Structural defects in poly(vinyl chloride)—V. Thermal and photodegradation of copolymers of vinyl chloride with various acetylene derivatives

Vinyl chloride has been copolymerized with various acetylene derivatives in bulk at 50. It has been shown by ozonolysis that these copolymers contain a significantly increased amount of internal double bonds. A comparison of the thermal and photodegradation behaviours of the copolymers has been made. The built-in double bonds show an effect on the reactivity of the adjacent allylic chlorine depending on the electron-withdrawing or repelling nature of the substituent. Among the comonomers investigated, copolymers containing 3-chloropropine have the least reactive defect sites, because of the electron-withdrawing chloromethyl substituent. On the contrary, the electron-repelling n-butyl group, built-in by using hexine-1 as comonomer, results in enhanced reactivity of the allylic chlorines.     

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.     

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.     

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.     

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.     

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.     

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).     

Highly selective thiocyanate poly(vinyl chloride) membrane electrode based on a cadmium–Schiff’s base complex

A PVC membrane electrode based on a cadmium–salen (N,N′-bis-salicylidene-1,2ethylenediamine) complex as an anion carrier is described. The electrode has an anti-Hofmeister selectivity sequence with a preference for thiocyanate at pH 1.5–11.0. It has a linear response to thiocyanate from 1.0 × 10^–6 to 1.0 × 10^–1 mol L^–1 with a slope of 59.1 ± 0.2 mV per decade, and a detection limit of 7 × 10^–7 mol L^–1. This electrode has high selectivity for thiocyanate relative to many common organic and inorganic anions. The proposed sensor has a fast response time of approximately 15 s. It was applied to the determination of thiocyanate in a milk sample. Received: 1 December 2000 / Revised: 19 April 2001 / Accepted: 30 April 2001     

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.     

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.     

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...     

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.     

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.     

Propane transformations on aluminum chloride—cobalt chloride clusters: a quantum chemical study

Density functional PBE/TZ2p quantum chemical calculations of activated complexes and pathways of model catalytic transformations of propane under the action of aluminum chloride-cobalt chloride ionic bimetallic complexes were carried out. The formation of an intermediate with a broken C-C bond can occur on the cationic cluster CoAlCl₄ ⁺ characterized by the strongest coordination of propane molecule. The activation barrier to the reaction is ΔG = 25.0 kcal mol⁻¹. Activation of alkane C-H bonds follows the alkyl pathway involving the formation of bimetallic alkyl complexes. The interaction of activated hydrocarbon fragments bound to transition metal atoms in cobalt-chloroaluminate clusters can result in alkane metathesis products (in this case, ethane and a polymetallic cluster containing an extendedchain alkyl radical).     

An approach to α-keto vinyl carbinols

Adducts from the radical addition of xanthates to ethyl vinyl sulfide readily undergo elimination of the xanthate group upon thermolysis to give vinylic and/or allylic sulfides, depending on the structure. In the case of α-xanthyl ketones, the adducts are converted into α-keto vinyl carbinols by rearrangement of the sulfoxides derived from the vinylic and allylic sulfides.     

Composite poly(vinyl alcohol)–poly(sulfone) membranes crosslinked by trimesoyl chloride: Characterization and dehydration of ethylene glycol–water mixtures

Composite membranes prepared from poly(vinyl alcohol) and poly(sulfone) were crosslinked with trimesoyl chloride (TMC) solutions. The degree of crosslinking, crystallinity, surface roughness and hydrophobicity of the crosslinked PVA–PSf membranes were determined from attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM) and contact angle measurements, respectively. Results showed a consistent trend of changes in the physicochemical properties: the degree of crosslinking, crystallinity, surface roughness, hydrophobicity and swelling degree all decrease with increasing crosslinking agent (TMC) concentration and reaction time. The crosslinked membrane performance was assessed with pervaporation dehydration of ethylene glycol solutions at a range of concentrations (30–90 wt% EG) in the feed mixtures. The total flux of permeation was found to decrease, while the selectivity to increase, with increasing TMC concentration and reaction time. The decrease in flux was most prominent at low EG concentrations in the feed mixtures. In addition, the temperature effect on the pervaporation dehydration was investigated in relation to solution–diffusion mechanisms.     

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.