Synthesis of poly(vinylidene chloride)-based composite latexes by emulsion polymerization from epoxy functional seeds for improved thermal stability

Poly(glycidyl methacrylate-co-butyl methacrylate)/poly(vinylidene chloride-co-methyl acrylate) (poly(GMA-co-BMA)/poly(VDC-co-MA)) composite latexes have been successfully synthesized via a two-stage emulsion polymerization process. In a first step, emulsion copolymerization of GMA and BMA was carried out in optimized conditions (low temperature, neutral pH, starved-feed conditions) to both limit the hydrolysis of epoxy groups and obtain small particle size (typically 30-50 nm size range). Composite latexes were then obtained by a second-stage seeded copolymerization of VDC and MA in the presence of tetrasodium pyrophosphate to control the pH and reach high molecular weight, leading to partial encapsulation of the seed particles (snow-man morphology, in agreement with theoretical expectations). Thermogravimetric analyses performed on the resulting composite particles showed that the epoxy-functionalized seed polymer behaved as an efficient thermal stabilizer of PVDC.     

IR laser-induced decomposition of poly(vinyl chloride-co-vinyl acetate): Control of products by irradiation conditions

IR laser-induced, ablative decomposition of poly(vinyl chloride-co-vinyl acetate) was examined under different irradiation conditions and its volatile and solid products were characterized by mass spectroscopy, infrared spectroscopy, Raman spectroscopy and UV spectroscopy and EDX-measurements. The laser decomposition of the copolymer, compared with that of poly(vinyl acetate) and poly(vinyl chloride), is revealed to be a more efficient process leading to solid films with the proportion of Cl- and CH₃C(O)O-groups controlled by irradiation conditions.     

A new route to obtain PVDF/PANI conducting blends

Electrically conductive poly(vinylidene fluoride)(PVDF) - polyaniline blends of different composition were synthesized by chemical polymerization of aniline in a mixture of PVDF and dimethylformamide (DMF) and studied by electrical conductivity measurement, UV-Vis-NIR and FTIR spectroscopy. The samples were obtained as flexible films by pressing the powder at 180 °C for 5 min. The electrical conductivity showed a great dependence on the syntheses parameters. The higher value of the electrical conductivity was obtained for the oxidant/aniline molar ratio equal to 1 and p-toluenesulfonic acid-TSA/aniline ratio between 3 and 6. UV-Vis-NIR and FTIR spectra of the blend are similar to the doped PANI, indicating that the PANI is responsible for the high electrical conductivity of the blend. The electrical conductivity of blend proved to be stable as a function of temperature decreasing about one order at temperature of 100 °C. The route used to obtain the polymer blend showed to be a suitable alternative in order to obtain PVDF/PANI-TSA blends with high electrical conductivity.     

Facile design of a metal-imprinted surface from a poly(vinyl chloride-co-acrylic acid) / poly(propylene glycol) blend

Porous thin films with memory for imprinted metals have been prepared by casting water-THF mixed solutions of a poly(vinyl chloride-co-acylic acid) / poly(propylene glycol) blend. When Cu²⁺ and Pb²⁺ ions are imprinted in the cast process, the films retain a memory for the original Cu²⁺ and Pb²⁺ ions. The imprinting processes can be thoroughly monitored by FT-IR spectroscopy.     

Stability of Dispersions of Fluorine-Containing Latexes and Its Effect on the Properties of Forming Films

The stability of latexes of poly(1,1-dihydroperfluoroheptyl acrylate) (LFM-3), poly(vinyl chloride-co-vinylidene chloride) (SVKh), poly(butadiene-co-methacrylic acid) (SKD-1), and their mixtures, as well as the wettability of the films produced on their basis are studied. It is revealed that, in some cases, the stability of binary systems exceeds that of individual dispersions. A correlation is established between the stability of latexes (varying in the film-formation process) and the critical concentration of their coagulation, on the one hand, and the water contact angles, on the other hand. It is shown that the aggregation of latex particles considerably affects the texture of hydrophobic films.     

