Hydrophilic films based on poly(acrylic acid)–poly(vinyl methyl ether) blends cross-linked by gamma-radiation

Hydrophilic polymeric films based on blends of poly(acrylic acid) and poly(vinyl methyl ether) (PVME) were prepared by casting technique and were cross-linked by gamma-radiation. The films are soft and elastic in a dry state and form hydrogels upon immersion in water. Effect of absorbed dose on the gel fraction as well as on the swelling of the films in aqueous solutions of different pH is studied. It was found that addition of lower molecular weight PVME decreases the gelation dose, which is likely related to a decrease in glass transition temperature of the blends. In acidic media the films have low swelling degree because of suppression of carboxylic groups ionisation and formation of additional physical cross-links via interpolymer hydrogen bonding.     

Optical properties of polymer blends composed of poly(methyl methacrylate) and ethylene–vinyl acetate copolymer

Optical properties for immiscible polymer blends composed of poly(methyl methacrylate), PMMA, and ethylene–vinyl acetate copolymer (EVA) are studied employing various EVA samples with different vinyl acetate contents. PMMA/EVA shows transparency at room temperature when the difference in refractive index between both phases is small. The light transmittance, however, decreases with increasing the ambient temperature. This phenomenon is attributed to the difference in the volume expansion ratio, leading to the difference in refractive index, between PMMA and EVA. It is found that addition of tricresyl phosphate, TCP, improves the transparency and its temperature dependence. As a result, a ternary PMMA/EVA/TCP blend shows high level of transparency in the wide temperature range, although it has apparent phase separated morphology.     

Preparation and characterization of microspheres based on blend of poly(lactic acid) and poly(ɛ-caprolactone) with poly(vinyl alcohol) as emulsifier

In this paper, microspheres were prepared by oil-in-water (o/w) emulsion solvent evaporation method. Biodegradable polymer such as blend of poly (lactic acid) (PLA) and poly(?-caprolactone) (PCL) with certain compositions and characteristics was used to prepare the microspheres with poly(vinyl alcohol) (PVA) as an emulsifier. This study observed the microspheres particle’s size distribution at various concentrations of PVA (1%, 1.5%, 2%, and 2.5% PVA). The PVA volume variations effects during the process (50, 100, 150, 200, and 250 mL) were also observed. The blend of PLA and PCL is formed only by physical interaction between them. This can be seen from the FTIR spectrum which shows both PLA and PCL component. The microspheres physical size and appearance were observed by optical microscope (MO). The overall results of this study showed that the formula which used 50–150 mL of 2.5% polyvinyl alcohol produced the microspheres with the most uniform size distribution.     

Chemical–physical behavior of hydrogels of poly(vinyl alcohol) and poly(ethylene glycol)

New hydrogels based on polyethylene glycol (PEG) and poly(vinyl alcohol) (PVA) of different degrees of hydrolysis were synthesized. To form the network the PEG was modified at their ends with acyl chloride groups to be used as the crosslinking agent. The compositions of the hydrogels were between 50% and 90% by weight of PEG and PVA of various degrees of hydrolysis were used. It was found that the degree of hydrolysis of the PVA and the PEG content influence the equilibrium water content of the hydrogel. The process of swelling of all the hydrogels prepared followed a second-order kinetics.     

Synergetic effect of poly(vinyl butyral) and calcium carbonate on thermal stability of poly(vinyl chloride) nanocomposites investigated by TG–FTIR–MS

In order to improve poly(vinyl chloride) (PVC) thermal stability, poly(vinyl butyral) (PVB) matrix and calcium carbonate nanoparticles were incorporated in plasticized PVC. Thermal properties of these composites were investigated by thermogravimetry analysis coupled with mass spectrometry and Fourier transform infrared spectroscopy (FTIR). This approach highlighted the efficiency of both PVB and CaCO₃ as HCl scavengers by postponing both the onset degradation temperature and the HCl release. Moreover, a synergetic effect was evidenced regarding the HCl release. Finally, kinetic parameters of the PVC first degradation stage, determined using the Flynn–Wall–Ozawa’s method, revealed a significant increase of the activation energy by incorporation of CaCO₃ in the presence or not of PVB.     

