Radical graft polymerisation

Instantly after plasma treatment, the LDPE foil is immersed in an aqueous solution of acrylic acid (AA) (10 vol%) and sodium metabisulfite (0.1 wt%) for 24 h at 30 °C, in order to initiate the radical graft polymerisation of AA onto the activated surface. Following AA polymerisation, polyacrylic acid (PAA) brushes are created on the LDPE surface which are suitable for binding antibacterial agents. To remove weakly bound PAA and unreacted AA species on the surface, the grafted foils should be washed with deionised water at 30 °C. 

Type AD-G is used in an entirely different sort of formulation. The polymer is designed for graft polymerisation with methyl methacrylate. Typically, equal amounts of AD-G and methyl methacrylate are dissolved together in toluene, and the reaction driven to completion with a free-radical catalyst, such as bensoyl peroxide. The graft polymer is usually mixed with an isocyanate just prior to use. It is not normally compounded with resin. The resulting adhesive has very good adhesion to plasticised vinyl, EVA sponge, thermoplastic mbber, and other difficult to bond substrates, and is of particular importance to the shoe industry (42,43). 

The common feature of these materials was that all contained a high proportion of acrylonitrile or methacrylonitrile. The Vistron product, Barex 210, for example was said to be produced by radical graft copolymerisation of 73-77 parts acrylonitrile and 23-27 parts by weight of methyl acrylate in the presence of a 8-10 parts of a butadiene-acrylonitrile rubber (Nitrile rubber). The Du Pont product NR-16 was prepared by graft polymerisation of styrene and acrylonitrile in the presence of styrene-butadiene copolymer. The Monsanto polymer Lopac was a copolymer of 28-34 parts styrene and 66-72 parts of a second monomer variously reported as acrylonitrile and methacrylonitrile. This polymer contained no rubbery component. 

In the early 1970s, surface modification of most polymers was achieved using redox initiators. Ce+4-induced initiation was employed to achieve surface grafting of acrylamide onto LDPE film [117]. The film was first oxidised by chromic acid and then reduced with diborane to form a hydroxyl-rich surface which was then used to initiate graft polymerisation of acrylamide using Ce+4/HN03. The mechanism of chromic-acid-facilitated surface oxidation of LDPE surface is shown in Scheme 6a and that of free-radical generation is represented in Scheme 6b. 

Graft copolymers are obtained by subsequent radical emulsion polymerisation of olefinic unsaturated monomers in the presence of functionalized siloxane particles. Scheme 3 illustrates that the graft... 

Graft copolymers can be prepared by radical grafting of a polymerisable monomer A onto a reactive polymer backbone B. As a result of the grafting reaction, a complex product is obtained comprising the graft copolymer AB, residual ungrafted polymer backbone B and homopolymer A. 

Functionalised PO as block and graft copolymers used as compatibilisers or to increase interactions with other materials are prepared by free radical grafting (the simplest method), metallocene-catalysed copolymerisation of olefins with functional monomers, or anionic polymerisation (silane-containing PO). They are also produced by controlled/living polymerisation techniques such as nitroxide-mediated controlled radical polymerisation, atom transfer radical polymerisation (ATRP), and reversible addition-fragmentation chain transfer (RAFT). 

Experiments were performed by varying both redox system concentration and reaction temperature (Table 1). Homopolymerization of vinyl acetate (Run VAO) was also carried out under the same experimental conditions in the absence of lignin. Moreover, in order to get an insight on the free-radical grafting mechanism, the polymerisation of vinyl acetate was performed under the same conditions in the presence of 2-methoxy-4-methylphenol (MAF), a model compound of lignin functional groups. 