Changes During Storage of Electrically Conductive Blends Polyaniline–Poly(Ethylene‐co‐vinyl Acetate)

Abstract

The electrical conductivity behavior of polyaniline–poly(ethylene‐co‐vinyl acetate) (PANI–EVA) blends was variable and dynamic during their storage. It was shown that the apparent concentration of the intrinsically conductive polymer at which a conductivity jump of the blends occurs (Φ _c ) is not a constant value over time. The electrical conductivity of the films of low PANI content (below 2.5 wt.%) increased by several (ca. 5) orders of magnitude. It was found that the PANI phase undergoes a flocculation process subsequently resulting in the formation of conductive pathways and a continuous network. Besides, the shape of percolation curves was found to change during storage of the films. Decreased conductivity deviations were registered for blends of low PANI content (<2.5 wt.%), indicating that an improvement (or decreasing number of defects) of the conductive pathways took place within the bulk of the insulating EVA matrix. These results and observed phenomena are discussed by means of the interfacial model for electrically conductive polymer blends. They supported the dispersion/flocculation phase transition within similar composite materials. The phase separation and conductivity jump are attributed to the interfacial interactions between the polymeric constituents. It was shown that the microstructure of the blends consists of highly ordered PANI paths embedded in the insulating EVA matrix. Long fibrils of PANI and interconnected fractal‐like networks were observed. It was found that the sizes of the PANI domains also varied during storage of the films. Due to the spontaneous flocculation of the primary PANI particles, conductive pathways are formed at extremely low percolation threshold (Φ _c , loading level ca. 5 × 10^?3 wt. fraction). Thus, an important property of the conductive constituent, namely its solid‐state rearrangement, was proved. This PANI self‐organization is also interpreted according to the interfacial model of polymer composites. On the other hand, the competition between self‐organization of the complex of PANI with dodecylbenzenesulfonic acid and crystallization of EVA matrix has resulted in structural changes and formation of continuous conductive networks within the blends, responsible for their significantly increased conductivity.     

Polyaniline-coated coconut fibers: Structure,properties and their use as conductive additives in matrix of polyurethane derived from castor oil

Electrically conducting fibers based on coconut fibers (CF) and polyaniline (PANI) were prepared through in situ oxidative polymerization of aniline (ANI) in the presence of CF using iron (III) chloride hexahydrate (FeCl_3.6H₂O) or ammonium persulfate (APS) as an oxidant. The PANI-coated coconut fibers (CF-PANI) displayed various morphologies, electrical conductivities and percentages of PANI on the CF surface. For both systems, a PANI conductive layer was present on the CF surface, which was responsible for an electrical conductivity of around 1.5 × 10⁻¹ and 1.9 × 10⁻² S cm⁻¹ for composites prepared with FeCl₃.6H₂O and APS, respectively; values that are similar to that of pure PANI. In order to modify the structure and properties of polyurethane derived from castor oil (PU) both CF-PANI and pure PANI were used as conductive additives. The PU/CF-PANI composites exhibited higher electrical conductivity than pure PU and PU/PANI blends. Additionally, the PU/CF-PANI composites showed a variation in electrical resistivity according to the compressive stress applied, indicating that these materials could be applied for pressure-sensitive applications.     

Studies of polymer blends. I. Compatibility of poly(vinyl chloride) and poly(ethylene-co-vinyl acetate-co-sulfur dioxide)

Various methods of determining polymeric molecular compatibility were applied to blends of poly(vinyl chloride) (PVC) and poly(ethylene-co-vinyl acetate-co-sulfur dioxide) (E/VA/SO₂). In one series, where the E/VA/SO₂ had a mole composition of 72.7/18.5/8.8, true compatible blends were demonstrated by phase-contrast microscopy, torsion pendulum studies, and differential scanning calorimetry experiments for blends containing up to 40% E/VA/SO₂. These blends exhibited a single T_g whose compositional variation was found to follow the Fox expression. Experimental densities were slightly greater than predicted on assuming volume additivity. This observation implies better packing and a negative heat of mixing and thus is in harmony with a negative free energy of mixing and the observed molecular compatibility.     

