Preparation of poly(ε-caprolactone)-co-poly(acrylic acid) by radiation-induced grafting

Acrylic acid was grafted onto poly(ε-caprolactone) (PCL) films by using electron beam (EB) preirradiation technique. The effect of reaction time, monomer concentration, radiation dose, time between irradiation and grafting, radiation atmosphere, and polymer crystallinity on the extent of grafting were studied. Silver and tin ions were attached to the grafted chains in order to study the grafting process. The irradiation in air was initially more rapid, but the final extent of grafting was the same when irradiated in nitrogen atmosphere. Maximum grafting extents exceeding 400% could be obtained. The optimal grafting was obtained at an acrylic acid to water ratio of 30 : 70. The grafting process could be initiated at a dose as low as 12 kGy. The grafting process proved to start at the surface and was extended into the bulk with time. The ability to form crystals was reduced as the grafting extent increased. The water uptake of the poly(ε-caprolactone)-graft-poly(acrylic acid) was increasing with increasing grafting extent, but reached a maximum of ca 100% for all grafting extents above 85%. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1805–1812, 1998     

Radiation preparation of PVA-g-NIPAAm in a homogeneous system and its application in controlled release

Thermosensitive PVA-g-NIPAAm copolymers were prepared by graft copolymerization of N-isopropylacrylamide (NIPAAm) onto poly (vinyl alcohol) (PVA) in homogeneous system of dimethyl sulfoxide (DMSO) by ⁶⁰Co-γ irradiation at room temperature. The factors of affecting the grafting yield, such as radiation dose, dose rate, acid concentration, were investigated. It was found that the grafting yield was increased with dose up to 30 kGy, but decreased slightly with dose rate from 61.2 to 50.1 Gy/min. The acid concentration also had influence on the grafting yield. Then the hydrogel of PVA-g-NIPAAm copolymer was made through a freezing–thawing process. The PVA-g-NIPAAm hydrogel exhibited obvious thermal sensitivity, which was observed from the differences of swelling behavior in water at different temperatures (below or above LCST). In addition, the release of Methylene Blue (MB) from this kind of hydrogel was studied. The release rate of MB from PVA-g-NIPAAm copolymer hydrogel at 48°C was faster than that at 15°C due to the shrinkage of the hydrogel at 48°C.     

Graft Copolymerization of Methyl Methacrylate on Potato Starch Using Potassium Trioxalatomanganate,K3[Mn(C2O4)3], as Initiator

Graft copolymerization of methyl methacrylate on potato starch was carried out in methanol-water medium at 35°C in the dark using potassium trioxalatomanganate, K₃[Mn(C₂O₄)₃], as initiator. The effect of different methanol-water ratios (v/v), the temperature of polymerization, the initiator concentration, the monomer concentration, the starch content, and the time of polymerization were studied. Percent total conversion, % grafting, and grafting efficiency (%) under different conditions were evaluated and compared. High grafting efficiency (～80%), high % total conversion (～85%), and high % grafting (-95%) were readily obtained. The reaction mechanism for graft copolymer formation is discussed.     

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.     

辐射接枝医用水凝胶的研究Ⅰ.硅橡胶辐射接技N-乙烯基吡咯烷酮

采用填加SiO_2增强的甲基乙烯基硅橡胶混炼压片。通过~(60)Co-γ射线引发辐射硫化,利用共辐照方法,将N-乙烯基吡咯烷酮接枝到该硅橡胶上,制备了高纯度医用水凝胶。本文较系统地研究了接枝单体浓度、辐照剂量率、剂量、温度和接枝试片厚度等因素对接枝共聚反应的影响。建立了接枝速率与单体浓度、剂量率之间的动力学关系式:R_g=k[M]~(4/5)D~(1/2)。讨论了反应机制和接枝区域。     

