Miscibility and surface characterization of a poly(vinylidene fluoride)‐poly(vinyl methyl ketone) blend by inverse gas chromatography

The miscibility of blends of semicrystalline poly(vinylidene fluoride)(PVF₂) and poly(vinyl methyl ketone) (PVMK) along with surface characterization were investigated using the inverse gas chromatography method (IGC), over a range of blend compositions and temperatures. Three chemically different families, alkanes, acetates, and alcohols, were utilized for this study. The values of the PVF₂‐PVMK interaction parameters were found to be slightly positive for most of the solutes used, although some degree of miscibility was found at all compositions. Miscibility was greatest at a 50:50 w/w composition of the blend. The interaction parameters obtained from IGC are in excellent agreement with those obtained using calorimetry on the same blends. The calculated molar heat of sorption of alkanes, acetates, and alcohols into the blend layer reveal the impact of the combination of dispersive and hydrogen bonding forces on the interaction of solutes with the blend's backbone. The dispersive component of the surface energy was found to range from 18.70–64.30 mJ/m² in the temperature range of 82–163 °C. A comparison of the blend's surface energy with that of mercury and other polymers is given. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1155–1166, 2000     

Fracture behavior of amorphous and semicrystalline blends of poly(vinylidene fluoride) and poly(methyl methacrylate)

The fracture behavior of blends of poly(vinylidene fluoride) and poly(methyl methacrylate) was investigated all over the composition range. A detailed analysis of the net stress versus crack opening displacement curves was performed. Fracture surface observations allowed statements on the process zone characteristics ahead of the crack tip. For the amorphous blends, the crack initiation energy is well related to the glass transition temperature. For the semicrystalline blends, the fracture energy is correlated with the degree of crystallinity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Fluorocyclopropanes. IV. Copolymers of perfluorocyclopropene

Perfluorocyclopropene undergoes free-radical copolymerization with ethylene, isobutylene, cis- and trans-2-butene, vinyl acetate, methyl vinyl ether, vinyl chloride, styrene, acrylonitrile, tetrafluoroethylene, vinyl fluoride, and vinylidene fluoride. The copolymerization proceeds most readily with electron-rich olefins such as methyl vinyl ether (to yield a 1:1 copolymer), but conditions were found to give copolymers with electron-deficient olefins such as tetrafluoroethylene and vinylidene fluoride. Copolymers with methyl vinyl ether, tetrafluoroethylene, vinyl fluoride, and vinylidene fluoride were examined in detail. Evidence is presented that the perfluorocycloproply ring is incorporated intact into the copolymer and can be subsequently isomerized to a perfluoropropenyl unit by heating at 200–300°C.     

Exploring amino acid‐tethered polymethacrylates as CO2‐sensitive macromolecules: A concealed property

Carbon dioxide (CO₂)‐responsive polymers have been gaining considerable interest because of their reactions with CO₂, giving rise to gas‐switchable properties, which can easily be reversed by mild heating or purging with inert gases. Herein, the synthesis of a series of side‐chain amino acids (alanine, leucine, isoleucine, phenylalanine, tryptophan) appending poly(meth)acrylates carrying primary amine (? NH₂) groups via reversible addition‐fragmentation chain transfer (RAFT) polymerization method was reported. It was found that alanine, leucine, isoleucine containing polymers displayed solubility–insolubility transition behavior and their associated property changes (solution transmittance, electrical conductivity, pH, zeta potential, and hydrodynamic diameter) in water upon alternate bubbling of CO₂/N₂ at room temperature. Among the three CO₂‐sensitive polymers only leucine based macromolecule was further chain extended with a thermoresponsive motif, di(ethylene glycol) methyl ether methacrylate (DEGMMA), via RAFT polymerization. CO₂‐tunable lower critical solution temperature and self‐assembling behavior of the diblock copolymer was carefully examined by UV–vis, ¹H NMR spectroscopy, dynamic light scattering (DLS), and field emission‐scanning electron microscopy (FE‐SEM) to establish dual thermo and gas‐tunable flip–flop micellizaion from the as‐synthesized block copolymer. Formation of polyammonium methacrylate bearing bicarbonate as counter anion is responsible for pendant primary amine containing polymer induced CO₂‐responsiveness. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2794–2803     

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     

Infrared spectroscopic investigation of chain conformations and interactions in P(VDF‐TrFE)/PMMA blends

