Radiation synthesis of acrylic acid onto poly(tetraflouroethylene-perflourovinyl ether) film: Chemical modifications and electrical conductivity

Graft-polymerization of acrylic acid (AAc) monomer onto poly(tetraflouroethylene-perflouro vinyl ether) (PFA) copolymer film was carried out using gamma irradiation technique to synthesize grafted copolymer film PFA-g-PAAc (PFA-COOH). The effect of the dose on the degree of grafting of AAc onto PFA film was investigated. The results showed that the degree of grafting increases with increasing the irradiation dose. The grafted [PFA-COOH] film was chemically modified by reaction with aniline to produce modified [PFA-CO-NH-ph] film, followed by sulphonation reaction to introduce sulfonic acid (SO₃H) groups to get other modified [PFA-CO-NH-ph-SO₃H] film. The chemical structures of the grafted and modified films were identified by FT-IR, XRD, and SEM. It is of particular interest to measure the electrical conductivity of grafted and modified membranes as a function of degree of grafting. It was found that the conductivity of the grafted films increases with increasing the degree of grafting, however a slightly increase in conductivity was observed in [PFA-CO-NH-ph-SO₃H] sample. The electrical conductivity property of the modified PFA membranes suggests their possible use for fuel cell applications.     

Membranes obtained by preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene–perfluorovinyl ether)

Some properties of the membranes obtained by preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene-perfluorovinyl ether) copolymer (PFA) films have been investigated. The dimensional change caused by grafting and swelling behavior, water uptake, electrical conductivity, and mechanical properties of the grafted films were found to increase as the grafting proceeds. The influence of the preparation conditions (such as preirradiation dose, monomer concentration, grafting temperature, and film thickness) on those properties was studied. These properties were found to be dependent mainly on the degree of grafting regardless of grafting conditions, except at higher monomer concentration (>40 wt %). The electric conductivity and mechanical properties for the membranes obtained at higher AAc concentrations were lower than those obtained at lower ones. Analysis by x-ray microscopy of the grafted films revealed that the grafting begins at the part close to the film surface and proceeds into the central part with progressive diffusion of monomer to give finally homogeneous distribution of the electrolytes in the whole bulk of the polymer. The membranes show good electrochemical and mechanical properties which make them acceptable for practical use as cation-exchange membranes.     

Grafting onto poly(vinyl alcohol). II. Graft copolymerization of methyl acrylate and vinyl acetate and their binary mixture using γ-rays as initiator

Methyl acrylate (MA), vinyl acetate (VAc) and their binary mixture (MA + VAc) have been graft copolymerized onto poly(vinyl alcohol) using γ-rays as initiator by mutual radiation method in aqueous medium. The optimum conditions for affording maximum grafting have been evaluated. The percentage of grafting has been determined as a function of total dose, concentrations of poly(vinyl alcohol), MA, VAc, and their binary mixture. Rate of grafting (R_p) and induction period (I_p) have been determined as a function of total initial mixed monomer concentration and concentration of poly(vinyl alcohol). The graft copolymer has been characterized by thermogravimetric method. The effect of donor monomer (vinyl acetate) on percent grafting of acceptor monomer (methyl acrylate) has been explained.     

Graft copolymerization. II. Grafting of benzyloxyethyl methacrylate on poly(vinyl alcohol)

New graft copolymers were produced by grafting benzyloxyethyl methacrylate, the benzyl ether of HEMA, on high-molecular-weight poly(vinyl alcohol) in dimethyl sulfoxide solution with Ce⁴⁺ as initiator. The effects of the concentration of the initiator, the concentration of the monomer, the total concentration of the reactants, the temperature, and the duration of reaction on the percentages of grafting and conversion were investigated. Further, also the relationships between the initiator concentration and the percentages of grafting and of conversion in the reaction with poly(vinyl alcohol)s of lower molecular weight and of different degrees of hydrolysis were studied.     

Radiation-Induced Grafting of Ethyl Vinyl Ether onto Polyvinyl Chloride)

The radiation-induced graft polymerization of ethyl vinyl ether (EVE) onto polyvinyl chloride) (PVC) was studied under a variety of conditions. Graft copolymer and homopoly(EVE) were formed in all cases. The presence of water reduced overall polymerization rates, percentage grafting, and homopoly(EVE) molecular weights. With “superdry” EVE, grafting reached 29% at a total dose of 6.9 Mrad. Grafting to PVC films was less efficient than grafting to PVC powder. Application of a relatively poor swelling agent for PVC resulted in an increase in the efficiency of grafting. From a comparison of studies of radiation-induced EVE homopolymerization and the present work, it was concluded that dry and superdry EVE are grafted to PVC by a cationic mechanism and wet EVE is grafted mainly by a free-radical mechanism.     

