Degradation of polymer mixtures. IV. Blends of poly(vinyl acetate) with poly(vinyl chloride) and other chlorine-containing polymers

The degradation of the binary polymer blends, poly(vinyl acetate)/poly(vinyl chloride), poly(vinyl acetate)/poly(vinylidene chloride) and poly(vinyl acetate)/polychloroprene has been studied by using thermal volatilization analysis, thermogravimetry, evolved gas analysis for hydrogen chloride and acetic acid, and spectroscopic methods. For the first two systems named, strong interaction occurs in the degrading blend, but the polychloroprene blends showed no indication of interaction. In the PVA/PVC and PVA/PVDC blends, hydrogen chloride from the chlorinated polymer causes substantial acceleration in the deacetylation of PVA. Acetic acid from PVA destabilizes PVC but has little effect in the case of PVDC because of the widely differing degradation temperatures of PVA and PVDC. The presence of hydrogen chloride during the degradation of PVA results in the formation of longer conjugated sequences, and the regression in sequence length at high extents of deacetylation found for PVA degraded alone is not observed.     

The estimation of phase modifications in polymers by the method of “molecular probes” in gas chromatography—III. Glass transition behaviour and compatibility in mixtures of poly(methyl methacrylate) with poly(vinyl chloride)

Using the method of “molecular probes” in gas chromatography, glass-transitions in mixtures of poly(methyl methacrylate) with poly(vinyl chloride) are found. The strong variation of T_g for poly (methyl methacrylate) in mixtures with more than 20% of that polymer suggests interactions although T_g for poly(vinyl chloride) remains constant. The existence of a single T_g in mixtures with less than 20% poly(methyl methacrylate), on the other hand, suggests possible compatibility in these mixtures.     

Synthesis of poly(vinyl acetate) block copolymers by successive RAFT and ATRP with a bromoxanthate iniferter

Poly(vinyl acetate)-b-polystyrene, poly(vinyl acetate)-b-poly(methyl acrylate) and poly(vinyl acetate)-b-poly(methyl methacrylate) block copolymers with low polydispersity (M(w)/M(n) < 1.25) were prepared by successive reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) employing a bromoxanthate iniferter (initiator-transfer agent-terminator).     

Effects of poly(methyl methacrylate)-block-poly(vinyl acetate) copolymer on the spinodal decomposition of corresponding homopolymer blends

Effects of adding a small amount of poly(methyl methacrylate)-block-poly(vinyl acetate) (PMMA-b-PVAc) to poly(methyl methacrylate)/poly(vinyl acetate) (PMMA/PVAc) blends with a lower critical solution temperature (LCST) phase diagram on the kinetics of late-stage spinodal decomposition (SD) were investigated by time-resolved light scattering at 160°C. It is found that the coarsening process of the structure was slowed down or accelerated upon addition of PMMA-b-PVAc depending on the composition of the block copolymer and the blend. The effect of the block copolymer on the domain size were interpreted as compatibilizing and incompatibilizing effects of the block copolymer on PMMA/PVAc blends based on the evaluation of changes in the stability limits of PMMA/PVAc with the addition of block copolymer using random phase approximation (RPA).     

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.     

Interactions and prediction of phase diagrams in ternary blends comprising poly(vinyl acetate), poly(vinyl p‐phenol), and poly(methyl methacrylate)

This study investigated and discovered a new miscible ternary blend system comprising three amorphous polymers: poly(vinyl acetate) (PVAc), poly(vinyl p‐phenol) (PVPh), and poly(methyl methacrylate) (PMMA) using thermal analysis and optical and scanning electron microscopies. The ternary compositions are largely miscible except for a small region of borderline ternary miscibility near the side, where the binary blends of PVAc/PMMA are originally of a borderline miscibility with broad T_g. In addition to the discovering miscibility in a new ternary blend, another objective of this study was to investigate whether the introduction of a third polymer component (PVPh) with hydrogen bonding capacity might disrupt or enhance the metastable miscibility between PVAc and PMMA. The PVPh component does not seem to exert any “bridging effect” to bring the mixture of PVAc and PMMA to a better state of miscibility; neither does the Δχ effect seem to disrupt the borderline miscible PVAc/PMMA blend into a phase‐separated system by introducing PVPh. Apparently, the ternary is able to remain in as a miscible state as the binary systems owing to the fact that PVPh is capable of maintaining roughly equal H‐bonding interactions with either PVAc or PMMA in the ternary mixtures to maintain balanced interactions among the ternary mixtures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1147–1160, 2006     

Stereoregularity of poly(vinyl ether)