PTFE辐射接枝对苯乙烯基三甲氧基硅烷制备质子交换膜

采用聚四氟乙烯(PTFE)膜室温下共辐射接枝单体p-苯乙烯基三甲氧基硅烷(StSi),之后经磺化和水解缩聚制备了含有亲水性的—Si—O—Si—交联结构和Si—OH基团的质子交换膜.研究了溶剂、吸收剂量、吸收剂量率以及单体浓度等参数对接枝率的影响,并对质子交换膜的离子交换容量(IEC)、吸水性、尺寸稳定性及电导率等性能进行了分析.结果表明,实验条件下接枝率随吸收剂量和单体浓度增加而增加,采用3mol·L-1的单体浓度减少均聚物;吸收剂量率为10～43Gy·min-1时,接枝率随剂量率变化不明显;以甲苯做溶剂可获得较高接枝率并保持膜的机械强度;IEC值、吸水性和电导率随接枝率增加而增大,是—SO3H、—Si—O—Si—交联结构和Si—OH基团共同作用的结果.接枝率72.5%时膜的IEC值为1.53mmol·g-1,高于Nafion117(0.89mmol·g-1),90℃吸水率为63%,尺寸稳定(优于Nafion117),质子电导率达1.5×10-2S·cm-1,获得了低于Nafion117的甲醇透过性,接枝率50.1%时甲醇透过系数0.82×10-6cm2·s-1.     

Graft Copolymerization of Methyl Methacrylate onto Chitosan Initiated by Potassium Ditelluratocuprate(III)

A novel redox system, potassium ditelluratocuprate(III) (DTC)–chitosan, was employed to initiate the graft copolymerization of methyl methacrylate (MMA) onto chitosan in alkali medium. The effects of reaction variables, such as the initiator concentration, ratio of monomer to chitosan, the pH value, as well as reaction temperature and time were investigated, and the grafting conditions were optimized. Graft copolymers with both high grafting efficiency (>90%) and percentage of grafting were obtained, and the rate of polymerization is higher, which indicated that the DTC–chitosan redox system is an efficient initiator for this graft copolymerization. The structures and the thermal property of chitosan and chitosan–g–PMMA were characterized by infrared spectroscopy (IR), X‐ray diffraction and thermogravimetric analysis (TGA). A mechanism is proposed to explain the generation of radicals and the initiation. The graft copolymer was used as the compatibilizer in blends of terpolyamide and chitosan. The scanning electron microscope (SEM) photographs indicated that the graft copolymer improved the compatibility of the blend.     

Use of polyacrylamide-grafted<Emphasis Type="Italic"> Plantago psyllium</Emphasis> mucilage as a flocculant for treatment of textile wastewater

The chemical modification of Plantago psyllium mucilage (Psy), an anionic polysaccharide, was done by grafting polyacrylamide (PAM) chains to prepare a graft-copolymer (Psy-g-PAM). It was synthesized in the presence of nitrogen using ceric ammonium nitrate–nitric acid redox initiator and characterized by IR spectroscopy, scanning electron microscopy and viscosity measurements. This grafted copolymer was tested for its flocculation efficiency in textile wastewater by the standard Jar test method. The effects of polymer concentration, pH and contact time on the percentage removal of solid wastes [total dissolved solids (TDS) and suspended solids (SS)] and color from textile effluent are reported. The optimum dose was found to be 1.6 mg l^–1, at which maximum solid removal (SS and TDS) was seen. The most suitable pH for TDS and color removal was neutral (7.0) and for SS removal alkaline pH (9.2) was found to be most suitable. The optimum treatment duration for solid waste removal was 5 h. The X-ray diffraction analysis of Psy-g-PAM and solid waste before and after treatment suggests the interaction of the solid waste and Psy-g-PAM copolymer.     

