Chye H. Ang

Novel additives for accelerating radiation grafting of monomers to polymers in acid media.

Abstract Mineral acid and polyfunctional monomers in additive amounts (1% v/v) are shown to act synergistically in enhancing radiation grafting yields for a typical system involving the copolymerization of styrene in methanol to the polyolefins. Polyethylene and polypropylene films have been used as representative backbone polymers with divinylbenzene and trimethylol-propane triacrylate as typical polyfunctionals in the current work. The effect of dose rate on the copolymerization yield is reported. Grafting efficiency is shown to be enhanced in the presence of both additives. A theory for the role of additives is proposed. The synergistic effect also operates with polypropylene powder. Such an observation is shown to be important in applications of these copolymers for enzyme immobilization, heterogenization of catalytically active homogeneous metal complexes, insolubilization of analytical reagents and art restoration.

The nature of bonding during film formation of polyolefins and cellulose using UV and ionizing radiation initiation

Abstract The problems involved in bonding when monomers and/or polymers are polymerized under the influence of ionizing radiation and UV onto representative polar and non-polar materials, namely cellulose and polypropylene, are discussed. Two type radiation systems are compared, i.e. the simultaneous technique where reaction occurs from a solvent medium and the rapid cure, solvent free type process. The formation of a true carbon-carbon bond between film and trunk polymer during such polymerization reactions is shown to be of advantage for certain radiation processing applications. The possible role of charge-transfer intermediates in rapid cure film formation on natural and synthetic polymers is also considered.

Radiation and UV Grafting of Monomers to Polyolefins and Cellulose Acetate. Significance of These Studies in Reagent Insolubilization Reactions

Abstract In the simultaneous irradiation procedure, sensitized W radiation is shown to be a complementary initiator to ionizing radiation for the grafting of monomers to polyolefins. Parameters influencing the yield of graft have been considered, including the role of sensitizer, solvent, and the type of monomer. These results indicate why difficulties have been experienced by previous authors in photografting monomers to polymers using analogous procedures. Grafting of styrene to cellulose acetate using ionizing radiation at low total doses is also reported. Difficulties associated with the poor grafting yield to gel beads as opposed to films are considered predominantly in terms of moisture content and swelling of the gel beads. The feasibility of using the polyolefins and cellulose acetate beads modified by the present grafting methods in reagent insolubilization reactions is discussed.

The Effect of Additives for Accelerating Radiation Grafting: The Use of the Technique for Modification of Polymers Especially Polyolefins

Radiation grafting is a convenient one-step method for modifying the properties of polymers1,2. Both ultraviolet light3–7 and ionizing radiation8–12 are useful initiators for the process, however the latter method possesses advantages, especially with cobalt-60 type ionizing sources, because of the penetrating effect of the gamma rays. There are a number of procedures using ionizing radiation which can lead to grafting. Of these, the mutual or simultaneous technique is generally the most useful and will be discussed in depth in this article. Any method for accelerating the procedure is valuable, especially for those backbone polymers which are especially sensitive to ionizing radiation. In such instances, it is preferable to use the lowest total radiation dose to achieve a particular percentage graft.

Application of Radiation Grafting in Reagent Insolubilization

Radiation grafting is shown to be a method with considerable research and industrial potential for the insolubilization of a wide range of organic reagents on polymer surfaces. The principle of the method is outlined in detail and involves radiation-induced copolymerization of a monomer containing an appropriate functional group to a polymer, then attachment of the reagent by subsequent chemical reactions. The relative merits of the two relevant grafting methods for this purpose, namely pre-irradiation and the mutual technique, are evaluated. Typical experimental procedures for each method are discussed. The mutual technique is shown to be more satisfactory for insolubilization reactions because of the lower radiation doses needed to achieve a particular percentage graft, resulting in less radiation damage to the backbone polymer. Variables influencing the efficiency of the mutual grafting method are reviewed, including solvent, dose rate, and dose. Additives for optimizing the grafting yield and properties are considered, including mineral acid and polyfunctional monomers. Methods for reducing competing homopolymerization are summarized. Three examples of the application of the mutual radiation grafting technique for insolubilization reactions are discussed in detail. These include immobilization of enzymes, heterogenization of catalytically active homogeneous metal complexes, and the anchoring of analytical reagents to form ion exchange resins.

Novel Radiation and UV Grafting Methods for the Immobilization of Enzymes and the Heterogenization of Catalytically Active Homogeneous Metal Complexes

UV is shown to be a valuable complementary initiator to ionizing radiation for the grafting of monomers to trunk polymers using the simultaneous irradiation procedure. The effect of sensitizer in these UV reactions has been studied. The results show why previous authors have experienced difficulty in photo-grafting to polymers using analogous procedures. Novel methods for accelerating both gamma ray and UV grafting to synthetic polymers are discussed. Typical applications of these unique copolymers for the immobilization of enzymes (e.g. trypsin, peroxidase, B-galactosidase), the heterogenization of homogeneous metal complexes possessing catalytic activity (e.g. hydrogenation) and the anchoring of reagents such as 8-hydroxyquinoline for use in catalysis are considered. For this work the UV method is shown to possess a number of advantages when compared with copolymers prepared by ionizing radiation. The present data confirm the initial promise of these grafting reactions for general reagent insolubilization processes, particularly catalysis.

Novel UV and Radiation Polymerisation Methods for Modifying Polyolefins, Cellulose and Leather

The possibility of being able to modify existing trunk polymers with monomers by one-step grafting methods is a potentially very useful technique for increasing the range of renewable resource materials available for polymer applications. Both ionising radiation1–7 and UV6–11are convenient initiatiors for these reactions. For high radiation grafting yields with certain materials, relatively large radiation doses or inert atmospheres are required during reaction. Methods for lowering the total radiation dose are thus useful, both economically and also for minimising competing degradation of the trunk polymer, especially where such materials are radiation sensitive.