Head to Head Polymers. 42. Head to Head Poly(Vinyl Halide) Blends: Thermal and Degradation Behavior

Abstract

Improved halogenation techniques for poly(1, 4-butadiene) have made well-defined head to head poly(vinyl chloride) and head to head poly(vinyl bromide) accessible in larger quantities. This allowed the preparation and study of blends of poly(vinyl chloride) or poly(vinyl bromide) with polycaprolactone and poly(methyl methacrylate); blends were also prepared between the poly(vinyl halides). The thermal behavior and the thermal degradation behavior of these blends were investigated. It was confirmed that head to head and head to tail poly(vinyl chloride) are immiscible over almost the entire range of compositions.     

Photo-Oxidative Degradation of Poly(vinyl Chloride) Based Nanocomposites Under Ultraviolet Irradiation

The poly(vinyl chloride) based nanocomposites with 3.0% weight content of the photo-active zinc oxide (ZnO) nanoparticles or the photo-inert calcium carbonate (CaCO₃) nanoparticles was prepared by the solution mixing method, respectively. Their photo-oxidative degradation under ultraviolet irradiation (365 nm) at room temperature were compared with the pure poly(vinyl chloride) via Fourier transform infrared spectroscopy, Thermogravimetric analysis and x-ray photoelectron spectroscopy analyses. The results showed that the photo-inert calcium carbonate (CaCO₃) nanoparticles hampered the photo-degradation of poly(vinyl chloride), whereas the photoactive zinc oxide (ZnO) nanoparticles accelerated the photodegradation of poly(vinyl chloride). Furthermore, the ZnO nanoparticles also favored the crosslinking reaction of the dehydrochlorinated poly(vinyl chloride).     

FT‐IR Investigation into the miscible interactions in new materials for optical devices

In this article we determine the miscibility of azobenzene derivative (poly(4‐(N‐(2‐methacryloyloxyethyl)‐N‐ethylamino)‐4′‐nitroazobenzene)₉₀‐co‐(methyl methacrylate)₁₀)/poly(vinyl acetate) (PVAc) and azobenzene derivative/poly(vinyl chloride) (PVC) blends using Fourier Transform infrared (FT‐IR) spectroscopy. With this method we can clearly identify the exact interactions responsible for miscibility. In the azobenzene derivative 50:50PVAc blend new peaks were evident at 2960, 2890, 1237 and 959 cm^?1, these peaks depict miscible interactions. These wavenumbers indicate that the miscible interactions occurring are from the C? H stretching band, the vinyl acetate C?O, conjugated to the ester carbonyl, the cis‐transformation N?N stretch frequency and the acetate ester weak doublet. The azobenzene derivative 80:20PVC blend display peaks identical in profile to the blend homopolymers, indicating no miscible interactions. However, this could be due to overlapping of peaks within the same wavenumber region, making resolution difficult. This research demonstrates FT‐IR can deduce favorable interactions for miscibility and therefore numerous miscible blends can successfully be calculated if possessing the same groups responsible for miscibility. This paves the way for a new generation of designer optical materials with the desired properties. Copyright © 2003 John Wiley & Sons, Ltd.     

Tin-Naphthalene Sulfonic Acid Complexes as Photostabilizers for Poly(vinyl chloride)

Poly(vinyl chloride) degrades when exposed to ultraviolet light for long durations; therefore, the photostability of polymeric materials should be enhanced through the application of additives. New organotin complexes containing 4-aminonaphthalene-1-sulfonic acid were synthesized and their role as poly(vinyl chloride) photostabilizers were evaluated. The reaction of 4-amino-3-hydroxynaphthalene-1-sulfonic acid and appropriate di- or trisubstituted tin chloride (triphenyltin chloride, tributyltin chloride, dibutyltin dichloride, and dimethyltin dichloride) in methanol under reflux gave the corresponding tin-naphthalene complexes with yields of 75%–95%. Elemental analyses and spectroscopic techniques including infrared and nuclear magnetic resonance (proton and tin) were used to confirm their structures. The tin complexes were added to poly(vinyl chloride) to produce thin films that irradiated with ultraviolet light. Various parameters were assessed, such as the weight loss, formation of specific functional groups, changes in the surface due to photoirradiation, and rate constant of photodegradation, to test the role played by the organotin complexes to reduce photodegradation in polymeric films. The results proved that organotin complexes acted as photostabilizers in these circumstances. The weight loss, formation of fragments containing specific functional groups, and undesirable changes in the surface of polymeric films were limited in the presence of organotin complexes. Organotin complexes containing three phenyl groups showed the most desirable stabilization effect. These act as efficient primary and secondary photostabilizers, and as decomposers for peroxides. In addition, such an additive inhibits the dehydrochlorination process, which is the main cause of poly(vinyl chloride) photodegradation.     