α-Methylvinyl isobutyl and methyl ethers were polymerized cationically and the structure of the polymers was studied by NMR. Poly(α-methylvinyl methyl ether) polymerized with iodine or ferric chloride as catalyst was found to be almost atactic, whereas poly(α-methylvinyl isobutyl ether) polymerized in toluene with BF₃OEt₂ or AlEt₂Cl as catalyst was found to be isotactic. In both cases, the addition of polar solvent resulted in the increase of syndiotactic structure as is the case with polymerization of alkyl vinyl ether. tert-Butyl vinyl ether was polymerized, and the polymer was converted into poly(vinyl acetate), the structure of which was studied by NMR. A nearly linear relationship between the optical density ratio D₇₂₂/D₇₃₆ in poly(tert-butyl vinyl ether) and the isotacticity of the converted poly(vinyl acetate) was observed.     

Thermal decomposition of poly(vinyl chloride) and chlorinated poly(vinyl chloride). II. Organic analysis

A concerted study of poly(vinyl chloride), chlorinated poly(vinyl chloride), and poly(vinylidene chloride) polymers by spectroscopy, thermal analysis, and pyrolysis-gas chromatography resulted in a proposed mechanism for their thermal degradation. Polymer structure with respect to total chlorine content and position was determined, and the influence of these polymer units on certain of the decomposition parameters is presented. Distinguishing differences were obtained for the kinetics of decomposition, reactive macroradical intermediates, and pyrolysis product distributions for these systems. It was determined that chlorinated poly(vinyl chloride) systems with long-chain ? CHCI? units were more thermally stable than the unchlorinated precursor, exhibited increasing activation energy for the dehydrochlorination, and produced chlorine-containing macroradical intermediates and chlorinated aromatic pyrolysis products. The poly(vinyl chloride) polymer was relatively less thermally stable, exhibited decreasing activation energy during dehydrochlorination, and produced polyenyl macro-radical intermediates and aromatic pyrolysis products.     

Compatibility studies on solutions of polymer blends by viscometric and ultrasonic techniques

Detailed viscometric and ultrasonic velocity studies have been conducted on solutions of blends of poly(methyl methacrylate) with poly(vinyl acetate), poly(vinyl chloride) with poly(vinyl acetate) and poly(methyl methacrylate) with polystyrene over an extended range of concentrations and temperatures in toluene, chlorobenzene and toluene respectively. The plots of both absolute viscosity and ultrasonic velocity vs composition deviate from linearity according to the degree of compatibility of polymer blends, at all concentrations and temperatures. The curves for compatible systems are linear. These investigations offer an entirely new approach to the study of the compatibility of polymer blends.     

Long branching in poly(vinyl acetate) and poly(vinyl alcohol). II. Polymerization of vinyl acetate in the presence of crosslinked poly(vinyl alcohol)

It is a common view that poly(vinyl acetate) has many branches at the acetyl side group, but that the corresponding poly(vinyl alcohol) has little branching. In order to study the branching in poly(vinyl acetate) and poly(vinyl alcohol) which is formed by chain transfer to polymer, the polymerization of ¹⁴C-labeled vinyl acetate in the presence of crosslinked poly(vinyl acetate), which was able to be decrosslinked to give soluble polymers, was investigated at 60°C and 0°C. This system made it possible to separate as well as to distinguish the graft polymer from the newly polymerized homopolymer. Furthermore, the degree of grafting onto the acetoxymethyl group and onto the main chain were estimated. It became clear that, in the polymerization of vinyl acetate, chain transfer to the polymer main chain takes place about 2.4 times as frequently at 60°C as that to the acetoxy group and about 4.8 times as frequently at 0°C.     

Thermal and photochemical stability of poly(methyl methacrylate) and its blends with poly(vinyl acetate)

An investigation of the thermal stability of poly(methyl methacrylate) (PMMA) blends with poly(vinyl acetate) (PVAc) revealed that PVAc acts as a stabilizer as concerns thermal and photochemical degradation when the processes take place in air. The temperatures of decomposition of these blends are higher than that of pure PMMA. The efficiency of photodegradation and photooxidation in the blends is lower than that of pure PMMA.     

