Polymerization Of Vinyl Acetate Research Articles

Synthesis of spherical core-shell poly(vinyl acetate)/poly(vinyl alcohol) particles for use in vascular embolization: Study of morphological and molecular modifications during shell formation

Transarterial vascular embolization and chemoembolization has become common medical procedures, where partially hydrolyzed poly(vinyl alcohol) (PVA) beads remains as one of the most used embolic agent materials. Although synthetic, PVA cannot be synthesized by direct polymerization and must be obtained by chemical modification of another polymer, usually poly(vinyl acetate) (PVAc). The aim of the present work is to synthesize spherical core-shell PVAc/PVA particles and study the morphological and molecular modifications during shell formation. The polymer particles where produced in two stages, where first the PVAc core was obtained by suspension polymerization of vinyl acetate (VAc) and then the PVA shell synthesized through hydrolysis. Spherical PVAc particles were successfully produced and isolated using an optimized suspension polymerization process. During the shell formation, it was shown that none of the conditions used affected the overall morphology of the particles although changes in the final size distribution could be observed. However, it was possible to identify the process variables and reaction condition that affect the molecular weight averages and polydispersities of the final copolymer. POLYM. ENG. SCI., 55:2237–2244, 2015. © 2015 Society of Plastics Engineers

Polyamide4‐block‐poly(vinyl acetate) via a polyamide4 azo macromolecular initiator: Thermal and mechanical behavior, biodegradation, and morphology

ABSTRACTA series of polyamide4‐block‐poly(vinyl acetate)s were synthesized by the radical polymerization of vinyl acetate (VAc) using an azo macromolecular initiator composed of polyamide4 (PA4). The block copolymers were investigated by examining their molecular weight, structure, thermal and mechanical properties, biodegradation, and the morphology of the film surface. The compositions and molecular weights (Mw) ranging from 46,800 to 163,700 g mol−1 of the block copolymers varied linearly with increasing molar ratio of VAc to azo‐PA4. The block copolymers have high melting points of 248.2–262.5°C owing to PA4 blocks and heats of fusion, which were linearly dependent on the PA4 content. The mechanical properties of the block copolymers were monotonically dependent on the composition, i.e., increasing the PA4 content increased the tensile strength, whereas increasing the poly(vinyl acetate) content increased the elongation at break. The morphology of the block copolymers suggested the appearance of microphase separation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42466.

Synthesis and properties of carboxylated poly(vinyl alcohol) hydrogels for wound dressings

The copolymer P(VA-AA) was synthesized by free radical solution polymerization of vinyl acetate (VAc) and acrylic acid (AA) and subsequent saponification. It was found that by increasing the mass ratio of AA, the content of –COOH groups in PVA copolymers increased, while \( \overline{Mw} \) increased with a broader molecular weight distribution. The carboxylated hydrogels of P(VA-AA) were prepared by the freezing/thawing method for wound dressings. By increasing the mass ratio of AA, the storage modulus (G’) and mechanical strength decreased, resulting from the reduced physical cross-link density (Dpc) and looser network structure. The value of G’ was larger than G” and practically independent of frequency, and tanδ values approached 0 for all hydrogels, indicating a dominant elastic property and strong network structure. Introduction of AA onto PVA chains significantly improved the swelling rate constant k and equilibrium swelling ratio, and most of the water in the hydrogel was in the form of free water. The Higuchi model was the most suitable model for describing crystal violet (CV) release kinetics from PVA hydrogels, and the dissolution constant k was higher for the carboxylated PVA hydrogel than that of the pure one.

Bifurcation control and eigenstructure assignment in continuous solution polymerization of vinyl acetate

The major difficulty in achieving good performance of industrial polymerization reactors lies in the lack of understanding of their nonlinear dynamics and the lack of well-developed techniques for the control of nonlinear processes, which are usually accompanied with bifurcation phenomenon. This work aims at investigating the nonlinear behavior of the parameterized nonlinear system of vinyl acetate polymerization and further modifying the bifurcation characteristics of this process via a washout filter-aid controller, with all the original steady state equilibria preserved. Advantages and possible extensions of the proposed methodology are discussed to provide scientific guide for further controller design and operation improvement.