Why does poly(acrylic acid) addition improve the quality of holograms recorded in dichromated poly(vinyl alcohol)?

Holographic measurements have shown that the addition of 0.5% of poly(acrylic acid) (PAA) can improve the quality of holograms recorded in poly(vinyl alcohol) (PVA) doped with ammonium dichromate (ADC). The purpose of this paper is to explain this improvement. First, an analytical approach investigated the structural and architectural modification of the polymeric matrix and the fate of the various chromium species within PVA/PAA/ADC films. The addition of PAA in dichromated PVA led to a pre-reticulation of the polymeric matrix. This process increased with the amount of PAA.Second, an analytical approach focused on the evolution of PVA/PAA/ADC films upon irradiation at 365 nm, which is representative of hologram formation. The improvement brought by the presence of 0.5% of PAA in PVA/ADC was assigned to an additional source of crosslinking through the formation of covalent bonds. This process paralleled the crosslinking through coordination bonds involving Cr(V) and PVA units. At 0.5% of PAA, the mobility of the medium before exposure was sufficient to allow the migration of the species involved in the reticulation process during hologram formation, whereas higher concentrations of PAA inhibited this migration.     

Binary blends based on poly(vinyl chloride) and multi-block copolymers containing poly(ϵ-caprolactone) and poly(ethylene glycol) segments

Binary blends based on poly(vinyl chloride) (PVC) were prepared both by casting from tetrahydrofuran (THF) and by mixing in the melt form, in a discontinuous mixer, PVC and multi-block copolymers containing poly(ϵ-caprolactone) (PCDT) and poly(ethylene glycol) (PEG) segments. PCDT-PEG copolymers were synthesized using a polycondensation reaction where the α,ω-bis-chloroformate of an oligomeric poly(ϵ-caprolactone) diol terminated (PCDT) and oligomeric PEG were employed as macromonomers. For comparison purposes, blends PVC with starting oligomers as well as with mixtures containing a typical low molecular plasticizer, dioctylphthalate (DOP), were also prepared. The copolymer miscibility was studied by differential scanning calorimetry (DSC) and FT-IR spectroscopy. The blend morphology was investigated by polarized light microscopy (PLM). A higher miscibility with PVC was observed for copolymers compared to PEG.     

Preparation and properties of poly(vinyl alcohol)/exfoliated α-zirconium phosphate nanocomposite films

In this work, poly(vinylalcohol)(PVA)/exfoliated α-zirconium phosphate(e-α-ZrP) nanocomposites of various compositions were created by a solution casting method. The α-ZrP compound was synthesized by refluxing. The characteristic properties of the PVA/e-α-ZrP composite films were examined by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and tensile tests. Tensile tests indicated that with the loading of e-α-ZrP, the tensile strength and the elongation at break were increased by 17.3% and 26.6% compared to neat PVA, respectively. It is noteworthy that optimum film properties were obtained with 0.8 wt% e-α-ZrP, and higher proportions of e-α-ZrP, may be related to the aggregation of e-α-ZrP particles and deterioration of the film properties. On the whole, the nanocomposite PVA/e-α-ZrP systems had mechanical and thermal properties which were superior to that of the neat polymer and its conventionally filled composites.     

