Monomers graft polymerization

Szymczak and Manson, 1974a,b White and Mann, 1967). As with electron-irradiated polyethylene, crosslinked poly(vinyl chloride) formulations (usually plasticized) are now of commercial interest as wire and cable coatings and insulation [see, for example, Nicholl (1969)]. In the following sections, typical properties will be described and discussed details of other standard polymer-monomer graft polymerizations are given by, e.g., Chapiro (1962) and Charlesby (1960). 

In all manufacturing processes, grafting is achieved by the free-radical copolymerization of styrene and acrylonitrile monomers in the presence of an elastomer. Ungrafted styrene—acrylonitrile copolymer is formed during graft polymerization and/or added afterward. 

Decabromodiphenyl Oxide—Polyacrylate Finishes. An alternative to the diffusion technique is the appHcation of decabromodiphenyl oxide on the surface of fabrics in conjunction with binders (131). Experimental finishes using graft polymerization, in situ polymerization of phosphoms-containing vinyl monomers, or surface halogenation of the fibers also have been reported (129,130,132,133). 

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. 

In the presence of radical initiators such as benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), persulfates (S208 ), etc., grafting of vinyl monomers onto polymeric backbones involves generation of free radical sites by hydrogen abstraction and chain transfer processes as described below ... 

The use of ceric ions to initiate graft polymerization was first discussed by Mino and Kaizerman in 1958 [12]. Schwab and coworkers [13] were among the first to extend this method to the grafting of cellulose. Following their work, numerous papers have appeared in the literature on the grafting of vinyl monomers onto cellulose by this technique. 

If a vinyl monomer is polymerized in the presence of cellulose by a free radical process, a hydrogen atom may be abstracted from the cellulose by a growing chain radical (chain transfer) or by a radical formed by the polymerization catalyst (initiator). This leaves an unshared electron on the cellulose chain that is capable of initiating grafting. As cellulose is a very poor transfer agent [10], very little copolymer results from the abstraction of hydrogen atoms by a growing chain radical. The... 

Graft polymerization of methylmethacrylate monomer onto pulps of different residual lignin contents using ceric ammonium nitrate as the initiator was carried out to study the influence of this residual lignin on the graft-ability of these pulps (Fig. 3). From this figure one can... 

Graft polymerization can be accomplished provided that active sites are available on the surface for reaction with monomers. Two fundamental methods of creating... 

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. 

Chromatographic Packings Prepared by Graft Polymerization of Monomers... 

Prior irradiation of the backbone polymer in the presence of oxygen and subsequent monomer grafting by polymeric peroxides... 

The theory of radiation-induced grafting has received extensive treatment [21,131,132]. The typical steps involved in free-radical polymerization are also applicable to graft polymerization including initiation, propagation, and chain transfer [133]. However, the complicating role of diffusion prevents any simple correlation of individual rate constants to the overall reaction rates. Changes in temperamre, for example, increase the rate of monomer diffusion and monomer... 

Mixtures of two or more monomers can polymerize to form copolymers. Many copolymers have been developed to combine the best features of each monomer. For example, poly(vinyl chloride) (called a homopolymer because it is made from a single monomers) is brittle. By copolymerizing vinyl chloride with vinyl acetate, a copolymer is obtained that is flexible. Arrangement of the monomer units in a copolymer depends on the rates at which the monomers react with each other. Graft copolymers are formed when a monomer is initiated by free radical sites created on an already-formed polymer chain. 

Photoinduced free radical graft copolymerization onto a polymer surface can be accomplished by several different techniques. The simplest method is to expose the polymer surface (P-RH) to UV light in the presence of a vinyl monomer (M). Alkyl radicals formed, e.g. due to main chain scission or other reactions at the polymer surface can then initiate graft polymerization by addition of monomer (Scheme 1). Homopolymer is also initiated (HRM-). 

The in situ bulk polymerization of vinyl monomers in PET and the graft polymerization of vinyl monomers to PET are potential useful tools for the chemical modification of this polymer. The distinction between in situ polymerization and graft polymerization is a relatively minor one, and from a practical point of view may be of no significance. In graft polymerization, the newly formed polymer is covalently bonded to a site on the host polymer (PET), while the in situ bulk polymerization of a vinyl monomer results in a polymer that is physically entraped in the PET. The vinyl polymerization in the PET is usually carried out in the presence of the swelling solvent, thereby maintaining the swollen PET structure during polymerization. The swollen structure allows the monomer to diffuse in sufficient quantities to react at the active centers that have been produced by chemical initiation (with AIBM) before termination takes place. 

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. 

As was shown, the rate of graft polymerization and the composition of grafted copolymers depend on the monomer concentration, temperature, and the composition of fluorpolymer support. The former also depends on the dose of previous irradiation of the fluoropolymer support. It was assumed that the structure of the composites obtained is close to the core-shell type. 

Grafting from method, 7 652-653 Grafting onto method, 7 654 Grafting process, 73 537 Grafting through method, 7 653 Graft polymerization. See also Graft copolymerization ABS, 7 419, 421 acrylic ester monomers, 7 386 of methacrylic ester polymers, 76 289-290... 

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