Liquid chromatography under limiting conditions of desorption 6: Separation of a four‐component polymer blend

Baseline separation was achieved of a model four‐component polymer blend of polystyrene‐poly(methyl methacrylate)‐poly(ethylene oxide)‐poly(2‐vinyl pyridine) in a single chromatographic run with help of the unconventional method of liquid chromatography under limiting conditions of desorption. Narrow barriers of liquids were employed, which selectively decelerated elution of particular kinds of macromolecules. Bare silica gel was the column packing, and the eluent was a mixture of dimethylformamide/tetrahydrofuran/toluene 30:50:20 w/w/w. Barrier compositions were neat toluene, B#1, neat tetrahydrofuran, B#2, and dimethylformamide/tetrahydrofuran/toluene 15:55:30, B#3. Minor blend constituents (∼1%) could be identified, as well. The result represents a step toward the separation and molecular characterization of triblock‐copolymers, many of which are expected to contain besides both parent homopolymers also the diblock chains and thus they are in fact four‐component polymer blends.     

Compatibility of binary systems of poly(methyl methacrylate), poly(vinyl chloride) and poly(vinyl acetate)

The influence of the thermal treatment on the stability in time of the dispersion degree of films containing binary polymer mixtures, poly(vinyl chloride)/poly(methyl methacrylate), poly(vinyl chloride)/poly(vinyl acetate) and poly(vinyl acetate)/poly(methyl methacrylate), was studied by thermogravimetry and optical microscopy with phase contrast. The dispersion degree depends particularly on the composition of the polymer mixture and can be improved by thermal treatment at temperatures above the glass temperatures of both homopolymers. It seems that this thermal treatment yields exclusively metastable structures with a general tendency to phase separation in a short time after thermal treatment, the heterogeneity mixtures (as film) being more pronounced.     

Tetrazole-containing paired polymers

Paired polymers are obtained by the reaction between linear poly(5-vinyltetrazole) and poly(vinyl chloride) in the presence of triethylamine. Poly(vinyl chloride) plays the role of a macromolecular alkylating agent with respect to the tetrazole-containing polymer. The combination of two types of covalently linked macromolecules promotes in the paired polymers the manifestation of some properties typical for both homopolymers.     

THE COMPATIBILITY OF BLENDS OF POLY(VINYL CHLORIDE) OR CHLORINATED POLY(VINYL CHLORIDE) WITH POLY(METHYL METHACRYLATE)

IR spectral shifts of carbonyl vibrational absorption for ethyl acetate, which acts analogically as the structural unit of poly(methyl methacrylate), in cyclohexane, chloroform, chlorinated paraffins, poly(vinyl chloride) and chlorinated poly(vinyl chloride) were measured. The results suggest that there are specific interactions between the carbonyl groups and the chlorinated hydrocarbons which could be responsible for the apparent compatibility of poly(vinyl chloride)—poly(methyl methacrylate) and chlorinated poly(vinyl chloride)—poly(methyl methacrylate) blends. Additionally, the effects of the preparation mode of blend films on phase separation and observed compatibility are discussed.     

Lactone polymers. I. Glass transition temperature of poly-ε-caprolactone by means on compatible polymer mixtures

Dynamic mechanical properties determined with a torsion pendulum were used to ascertain the glass transition temperature T_g of poly-ε-caprolactone. By measurements on compatible blends of poly-ε-caprolactone and poly(vinyl chloride), the T_g of amorphous poly-ε-caprolactone was shown to be 202°K at about 1 cps. This is 16°K lower than the T_g of annealed, crystalline polymer. The blend transition data were well fitted by both the Fox and the Gordon-Taylor expressions. The Fox expression was also used to describe the decrease from 233°K of the secondary low-temperature relaxation due to poly(vinyl chloride) by assuming the low temperature relaxation of poly-ε-caprolactone, 138°K, was responsible for the decrease in the blends. The 138°K relaxation due to poly-ε-caprolactone was decreased when more than 50% poly(vinyl chloride) was present.     

Electrical conductivity of thermally degraded poly(vinyl chloride)–polyacrylonitrile blends

Finely powdered blends of poly(vinyl chloride) (PVC) and polyacrylonitrile (PAN) have been thermally degraded at 275°C for 24 h in an inert atmosphere to effect complete de-hydrochlorination of PVC to a conjugated polyene structure and simultaneous internal polymerization of nitrile groups in PAN to a conjugated polyimine sequence. The room temperature d.c. conductivity of the degraded blends showed clear synergistic behavior. A maximum conductivity has been observed with a blend of 60 PAN/40 PVC which is about 4 orders of magnitude over the linearly weighted average conductivity of the individual degraded homopolymers. The results have been interpreted in terms of a possible donor-acceptor interaction between the degraded homopolymers leading to mutual doping and, hence, an enhanced electrical conductivity. © 1995 John Wiley & Sons, Inc.     