Characterization of commercial artists’ acrylic paints and the influence of UV light on aging

A large part of Mexican artistic heritage was created with artists’ acrylic emulsion paints, so it is crucial to investigate their composition, behavior, and decay. Acrylic films are complex chemical systems combining organic and inorganic compounds; therefore, the degradation studies require a variety of techniques. We characterize three acrylic films before and after ultraviolet aging. The relative composition of the polymer matrix was studied by nuclear magnetic resonance, pyrolysis—gas chromatography—mass spectrometry and direct analysis in real time mass spectrometry with direct analysis in real time. The inorganic compounds and surfaces were characterized by microscopic techniques, such as digital microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and micro X-ray diffraction. The combined use of these techniques proved to be effective for an in-depth study of the acrylic painting degradation process. The main results were the gradual degradation for the organic surfactant and the loss of inorganic aggregates (talc and carbonates), that led to the disruption of the paint film, which points out the importance of studying the role and interaction of all compounds.     

The co-continuous morphology of biocompatible ethylene-vinyl acetate copolymers/poly(��-caprolactone) blend: effect of viscosity ratio and vinyl acetate content

The phase behavior and its linear viscoelastic responses of a biocompatible blend based on ethylene-vinyl acetate copolymers and poly(??-caprolactone) (EVA/PCL) were studied in this work in terms of blending ratios and annealing. The effects of viscosity ratios and vinyl acetate contents of the EVA on the co-continuous morphology were addressed. The results show that EVA/PCL is a typical immiscible blend due to the high interfacial tension between the two polymers. Thus, the blend shows a wide percolation range with a narrow fully co-continuous region. Although the phase inversion point can be well predicted by the viscous Utracki model, the dynamic viscoelastic responses of the blend cannot be well described by the emulsion model. The elasticity ratio was proposed to play an important role together with the viscosity ratio on the phase inversions. During dynamic annealing, the phase size of both the sea?Cisland and the co-continuous structures increases evidently, but the principle of time?Ctemperature superposition is only valid for the co-continuous blend while fails with that with the sea?Cisland phase structure. Beside, the phase size of the co-continuous structure is dependent strongly on the viscosity ratio between EVA and PCL. With reduced viscosity ratio, the phase size increases remarkably. However, vinyl acetate (VA) contents of the EVA have little influences on the interfacial properties and phase size of the co-continuous blends in the experimental content ranges (28?C12?wt.%).     

Study on formation of poly(β-hydroxybutyrate-co-hydroxyvalerate) (PHBV) fiber

In this paper, the crystallization behavior, thermal degradation properties, rheological behavior and the spinnability of poly(β-hydroxybutyrate-co-hydroxyvalerate) (PHBV) fiber were studied. Experimental results indicated that the spherulite growth rate of PHBV was very slow and its size was very large. PHBV began to degrade above 170°C. The flowing curve indicated that the processing temperature and the residential time had important effects on PHBV melts. When the equipment of melting spinning was improved and processing conditions were strictly controlled, the mechanical properties of the PHBV filament can comply with the requirements of the American Pharmacopoeia. __________ Translated from Journal of Donghua University (Natural Science Edition), 2007, 33(4): 425–430     

Pyrolysis mass spectrometry analysis of poly(vinyl acetate), poly(methyl methacrylate) and their blend coalesced from inclusion compounds formed with γ-cyclodextrin

Direct insertion probe pyrolysis mass spectrometry (DIP-MS) analyses of poly(methyl methacrylate) (PMMA), poly(vinyl acetate) (PVAc) and binary PMMA/PVAc guests, coalesced from their inclusion compounds (ICs) formed with host γ-cyclodextrin (γ-CD) through removal of the γ-CD host, have been performed. A slight increase in the thermal stabilities of the coalesced polymers were recorded both by TGA and DIP-MS compared to the corresponding as-received polymers. The DIP-MS observations pointed out that the thermal stability and degradation products of these polymers are affected once they are included inside the IC channels created by the stacked host γ-CDs. DIP-MS observations suggested that the degradation mechanisms for PMMA and PVAc chains in their coalesced blend were significantly altered from those observed in their as-received and solution blended samples. This was attributed to the presence of specific molecular interactions between the intimately mixed PMMA and PVAc chains in their coalesced blend.     

