Grafting free radical initiator

Etherification and esterification of hydroxyl groups produce derivatives, some of which are produced commercially. Derivatives may also be obtained by graft polymerization wherein free radicals, initiated on the starch backbone by ceric ion or irradiation, react with monomers such as vinyl or acrylyl derivatives. A number of such copolymers have been prepared and evaluated in extmsion processing (49). A starch—acrylonitrile graft copolymer has been patented (50) which rapidly absorbs many hundred times its weight in water and has potential appHcations in disposable diapers and medical suppHes. 

Polymers ndResins. / fZ-Butyl peroxyneopentanoate and other peroxyesters of neopentanoic acid can be used as free-radical initiators for the polymeri2ation of vinyl chloride [75-01-4] (38) or of ethylene [74-85-1]. These peresters have also been used in the preparation of ethylene—vinyl acetate copolymers [24937-78-8] (39), modified polyester granules (40), graft polymers of arninoalkyl acrylates with vinyl chloride resins (41), and copolymers of A/-vinyl-pyrrohdinone [88-12-0] and vinyl acetate [108-05-4] (42). They can also be used as curing agents for unsaturated polyesters (43). 

A waterborne system for container coatings was developed based on a graft copolymerization of an advanced epoxy resin and an acryHc (52). The acryhc-vinyl monomers are grafted onto preformed epoxy resins in the presence of a free-radical initiator grafting occurs mainly at the methylene group of the aHphatic backbone on the epoxy resin. The polymeric product is a mixture of methacrylic acid—styrene copolymer, soHd epoxy resin, and graft copolymer of the unsaturated monomers onto the epoxy resin backbone. It is dispersible in water upon neutralization with an amine before cure with an amino—formaldehyde resin. 

Free radical grafting without using a free radical initiator. 

The creation of active sites as well as the graft polymerization of monomers may be carried out by using radiation procedures or free-radical initiators. This review is not devoted to the consideration of polymerization mechanisms on the surfaces of porous solids. Such information is presented in a number of excellent reviews [66-68]. However, it is necessary to focus attention on those peculiarities of polymerization that result in the formation of chromatographic sorbents. In spite of numerous publications devoted to problems of composite materials produced by means of polymerization techniques, articles concerning chromatographic sorbents are scarce. As mentioned above, there are two principle processes of sorbent preparation by graft polymerization radiation-induced polymerization or polymerization by radical initiators. We will also pay attention to advantages and deficiencies of the methods. 

A polymeric composition for reducing fluid loss in drilling muds and well cement compositions is obtained by the free radical-initiated polymerization of a water-soluble vinyl monomer in an aqueous suspension of lignin, modified lignins, lignite, brown coal, and modified brown coal [705,1847]. The vinyl monomers can be methacrylic acid, methacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, vinylacetate, methyl vinyl ether, ethyl vinyl ether, N-methylmethacrylamide, N,N-dimethylmethacrylamide, vinyl sulfonate, and additional AMPS. In this process a grafting process to the coals by chain transfer may occur. 

As already shown, it is technically possible to incorporate additive functional groups within the structure of a polymer itself, thus dispensing with easily extractable small-molecular additives. However, the various attempts of incorporation of additive functionalities into the polymer chain, by copolymerisation or free radical initiated grafting, have not yet led to widespread practical use, mainly for economical reasons. Many macromolecular stabiliser-functionalised systems and reactive stabiliser-functionalised monomers have been described (cf. ref. [576]). Examples are bound-in chromophores, e.g. the benzotriazole moiety incorporated into polymers [577,578], but also copolymerisation with special monomers containing an inhibitor structural unit, leading to the incorporation of the antioxidant into the polymer chain. Copolymers of styrene and benzophenone-type UV stabilisers have been described [579]. Chemical combination of an antioxidant with the polymer leads to a high degree of resistance to (oil) extraction. 

A radical initiator based on the oxidation adduct of an alkyl-9-BBN (47) has been utilized to produce poly(methylmethacrylate) (48) (Fig. 31) from methylmethacrylate monomer by a living anionic polymerization route that does not require the mediation of a metal catalyst. The relatively broad molecular weight distribution (PDI = (MJM ) 2.5) compared with those in living anionic polymerization cases was attributed to the slow initiation of the polymerization.69 A similar radical polymerization route aided by 47 was utilized in the synthesis of functionalized syndiotactic polystyrene (PS) polymers by the copolymerization of styrene.70 The borane groups in the functionalized syndiotactic polystyrenes were transformed into free-radical initiators for the in situ free-radical graft polymerization to prepare s-PS-g-PMMA graft copolymers. 

The possibility of using graft polymerization of styrene on to allylated wood to provide covalent bonding between surfaces was also investigated (Ohkoshi, 1991). In this case, a free-radical initiator (BPO) was present in the styrene monomer that was used to impregnate the allylated wood, prior to hot-pressing. Bond strength was determined by... 

It is worth noting in advance that nearly all methods worked with, so far,-involve the free radical initiating of actual polymerization of the monomer forming the grafted side chains rather than directly linking... 

Usually, free-radical initiators such as azo compounds or peroxides are used to initiate the polymerization of acrylic monomers. Photochemical and radiation-initiated polymerizations are also well known. Methods of radical polymerization include bulk, solution, emulsion, suspension, graft copolymerization, radiation-induced, and ionic with emulsion being the most important. 

Graft and block copolymers of cotton cellulose, in fiber, yam, and fabric forms, were prepared by free-radical initiated copolymerization reactions of vinyl monomers with cellulose. The properties of the fibrous cellulose-polyvinyl copolymers were evaluated by solubility, ESR, and infrared spectroscopy, light, electron, and scanning electron microscopy, fractional separation, thermal analysis, and physical properties, including textile properties. Generally, the textile properties of the fibrous copolymers were improved as compared with the properties of cotton products. 

The modification of the properties of fibrous cotton cellulose through free-radical initiated copolymerization reactions with vinyl monomers has been investigated at the Southern Laboratory for a number of years. Both graft and block copolymers are formed. Under some experimental conditions the molecular weight of the polyvinyl polymer, covalently... 

Elastomers, prepared by free-radical initiated copolymerization of ethyl acrylate with cellulose to several hundred percent extent of grafting of poly (ethyl acrylate) onto cellulose, exhibited rubber-like behavior and second-order transition temperatures. Cellulose-poly (ethyl acrylate) elastomers had transition temperatures below —35°C, about — 20°C, and below 5°C when measured in ethyl acetate, dry air, and water, respectively (43, 44). 

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-... 

This method involves graft copolymerisation using redox initiators [70] or free radical initiators [71, 72, 73] usually in the solution phase, occasionally under the influence of temperature, predominantly in the latter case. Redox systems have extensively been used to generate active sites especially on the natural polymers [74] (like cellulose). Transition metals viz. Cr+6, V+5, Ce+4,... 

Co+3, Mn+2 and Fe+2 have been found to be effective in producing free radical sites on the polymer backbone through the alcohol groups present on them [75]. In an alternative method, free radical initiators like BPO and AIBN are thermo-chemically activated to give rise to macro-radical sites on polymer backbone to initiate grafting of desired vinylic monomer. The efficiency of these initiators was found to be predominantly dependent on the nature of monomer while the course of reaction depended on the relative reactivity of monomer versus that of the macro-radical. 

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