Typically, a solid epoxy of 3000 to 4000 EEW (Epikote 1007 or 1009 types or an analogue material manufactured by the chain extension of a lower M liquid epoxy resin) is modified to provide an acid functional epoxy. In general, the acid functionality ctm be conferred by two methods, acid capping (see resin 1 and resin 2) of the oxirane groups or by the graft polymerisation of an epoxy with a carbonyl functional co-polymer (see resin 3). The co-polymer can consist of Ae reaction product of a free radical polymerisation of any approved ethylenic unsaturated monomers containing carbon-carbon unsaturadon, e.g. carboxyl functional acrylic monomers, (acrylic add, methacrylic acid, etc.), the lower alkyl esters, vinyl monomers (acrylamides), vinyl esters (vinyl acetate, vinyl butyrate), vinyl aromatic monomers (styrene, a methylstyrene) etc. The acrylic caj ing resin is add fimctional, being based upon either methacrylic or acrylic acid. The former is normally preferred. An acid value of 50-100 mg KOH/g would be typical. 

The monomers are added to the solution of epoxy in order that a free radical initiated polymerisation can take place in the presence of the epoxy. The grafting of the addition polymer onto the aliphatic carbons of the epoxy, takes place during this polymerisation stage. 

Mention may finally be made of graft polymers derived from natural rubber which have been the subject of intensive investigation but which have not achieved commercial significance. It has been found that natural rubber is an efficient chain transfer agent for free-radical polymerisation and that grafting appears to occur by the mechanism shown in Figure 30.8. 

In the second stage of the reaction, the free radical produced on the backbone of the base polymer initiates polymerisation which results in the formation of graft copolymerisation as under ... 

Similar surface-supported amides have been derived from the Sm" amide Sm N-(SiHMe)2 2(thf)x by grafting on MCM-41, MCM-48 or AS-200 further elaboration led to the formation of the corresponding Sm-fluorenone ketyl, which was shown to contain surface-confined ketyl radicals.Treatment of Sm N(SiHMe2)2 (thf)x MCM-41 with MeOH, AlHBu 2 or Si(H)Me2-substituted indene gave surface-supported catalysts for methyl methacrylate polymerisation. 

When the decomposition is performed in the presence of unsaturated monomers (styrenic, acrylic...) a free-radical polymerisation can be initiated and grafting occurs ... 

The use of reactive antioxidants containing two polymerisable polymer-reactive functions in the same antioxidant molecule is outlined here. Careful choice of the processing parameters, the type, and the amount of free radical initiator can lead to very high levels of antioxidant grafting [53, 57]. For example, melt grafting of concentrates (e.g. 5-20 wt%) of the di-acrylate hin-... 

Metallic ions such as Fe+3, Fe+2 and Cu+2 are known to have an inhibitory effect on free-radical polymerisation and have been used for several years in the radiation grafting systems to interdict homopolymer formation. The mechanism of their action is meticulously discussed in the literature [195,... 

Polymer brushes are polymers tethered to a surface via one end. The connection to the surface can be covalent or non-covalent, and the brushes can be made via grafting to or grafting from the surface. In the past few years, there has been considerable interest in the growth of polymer brushes via surface-initiated polymerisations from (patterned) initiator-functionalised SAMs.62,63 For example, we have recently shown that surface confined Atom Transfer Radical Polymerisations (ATRP) in aqueous solvents leads to rapid and controlled... 

This explanation for the acid effect on the radiation polymerisation of styrene solutions has a direct application in a grafting context in that higher G(H) yields or lowered effective concentrations of radical scavenging impurities will enhance existing hydrogen abstraction reactions from the substrate to create potential grafting sites as well as increasing the... 

The use of borane-containing monomers clearly presents an effective and general approach in the functionalisation of polyolefins, which has the following advantages stability of the borane moiety to coordination catalysts, solubility of borane compounds in hydrocarbon solvents (such as hexane and toluene) used as the polymerisation medium, and versatility of borane groups, which can be transformed to a remarkable variety of functionalities as well as to free radicals for graft-form polymerisations. The functionalised polymers are very effective interfacial modifiers in improving the adhesion between polyolefin and substrates and the compatibility in polyolefin blends and composites [518],... 

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