Effect of poly(amid–imide)/Al2O3 hybrid with various ratios on the physicochemical properties of poly(vinyl alcohol) nanocomposites films

To study the effect of the various ratios of poly(amide–imide)/Al₂O₃ nanocomposites (PANC)s on the mechanical and thermal properties of nanocomposites films, poly(vinyl alcohol) (PVA)/PANCs based on various ratios of 2, 4, and 6 wt% were prepared and characterized. In the first step, the surface of alumina nanoparticles was treated with 15 wt% of biosafe diacid and consequently, about 10 wt% of these modified nanoparticles were loaded into the poly(amide–imide) matrix. Then, various contents of the obtained PANCs were incorporated into a PVA solution using a sonochemical treatment. The effects of PANC on the structure and morphology of PVA matrix were studied using powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy (AFM), and thermal gravimetric analysis (TGA). The results show that the tensile strength and decomposition temperature were improved as the portion of PANC into PVA matrix are increased from 2 to 6 wt%. Also, AFM pictures of the fracture surfaces of PVA/PANCs showed a significantly rougher surface than the neat PVA.     

Study on poly(3,4-ethylenedioxythiophene) behaviour in the I−/I2 solution

The properties of poly(3,4-ethylenedioxythiophene) (PEDT) film have been studied in iodide solutions by cyclic voltammetry and stripping voltammetry methods. It has been shown that formation of charge-transfer complexes between iodine species and polymeric rings promotes storage of iodine on an electrode covered by PEDT film. Due to this behaviour the PEDT layer can be employed for electroanalysis of dilute (10⁻⁴–10⁻³ M) solutions of iodide salts by stripping voltammetry methods. The possibility of PEDT film application for zinc-iodide rechargeable batteries was also examined.     

UV-light and visible-light photochromism of inorganic–organic multilayer films based on polyoxometalate and poly(acrylamide)

Novel UV-light and visible-light photochromic inorganic–organic multilayers composed of polyoxometalates (phosphomolybdic acid (PMoA)) and poly(acrylamide) (PAM) were prepared by the layer-by-layer (LbL) self-assembly method. The grown process, composition, surface topography, and photochromic properties and mechanism of the multilayer films were investigated by ultraviolet–visible (UV–vis) spectra, Fourier transform infrared spectra (FT-IR), atomic force microscopy (AFM), electron resonance spectra (ESR), and X-ray photoelectron spectra (XPS). Irradiation with UV-light or visible-light, the transparent films changed from colorless to blue and showed reversible photochromism. PMoA/PAM LbL films had higher photochromic efficiency under UV-light irradiation than visible-light irradiation. The bleaching process occurred when the films were in contact with O₂ in the dark or heated in air. The photochromic process of PMoA/PAM LbL film was in accordance with radical mechanism.     

The effects of the molecular weight and structure of poly(acrylic acid) on the formation of “blue silver”

Using UV-spectroscopy and transmittance electron microscopy it was shown that the structure of macromolecules and molecular weight of poly(acrylic acid) can significantly affect the synthesis and stabilization of so-called “blue silver.”     

The effect of silane concentration on the adsorption of poly(vinyl acetate-co-maleate) and γ -methacryloxypropyl- trimethoxysilane onto E-glass fibers

The adsorption of a poly(vinyl acetate-co-maleate) (PVAM) emulsion onto E-glass fibers was investigated along with sizing formulations prepared by mixing the PVAM with varying concentrations of -methacryloxypropyltrimethoxysilane (MPS). The sized E-glass fibers were then characterized using Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM). Loss on Ignition (LOI) along with the DRIFT spectra indicated that the addition of silane to the PVAM emulsion caused a decrease in the amount of size on the fiber. The decrease in amount of size on the E-glass fibers did not coincide with a decrease in surface coverage, instead the XPS results indicated surface coverage had increased with silane addition. These results showed that small increases in the silane concentration appear to affect the amount of size adsorbed to the E-glass fibers