly(vinylidene fluoride) (PVDF) and poly(vinyl acetate) (PVA) blends has been investigated by dielectric spectroscopy in a broad frequency and temperature range. Blends with PVDF content higher than 60% in weight are semicrystalline. Semicrystalline blends show a relaxation (α_c) occurring in the crystalline phase of PVDF. Both semicrystalline and amorphous blends exhibit two processes, α and β associated to the overall segmental dynamics and to localized motions in the amorphous phase, respectively. For high PVDF content samples, the β relaxation exhibits an anomalous behavior characterized by a crossover from segmental to local dynamics, upon decreasing temperature, attributed to confinement effects taking place in PVDF segregated regions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1653–1661, 2007     

Comparative studies on miscibility and phase behavior of linear and star poly(2‐methyl‐2‐oxazoline) blends with poly(vinylidene fluoride)

The comparative studies on the miscibility and phase behavior between the blends of linear and star‐shaped poly(2‐methyl‐2‐oxazoline) with poly(vinylidene fluoride) (PVDF) were carried out in this work. The linear poly(2‐methyl‐2‐oxazoline) was synthesized by the ring opening polymerization of 2‐methyl‐2‐oxazoline in the presence of methyl p‐toluenesulfonate (MeOTs) whereas the star‐shaped poly(2‐methyl‐2‐oxazoline) was synthesized with octa(3‐iodopropyl) polyhedral oligomeric silsesquioxane [(IC₃H₆)₈Si₈O₁₂, OipPOSS] as an octafunctional initiator. The polymers with different topological structures were characterized by means of Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. It is found that the star‐shaped poly(2‐methyl‐2‐oxazoline) was miscible with poly(vinylidene fluoride) (PVDF), which was evidenced by single glass‐transition temperature behavior and the equilibrium melting‐point depression. Nonetheless, the blends of linear poly(2‐methyl‐2‐oxazoline) with PVDF were phase‐separated. The difference in miscibility was ascribed to the topological effect of PMOx macromolecules on the miscibility. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 942–952, 2006     

Device model for poly(o‐methoxyaniline) field‐effect transistor

We present a detailed study of the electric mechanism of a thin poly(o‐methoxyaniline) (POMA) field‐effect transistor. The device was prepared using Al‐Si/SiO₂/(interdigitated gold lines array)/POMA structure as the gate electrode, insulating layer, source‐drain electrodes, and active layer, respectively. A model is presented for the electrical characteristics of such a device that encompasses the disordered properties of the POMA, the source‐drain electrical‐field dependence of hole mobility, and the carrier and mobility gradients in directions perpendicular to the polymer–oxide interface. The fittings of source‐drain current versus source‐drain voltage, having as parameters the gate voltage, is in good agreement with the experimental data, and the dependence of both the carrier saturation velocity and of the carrier mobility with the gate voltage are obtained. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 74–78, 2005     

Secondary doping in poly(3,4‐ethylenedioxythiophene):Poly(4‐styrenesulfonate) thin films

The electrical and structural properties of poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) thin films deposited from aqueous dispersion using different concentrations of selected secondary dopants are studied in detail. An improvement of the electrical conductivity by three orders of magnitude is achieved for dimethyl sulfoxide, sorbitol, ethylene glycol, and N,N‐dimethylformamide, and the secondary dopant concentration dependence of the conductivity exhibits almost identical behavior for all investigated secondary dopants. Detailed analysis of the surface morphology and Raman spectra reveals no presence of the secondary dopant in fabricated films, and thus the dopants are truly causing the secondary doping effect. Although the ratio of benzenoid and quinoid vibrations in Raman spectra is unaffected by doping, the phase transition in PEDOT:PSS films owing to doping is confirmed. Further analysis of temperature‐dependent conductivity reveals 1D variable range hopping (VRH) charge transport for undoped PEDOT:PSS, whereas highly conductive doped PEDOT:PSS films exhibit 3D VRH charge transport. We demonstrate that the charge ‐ hopping dimensionality change should be a fundamental reason for the conductivity enhancement. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1139–1146     