Reversible addition‐fragmentation chain transfer polymerization of vinyl acetate under high pressure

ABSTRACTIn this work, high molecular weight polyvinyl acetate (PVAc) (Mn,GPC = 123,000 g/mol, Mw/Mn = 1.28) was synthesized by reversible addition‐fragmentation chain transfer polymerization (RAFT) under high pressure (5 kbar), using benzoyl peroxide and N,N‐dimethylaniline as initiator mediated by (S)‐2‐(ethyl propionate)‐(O‐ethyl xanthate) (X1) at 35 °C. Polymerization kinetic study with RAFT agent showed pseudo‐first order kinetics. Additionally, the polymerization rate of VAc under high pressure increased greatly than that under atmospheric pressure. The “living” feature of the resultant PVAc was confirmed by 1H NMR spectroscopy and chain extension experiments. Well‐defined PVAc with high molecular weight and narrow molecular weight distribution can be obtained relatively fast by using RAFT polymerization at 5 kbar. © 2015 Wiley Periodicals, Inc. J. Polym. Sci. Part A: Polym. Chem. 2015, 53, 1430–1436

Kriging Surrogate Based Multi-objective Optimization of Bulk Vinyl Acetate Polymerization with Branching

Despite the established superiority in finding the global as well as well-spread Pareto optimal (PO) points, the need of more numbers of function evaluations for population based evolutionary optimization techniques leads to a computationally demanding proposal. The case becomes more miserable if the function evaluations are carried out using a first principle based computationally expensive model, making the proposal not fit for online usage of the application. In this work, a Kriging based surrogate model has been proposed to replace a computationally expensive model to save execution time while performing an optimization task. A multi-objective optimization study has been carried out for the bulk vinyl acetate polymerization with long-chain branching using these surrogate as well as expensive models and Kriging PO solutions similar to those found by the first principle models are obtained with a close to 85% savings in function evaluations.

Effect of EVA Content upon the Dielectric Properties in LDPE-EVA Films

Low density polyethylene (LDPE) blends with different percentages of ethylene vinyl acetate polymer membranes were prepared by a hot press casting method. The effects of EVA content on the electrical properties of LDPE were studied. The results on the electrical properties revealed that the surface resistance, volume resistivity, and breakdown voltage of the LDPE decrease with EVA content and reach a minimum at a 30 wt% of EVA. Dielectric constant and dielectric loss factor were increased with increasing EVA content up to 30 wt% of EVA. It can be deduced that the electrical properties of LDPE are improved by blending with EVA.

Preparation and Study of Polyvinyl Alcohol Fiber

The preparation of polyvinyl alcohol fibers mainly consists of three steps: 1. The polymerization of vinyl acetate. Need the preparation of vinyl acetate and polymerization of vinyl acetate. The polymerization of vinyl acetate uses acetylene method and ethylene method.2. Preparation of PVA. Mainly to let the polyvinyl acetate taking alcoholysis reaction to the effect of methanol or sodium hydroxide. 3. Preparation of polyvinyl alcohol fiber. Complete dope preparation through washing and dehydration, dissolving, mixing, filtering and deaeration, and uses the dry, wet two methods to form the spinning. Finally, through the follow-up processing, to accomplish the preparation of polyvinyl alcohol fiber. Water soluble and high concentration polyvinyl alcohol fiber ‘s performances are fine and is application widely.

Synthesis of functionalized poly(vinyl acetate) mediated by alkyne-terminated RAFT agents

Two new xanthates with alkyne functionalities were synthesized for the reversible addition fragmentation chain transfer (RAFT) polymerization of vinyl acetate (VAc).

