Structural defects in poly(vinyl chloride)—IV. Thermal degradation of vinyl chloride/acetylene copolymers

Vinyl chloride/acetylene copolymers have been prepared under subsaturation conditions. Copolymerization rates and molecular weights of the copolymers decrease with increasing concentration of acetylene in the monomer feed, indicating that acetylene is a retarder in vinyl chloride polymerization. The concentration of internal double bonds in the copolymers determined by ozonolysis increases with increasing amount of acetylene in the feed. Thermal degradation has been performed at 110 with solid samples and at 170° in solution under inert atmosphere. The extent of HCl loss as a function of time shows a rapid initial phase followed by a slower steady rate The initial dehydrochlorination rates are higher for copolymer samples containing higher concentrations of internal double bonds. Quantitative analysis of the u.v. and visible spectra of degraded copolymers shows that the sum of the concentration of polyenes with 4–12 conjugated double bonds increases rapidly in the first phase of degradation, but then decreases slowly, due to secondary reactions of polyene sequences.     

Synthesis of β-trifluoroacetyl-substituted vinyl sulfones and vinyl sulfides

Oxidation of -(trifluoroacetyl)vinyl sulfides afforded a series of the corresponding sulfones. The reactions of sulfones with various alkyl- and arylthiols were studied. These reactions provide the basis for a new procedure for the synthesis of -(trifluoroacetyl)vinyl sulfides.     

IR Spectroscopic Study of Chemical Transformations upon Irradiation of the Poly(vinyl chloride)–Triallyl Cyanurate System

Chemical transformations resulting from irradiation of the poly(vinyl chloride) (PVC)–triallyl cyanurate (TAC) system were studied by IR spectroscopy. It was shown that crosslinking was accompanied by scission of the network structure formed in the initial dose range, and the scission process occurred even at small irradiation doses. The scission is assumed to be localized at the interface boundary between PVC and poly(iso-TAC) or poly(TAC).     

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.     

Fabrication and Performance of a Low Operating Pressure Nanofiltration Poly（vinyl chloride） Hollow Fiber Membrane

A low operating pressure nanofiltration membrane is prepared by interfacial polymerization between m-phenylenediamine(MPDA) and trimesoyl chloride(TMC) using PVC hollow fiber membrane as supporting.A series of PVC nanofiltration membranes with different molecular weight cutoff(MWCO) can be obtained by controlling preparation conditions.Chemical and morphological characterization of the membrane surface was carried out by FTIR-ATR and SEM.MWCO was characterized by filtration experiments.The preparation conditions were investigated in detail.At the optimized conditions(40 min air-dried time,aqueous phase containing 0.5% MPDA,0.05% SDS and 0.6% acid absorbent,oil phase containing 0.3% TMC,and 1 min reaction time),under 0.3 MPa,water flux of the gained nanofiltration membrane reaches 17.8 L/m2·h,and the rejection rates of methyl orange and MgSO4 are more than 90% and 60%,respectively.     

Synthesis of β-amino alcohols catalyzed by poly(vinyl chloride)-supported Schiff base metal complexes

Abstract  

Eight transition metal complexes of various Schiff bases supported on poly(vinyl chloride) (PVC) were prepared and characterized. These metal complexes were screened as heterogeneous catalysts in the synthesis of β-amino alcohols by ring opening of epoxides with amines. The best catalyst was identified as a Ni(II) complex of PVC-supported 2-[(2-aminoethylimino)methyl]phenol and it was used in the synthesis of a number of different β-amino alcohols. The catalyst was found to be reusable for up to five cycles.     