UV-induced Self-initiated Graft Polymerization of Acrylamide onto Poly(ether ether ketone)

Photo-grafting of hydrophilic monomer was used to enhance the hydrophilicity of poly(ether ether ketone) (PEEK) with the aim of extending its applications to biological fields. PEEK sheets were surface modified by grafting of acrylamide(AAm) with ultraviolet(UV) irradiation in the presence or absence of benzophenone(BP). The effects of BP, irradiation time and monomer concentration on the surface wettability of PEEK were investigated. Characterization of modified PEEK using scanning electron microscopy(SEM), energy-disperse spectrometer(EDS) and water contact angle measurements shows that AAm was successfully grafted on PEEK surface both in presence and absence of BP. With the increase in irradiation time and monomer concentration, contact angles decrease to as low as 30°, demonstrating a significant improvement of surface hydrophilicity. In agreement with the decrease in contact angle, under identical conditions, the nitrogen concentration increases, suggesting the increase in grafting degree of the grafting polymerization. This investigation demonstrates a self-initiation of PEEK due to its BP-like structure in the backbone of the polymer. Though the graft polymerization proceeds more readily in the presence of BP, the self-initiated graft polymerization is clearly observed.     

Radiation-induced grafting of perfluorinated vinyl ether into fluorinated polymer films

We report herein the first successful grafting of perfluorinated vinyl ether monomer into base polymer films by simultaneous radiation method. 2-Bromotetrafluoroethyl trifluorovinyl ether (BrTFF) could be grafted into poly(ethylene-co-tetrafluoroethylene) (ETFE) films by γ-rays irradiation at room temperature. The grafting yield increased linearly with an increase in the dose up to 1400 kGy. The required dose for a satisfactory grafting yield, such as 20%, was as high as ca. 400 kGy probably due to low polymerization reactivity of fluorinated monomers. However, the solvent and catalyst had no positive influence for improving the grafting yield. FTIR spectra and SEM-EDS testified that BrTFF was successfully grafted into ETFE films homogeneously in the perpendicular direction. The thermal analysis of the grafted films further indicated no phase separation between poly(BrTFF) grafts and ETFE films, probably owing to high compatibility of the fluorinated grafts and base polymers.     

Graft copolymerization. I. Grafting of hydroxyalkyl methacrylates on poly(vinyl alcohol)

New graft copolymers were synthesized by grafting hydroxyethyl methacrylate and hydroxpropyl methacrylate on poly(vinyl alcohol) in aqueous solution with Ce⁺⁴ions as initiator. The dependence of the percentage of grafting and monomer conversion on the concentration of the monomer, on the concentration of the initiator, on the total concentration of the reactants, and on temperature and duration of the reaction were investigated. Some basic properties of the graft copolymers and some preliminary permeation measurements of water vapors through films, made from these copolymers, are also reported.     

Synthesis,Characterization and Application of Amphiphilic Copolymer Poly(vinyl alcohol)-g-Poly(butyl acrylate)

An amphiphilic graft copolymer poly(vinyl alcohol)-g-poly(butyl acrylate) (PVA-g-PBA) was synthesized by grafting butyl acrylate (BA) onto poly(vinyl alcohol) (PVA) with potassium persulfate (KPS) as free radical initiator in N₂ atmosphere and aqueous medium. The formation of graft copolymer was confirmed by means of infrared spectroscopy (IR). The influences of initiator, monomer concentration and reaction time on the percentage of monomer conversion(C _M), graft degree(Gd) and graft efficiency(Ge) have been discussed in detail. PVA-g-PBA was used as compatibilizer in blends of chlorinated polyethylene (CPE)/ poly(acrylic acid-co-acrylamide)[P(AA-AM)], and the compatibility between CPE and P(AA-AM) was also investigated.     

WATER-SOLUBLE AMPHOLYTIC GRAFTED POLYSACCHARIDES. 1. GRAFTING OF THE ZWITTERIONIC MONOMER 2-(2-METHACRYLO-ETHYLDIMETHYLAMMONIO) ETHANOATE ONTO HYDROXYETHYL CELLULOSE

Novel ampholytic grafted polysaccharides were prepared by grafting the Zwitterionic monomer 2-(2-methacryloethyldimeth-ylammonio) ethanoate onto hydroxyethyl cellulose. Ethylenediamine tetraacetic acid was used in combination with ceric ammonium nitrate as the redox initiator. The effects of various factors such as initiator amount, monomer concentration, reaction temperature and time on the grafting were studied and the optimum reaction conditions to obtain maximum degree of grafting were found. The resulted graft copolymer was characterized by IR and thermal analyses.     