Economic production of VAc and VEOVA 10 emulsion polymer using factorial design

Emulsion polymerisation of vinyl acetate (VAc) and vinyl ester of versatic acid (VEOVA 10) was carried out using different feed composition ratios. The copolymer emulsion was characterised by measuring the morphological properties (average particle diameter, D) by using the transmission electron microscope (TEM), minimum film forming temperature (MFFT) and filtration residue (ppm). The results of the study indicate that the average particle diameter of emulsion (D) decreases with the increase of the amount of VEOVA 10 content (and subsequently decreases the amount of VAc), also the ppm and the MFFT is decreased. These results were illustrated using response surface methodology and contour plots. In this paper, the economic production of VAc and VEOVA 10 emulsion polymer was studied to ensure the best performance of all properties at minimum cost utilising multi-objective optimisation methodology.

Living radical polymerization of vinyl acetate mediated by iron(iii) acetylacetonate in the presence of a reducing agent

The Fe(acac)3-mediated OMRPs of VAc in the presence of a reducing agent were reported.

ChemInform Abstract: Reversible Deactivation Radical Polymerization Mediated by Cobalt Complexes: Recent Progress and Perspectives

AbstractReview: 68 refs.

Kinetics and monomer partitioning during polymerization of vinyl acetate in microemulsions stabilized with AOT and n-butanol

Vinyl acetate (VAc) was polymerized in microemulsion using sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as surfactant and n-butanol (n-BuOH) as the cosurfactant (1:1, wt/wt) with potassium persulfate (KPS) as initiator. The effects of monomer, surfactant, and initiator concentration, as well as the temperature on the kinetics, particle size, and molar masses were studied. It was observed that polymerization rate increases as monomer, initiator, and temperature increases; however, the opposite was observed as surfactant concentration increases. Average particle diameters (Dp) < 50 nm and polymers with weight average molar masses (Mw) between 2.7 × 105 and 7.5 × 105 g/mol were obtained. For low amounts of stabilizing agents (AOT and n-BuOH), a bimodal molar mass distribution (MMD) was obtained. As n-butanol concentration increased, Mw decreases and a monomodal MMD was observed, which can be explained because chain transfer events are promoted by the presence of n-BuOH. A thermodynamic model was implemented to simulate the partitioning of VAc in the presence of n-BuOH between the phases throughout polymerization. It was found from simulations that microemulsion droplets are depleted fast at 5 % conversion and, due to the high water solubility of VAc, most of the monomer (70 %) and n-BuOH (97 %) reside in the aqueous phase at the beginning of polymerization, which indicates that both homogeneous and micellar nucleation are present.

Compatibilization of PUR/PVAC polymer blend by addition of calcium carbonate filler

The influence of untreated and stearic acid surface pretreated calcium carbonate (CaCO3) nanofiller (U1 – untreated CaCO3 and U1S2 – stearic acid treated CaCO3) on the properties of polyurethane/poly(vinyl acetate) (PUR/PVAC) polymer blends was investigated. Adhesion between fillers and polymers in the polymer blend composite, and filler position in regard to the polymer phases, are predicted on the basis of calculated adhesion parameters and wetting factor ωa of PUR, PVAC, U1, and U1S2. U1 is located in the PUR matrix phase and U1S2 is located at the interface between matrix PUR domain and dispersed PVAC domain. Polymer blend composites with predominant U1S2 showed lower tensile strength and elongation compared to these of polymer blend composites with predominant U1 mainly due to the fillers' different surface properties, which confirmed that the mechanical properties of polymer blend composites were dependent on overall system morphology rather than the filler location. POLYM. COMPOS. 37:1274–1281, 2016. © 2014 Society of Plastics Engineers

Cobalt Bipyridine Bisphenolate Complex in Controlled/Living Radical Polymerization of Vinyl Monomers