Poly(ethylene-co-vinyl alcohol) and poly(methyl methacrylate) blends: Phase behavior and morphology

In this work blends of poly(ethylene-co-vinyl alcohol) (EVOH) with different ethylene contents (27, 32, 38 and 44 mol%) and poly(methyl methacrylate) (PMMA) were prepared by mechanical mixing in the melted state. The miscibility and melting behavior as a function of blend composition and the ethylene content in EVOH copolymers were investigated by means of differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The morphology of the cryofractured surfaces was examined by scanning electron microscopy (SEM). DSC and DMTA data show that EVOH/PMMA blends are immiscible, independent of EVOH and blend composition. The SEM analysis in agreement with DMTA analysis indicates that the morphology of phases depends on the blend composition, with phase inversion occurring as the concentration of one or other polymer component increases. However, the copolymer composition apparently does not affect the domain size distribution for blends containing 20 wt% of EVOH or 20 wt% of PMMA. A better phase adhesion is observed mainly for blends with 50 wt% of each polymer component.     

Effect of poly(ethylene glycol) on the dielectric properties of poly(vinylidene fluoride)/BiFeO<Subscript>3</Subscript>/poly(ethylene glycol) composite films for electronic applications

In the present work a series of poly(vinylidene fluoride)/BiFeO₃/poly(ethylene glycol) composite films were prepared by solvent casting method with poly(vinylidene fluoride) as polymer matrix, bismuth ferrite as ceramic filler and poly(ethylene glycol) as binding agent as well as enhancer. The structural analysis of the composite films by X-ray diffraction confirms that the composites have a distorted rhombohedral structure. The micro-structural analysis shows that the use of poly(ethylene glycol)in the composite films enhances the homogeneity as well as compatibility of BiFeO₃ particles within the poly(vinylidene fluoride) matrix. The dielectric and electrical study done by impedance analyzer reveals that with an increase in poly(ethylene glycol) concentration, there is a subsequent increase in dielectric constant as well as AC electrical conductivity. Finally, the ferroelectric behavior of the composite confirms that the ferroelectric properties of the composites are enhanced by the addition of BiFeO₃ with an increase in poly(ethylene glycol) concentrations. These preliminary results give an idea for possible applications of this type of composites in the field of electronic applications.     

Bioartificial materials based on blends of dextran and poly(vinyl alcohol-co-acrylic acid)

Bioartificial polymeric materials based on blends of dextran and poly(vinyl alcohol-co-acrylic acid) P(VA-co-AA) were prepared in the form of films and characterised to evaluate the miscibility of the natural component with the synthetic one. The idea of this work was to compatibilise PVA and dextran by introducing carboxylic groups along the PVA chains.The copolymer was synthesised and characterised in our laboratories. The results evidenced that the copolymer had an appropriate molecular weight and the content of PAA in the copolymer was 45% (weight). Then, films with different composition ratios were prepared by solution casting and analysed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), chemical imaging analysis and mechanical tests. The results obtained indicated that the introduction of carboxylic groups along the PVA chains had a positive effect on the miscibility degree of the synthetic component with the biological one.     

Morphology and properties of super-toughened bio-based poly(lactic acid)/poly(ethylene-co-vinyl acetate) blends by peroxide-induced dynamic vulcanization and interfacial compatibilization

Super-toughened poly(lactic acid) (PLA)/poly(ethylene-co-vinyl acetate) (EVA) blends were prepared via 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD) induced dynamic vulcanization and in situ interfacial compatibilization. The effects of AD on the morphology and properties of PLA/EVA blends were studied using a Brabender torque rheometer, gel content test, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and mechanical properties test. The torque and gel content demonstrated that EVA and PLA was successfully vulcanized in the presence of free radicals obtained by the decomposition of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD). Additionally, the gel content results indicated that, compared with PLA, EVA is more aggressive with free radicals. The SEM revealed that a relatively uniform phase morphology and good interfacial compatibilization were achieved in the dynamically vulcanized PLA/EVA/AD blends. The interfacial reaction and compatibilization between the component polymers resulted in the formation of super-toughened PLA/EVA blended materials.     

