Ronald Levot

Insolubilisation of biologically active materials with novel radiation graft copolymers

Abstract The use of radiation grafting to immobilise a typical enzyme, trypsin, is reported. The technique involves radiation grafting to a backbone polymer a monomer containing an appropriate functional group to which the enzyme is bonded. In the present work, p-nitrostyrene has been grafted to representative trunk polymers, polypropylene and PVC, the nitro group in the resulting copolymer converted to the isothiocyanato derivative to which trypsin is attached. Of importance to this insolubilisation process, especially for radiation sensitive backbone polymers, is the inclusion of additives which enhance grafting. A new class of additives which increase the grafting yields is reported using as representative backbone polymers, naturally occurring cellulose and synthetic low density polyethylene. The new additives are specific metal salts such as LiClO4. The reactivity of these salts in grafting enhancement has been compared with that of mineral acid which has previously been used as an additive to increase grafting yields in both preirradiation and simultaneous techniques. A new model for grafting enhancement in the presence of the metal salts as well as acids is proposed whereby increased grafting yields are attributed to increased partitioning of monomer into the graft region in the presence of ionic solutes. The value of these additives in preparing copolymers suitable for general reagent insolubilisation reactions is discussed.

Use of Additives to Enhance Radiation Grafting of Monomers to Polyvinyl Chloride) and Application of These PVC Copolymers to Immobilization of Enzymes and Heterogenization of Homogeneous Metal Complexes

Abstract The effect of solvent structure, particularly the application of the low molecular weight aliphatic alcohols, on the radiation grafting of monomers to PVC with the use of cobalt-60 and the simultaneous procedure is discussed. The addition of sulfuric acid to a typical system such as styrene/methanol/PVC enhances both the grafting yield and the size of the Trommsdorff peak. The results are shown to be consistent with a mechanism involving charge-transfer complex formation between monomer and grafting site in PVC. The role of hydrogen atoms in these reactions, particularly in the presence of sulfuric acid, is emphasized, and the importance of the magnitude of G(H) on the grafting yields and the Trommsdorff effect is discussed. These principles, developed for radiation grafting styrene, are shown to be of value for the radiation copolymerization of p-nitrostyrene and vinyl phosphorus monomers to PVC. The use of these PVC copolymers for immobilizing enzymes such as trypsin and heterogenizing typical ...

Acid Enhancement Effects in the Radiation Grafting of Monomers to Polyethylene and the Use of These Copolymers for Enzyme Immobilization and Related Reactions

Abstract The use of mineral acid to enhance the radiation grafting of monomers to trunk polymers such as polyethylene is shown to be of value for the insolubilization of enzymes and the hetero-genization of catalytically active homogeneous complexes. Two general methods are described showing how acid enhancement effects can be used in the immobilization reactions. In the first technique, styrene is grafted, and the resulting co-polymer can be nitrated followed by subsequent chemical reactions to yield an appropriate substituent to which the attach ment processes can occur. Alternatively, p-nitrostyrene can be grafted directly. In the latter method, the acid enhancement is shown to be valuable, since the monomer is deactivating in radiation grafting and any technique for improving yields is useful. The acid enhancement effect is also shown to be of value for grafting to polyethylene, since this backbone polymer is less susceptible to grafting than the other two trunk polymers studied, i. e., polypropylene ...

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.

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.

Negative ion mass spectra of organometallic compounds; electron capture-induced decarbonylation of an ester group in a π-arene metal carbonyl

Secondary electron capture by (π-methyl benzoate)tricarbonylchromium yields a molecular anion which undergoes decarbonylation and further loss of three CO groups; in addition, Cr– ions have been identified in the 70 eV negative ion mass spectrum of this compound.