The blending between poly(methyl methacrylate) (PMMA) and ferroelectric (vinylidene fluoride‐trifluorethylene) [P(VDF‐TrFE)] copolymer chains has been investigated by Fourier transform infrared (FTIR) spectroscopy over the full range of composition, for the copolymer with 50 mol % of trifluorethylene [TrFE]. The FTIR spectra revealed an absorption band at 1643 cm⁻¹, characteristic of the blend and absent in the individual constituents. We attributed this band to the interaction of the carbonyl group of the PMMA side chains with the disordered helical chains present in the amorphous region of the P(VDF‐TrFE). We investigated the consequences of adding PMMA onto the formation of the all trans conformation of the copolymer chains and we demonstrated that the effects of thermal heating on the spectra are relevant only for the samples where the ferroelectric semicrystalline phase is present. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 34–40, 2000     

Microhardness measurements of poly(methyl methacrylate) and poly(vinylidene fluoride) polyblends

The preparation of polymer blends of poly(methyl methacrylate) and poly(vinylidene fluoride) in different weight percentages is described. Vickers microhardness measurements have been made to study the effects of load and compositional ratio of the two polymers in polyblend. It is observed that poly(vinylidene fluoride) acts as a plasticizer for poly(methyl methacrylate). Evidence of increasing and decreasing strength of polyblends has been obtained for different compositional ratios of the two polymers.     

High‐pressure rheology and viscoelastic scaling predictions of polymer melts containing liquid and supercritical carbon dioxide

High‐pressure rheological behavior of polymer melts containing dissolved carbon dioxide (CO₂) at concentrations up to 6 wt % were investigated using a high‐pressure extrusion slit die rheometer. In particular, the steady shear viscosity of poly(methyl methacrylate), polypropylene, low‐density polyethylene, and poly(vinylidene fluoride) with dissolved CO₂ were measured for shear rates ranging from 1 to 500 s^?1 and under pressure conditions up to 30 MPa. The viscosity of all samples revealed a reduction in the presence of CO₂ with its extent dependent on CO₂ concentration, pressure, and the polymer used. Two types of viscoelastic scaling models were developed to predict the effects of both CO₂ concentration and pressure on the viscosity of the polymer melts. The first approach utilized a set of equations analogous to the Williams–Landel–Ferry equation for melts between the glass‐transition temperature (T_g) and T_g + 100 °C, whereas the second approach used equations of the Arrhenius form for melts more than 100 °C above T_g. The combination of these traditional viscoelastic scaling models with predictions for T_g depression by a diluent (Chow model) were used to estimate the observed effects of dissolved CO₂ on polymer melt rheology. In this approach, the only parameters involved are physical properties of the pure polymer melt that are either available in the existing literature or can be measured under atmospheric conditions in the absence of CO₂. The ability of the proposed scaling models to accurately predict the viscosity of polymer melts with dissolved high‐pressure CO₂ were examined for each of the polymer systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 3055–3066, 2001     

Controlled grafting from poly(vinylidene fluoride) films by surface‐initiated reversible addition–fragmentation chain transfer polymerization

A reversible addition–fragmentation chain transfer (RAFT) polymerization technique was applied to graft polymerize brushes of poly(methyl methacrylate) (PMMA) and poly(poly(ethylene glycol) monomethacrylate) (PPEGMA) from poly(vinylidene fluoride) (PVDF) surfaces. PVDF surfaces were exposed to aqueous LiOH, followed by successive reductions with NaBH₄ and DIBAL‐H to obtain hydroxyl functionality. Azo‐functionalities, as surface initiators for grafting, were immobilized on the PVDF surfaces by esterification of 4,4′‐azobis(4‐cyanopentanoic acid) and the surface hydroxyl groups. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance‐FTIR spectroscopy, and atomic force microscopy. Kinetics studies revealed a linear increase in the graft concentration of PMMA and PPEGMA with the reaction time, indicating that the chain growth from the surface was consistent with a “controlled” or “living” process. The living chain ends were used as the macroinitiator for the synthesis of diblock copolymer brushes. Water contact angles on PVDF films were reduced by surface grafting of PEGMA and MMA. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3071–3082, 2006     

Electrochemical studies on PVC/PVdF blend-based polymer electrolytes

In recent years, special attention has been focused on the development of gel polymer electrolytes consisting of host polymers such as poly (acrylonitrile), PVC, poly (methyl methacrylate), poly (vinylidene fluoride) (PVdF), etc., as they may be found to have unique applications in consumer electronic and electric vehicle products. In the present study, blend-based polymer electrolytes composed of PVC, PVdF, NaClO₄, and propylene carbonate is prepared using the solvent casting technique. The thermal behaviors of PVC/PVdF polyblend films have been examined using differential scanning calorimetry and scanning electron microscopy. Miscibility studies were performed using X-ray diffraction and Fourier transform infrared. The role of interaction between polymer hosts on conductivity is discussed using the results of AC impedance studies.     