Thermal properties of poly(vinyl chloride)/polyurethane blends

Blends of poly(vinyl chloride) and a polyurethane elastomer were investigated by DSC and tensile testing. Up to 30 wt% single glass transition was found. It was concluded that the polyurethane forms partly a true blend and is partly disperged in the continuous blend phase.     

Highly selective GC stationary phases consisting of binary mixtures of polymeric ionic liquids

GC stationary phases composed of binary mixtures of two polymeric ionic liquids (PILs), namely, poly(1‐vinyl‐3‐hexylimidazolium) bis[(trifluoromethyl)sulfonyl]imide (poly(ViHIm‐NTf₂))/poly(1‐vinyl‐3‐hexylimidazolium) chloride (poly(ViHIm‐Cl)) and poly(1‐vinyl‐3‐hexadecylimidazolium) bis[(trifluoromethyl)sulfonyl]imide (poly(ViHDIm‐NTf₂))/poly(1‐vinyl‐3‐hexadecylimidazolium) chloride (poly(ViHDIm‐Cl)), were evaluated in terms of their on‐set bleed temperature and separation selectivity. A total of six neat or binary PIL stationary phases were characterized using the solvation parameter model to investigate the effects of the polymeric cation and anion and PIL composition on the system constants of the resulting stationary phases. The hydrogen bond basicity of the mixed poly(ViHIm‐NTf₂)/poly(ViHIm‐Cl) stationary phases was enriched linearly with the increase in the poly(ViHIm‐Cl) content. Results revealed that tuning the composition of the stationary phase allowed for fine control of the retention factors and separation selectivity for alcohols and carboxylic acids as well as selected ketones, aldehydes, and aromatic compounds. A reversal of elution order was observed for particular classes of analytes when the weight percentage of the chloride‐based PIL was increased.     

Effect of graft copolymer on demixing of immiscible polymers in solution

The effect of graft copolymer on the demixing of solutions of two immiscible homopolymers and critical conditions for emulsion formation were studied. The graft copolymer used in the present work consists of one backbone poly(vinyl acetate) (PVAc) and one branch polystyrene (PS). PVAc and PS of various degrees of polymerization were used as immiscible homopolymers. The common solvent was benzene. When the concentration of homopolymer blend was not sufficiently higher than the critical concentration for demixing of the blend solution, no stable emulsion was formed, even when a considerable amount of graft copolymer was present, and the added graft copolymer merely reduced the demixing rate. However, as the blend concentration was increased, a stable emulsion could readily be obtained by addition of rather small amounts of graft copolymer. The radius of emulsion droplets was inversely proportional to the weight ratio of the graft copolymer to the dispersed component polymer, in accordance with the theoretical prediction. It was concluded that the emulsions were stabilized against coagulation by graft copolymer molecules fixed strongly as a monolayer on the interface of the emulsion.     

Polymerization of vinyl chloride by the Ti(O-n-Bu)4–AlEt3–epichlorohydrin catalyst system

The polymerization of vinyl chloride was carried out by using a catalyst system consisting of Ti(O-n-Bu)₄, AlEt₃, and epichlorohydrin. The polymerization rate and the reduced viscosity of polymer were influenced by the polymerization temperature, AlEt₃/Ti(O-n-Bu)₄ molar ratios, and epichlorohydrin/Ti(O-n-Bu)₄ molar ratios. The reduced viscosity of polymer obtained in the virtual absence of n-heptane as solvent was two to three times as high as that of polymer obtained in the presence of n-heptane. The crystallinity of poly(vinyl chloride) thus obtained was similar to that of poly(vinyl chloride) produced by a radical catalyst. It was concluded that the polymerization of vinyl chloride by the present catalyst system obeys a radical mechanism rather than a coordinated anionic mechanism.     

Preparation and Characterization of Blend Films of Poly(Vinyl Alcohol) and Sodium Alginate

Blend films of poly(vinyl alcohol) (PVA) and sodium alginate (NaAlg) were prepared by casting from aqueous solutions. This blend films were characterized by tensile strength test, Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The miscibility in the blends of PVA and NaAlg was established on the basis of the thermal analysis results. DSC showed that the blends possessed single, composition‐dependent glass transition temperatures (T_gs), indicating that the blends are miscible. FT‐IR studies indicate that there is the intermolecular hydrogen bonding interactions, i.e. –OH…^?OOC– in PVA/NaAlg blends. The blend films also exhibited the higher thermal stability and their mechanical properties improved compared to those of homopolymers.     