Polymer–Metal Complexes Obtained by Radiation‐Induced Grafting Process onto Polyester Fabrics

Abstract

This paper reports the preparation of chelating copolymers via grafting of acrylic acid, and/or acrylamide onto polyester microfiber (PETMF) fabrics using a γ‐radiation technique. The effect of monomer concentration on the grafting process at irradiation dose 20?kGy was studied. The prepared graft chains (PETMF‐g‐AA), (PETMF‐g‐AAm), and (PETMF‐g‐PAAc/PAAm) acted as chelating sites for some selected transition metal ions. The effect of grafting on mechanical properties of PETMF and its copolymer–metal complexes was investigated. The prepared chelating copolymers and their metal complexes were characterized using x‐ray (energy dispersive x‐ray, EDX), differential scanning calorimeter (DSC), color parameters, and electrical conductivity measurements. The possibility of practical uses for such prepared graft copolymer–metal complexes was discussed and determined. The observed results showed that the electrical conductivity of the grafted copolymers and their metal complexes are thermally activated. Moreover, the degree of grafting enhanced the conductivity values of the grafted and non‐complexed copolymer up to three orders of magnitude, on the other hand, the conductivity of the copolymer–metal complexes slightly increased.     

Preparation of cation-exchange membrane containing bi-functional groups by radiation induced grafting of acrylic acid and sodium styrene sulfonate onto HDPE: Influence of the synthesis conditions

Electron beam radiation induced grafting of acrylic acid (AA) and sodium styrene sulfonate (SSS) onto high-density polyethylene (HDPE) membranes was investigated by the pre-irradiation method, and a cation-exchange membrane containing bifunctional groups was synthesized. The effects of grafting conditions such as monomer concentration, radiation dose and temperature on grafting yield were studied. The dependence of grafting yield on pre-irradiation dose and monomer concentration was found to be 0.54 and 2.21, respectively. The activation energy for the grafting was calculated to be 22.2 kJ/mol. Infrared spectroscopy analysis of the grafted membrane confirmed the existence of sulfonate and carboxylic acid groups.     

Spectroscopic study of the penetration depth of grafted polystyrene onto poly(tetrafluoroethylene‐co‐perfluoropropylvinylether) substrates. 1. Effect of grafting conditions

This study concerns the radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐perfluoropropylvinylether) (PFA) substrates and the penetration depth of the graft. Grafting was obtained by the simultaneous irradiation method, and the spectroscopic analysis was made with the micro‐Raman technique. Effects of grafting conditions such as the type of solvent, dose rate, and irradiation dose on the grafting yield were investigated. Of the different solvents used, the most efficient in terms of increasing grafting yield were dichloromethane, benzene, and methanol, respectively. A mixture of methanol and dichloromethane used as a solvent for styrene achieved a higher degree of grafting and concentration of grafted polystyrene onto the surface of PFA substrates than solutions of the monomer in the separate solvents. The degree of grafting increased with increasing radiation dose up to 500 kGy, stabilizing above this dose. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield was accompanied by a proportional increase in the penetration depth of the grafts into the substrate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3191–3199, 2002     

Radiation grafting from binary monomer mixtures. I. Vinyl ether of monoethanolamine and vinyl ether of ethyleneglycol

Gamma-radiation grafting of vinyl ether of monoethanolamine and vinyl ether of ethyleneglycol (VEEG) on polyethylene films has been studied from binary monomer mixtures. The effect of co-monomer composition and total exposure radiation dose on the grafting process is investigated. A combination of potentiometric and gravimetric techniques is applied to determine the grafting degree of each monomer in the final graft copolymer. The presence of more active monomer VEEG in the mixture was found to enhance the grafting of both monomers because the increasing of copolymerization rate which in turn increases the total grafting degree. The modification of the hydrophilic properties of the graft copolymer is studied by examining the grafted films for water- and copper (II) ions uptake.     