Water sorption by poly(tetrahydrofurfuryl methacrylate‐co‐2‐hydroxyethyl methacrylate). I. A mass‐uptake study

Cylindrical samples (≈5 mm × 20 mm) of poly(2‐hydroxyethyl methacrylate) and copolymers of 2‐hydroxyethyl methacrylate and furfuryl methacrylate were prepared, and the sorption of water into these cylinders was studied by the mass‐uptake method and by the measurement of the volume change at equilibrium. The equilibrium water content and volume change for the cylinders both varied systematically with the copolymer composition. The diffusion of water into the cylinders followed Fickian behavior, with the diffusion coefficients, dependent on the copolymer composition, varying from 2.00 × 10⁻¹¹ m²s⁻¹ for poly(2‐hydroxyethyl methacrylate) to 5.00 × 10⁻¹² m²s⁻¹ for poly(2‐hydroxyethyl methacrylate‐co‐tetrahydrofurfuryl methacrylate) with a 1 : 4 composition. The polymers that were rich in 2‐hydroxyethyl methacrylate were characterized by a water‐sorption overshoot, which was attributed to a slow reorientation of the polymer chains in the swollen rubbery regions formed after water sorption. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1939–1946, 2000     

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     

Cooperative chain relaxation in miscible polymer blends

Orientation relaxation of dissimilar chains in the molten miscible blends, poly(methyl methacrylate)/poly(vinylidene fluoride) and poly(methyl methacrylate)/poly(vinylidene fluoride-co-trifluoroethylene), were investigated by measuring (1) the change of infrared dichroic ratio with time after the uniaxial stretching of film specimens, (2) the shear stress relaxation spectrum, and (3) birefringence relaxation in shear. The dissimilar polymers showed an identical time variation of the normalized Hermans orientation function. The blend showed a relaxation spectrum with a single characteristic relaxation time τ_c, depending on the blend composition. The birefringence relaxed monotonically, remaining positive. These results suggest that the dissimilar polymers do not relax independently but cooperatively. This behavior may be induced by a constraint due to the specific interactions between the dissimilar polymers, e.g., weak hydrogen bonding. For the cooperative chain relaxation, a third power relationship was found; τ_c/τ_e vprop; (M/M_e),³ where τ_e and M_e are the relaxation time and molecular weight of entanglement strand, respectively, and M is the number average molecular weight in the blend.     

Analysis of the hysteresis curve of ferroelectric polymers by a phenomenological relaxation theory

A simple relaxation theory for the displacement versus electric field hysteresis of ferroelectric polymers is developed in which the relaxation time is assumed to be a function of electric field, as has been experimentally evidenced by polarization-reversal switching. The theory gives an analytical expression for the hysteresis curve. The coercive field E_c predicted by the theory agrees well with data on E_c as a function of temperature for poly(vinylidene fluoride) from ?60 to 20°C and with data on E_c as a function of frequency for vinylidene fluoride/trifluoroethylene copolymer (73/27 molar ratio) at 20°C over the range 0.01–0.7 Hz.     

Block copolymer mediated synthesis of amphiphilic gold nanoparticles in water and an aqueous tetrahydrofuran medium: An approach for the preparation of polymer–gold nanocomposites

The synthesis of polymer‐matrix‐compatible amphiphilic gold (Au) nanoparticles with well‐defined triblock polymer poly[2‐(N,N‐dimethylamino)ethyl methacrylate]‐b‐poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate] and diblock polymers poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate], polystyrene‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate], and poly(t‐butyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate] in water and in aqueous tetrahydrofuran (tetrahydrofuran/H₂O = 20:1 v/v) at room temperature is reported. All these amphiphilic block copolymers were synthesized with atom transfer radical polymerization. The variations of the position of the plasmon resonance band and the core diameter of such block copolymer functionalized Au particles with the variation of the surface functionality, solvent, and molecular weight of the hydrophobic and hydrophilic parts of the block copolymers were systematically studied. Different types of polymer–Au nanocomposite films [poly(methyl methacrylate)–Au, poly(t‐butyl methacrylate)–Au, polystyrene–Au, poly(vinyl alcohol)–Au, and poly(vinyl pyrrolidone)–Au] were prepared through the blending of appropriate functionalized Au nanoparticles with the respective polymer matrices {e.g., blending poly[2‐(N,N‐dimethylamino)ethyl methacrylate]‐b‐poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate‐stabilized Au with the poly(methyl methacrylate)matrix only}. The compatibility of specific block copolymer modified Au nanoparticles with a specific homopolymer matrix was determined by a combination of ultraviolet–visible spectroscopy, transmission electron microscopy, and differential scanning calorimetry analyses. The facile formation of polymer–Au nanocomposites with a specific block copolymer stabilized Au particle was attributed to the good compatibility of block copolymer coated Au particles with a specific polymer matrix. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1841–1854, 2006     