Cobalt(II) bipyridine bisphenolate (CoII(BpyBph)) was applied to mediate the controlled/living radical polymerization of vinyl acetate (VAc), methyl acrylate (MA), and other vinyl monomers such as N-vinylpyrrolidone (NVP) and acrylonitrile (AN). The living characters of linear increased molecular weight with monomer conversion, relatively narrow molecular weight distribution, and the synthesis of block copolymer demonstrated by the formation of PVAc-b-PNVP were all observed. The polymerization of VAc was proposed to be mediated by the degenerative transfer (DT) process, but the polymerization of MA should be mainly controlled by the reversible termination (RT) process since the equilibrium constant (Keq = [CoIII–R]/[CoII][R•]) between cobalt(II) and organocobalt(III) was measured as 8.6 × 107 M–1. The correlation between Keq and the redox potential (E1/2) of cobalt complexes was preliminarily observed as a higher E1/2 leading to a larger Keq.

Ethylene vinyl acetate polymer as a tool for passive sampling monitoring of hydrophobic chemicals in the salmon farm industry

Current monitoring programs are focused on hydrophobic chemicals detection in aquatic systems, which require the collection of high volumes of water samples at a given time. The present study documents the preliminary use of the polymer ethylene vinyl acetate (EVA) as a passive sampler for the detection of a hydrophobic chemical used by salmon industries such as cypermethrin. Initially, an experimental calibration in laboratory was performed to determine the cypermethrin equilibrium between sampler and aquatic medium, which was reached after seven days of exposure. A logarithm of partitioning coefficient EVA–water (logKEVA–W) of 5.6 was reported. Field deployment of EVA samplers demonstrated average concentrations of cypermethrin in water to be 2.07±0.7ngL−1 close to salmon cages, while near-shore was 4.39±0.8ngL−1. This was a first approach for assessing EVA samplers design as a tool of monitoring in water for areas with salmon farming activity.

Reversible deactivation radical polymerization mediated by cobalt complexes: recent progress and perspectives.

Mediation of reversible deactivation radical polymerization (RDRP) by cobalt(II) complexes (CMRP) is the most highly developed subcategory of organometallic mediated RDRP (OMRP). Attention was paid to CMRP for its unusual high efficiency observed for the control of acrylate and vinyl acetate polymerization that produced homo- and block copolymers with narrow molecular weight distribution and a predictable molecular weight. The reactions of organic radicals with cobalt(II) metallo-radicals and organo-cobalt(III) complexes have a central role in the pathways that mediate this type of reversible deactivation radical polymerization. The reversible deactivation pathway dominates the polymerization when cobalt(II) complexes can reversibly deactivate the radicals to form organo-cobalt(III) complexes. Degenerative transfer becomes the major pathway when the cobalt(II) species fully convert to organo-cobalt(III) complexes and the radicals in solution rapidly exchange with radicals in organo-cobalt(III) complexes. This review describes the polymerization behavior and control mechanisms used by cobalt complexes in the mediation of reversible deactivation radical polymerization. The emerging developments for CMRP in the aqueous phase and with photo-initiation are also described, followed by the challenges and future applications of this method.

Synthesis of polyvinyl alcohol stereoblock copolymer via the combination of living cationic polymerization and RAFT/MADIX polymerization using xanthate with vinyl ether moiety