Conformational changes and phase transformation mechanisms in PVDF solution‐cast films

The supramolecular crystal structure in poly(vinylidene fluoride) (PVDF) solution‐cast films is studied through changing crystallization conditions in two solvents of different structures and polarities. The crystalline‐state chain conformations of isothermally solution‐crystallized PVDF in N, N‐dimethylacetamide (DMAc), and cyclohexanone are studied through the specific FTIR absorption bands of α, β, and γ phase crystals. There are no changes in the FTIR spectra of cyclohexanone solution‐crystallized films in the temperature range of 50–120 °C. In the case of DMAc solution‐crystallized films, low temperature crystallization mainly results in formation of trans states (β and γ phases), whereas at higher temperatures gauche states become more populated (α phase). This is due to the variations in solvent polarity and ability to induce a specific conformation in PVDF chains, through the changes in chain coil dimensions. This indicates that in spite of cyclohexanone solutions, the intermolecular interactions between PVDF and DMAc are temperature‐sensitive and more important in stabilizing conformations of PVDF in crystalline phase than temperature dependence of PVDF chain end‐to‐end distance <r²>. The high‐resolution ¹⁹F NMR spectroscopy also showed little displacement in PVDF characteristic chemical shifts probably due to changes in PVDF chain conformation resulting from temperature variations. Upon uniaxial stretching of the prepared films under certain conditions, contribution of trans state becomes more prominent, especially for the originally higher α phase‐containing films. Due to formation of some kink bands during film stretching and phase transformation, α phase absorption bands are still present in infrared spectra. Besides, uniaxial stretching greatly enhances piezoelectric properties of the films, maybe due to formation of oriented β phase crystals, which are of more uniform distribution of dipole moments. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3487–3495, 2004     

Lamellar structural changes in miscible crystalline polymer blends during melting and crystallization processes,as studied by real‐time small‐angle X‐ray scattering measurements

Real‐time small‐angle X‐ray scattering (SAXS) measurement using synchrotron radiation was applied to study the lamellar structural changes in miscible crystalline polymer blends of poly(1,4‐butylene succinate) (PBSU) and poly(vinylidene fluoride) (PVDF) during melting and crystallization processes. The lamella of PBSU is either included in the interlamellar region of PVDF (interlamellar inclusion structure), or rejected from the interlamellar region of PVDF (interlamellar exclusion structure). The two lamellar structures coexists in the melt‐quenched samples of the PBSU/PVDF = 30/70 blend. Only the interlamellar exclusion structure exists in the drawn films of the PBSU/PVDF = 30/70 blend. The real‐time SAXS results show that the interlamellar exclusion structure in these samples is irreversibly transformed into the interlamellar inclusion structure by heating the sample above the melting temperature of PBSU and that the PBSU chains are crystallized between the lamellae of PVDF during the cooling process. The factors controlling the lamellar structural changes are possibly a balance of the miscibility and the chain exclusion by tie‐molecules and/or the chain diffusion under confinement by the lamellae of PVDF with higher melting temperature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1959–1969, 2007     

Investigation on LCST behavior of a new amorphous/crystalline polymer blend: Poly(n‐methyl methacrylimide)/poly(vinylidene fluoride)