Grafting acrylic acid monomer to poly-(vinyl alcohol) and methyl cellulose by ceric ion

A graft copolymer of acrylic acid on poly(vinyl alcohol) was prepared by use of the ceric ion–polyol redox system in aqueous medium. The graft copolymer obtained was water-soluble under the specified experimental conditions. The efficiency of grafting was determined by measuring carboxyl group content (as expected from acrylic acid unit) in the copolymer by applying the newly developed reverse dye-partition technique. The graft copolymer was also characterized by viscosity and solubility measurements. The effect of varying concentration of catalyst, monomer, and grafting time has also been determined.     

Photograft Copolymerization of Methyl Methacrylate and Natural Rubber Using Quinoline-Bromine C.T. Complex as Photoinitiator in Benzene Solution

Photografting of poly(methyl methacrylate), PMMA chains on natural rubber (NR) chain backbones was studied in benzene solution using quinoline-bromine (Q-Br₂) charge transfer complex as photoinitiator and MMA as monomer at 35°C in visible light. Analysis of overall products for determination of grafting efficiencies was done following a method of selective extraction of only the free rubber fraction by benzene-petroleum ether mixtures followed by separation of the NR-PMMA graft copolymer from free PMMA in the residue (taken in benzene solution) by fractional precipitation with methanol. High grafting efficiencies in the range of 75–95% were easily and generally obtained. Effects of variation of concentrations of initiator, rubber, and monomer on grafting efficiencies were examined and reported. Prior photodegradation of the rubber resulted in substantial lowering in grafting efficiencies. Overall mechanism of graft copolymerization has been discussed.     

Preparation of poly(ether ether ketone)-based polymer electrolytes for fuel cell membranes using grafting technique

Poly(ether ether ketone) (PEEK)-based polymer electrolyte membranes (PEMs) was successfully prepared by radiation grafting of a styrene monomer into PEEK films and the consequent selective sulfonation of the grafting chains in the film state. Using milder sulfonation, the sulfonation reactions proceeded at the grafted chains in preference to the phenylene rings of PEEK main chains; as a result, the grafted films could successfully transform to a PEM with conductivity of more than 0.1 S/cm. The ion exchange capacity (IEC) and conductivity of the grafted PEEK electrolyte membranes were controlled to the ranges of 1.2–2.9 mmol/g and 0.03–0.18 S/cm by changing the grafting degree. It should be noted that this is the first example of directly transforming super-engineering plastic films into a PEM using radiation grafting.     

A new procedure for preparing butyl acrylate-vinyl n-butyl ether copolymer as effective thickening additive to oils

The possibility of preparing copolymers by radical copolymerization on adding an active monomer, butyl acrylate, to refluxing inactive vinyl n-butyl ether was examined. The copolymer composition was studied by IR and NMR spectroscopy and by gravimetric analysis. The molecular weight and polydispersity coefficient of the copolymer were determined.     

Effect of dimethylaminoethyl methacrylate on the graft copolymerization of ethyl acrylate onto hydroxypropyl methylcellulose in aqueous medium

Graft copolymerization of an ethyl acrylate (EA) and dimethylaminoethyl methacrylate (DMAEMA) monomer mixture onto water-soluble hydroxypropyl methylcellulose was investigated with potassium persulfate (KPS) as the initiator in an aqueous medium. The effects of introducing DMAEMA onto the graft copolymerization and the properties of the resulting latex that was produced were studied systematically. The optimum conditions for the graft copolymerization in terms of percentage of grafting and grafting efficiency were determined. The graft copolymer was characterized by Fourier transform infrared spectra, elemental analyses, nuclear magnetic resonance, transmission electron microscopy, and dynamic light scattering methods. The results suggest that the introduction of the DMAEMA monomer clearly accelerates the initial rate of the graft copolymerization, whereas the grafting parameters decrease significantly with increasing amounts of DMAEMA. These results can be attributed to the relatively large size of the DMAEMA molecule, its redox reaction with KPS, its hydrophilicity in water, and its chain transfer effect. The equilibrium humidity adsorption behavior and acid solubility of graft the copolymer films were also studied.     