Immiscibility,upper critical solution temperature,and miscibility in blends of poly(vinyl ether)s with polyacrylics: Effects of pendant groups

Various phase behavior of blends of poly(vinyl ether)s with homologous acrylic polymers (polymethacrylates or polyacrylates) were examined using differential scanning calorimetry, optical microscopy (OM), and Fourier‐transformed infrared spectroscopy. Effects of varying the pendant groups of either of constituent polymers on the phase behavior of the blends were analyzed. A series of interestingly different phase behavior in the blends has been revealed in that as the pendant group in the acrylic polymer series gets longer, polymethacrylate/poly(vinyl methyl ether) (PVME) blends exhibit immiscibility, upper critical solution temperature (UCST), and miscibility, respectively. This study found that the true phase behavior of poly(propyl methacrylate)/PVME [and poly(isopropyl methacrylate)/PVME)] blend systems, though immiscible at ambient, actually displayed a rare UCST upon heating to higher temperatures. Similarly, as the methyl pendant group in PVE is lengthened to ethyl (i.e., PVME replaced by PVEE), phase behavior of its blends with series of polymethacrylates or polyacrylates changes correspondingly. Analyses and quantitative comparisons on four series of blends of PVE/acrylic polymer were performed to thoroughly understand the effects of pendant groups in either polyethers (PVE's) or acrylic polymers on the phase behavior of the blends of these two constituents. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1521–1534, 2007     

Synthesis of poly(vinyl acetate-methyl methacrylate) copolymer microspheres using suspension polymerization

Poly(vinyl acetate-methyl methacrylate) (VAc-MMA) copolymer microspheres were prepared using suspension polymerization at low temperature initiated with 2,2'-azobis(2,4-dimethyl valeronitrile) (ADMVN). The poly(VAc-MMA) copolymer microspheres can be used over a large area where homopolymers, polyvinyl acetate (PVAc) and methyl methacrylate (PMMA) microspheres are capable of being put to use. The prepared microspheres were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Obtained copolymer microspheres which have 200 μm average diameter and higher thermal stability than those of homopolymer.     

Long branching in poly(vinyl acetate) and poly(vinyl alcohol). I. Crosslinking and crosslinking cleavage of poly(vinyl acetate)

A crosslinked network was formed by the reaction of partially saponified poly(vinyl acetate) and toluylene diisocyanate in benzene. The yield of gel was markedly dependent on the degree of saponification and the concentrations of polymer and diisocyanate. Crosslinked poly(vinyl alcohol) was obtained by treating the poly(vinyl acetate) with a catalytic amount of sodium hydroxide in methanol without any change of the urethane crosslinks. The crosslink based on the urethane linkage was quantitatively cleaved by acids, especially by hydrobromic acid, releasing polymers of the same molecular weight as the original.     

Graft polymers from poly(vinyl chloride) and chlorinated rubber

Graft polymers from poly(vinyl chloride) (PVC) and chlorinated rubber (CIR) with side chains of poly(methyl methacrylate) (PMMA), poly(methyl acrylate) (PMA), or poly(ethyl methacrylate) (PEMA) were synthesized. For this purpose, a vinyl monomer was polymerized in the presence of small quantities of PVC or CIR with benzoyl peroxide as catalyst. The graft polymers were separated from both homopolymers by precipitation with methanol from methyl ethyl ketone solutions of the reaction products and the grafting efficiency was calculated. The graft polymers were characterized by infrared spectra, elemental analysis, NMR, and osmometric or light-scattering determinations. From the results it is concluded that the PVC or CIR molecules contain side chains of PMMA, PMA, or PEMA. The graft polymers showed higher molecular weights, and the values of second virial coefficient for these polymers were much different from those of the starting polymers.     

Effects of ceramic filler in poly(vinyl chloride)/poly(ethyl methacrylate) based polymer blend electrolytes

Effects of nano-ceramic filler titanium oxide (TiO₂) have been investigated on the ionic conductance of polymeric complexes consisting of poly(vinyl chloride) (PVC)/poly(ethyl methacrylate) (PEMA), and lithium perchlorate (LiClO₄). The composite polymer blend electrolytes were prepared by solvent casting technique. The TiO₂ nanofillers were homogeneously dispersed in the polymer electrolyte matrix and exhibited excellent interconnection with PVC/PEMA/PC/LiClO₄ polymer electrolyte. The addition of TiO₂ nanofillers improved the ionic conductivity of the polymer electrolyte to some extent when the content of TiO₂ is 15 wt%. The addition of TiO₂ also enhanced the thermal stability of the electrolyte. The changes in the structural and complex formation properties of the materials are studied by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The scanning electronmicroscope image of nano-composite polymer electrolyte membrane confirms that the TiO₂ nanoparticles were distributed uniformly in the polymer matrix.     