The liquid–liquid phase‐separation (LLPS) behavior of poly(n‐methyl methacrylimide)/poly(vinylidene fluoride) (PMMI/PVDF) blend was studied by using small‐angle laser light scattering (SALLS) and phase contrast microscopy (PCM). The cloud point (T_c) of PMMI/PVDF blend was obtained using SALLS at the heating rate of 1 °C min^?1 and it was found that PMMI/PVDF exhibited a low critical solution temperature (LCST) behavior similar to that of PMMA/PVDF. Moreover, T_c of PMMI/PVDF is higher than its melting temperature (T_m) and a large temperature gap between T_c and T_m exists. At the early phase‐separation stage, the apparent diffusion coefficient (D_app) and the product (2Mk) of the molecules mobility coefficient (M) and the energy gradient coefficient (k) arising from contributions of composition gradient to the energy for PMMI/PVDF (50/50 wt) blend were calculated on the basis of linearized Cahn‐Hilliard‐Cook theory. The kinetic results showed that LLPS of PMMI/PVDF blends followed the spinodal decomposition (SD) mechanism. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1923–1931, 2008     

Crystallization and morphology of poly(vinylidene fluoride)/poly(3‐hydroxybutyrate) blends. I. Spherulitic morphology and growth by polarized microscopy

The development of the poly(3‐hydroxybutyrate) (PHB) morphology in the presence of already existent poly(vinylidene fluoride) (PVDF) spherulites was studied by two‐stage solidification with two separate crystallization temperatures. PVDF formed irregular dendrites at lower temperatures and regular, banded spherulites at elevated temperatures. The transition temperature of the spherulitic morphology from dendrites to regular, banded spherulites increased with increasing PVDF content. A remarkable amount of PHB was included in the PVDF dendrites, whereas PHB was rejected into the remaining melt from the banded spherulites. When PVDF crystallized as banded spherulites, PHB could consequently crystallize only around them, if at all. In contrast, PHB crystallized with a common growth front, starting from a defined site in the interfibrillar regions of volume‐filling PVDF dendrites. It formed by itself dendritic spherulites that included a large number of PVDF spherulites. For blends with a PHB content of more than 80 wt %, for which the PVDF dendrites were not volume‐filling, PHB first formed regular spherulites. Their growth started from outside the PVDF dendrites but could later interpenetrate them, and this made their own morphology dendritic. These PHB spherulites melted stepwise because the lamellae inside the PVDF dendrites melted at a lower temperature than those from outside. This reflected the regularity of the two fractions of the lamellae because that of those inside the dendrites of PVDF was controlled by the intraspherulitic order of PVDF, whereas that from outside was only controlled by the temperature and the melt composition. The described morphologies developed without mutual nucleating efficiency of the components. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 873–882, 2003     

Oriented crystallization of poly(L‐lactic acid) in uniaxially oriented blends with poly(vinylidene fluoride)

This article describes the oriented crystallization of poly(L ‐lactic acid) (PLLA) in uniaxially oriented blends with poly(vinylidene fluoride) (PVDF). Uniaxially drawn films of PLLA/PVDF blend with fixed ends were heat‐treated in two ways to crystallize PLLA in oriented blend films. The crystal orientation of PLLA depended upon the heat‐treatment process. The crystal c‐axis of the α form crystal of PLLA was highly oriented in the drawing direction in a sample cold‐crystallized at T_c = 120 °C, whereas the tilt‐orientation of the [200]/ [110] axes of PLLA was induced in the sample crystallized at T_c = 120 °C after preheating at T_p = 164.5–168.5 °C. Detailed analysis of the wide‐angle X‐ray diffraction (WAXD) indicated that the [020]/ [310] crystal axes were oriented parallel to the drawing direction, which causes the tilt‐orientation of the [200]/ [110] axes and other crystal axes. Scanning electron microscopy (SEM) suggested that oriented crystallization occurs in the stretched domains of PLLA with diameters of 0.5–2.0 μm in the uniaxially drawn films of PVDF/PLLA = 90/10 blend. Although the mechanism for the oriented crystallization of PLLA was not clear, a possibility was heteroepitaxy of the [200]/[110] axes of the α form crystal of PLLA along the [201]/[111] axes of the β form crystal of PVDF that is induced by lattice matching of d₁₀₀(PLLA) ≈ 5d₂₀₁(PVDF). © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1376–1389, 2008     