Evaluation of piezoelectric PVDF polymers for use in space environments. II. Effects of atomic oxygen and vacuum UV exposure

The effects of atomic oxygen (AO) and vacuum UV radiation simulating low Earth orbit conditions on two commercially available piezoelectric polymer films, poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride‐trifluoroethylene) P(VDF‐TrFE), have been studied. Surface erosion and pattern development are significant for both polymers. Erosion yields were determined as 2.8 × 10^?24 cm³/atom for PVDF and 2.5 × 10^?24 cm³/atom for P(VDF‐TrFE). The piezoelectric properties of the residual material of both polymers were largely unchanged after exposure, although a slight shift in the Curie transition of the P(VDF‐TrFE) was observed. A lightly cross‐linked network was formed in the copolymer presumably because of penetrating vacuum ultraviolet (VUV) radiation, while the homopolymer remained uncross‐linked. These differences were attributed to varying degrees of crystallinity and potentially greater absorption, and hence damage, of VUV radiation in P(VDF‐TrFE) compared with PVDF. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2503–2513, 2005     

Synthesis and radiation degradation of vinyl polymers with fluorine: Search for improved lithographic resists

Homopolymers of methyl α-fluoroacrylate (MFA), trifluoroethyl methacrylate (TFEM), and hexafluoroisopropyl methacrylate (HFIM) were prepared, as were their methyl methacrylate (MMA) copolymers. Copolymers of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) with MMA were also prepared. The radiation susceptibilities of these polymers were measured by the ⁶⁰Co γ-irradiation method, in which molecular weights were measured by membrane osmometry and gel permeation chromatography (GPC). All the copolymers degraded by predominant chain scission except poly(methyl α-fluoroacrylate), (PMFA), which crosslinks even at low doses (ca. 1 Mrad). The G_s - G_x and G_s values of the chain scissioning polymers and copolymers are higher than those of poly(methyl methacrylate) PMMA reference. The high susceptibility of PMFA homopolymer to crosslinking is in contrast to that of poly(methyl α-chloroacrylate), as we reported earlier. This effect is interpreted as resulting from extensive hydrogen fluoride and polyenlyl radical formation, which leads to facile crosslinking. However, incorporation of the MFA monomer unit causes the (22/78) MFA/MMA copolymer to degrade with a larger value of G_s that PMMA. Apparently a second-order process leads to crosslinking in PMFA and this is retarded in the copolymer. In the hehomopolymers of HFIM and TFEM and in the HFIM-MMA and TFEM-MMA copolymers the HFIM and TFEM components facilitate degradation with negligible crosslinking. The increased degradation susceptibility of VDF and CTFE copolymers with MMA over that of PMMA is attributed to processes at the VDF or CTFE components present in smaller concentrations (3-5 mole %) than the threshold levels (25-50% necessary for significant crosslinking).     

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     

Review on gel polymer electrolytes for lithium batteries

This paper reviews the state-of-art of polymer electrolytes in view of their electrochemical and physical properties for the applications in lithium batteries. This review mainly encompasses on five polymer hosts namely poly(ethylene oxide) (PEO), poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA), poly(vinylidene fluoride) (PVdF) and poly(vinylidene fluoride-hexafluoro propylene) (PVdF-HFP) as electrolytes. Also the ionic conductivity, morphology, porosity and cycling behavior of PVdF-HFP membranes prepared by phase inversion technique with different non-solvents have been presented. The cycling behavior of LiMn₂O₄/polymer electrolyte (PE)/Li cells is also described.     

Preparation and Characterization of Head-to-Head Polymers. II. Head-to-Head Poly(methyl Acrylate)

Head-to-head poly(methyl acrylate) was prepared by esterification of the known alternating copolymer of ethylene and maleic anhydride. Some of the chemical,physical, and mechanical properties and the thermal degradation behavior of head-to-head poly(methyl acrylate) were studied and compared with those of head-to-tail poly(methyl acrylate). The T_g of the head-to-head polymer was higher than that of the head-to-tail polymer, but the solubilities of both types of polymers of comparable molecular weight were similar. Head-to-head poly(methyl acrylate) degraded thermally at approximately the same temperature and with a rate similar to head-to-tail poly(methyl acrylate). Unlike poly(methyl cinnamates) which cleanly degraded to monomers, poly(methyl acrylates), head-to-head and head-to-tail, degrade to very small molecules, such as CO₂, methanol, but also larger polymer fragments and char. Trace amounts of monomers (methyl acrylate) were also observed.