Synthesis and characterization of fluorescently labelled poly(vinyl acetate) particles

Nonaqueous dispersions of poly(vinyl acetate) particles stabilized with poly(2-ethylhexyl methacrylate) and labelled with fluorescent dyes in the core and stabilizer polymer phases were prepared. The materials were characterized using a broad range of techniques (NMR, UV, and fluorescence spectroscopy. GPC, particle sizing, and DSC). The data show that dispersion polymerization of vinyl acetate in the presence of stabilizers containing certain fluorescent dye derivatives, instead of unlabelled stabilizer, results in changes in the mean particle size, size distribution, composition, and molecular weights of the colloidal polymer particles. It was found that increasing the amounts of fluorescent groups in the stabilizer resulted in smaller mean particle sizes and larger amounts of irreversibly attached stabilizer. When the average number of labels in stabilizer exceeded one per chain, a new ultra-high molecular weight polymer fraction appeared. The fluorescence spectra for several of these materials are reported. We describe how fluorescence decay curves can be used to assess block formation and local phase separation in particles labelled with phenanthrene groups. These materials are intended to be used for more detailed studies by fluorescence spectroscopy. Those results will be published in due course.     

Investigation of polymer miscibility by spectroscopic methods. III. Labeling of poly(vinyl chloride), poly(methyl methacrylate) and poly(styrene-co-acrylonitrile) with fluorescent chromophores for nonradiative energy transfer studies

Poly(vinyl chloride) (PVC) is generally recognized as miscible with s.poly(methyl methacrylate) (s.PMMA), poly(?-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) copolymer (SAN) containing 27 wt % AN. Nonradiative energy transfer (NRET) is a very sensitive technique in the investigation of the polymer miscibility. To compare by NRET the actual degree of miscibility of the PVC/s.PMMA, PVC/PCL, and PVC/SAN polymer pairs, each polymer is to be labeled with a fluorescent chromophore to an extent of 1 or 2 mol %. This paper reports efficient pathways to attach anthracene (acceptor) or naphthalene (donor) onto preformed PVC, s.PMMA, and SAN samples. All the attempts for grafting carbazole (donor) moieties have failed, as well as any labeling of PCL whatever the nature of the chromophore.     

Long-lived polymer radicals. IV. Reactions of poly(N-methylacrylamide) and poly(N-methylmethacrylamide) radicals with binary mixtures of vinyl monomers

N-methylacrylamide (NMAAm) and N-methylmethacrylamide (NMMAm) were polymerized to give polymer microspheres containing living propagating radicals. The microsphere polymer radicals were allowed to react with some binary mixtures of vinyl monomers including alternating copolymerization combinations. The reaction processes were investigated by ESR spectroscopy. In the poly(NMMAm) radical/methyl methacrylate (MMA)/styrene (St) system, the propagating radical from MMA was mainly observed at the higher MMA concentration, while polySt radical prevailed at the lower MMA concentration. In the poly(NMMAm) radical/α-methylstyrene (α-MeSt)/diethyl fumarate system, the α-MeSt radical was exclusively observed, while the maleic anhydride (MAn) radical was predominantly observed in the α-MeSt/MAn system. In the MAn/diphenylethylene system, the propagating radicals from both monomers were observed at comparable concentrations. The poly(NMAAm) microsphere radical behaved differently in the reaction with the MMA/St mixture. The poly(NMAAm) microsphere was found to incorporate preferentially St, leading to formation of the St radical. The St preference was enhanced in the St/cyclohexyl methacrylate (CHMA) system. These results were in agreement with those of block copolymerization via the reaction of poly(NMAAm) radical with the MMA/St or CHMA/St mixture, where the compositions of the resulting polymers were analyzed by pyrolysis gas chromatography.     

Viscometric study of poly(vinyl chloride)/poly(vinyl acetate) blends in various solvents

The intermolecular interactions between poly(vinyl chloride) (PVC) and poly(vinyl acetate) (PVAc) in tetrahydrofuran (THF), methyl ethyl ketone (MEK) and N,N^′-dimethylformamide (DMF) were thoroughly investigated by the viscosity measurement. It has been found that the solvent selected has a great influence upon the polymer-polymer interactions in solution. If using PVAc and THF, or PVAc and DMF to form polymer solvent, the intrinsic viscosity of PVC in polymer solvent of (PVAc+THF) or (PVAc+DMF) is less than in corresponding pure solvent of THF or DMF. On the contrary, if using PVAc and MEK to form polymer solvent, the intrinsic viscosity of PVC in polymer solvent of (PVAc+MEK) is larger than in pure solvent of MEK. The influence of solvent upon the polymer-polymer interactions also comes from the interaction parameter term Δb, developed from modified Krigbaum and Wall theory. If PVC/PVAc blends with the weight ratio of 1/1 was dissolved in THF or DMF, Δb<0. On the contrary, if PVC/PVAc blends with the same weight ratio was dissolved in MEK, Δb>0. These experimental results show that the compatibility of PVC/PVAc blends is greatly associated with the solvent from which polymer mixtures were cast. The agreement of these results with differential scanning calorimetry measurements of PVC/PVAc blends casting from different solvents is good.