Different types of novel xanthates containing a vinyl ether moiety, S-benzyl O-2-(vinyloxy)ethyl carbonodithioate (Xanthate 1) and S-1-(ethoxycarbonyl)ethyl O-2-(vinyloxy)ethyl carbonodithioate (Xanthate 2) were synthesized. In particular, the Xanthate 2 enabled to design polyvinyl alcohol (PVA) stereoblock copolymer via the combination of living cationic vinyl polymerization and RAFT/MADIX polymerization. For cationic polymerization of isobutyl vinyl ether (IBVE) and tert-butyl vinyl ether (TBVE), the polymerizations were conducted under Xanthate 1-HCl adduct/SnCl4 and Xanthate 1 or 2-CF3COOH adduct/EtAlCl2 initiating system in the presence of ethyl acetate. Both systems proceeded in living polymerization fashion because the calculated Mn of both poly(IBVE) and poly(TBVE) matches with the Mn polymerized assuming that one polymer chain is formed per one molecule of the Xanthate 1 or 2. The resulting poly(TBVE) had a high number average α-end functionality as determined by MALDI-TOF-MS spectrometry. Xanthate 2 is more efficient for the following RAFT/MADIX polymerization of vinyl acetate (VAc). The RAFT/MADIX polymerization of vinyl acetate (VAc) using azobis(isobutyronitrile) (AIBN) at 60 °C was conducted using either poly(IBVE) or poly(TBVE) macro-CTA. The poly(TBVE) macro-CTAs synthesized from the Xanthate 2 were able to polymerize VAc smoothly via RAFT/MADIX polymerization, to prepare well-defined diblock copolymer, poly(TBVE)-b-poly(VAc). The resulting block copolymer was then hydrolyzed using KOH in methanol and followed by acid hydrolysis using HBr gas bubbling. The resulting polymer is inherently stereoblock like copolymer, isotactic rich PVA-b-atactic PVA (iPVA-b-aPVA). From the DSC measurement, the iPVA-b-aPVA has one glass transition at 69.5 °C and two melting points according to iPVA and aPVA at 237.9 and 198.1 °C, respectively. Thus, it can be suggested that the obtained PVA has two different geometries by the combination of living cationic polymerization and RAFT/MADIX polymerization.

Zinc powder-alkyl halide: a radical initiation system for living/controlled polymerization of vinyl monomers

An initiation system comprising activated zinc powder and alkyl bromide is presented for polymerization of vinyl monomers, including vinyl acetate (VAc). The polymerization was demonstrated to be effected in dry conditions at 70 °C and very sensitive to moisture. A radical mechanism was evidenced by spin-trapping method using TEMPO as capping agent and followed block copolymer formation. First order kinetics with respect to concentration of the monomers, methylmethacrylate(MMA), styrene and VAc, relatively long induction periods, and moderate polydispersities (PDI: 1.6–2.4) were determined as typical characteristics of the polymerization system in bulk conditions. The polymerization system was demonstrated to be living, as evidenced by chain extension of the poly (vinyl acetate) (PVAc) with MMA. A ZnBr radical fragment was proposed as key intermediate controlling the chain growth by reversible combination with the active chain ends. The system was also combined with typical copper-mediated atom transfer radical polymerization (ATRP), in which ATRP-growth polystyrene (PS) was directly used as macroinitiator to initiate VAc polymerization yielding block copolymer.

Reversible addition-fragmentation chain transfer polymerization of vinyl acetate and vinyl pivalate in supercritical carbon dioxide

Two highly supercritical CO2-soluble, poly(vinyl acetate) (PVAc)-based macro-reversible addition-fragmentation chain transfer (RAFT) agents were synthesized. The RAFT agents were used for the first time in RAFT/macromolecular design via the interchange of xanthates (MADIX) and polymerization of vinyl acetate (VAc) and vinyl pivalate (VPi) in supercritical carbon dioxide (scCO2). A homopolymer PVAc and a block copolymer PVAc-b-PVPi made by RAFT/MADIX polymerization were characterized, and the effects of time and RAFT agents on polymerization were examined. For the 8.4 wt% RAFT agent in VAc, the molecular mass (M n ) of homopolymer PVAc was 26,000 g mol−1 and PDI was 1.35. For the copolymerization of VPi using 9.8 wt% PVAc-RAFT agent in VPi for 24 h, the M n and PDI of PVAc-b-PVPi reached 32,400 g mol−1 and 1.42, respectively. These results suggest that the polydispersity can be controlled during the clean production of PVAc and PVPi by RAFT/MADIX polymerization in scCO2.