Kinetic study of preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene–perfluorovinyl ether) copolymer

A kinetic study has been made on the preirradiation grafting of acrylic acid (AAc) onto poly(tetrafluoroethylene–perfluorovinyl ether) (PFA) film. The effect of grafting conditions was investigated. The dependences of the grafting rate on preirradiation dose and monomer concentration was found to be of the order of 0.5 and 1.3, respectively. The final degree of grafting was found to increase with dose and monomer concentration. However, it decreases as the grafting temperature increase. The overall activation energy for the graft polymerization was calculated from Arrhenius plots to be 5.6 kcal/mol. The activation energy for this grafting system was found to be independent of preirradiation dose used in the range from 10 to 100 kGy. The relationship between the grafting rate and film thickness gave a negative first-order dependence. The results suggest that the grafting proceeds by radical mechanism with bimolecular termination of growing chain radicals. It was reasonable concluded that this grafting proceeds from the surface to the center of film with progressive monomer diffusion through the grafted layer which swells in the monomer solution.     

γ-Rays-induced synthesis of hydrogels of vinyl ethers with stimuli-sensitive behavior

γ-Radiation method was applied to synthesize novel water-soluble and water-swelling polymers. Vinyl ether of ethylene glycol (VEEG), vinyl butyl (VBE) and vinyl isobutyl (VIBE) ethers were used as monomers. The synthesis of VEEG–VBE and VEEG–VIBE copolymers was carried out in a wide range of feed composition and absorbed dose. It was found that the hydrophobic–hydrophilic balance of the copolymers could be delicately varied by the copolymer composition as well as by the chemical structure of the alkyl substitute in the hydrophobic moiety. The copolymers exhibit thermo-sensitive behavior in water solutions. The value of transition temperature is considerably decreased at a higher concentration of the hydrophobic component in the copolymer composition.     

Effect of comonomer sorption on radiation-induced copolymer grafting onto polyethylene and EVA films in the vapor phase

Radiation-induced copolymer grafting of acenaphthylene and maleic anhydride onto polyethylene or EVA film in the vapor phase was carried out and the effect of comonomer sorption on the grafting was studied. When polyethylene film was used as a backbone polymer, the sorption of the binary monomers during the grafting increased linearly as the grafting reaction proceeded. The marked increase was probably caused by the formation of a grafted layer. Particularly, the sorption of maleic anhydride was brought about by the existence of a grafted layer. In grafting onto EVA film, the content of maleic anhddride in the grafted copolymer increased with the increasing content of vinyl acetate in EVA. Continuous measurements of sorption of the comonomers onto EVA and grafted EVA films were carried out by use of an electrobalance. The distinctive feature of the sorption was that the equilibrium sorption of acenaphthylene or maleic anhydride onto the grafted EVA film increased and the diffusion constants for both comonomers decreased markedly with increasing percentage of graft. The copolymer grafting was explained from these results by assuming that the monomer molecules are supplied to the propagating chain ends mostly through a sorbed state on the polymer film.     

Design of composite films and ultrathin membranes of interpolymer complexes

The formation of stoichiometric interpolymer complexes (IPCs) between the poly(vinyl ether) of ethyleneglycol and the copolymer of acrylic acid–butyl vinyl ether, between copolymers of vinyl ether of ethyleneglycol–butyl vinyl ether, and the copolymer of acrylic acid–vinylbutyl ether is demonstrated by conductimetric, potentiometric, viscometric and spectroturbidimetric methods in aqueous solution. The swelling/deswelling behavior of composite films derived from the IPC has been studied in water, alcohol and water–alcohol mixtures, depending on various factors. The formation of polyelectrolyte complexes (PECs) between the copolymer of acrylic acid–vinyl butyl ether and poly(vinyl ether of monoethanolamine) on a dimeric interface of water–butanol has been studied by the potentiometric method. The kinetics of PEC formation on a dimeric interface was measured and the activation energy of this process was calculated. Copyright © 2000 John Wiley & Sons, Ltd.     

Irradiation-grafted polymeric films. I. Preparation and properties of acrylic acid–grafted polyethylene films

Graft copolymers of low-density polyethylene film and acrylic acid have been prepared by the direct grafting technique. The properties of 27.4, 33.9, 41.2, and 46.4 wt-% poly(acrylic acid) graft copolymer films have been compared. Measurements include degree and uniformity of grafting, gel water content, degree of swelling on wetting, tensile strength, elongation, ion-exchange capacity, water-vapor transmission, and water flux and solute rejection under reverse osmosis conditions. These properties were found to vary as the composition of the graft copolymer changed; most properties were found to be a linear function of the degree of grafting.