Chromatic changes in the blends of electroactive polymers with comb-shaped flexible polymers

The effect of blending of alkylated polymers, which have different backbone structures, was investigated in order to improve the electronic properties of conducting polymers. Comb-shaped flexible polymer, poly(octadecyl acrylate) (PODA), was blended with rigid alkylated conducting polymers, poly(3-dodecyl-thiophene)(PDDT), and polyaniline emeraldine base (PANI)/p-dodecyl-benzenesulfonic acid (DBSA) complex, respectively, to investigate the effect of long alkyl chain of flexible polymer on the conformational mode change of rigid backbones and the effect of intermolecular interaction between these alkylated polymers. Optical microscopy was applied to observe the morphology change and obtain the phase diagrams of these blends. The intermolecular interactions that occurred in these blends were explained for each different characteristic peak obtained with FT-IR spectra. Solvatochromism (red-shift) of PDDT/PODA binary blends in solid state due to the planarity change of rigid backbone in the presence of PODA and electrochromism of PANI(DBSA)₄/PODA ternary blends due to the hydrogen bonding between the nitrogen cation of PANI complex and carbonyl group of PODA are observed in UV-Vis-NIR spectra. Interestingly, the increase of conductivity was observed in the presence of 5 wt% of PODA in PDDT/PODA binary blends and a homogeneous smectic liquid crystalline structure was clearly confirmed by cross polarized optical microscopy in PANI(DBSA)₄/PODA ternary blends.     

Influence of graphene reinforcement in conductive polymer: Synthesis and characterization

Lightweight conductive polymers are considered for lightning strike mitigation in composites by synthesizing intrinsically conductive polymers (ICPs) and by the inclusion of conductive fillers in insulating matrices. Conductive films based on polyaniline (PANI) and graphene have been developed to improve through‐thickness conductivity of polymer composites. The result shows that the conductivity of PANI enhanced by blending polyvinylpyrrolidone (PVP) and PANI in 3:1 ratio. Conductive composite thin films are prepared by dispersing graphene in PANI. The conductivity of composite films was found to increase by 40× at 20 wt% of graphene inclusion compared with PVP and PANI blend. Fourier‐transform‐infrared (FTIR) spectra confirmed in situ polymerization of the polymer blend. The inclusion of graphene also exhibits an increase in Tg by 21°C. Graphene additions also showed an increase in thermal stability by approximately 148°C in the composite films. The mechanical result obtained from DMA shows that inclusion of graphene increases the tensile strength by 48% at 20 wt% of graphene reinforcement. A thin, highly conductive surface that is compatible with a composite resin system can enhance the surface conductivity of composites, improving its lightning strike mitigation capabilities.     

Synthesis of poly[(2‐oxo‐1,3‐dioxolane‐4‐yl) methyl methacrylate‐co‐ethyl acrylate] by incorporation of carbon dioxide into epoxide polymer and the miscibility behavior of its blends with poly(methyl methacrylate) or poly(vinyl chloride)

This study was related to the investigation of the chemical fixation of carbon dioxide to a copolymer bearing epoxide and the application of the cyclic carbonate group containing copolymer‐to‐polymer blends. In the synthesis of poly[(2‐oxo‐1,3‐dioxolane‐4‐yl) methyl methacrylate‐co‐ethyl acrylate] [poly(DOMA‐co‐EA)] from poly(glycidyl methacrylate‐co‐ethyl acrylate) [poly(GMA‐co‐EA)] and CO₂, quaternary ammonium salts showed good catalytic activity. The films of poly(DOMA‐co‐EA) with poly(methyl methacrylate) (PMMA) or poly(vinyl chloride) (PVC) blends were cast from N,N′‐dimethylformamide solution. The miscibility of the blends of poly(DOMA‐co‐EA) with PMMA or PVC have been investigated both by DSC and visual inspection of the blends. The optical clarity test and DSC analysis showed that poly(DOMA‐co‐EA) containing blends were miscible over the whole composition range. The miscibility behaviors were discussed in terms of Fourier transform infrared spectra and interaction parameters based on the binary interaction model. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1472–1480, 2001     

Synthesis and characterization of polyaniline/silicon dioxide composites and preparation of conductive films