Novel fluorinated stabilizers for ring‐opening polymerization in supercritical carbon dioxide

Ring‐opening polymerization (ROP) in supercritical carbon dioxide (scCO₂) has been the subject of much recent interest, although few publications describe the development of stabilizers to produce biodegradable particles of poly(L ‐lactide) (PLLA) and polyglycolide (PGA). Here we describe the synthesis of a series of novel fluorinated diblock copolymers by the acid‐catalyzed esterification of well‐defined blocks of polycaprolactone (PCL) with Krytox 157FSL, a carboxylic acid terminated perfluoropolyether. These diblock copolymers were then tested as stabilizers in the ROP of glycolide and L ‐lactide, or a mixture of the two, in scCO₂, and this resulted in the corresponding homopolymers or random copolymers. In the absence of stabilizers, only aggregated solids were formed. When the reaction was repeated with a stabilizer, PGA and PLLA were obtained as discrete microparticles. The stabilizer efficiency increased as the length of the polymer‐philic PCL block increased. One optimized stabilizer worked at loadings as low as 3% (w/w) with respect to the monomer, demonstrating these to be extremely effective stabilizers. It was found that to produce microparticles with this process, the product polymers must be semicrystalline; amorphous polymers, such as poly(lactide‐co‐glycolide), are plasticized by scCO₂ and yield only aggregated solids rather than discrete particles. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6573–6585, 2005     

Radical block polymerization of vinyl chloride. II. Synthesis and characterization of vinyl chloride block copolymers

Peroxidized polypropylene has been used as a heterofunctional initiator for a two-step emulsion polymerization of a vinyl monomer (M₁) and vinyl chloride with the production of vinyl chloride block copolymers. Styrene, methyl-, and n-butyl methacrylate and methyl-, ethyl-, n-butyl-, and 2-ethyl-hexyl acrylate have been used as M₁ and polymerized at 30–40°C. In the second step vinyl chloride was polymerized at 50°C. The range of chemical composition of the block copolymers depends on the rate of the first-step polymerization of M₁ and the duration of the second step; e.g., with 2-ethyl-hexyl acrylate block copolymers could be obtained with a vinyl chloride content of 25–90%. The block copolymers have been submitted to precipitation fractionation and GPC analysis. Noteworthy is the absence of any significant amount of homopolymers, as well as poly(M₁)n as PVC. The absence of homo-PVC was interpreted by an intra- and intermolecular tertiary hydrogen atom transfer from polypropylene residue to growing PVC sequences. The presence of saturated end groups on the PVC chains is responsible for the improved thermal stability of these block polymers, as well as their low rate of dehydrochlorination (180°C). Molecular aggregation in solution has been shown by molecular weight determination in benzene and tetrahydrofuran.     

Diffusion and partition coefficients of small organic solvents in molten miscible polymer blends: Correlations with thermodynamic interactions

The transport properties of small organic molecules in molten poly(vinyl chloride) (PVC)/atactic poly(methyl methacrylate) (PMMA) blends and their homopolymers were studied with inverse gas chromatography. The elution profiles resulting from various organic solvents and different experimental conditions were used for measuring diffusion and partition coefficients. With the van Deemter equation and retention volumes at infinite dilution, diffusion coefficients of 10^?7 to 10^?8 cm²/s and partition coefficients of 10–50 were calculated. The dependence of the diffusion and partition coefficients on experimental variables such as the blend concentration, temperature, and solute nature was examined. The presence of PMMA in PVC blends affected the sorption behavior of the PVC matrix up to a certain concentration. Beyond that, it was hard to derive any composition–diffusivity dependence. On the contrary, the diffusion and partition coefficients were greatly influenced by changes in the temperature and by the nature of the solute. For those solutes (e.g., chlorinated hydrocarbons) showing stronger interactions with polymer blends (higher negative values for the Flory–Huggins interaction parameter χ₁₍₂₃₎), higher diffusion and partition coefficients were obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 267–279, 2004     

Photodegradation of poly(vinyl esters)—I. Formation and quantitative measurement of volatile products

The high vacuum distillation technique for the analysis of photolysis products has highlighted both the extreme difficulty of removing residual solvent and the slow diffusion of photodegradation products from thin cast poly(vinyl ester) films, even at temperatures 130°C above T_g. Very long product collection periods at temperatures just below the onset of thermal degradation were used in order to obtain reliable quantitative data. The distributions of liquid-nitrogen condensable products indicated that a closer relationship exists between the photodegradation of poly(vinyl esters) and the photolysis of low molecular mass esters than previous results had suggested.     

环氧树脂基多孔光学增透膜的制备及其性能研究

利用低分子量环氧树脂(DGEBA)在固化后和与之共混的聚氯乙烯(PVC)之间产生的相分离,用丁酮抽提其中的PVC组分,制备了环氧树脂基多孔增透膜。测试结果表明,当mDOEBA／mPVC=30／70、膜厚为110nm时,增透膜的透过率最高,达96％以上。薄膜在水或甲苯中煮沸不发生收缩、脱落,表现良好的粘附力和机械强度。