Encapsulation of β-cyclodextrin by in situ polymerization with vinyl chloride leading to suppressing the migration of endocrine disrupting phthalate plasticizer

We performed the encapsulation of β-cyclodextrin (β-CD) in PVC by in situ polymerization with vinyl chloride monomer (VCM), and investigated the effect of CD encapsulation on the suppression of dioctyl phthalate (DOP) migration suspected as endocrine disruptor. β-CD was partially modified with 3-(methacryloxy)propyl trimethoxysilane and modified β-CD (MCD) was then encapsulated in PVC through suspension polymerization via radical reaction between double bonds MCD and VCM. Resulting MCD-encapsulated PVC (MCD_x-PVC) exhibited the similar morphology and characteristics to commercial PVC. For MCD_x-PVCs plasticized with DOP, they showed the considerably suppressed DOP migration as well as the similar optical and mechanical properties to conventionally plasticized PVC. In particular, the plasticized MCD_x-PVCs exhibited the superior suppression of DOP migration compared to the plasticized PVC where MCD and DOP were introduced by conventional melt mixing. Therefore, the encapsulation of MCD in PVC is thought to be an effective approach to producing the ecological PVC material.     

Knoevenagel condensation catalysed by poly（vinyl chloride） supported tetraethylenepentamine （PVC-TEPA）

Poly(vinyl chloride) supported tetraethylenepentamine (PVC-TEPA) has been found to be an efficient catalyst for the Knoevenagel condensation. A wide range of aromatic aldehydes easily undergo condensations with ethyl cyanoacetate and malononitrile in the commercial 95% ethanol in refluxing using PVC-TEPA as catalyst to afford the desired products of good purity in moderate to excellent yields. A recycling study confirmed that the catalyst could be reused, the yield of the desired condensation product were not reduced. The merits of this protocol are environmentally benign, simple operation, convenient work-up and good yields. Furthermore, the catalyst can easily be recovered and reused at five times with comparable yields.     

Stability,antibacterial ability,and inhibition of “zinc burning” of amitrole as thermal stabilizer for transparent poly(vinyl chloride)

Journal of Thermal Analysis and Calorimetry - Amitrole is reported as a novel kind of transparent poly(vinyl chloride) (PVC) thermal stabilizer that has both excellent inhibition of “zinc...     

Stabilization of poly(vinyl chloride) with organotin compounds: Part VIII—Catalytic action of organic acids and anhydrides with organotin carboxylate

When maleic acid or maleic anhydride are added to a dichlorobutane solution of chlorohexene (as a model compound for allylic chlorides in poly(vinyl chloride)) and organotin carboxylates (maleates or laurate) heated at 80°C, the esterification reaction is strongly accelerated; moreover, the formation of hexadiene, which is the expected product of the competitive elimination reaction, is not observed. The reaction is first order with respect to both chlorohexene and the organic acid or anhydride, and may either be zero or first order with respect to the organotin carboxylate. ¹H-NMR spectra and solubility experiments indicate the formation of complexes between the organotin carboxylate and the organic acid or anhydride. A concerted mechanism between the chlorohexene and these complexes is suggested. A few experiments show that the addition of these organic acids or anhydrides to a PVC formulation leads to improvement of the thermal stability.Finally, other organic acids and anhydrides were also used to complex the organotin carboxylate in order to rule out the complexation mechanism and to discuss the activated complex.     

Chemistry of imidobis(sulphuryl chloride)—IV measurements of physical properties of imidobis(sulphuryl chloride)

Density, viscosity and specific conductance have been measured at 5° interval between 25 to 50° for imidobis(sulphuryl chloride). The surface tension, freezing point and cryoscopic constant have also been determined. Its IR and proton NMR spectra have been recorded. Relative acidity strength measurements in acetic acid suggest that imidobis(sulphuryl chloride) is a stronger protonic acid than HBr, HSO₃Cl and (CF₃)₂POOH.     

Nonenzymatic glucose sensing at ruthenium dioxide–poly(vinyl chloride)–Nafion composite electrode