The focus of this study was to synthesize the inherently conductive polymer polyaniline using an optimized process to prepare polyaniline/silicon dioxide (PANI/SiO₂) composites by in situ polymerization and ex situ solution mixing. PANI and PANI/SiO₂ composite films were prepared by drop‐by‐drop and spin coating methods. The electrical conductivities of HCl doped PANI film and PANI/SiO₂ composite films were measured according to the standard four‐point‐probe technique. The composite films exhibited an increase in electrical conductivity over neat PANI. PANI and PANI/SiO₂ composites were also investigated by spectroscopic methods including UV‐Vis, FT‐IR, and Photoluminescence. UV‐Vis and FT‐IR studies showed that SiO₂ particles affect the quinoid units along the polymer backbone and indicate strong interactions between the SiO₂ particles and the quinoidal sites of PANI (doping effect). The photoluminescence properties of PANI and PANI/SiO₂ composites were studied and the PANI/SiO₂ composites showed increased intensity as compared to neat PANI. The increase of conductivity of PANI/SiO₂ composite may be partially due to the doping or impurity effect of SiO₂ where the silicon dioxides compete with chloride ions. The morphology of particles and films were examined by a scanning electron microscope (SEM). SEM measurements indicated that the SiO₂ were well dispersed and isolated in composite films. Copyright © 2009 John Wiley & Sons, Ltd.     

Miscibility in blends of poly(3-hydroxybutyrate) and poly(vinylidene chloride-co-acrylonitrile)

Miscibility behavior of poly(3-hydroxybutyrate) [PHB]/poly(vinylidene chloride-co-acrylonitrile) [P(VDC-AN)] blends have been investigated by differential scanning calorimetry and optical microscopy. Each blend showed a single T_g, and a large melting point depression of PHB. All the blends containing more than 40% PHB showed linear spherulitic growth behavior and the growth rate decreased with P(VDC-AN) content. The interaction parameter χ₁₂, obtained from melting point depression analysis, gave the value of −0.267 for the PHB/P(VDC-AN) blends. All results presented in this article lead to the conclusion that PHB/P(VDC-AN) blends are completely miscible in all proportions from a thermodynamic viewpoint. The miscibility in these blends is ascribed to the specific molecular interaction involving the carbonyl groups of PHB. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2645–2652, 1997     

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 characterization of PVC/PANI conductive composite with extremely low percolation threshold

Aniline was polymerized in the presence of poly(vinyl chloride) (PVC) powders in hydrochloric acid to in situ prepare poly(vinyl chloride)/polyaniline (PVC/PANI) composite particles. UV‐vis spectra and FT‐IR spectra indicate PANI in PVC/PANI composite particles possessed a higher oxidation state with decreased aniline content in reactants. Both conductivity and impact strength of the dodecylbenzenesulfonic acid (DBSA) doped PANI composites (PVC/PANI‐DBSA), which were compression molded from the in situ prepared PVC/PANI particles, increase with the pressing temperature and decrease with the increase of DBSA doped PANI (PANI‐DBSA) loading. An excellent electric conductivity of 5.06 × 10^?2 S/cm and impact strength of 0.518 KJ/m² could be achieved for the in situ synthesized and subsequently compression molded composite. Copyright © 2004 John Wiley & Sons, Ltd.     

Conductive poly(butadiene-co-acrylonitrile)-polyaniline dodecylbenzenesulfonate [NBR-PAni.DBSA] blends prepared in solution

Blends of poly(butadiene-co-acrylonitrile) elastomer [NBR] and polyaniline dodecylbenzenesulfonate [PAni.DBSA], with electrical conductivities up to 10⁻² S cm⁻¹, have been prepared by solution mixing and casting. Miscibility was maximised for NBR with high acrylonitrile (ACN) content, as predicted on the basis of simple solubility parameter calculations. Blends prepared using NBR with 48 wt% ACN had the lowest electrical conductivity percolation thresholds, and were much more conductive than previous thermally mixed blends. Optical and electron micrographs of blends prepared from NBR 48 wt% ACN also showed the lowest levels of phase separation. The FT-IR spectra of NBR-PAni.DBSA blends resembled a superposition of the spectra of the pure materials, but with significant peak shifts due to changing intermolecular interactions between the polymers. Under DSC analysis, thermal events for blends prepared with NBR 48 wt% ACN also showed the largest temperature shifts relative to those for the pure polymers, supporting the other evidence for interaction between the two polymers.