Process parameters and their effect on grafting reactions in core/shell latexes

The grafting of methyl methacrylate (MMA) onto polybutadiene (PB) latexes prepared by seeded emulsion polymerization at 50°C was investigated as a function of: (a) initiator concentration used in the secondary polymerization, (b) monomer-to-polymer ratio, (c) the specific surface area of the seed latex, and (d) the degree of conversion. The thin layer chromatography/flame ionization detection (TLC/FID) technique was used to determine the proportion of graft copolymer in the core/shell latex, It was found that grafting PMMA onto PB depended upon the concentration of initiator, decreasing as the concentration was increased. The amount of grafting increased with increasing specific surface area of the seed latex, while the molecular weight of the acetone-soluble graft copolymer decreased. The amount of graft copolymer was found to decrease concurrently with increasing monomer-to-polymer ratio and degree of conversion. These results suggest a hydrogen abstraction mechanism in the formation of graft PB–PMMA through a chain transfer process.     

Graft copolymerisation of acrylamide onto cashew gum

The synthesis of cashew gum-g-polyacrylamide was carried out at 60 °C by a radical polymerisation using potassium persulphate as the redox initiator under N₂ atmosphere. A series of graft copolymers, varying in acrylamide concentration and keeping the concentration of the initiator and polysaccharide constant, was prepared. These graft copolymers were characterised by elemental analysis, infrared and ¹³C NMR spectroscopy, rheological studies, differential scanning calorimetry and thermogravimetric analysis. Comparisons amongst grafting parameters of the reaction of various natural polysaccharides with polyacrylamide (PAM) were carried out. High percentages of acrylamide conversion (%C) and grafting efficiency (%E) were obtained for cashew gum (CG), even with a low acrylamide/gum ratio. All copolymers had intrinsic viscosity and thus the hydrodynamic volume much higher than the CG value and closer to the PAM. The CG-g-PAM solution had an absolute viscosity at 2.5% concentration (wt./vol.) up to 33 and 3.3 times the CG and PAM values, respectively. Grafting of PAM chains onto the polysaccharide enhances its thermal stability.     

Radiation-induced graft polymerization of acrylamide I. Preparation conditions and gel determination for polyethylene-grafted films

Radiation-induced graft polymerization of acrylamide (AAm) onto low-density polyethylene(LDPE) film has been investigated. The appropriate reaction conditions at which the graft polymerization was carried out successfully were selected. It was observed that the grafting process was enhanced remarkably by using distilled water as diluent. In this grafting system ammonium ferrous sulphate (Mohr's salt) was used as inhibitor to minimize the homopolymerization of AAm and the suitable concentration of such inhibitor was found to be 3 wt %. The dependence of the grafting rate on the monomer concentration was calculated to be 2.9 order, regardless of the irradiation atmosphere (N₂ gas or under vacuum). When the radiation grafting process was carried out under vacuum, higher degrees of grafting were obtained as compared to those in nitrogen gas or in air atmosphere. Network structure was formed in the graft copolymer and the gel formation was determined in the p-xylene-extracted grafted films. Results showed good evidence that the grafting process takes place by the front mechanism.     

Superabsorbent materials derived from hydroxyethyl cellulose and bentonite: Preparation,characterization and swelling capacities

Superabsorbent polymers (SAPs) and composites (SAPCs) were prepared entirely by graft copolymerization of polyacrylamide (PAM) onto hydroxyethyl cellulose (HEC), using potassium persulfate (KPS) as an initiator, and N,N′-methylenebisacrylamide (MBA) as a crosslinker, in an aqueous solution. The extent of grafting was evaluated from % grafting efficiency (%GE) for various HEC/AM ratios, and a near optimal ratio was determined. Influences of various preparation parameters, i.e., the ratio of HEC/AM, amount of initiator and crosslinker, reaction temperature and time, and amount of filler on water swelling capacity of SAPs and SAPCs were studied. An FT-IR determination confirmed that the PAM was successfully grafted onto the HEC backbone, by showing absorption bands of the HEC backbone and new absorption bands from the grafted copolymer. The swelling capacity of SAPs and SAPCs depended strongly on different parameters, and the maximum swelling capacity was over 426 g/g and 538 g/g for the SAPs and SAPCs, respectively.     