Polymer electrolyte membranes by in situ polymerization of poly(ethylene carbonate‐co‐ethylene oxide) macromonomers in blends with poly(vinylidene fluoride‐co‐hexafluoropropylene)

Salt‐containing membranes based on polymethacrylates having poly(ethylene carbonate‐co‐ethylene oxide) side chains, as well as their blends with poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP), have been studied. Self‐supportive ion conductive membranes were prepared by casting films of methacrylate functional poly(ethylene carbonate‐co‐ethylene oxide) macromonomers containing lithium bis(trifluorosulfonyl)imide (LiTFSI) salt, followed by irradiation with UV‐light to polymerize the methacrylate units in situ. Homogenous electrolyte membranes based on the polymerized macromonomers showed a conductivity of 6.3 × 10^?6 S cm^?1 at 20 °C. The preparation of polymer blends, by the addition of PVDF‐HFP to the electrolytes, was found to greatly improve the mechanical properties. However, the addition led to an increase of the glass transition temperature (T_g) of the ion conductive phase by ～5 °C. The conductivity of the blend membranes was thus lower in relation to the corresponding homogeneous polymer electrolytes, and 2.5 × 10^?6 S cm^?1 was recorded for a membrane containing 10 wt % PVDF‐HFP at 20 °C. Increasing the salt concentration in the blend membranes was found to increase the T_g of the ion conductive component and decrease the propensity for the crystallization of the PVDF‐HFP component. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 79–90, 2007     

Preparation and properties of dynamically cured poly(vinylidene fluoride)/silicone rubber blends

Blends of poly(vinylidene fluoride) (PVDF) and silicone rubber (SR) were prepared through dynamic vulcanization. The effects of SR content on crystallization behavior, rheology, dynamic mechanical properties and morphology of the blends were investigated. Morphology characterization shows that the crosslinked spherical SR particles with an average diameter of 2-4 μm form a “network” in the PVDF continuous phase. The dynamic mechanical properties indicate the interface adhesion between PVDF and rubber phase is improved by the dynamic vulcanization. The rheology study shows that with the increase of rubber content the blends pseudoplastic nature is retained, while the viscosity increases, and hence the processability is less good. The incorporation of SR phase promotes the nucleation process of PVDF, leading to increased polymer crystallization rate and crystallization temperature. However, a higher content of SR seems to show a negative effect on the crystallinity of the PVDF component.     

A polymer of bisphenol A and bisphenol A diglycidyl ether and its blends with poly(styrene‐co‐acrylonitrile): In situ polymerization preparation,morphology, and mechanical properties

The poly(hydroxy ether of bisphenol A)‐based blends containing poly(acrylontrile‐co‐styrene) (SAN) were prepared through in situ polymerization, i.e., the melt polymerization between the diglycidy ether of bisphenol A (DGEBA) and bisphenol A in the presence of poly(acrylontrile‐co‐styrene) (SAN). The polymerization reaction started from the initial homogeneous ternary mixture of SAN/DGEBA/bisphenol A, and the phenoxy/SAN blends with SAN content up to 20 wt % were obtained. Both the solubility behavior and Fourier transform infrared (FTIR) spectroscopy studies demonstrate that no intercomponent reaction occurred in the reactive blend system. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electronic microscopy (SEM) were employed to characterize the phase structure of the as‐polymerized blends. All the blends display the separate glass transition temperatures (T_g's); i.e., the blends were phase‐separated. The morphological observation showed that all the blends exhibited well‐distributed phase‐separated morphology. For the blends with SAN content less than 15 wt %, very fine SAN spherical particles (1–3 μmm in diameter) were uniformly dispersed in a continuous matrix of phenoxy and the fine morphology was formed through phase separation induced by polymerization. Mechanical tests show that the blends containing 5–15 wt % SAN displayed a substantial improvement of tensile properties and Izod impact strength, which were in marked contrast to those of the materials prepared via conventional methods. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 525–532, 1999     