Development of nonenzymatic glucose sensors with high reproducibility and stability is an urgent need to reduce cost of regular diabetic monitoring. Here, we have fabricated ruthenium dioxide–poly(vinyl chloride)–Nafion (RuO₂–PVC–Nafion) composite for direct glucose sensing in sodium hydroxide and phosphate buffer nonenzymatically for the first time. The restricted activity of the RuO₂–PVC film electrode in alkaline pH is extended to neutral pH using Nafion as an outer membrane, which reduces the distance between Ru active sites by bridging effect and improves the electrode stability. The catalytic rate, measured in terms of change of RuO₂ resistance, is similar irrespective of the medium for the high temperature annealed RuO₂ (700 °C), whereas the low temperature annealed RuO₂ (300 °C) is highly sensitive for the change in the pH of the solution. This is revealed by observing large Michaelis–Menten kinetic constant K _M for the RuO₂ (700 °C) than the low temperature annealed RuO₂ (300 °C) due to effective increase in the catalytic active sites similar to oxygen evolution reaction. Contrast to this, the buffer solution does not influence significantly the apparent K _M observed for RuO₂ (300 °C) and has greater impact on the high temperature 500 and 700 °C annealed RuO₂ samples. Cyclic voltammetry, chrono amperommetry, and electrochemical impedance spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction techniques are used for characterization of the sensor behavior. The RuO₂–PVC–Nafion senses glucose selectively in the presence of potential interferences like fructose, galactose, mannose, sucrose, starch, uric acid, ascorbic acid, dopamine, and catechol in NaOH and phosphate buffer. Glucose sensing in the blood serum of the diabetic and nondiabetic patients is made. The results suggest that the RuO₂–PVC–Nafion is a promising candidate for the development of nonenzymatic glucose sensors.     

Reactions of sulfenyl chloride derivatives of metal β-diketonates

The reactions of sulfenyl chloride derivatives of rhodium and ruthenium acetylacetonates as well as of chromium(III) and cobalt(III) β-diketonates (with β-phenyl groups) have been studied. The studied complexes can participate in the substitution and addition reactions. As compared with the previously studied sulfenyl chlorides of acetylacetonate complexes, many side processes occur in the case of β-phenyl chelates; they decrease the products yield and complicate their purification. In the case of dibenzoylmethenate complexes, reduction reactions can easily occur, giving the partially substituted chelates impurity.     

Synthesis and structures of α-lithiated vinyl ethers

The structures of α-lithiated vinyl ethers were explored on the basis of a combined computational and NMR study. Calculations (M06/6-31 + G(d)) on free energies of aggregate formation for a series of α-lithiated vinyl ethers indicated that the tetramer is generated preferentially in both the gas phase and THF solution, except for cyclohexylidene derivatives. (1-(Methoxymethoxy)vinyl)lithium, (2,2-difluoro-1-(methoxymethoxy)vinyl)lithium, and (1-butoxyvinyl)lithium were prepared in NMR tubes by the deprotonation of alkyl/alkoxylalkyl vinyl ethers or by the transmetalation of tin compounds. The NMR spectra of these lithium species in THF solution showed that in each species one aggregate is primarily present at 173 K, which is consistent with the preference of the tetramer.     

Synthesis of γ-ketophosphonates via aerobic hydroacylation of vinyl phosphonates

γ-Ketophosphonates are commonly employed as non-hydrolysable phosphate mimetics and as tools in synthesis. The synthesis of γ-ketophosphonates under mild conditions via interception of acyl radicals generated by aldehyde auto-oxidation is described.     

Radical-mediated thiodesulfonylation of the vinyl sulfones: access to (α-fluoro)vinyl sulfides

Radical-mediated thiodesulfonylation of the vinyl and (α-fluoro)vinyl sulfones, derived from aldehydes and ketones, with aryl thiols in organic or aqueous medium provided access to vinyl and (α-fluoro)vinyl sulfides. The vinyl sulfides were formed predominantly with E stereochemistry independent of the stereochemistry of the starting vinyl sulfones.     

Catalytic asymmetric synthesis of γ-substituted vinyl sulfones

A fast new entry for the stereoselective construction of γ-substituted vinyl sulfones is presented. The key for success is the use of a readily available chiral secondary amine catalyst that allows the use of base-sensitive β-nitroethyl sulfones as masked β-sulfonyl vinyl anions in conjugate additions. The method performed in a three-step one-pot operation gives access to a great variety of vinyl sulfones in good yields and with excellent enantioselectivities. The method has also been extended to other relatively base-sensitive β-electron-withdrawing-substituted nitroalkanes to afford products with manifold functionality, providing a quick entry to very attractive synthetic intermediates for organic synthesis.