Surface modification of polyethylene terephthalate using PEO-polybutadiene-PEO triblock copolymers

The initial step of thrombus formation on blood-contacting biomaterials is known to be adsorption of blood proteins followed by platelet adhesion. It is generally accepted that surface modification of the biomaterials with poly(ethylene oxide) (PEO) substantially reduces protein adsorption and cell adhesion. Dacron® (polyethylene terephthalate) fabric, which is one of the biomaterials commonly used in blood-contacting devices, was grafted with PEO. A simple two-step procedure for covalent grafting of PEO onto the surface of Dacron® fabric was used. The surface was first treated with PEO-polybutadiene-PEO (PEO-PB-PEO) triblock copolymer, to introduce a layer of double bonds onto the surface. The Dacron® surface was then exposed to a solution of Pluronic® F108 (PF108), a commercially available PEO-poly(propylene oxide)-PEO (PEO-PPO-PEO) triblock copolymer. The surface with two adsorbed layers of PEO-PB-PEO and PF108 was γ-irradiated in the presence of PF108 in the bulk solution for a total radiation dose of 0.8 Mrad. The bulk concentrations of PEO-PB-PEO and PF108 were varied to maximize the efficiency of PEO grafting. Fibrinogen adsorption on PEO-grafted surfaces was reduced more than 90%, compared with that on control surfaces, irrespective of the bulk concentrations of polymers used for grafting. Platelet adhesion was also reduced substantially by PEO grafting. Only a few round platelets were able to adhere to the PEO-grafted surface, while the control surface was fully covered with aggregates of activated platelets. PEO grafting on polyethylene terephthalate using PEO-PB-PEO and PEO-PPO-PEO block copolymers is a simple approach that can be used for various other biomaterials.     

Synthesis of antibacterial cotton fabric by radiation-induced grafting of [2-(Methacryloyloxy)ethyl]trimethylammonium chloride (MAETC) onto cotton

Gamma radiation has been used to covalently link polymer chains of [2-(Methacryloyloxy)ethyl]trimethylammonium chloride (MAETC) to cotton fabric by mutual radiation grafting. The grafted samples have been characterized for water uptake, surface morphology and thermal stability. Grafting extent was found to increase with the dose and monomer concentration. However high dose rate, O₂, inorganic salts and alcohols suppressed grafting. Radiation polymerized poly(MAETC) and MAETC-g-cotton samples were tested for their antibacterial efficacy against various bacteria and were found to possess significant antibacterial activity.     

SYNTHESIS OF POLYACRYLAMIDE WITH PENDANT POLY(BUTYL ACRYLATE) CHAINS USING THE MACROMER TECHNIQUE AND STUDIES ON THEIR PROPERTIES

INTRODUCTIONSince Milkovich and Chiang[1] developed a method of preparing copolymers with uniform side chains by usingthe macromer technique, the synthesis of copolymers with uniform side chains from different macromers hasbeen studied extensively. Milkovich et al. reported the synthesis of polystyrene macromer through termination ofliving polystyrene anions with methacryloyl chloride and its copolymerization with butyl acrylate to formthermoplastic elastomer[2]. Rempp[3] obtained polyoxy…     

Grafting polyelectrolytes onto polyacrylamide for flocculation 2. Model suspension flocculation and sludge dewatering

Low-molecular-weight high-charge-density cationic poly(diallyldimethylammonium chloride) (polyDADMAC) was grafted onto high-molecular-weight nonionic polyacrylamide (PAM) via a free radical mechanism using a gamma radiation technique. The graft copolymers having various charge densities were evaluated as flocculants for titanium dioxide (TiO₂) model suspensions, and as conditioners for a pulp and paper mill sludge. Their flocculation performance was optimized with respect to polymer composition, gamma irradiation time and polymer dosage. Measurements included turbidity, particle size distribution and drainage rates. The graft copolymers showed a significant improvement over the homopolymers and dual polymer systems in their flocculation and sludge dewatering performance. Received: 6 April 1998 Accepted in revised form: 28 August 1998