Non‐equilibrium phase behavior of diblock copolymer melts and binary blends in the intermediate segregation regime

The phase behavior of intermediately segregated (χN = 45) poly(ethylene)‐poly(ethylethylene) (PE–PEE) diblock copolymers and PE–PEE binary blends are characterized using transmission electron microscopy and small‐angle X‐ray scattering. Surprisingly, the preparation‐dependent, nonequilibrium phase behavior can be overwhelming even at this degree of segregation. A pure diblock with a poly(ethylene) volume fraction of f_PE = 0.46 exhibited coexisting lamellae and perforated layers when prepared using a precipitation technique, but contained only the lamellar morphology when solvent cast. This preparation dependence was more dramatic in binary diblock copolymer blends with average compositions of 〈f_PE〉 = 0.44, 0.46, and 0.48. Precipitated blends exhibited a microphase separated structure that was disordered and bicontinuous; however, solvent cast samples exhibited either a cylindrical, coexisting cylindrical and lamellar, or lamellar morphology. This nonequilibrium behavior is attributed to the high degree of segregation and the proximity to the cylinder/lamellae phase boundary. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2229–2238, 1999     

Thin poly(ionic liquid) and poly(vinylidene fluoride) blend films with ferro‐ and piezo‐electric polar γ‐crystals

Ferro‐ and piezo‐electric poly(vinylidene fluoride) (PVDF) thin film is reported to be obtained by using a poly(ionic liquid) (PIL) [poly(2‐(dimethylamino)ethyl methacrylate) methyl chloride quaternary salt] through solution route. The short range interactions between localized cationic ions of PIL and polar >CF₂ of PVDF are responsible for modified polar γ‐PVDF (T₃GT₃Ḡ) formation. Modification in chain conformation of PVDF is confirmed by FTIR, XRD, and DSC studies suggesting the miscible PVDF–PIL (PPIL) blend. Up to 40 wt % loading of PIL in PVDF matrix enhances relative intensity of γ‐phase up to 50% in the entire crystalline phase. The P‐E hysteresis loop of PVDF‐PIL blends at 25 wt % PIL loading (PPIL‐25) thin film at sweep voltage of ±50 V shows excellent ferroelectric property with nearly saturated high remnant polarization ∼6.0 µC cm⁻² owing to large proportion of γ‐PVDF. However, non‐polar pure PVDF thin film shows unsaturated hysteresis loop with 1.4 µC cm⁻² remnant polarization. The operation voltage decreases effectively because of the polar γ‐phase formation in PPIL blended film. High‐sensitivity piezo‐response force microscopy shows electromechanical switching property at low voltages in PPIL‐25 thin films through local switching measurements, making them potentially suitable as ferroelectric tunnel barriers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 795–802     

Phase separation and crystallinity in proton conducting membranes of styrene grafted and sulfonated poly(vinylidene fluoride)

A series of proton exchange membranes have been prepared by the preirradiation grafting method. Styrene was grafted onto a matrix of poly(vinylidene fluoride) (PVDF) after electron beam irradiation. Part of the samples was crosslinked with divinylbenzene (DVB) or bis(vinylphenyl)ethane (BVPE). Subsequent sulfonation gave membranes grafted with poly(styrene sulfonic acid) and marked PVDF‐g‐PSSA. It was found that the intrinsic crystallinity of the matrix decreased in both the grafting and the sulfonation reaction in all the membranes. The graft penetration and the ion conductivity are influenced strongly by the crosslinker. The ion conductivity is considerably lower in crosslinked membranes than in noncrosslinked ones. Generally, the mechanical strength decreases with crosslinking. The membranes show a regular phase separated structure in which the sulfonated grafts are incorporated in the amorphous parts of the matrix polymer. The phase separated domains are small, of the order of magnitude of 100–250 nm. These were resolved on transmission electron micrographs and on atomic force images but could not be resolved with microprobe Raman spectroscopy. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1741–1753, 1999