Poly vinyl monomer grafted

The polymerization reaction in aqueous suspension of vinyl chloride in the presence of an ethylene-propylene saturated elastomer occurs with the formation of poly (vinyl chloride) homopolymer and rubber-poly (vinyl chloride) grafted copolymers. The first grafting reaction proceeds as far as diffusion of the monomer inside the particles in suspension is possible afterwards, some chain branching of grafted PVC is possible. Under our experimental conditions the amount of grafted rubber does not exceed 60% of the initial rubber and is little influenced by the type of initiator used. 

The macromonomers thus obtained exhibit molecular weights as low as 1000. They were copolymerized with monomers such as styrene and butyl acrylate whereby graft copolymers with poly(vinyl chloride) grafts were obtained. 

T. Nonaka, T. Ogata and S. Kurihara, Preparation of poly(vinyl alcohol)-graft-A-isopropylacrylamide copolymer membranes and permeation of solutes through the membranes, J. Appl. Polym. Sci., 1997, 66, 209 T. Ogata, S. Kurihara and T. Nonaka, Preparation and properties of poly(vinyl alcohol)-graft-A-isopropylacrylamide and other monomers terpolymer membranes, Nippon Kagaku Zasshi, 1995, 909-915. 

Table 2. Contact angles of water on poly (vinyl alcohol) grafted with various monomers...

FIG. 13 Experimental and calculated poly(vinyl acetate) graft yield data. The initial monomer, surface vinylsilane, and ABVN initiator concentrations are [Mq ] = 4.33 M, =... 

In the suspension polymerization of PVC, droplets of monomer 30—150 p.m in diameter are dispersed in water by agitation. A thin membrane is formed at the water—monomer interface by dispersants such as poly(vinyl alcohol) or methyl cellulose. This membrane, isolated by dissolving the PVC in tetrahydrofuran and measured at 0.01—0.02-p.m thick, has been found to be a graft copolymer of polyvinyl chloride and poly(vinyl alcohol) (4,5). Early in the polymerization, particles of PVC deposit onto the membrane from both the monomer and the water sides, forming a skin 0.5—5-p.m thick that can be observed on grains sectioned after polymerization (4,6). Primary particles, 1 p.m in diameter, deposit onto the membrane from the monomer side (Pig. 1), whereas water-phase polymer, 0.1 p.m in diameter, deposits onto the skin from the water side of the membrane (Pig. 2) (4). These domain-sized water-phase particles may be one source of the observed domain stmcture (7). 

The theory of radiation-induced grafting has received extensive treatment. The direct effect of ionizing radiation in material is to produce active radical sites. A material s sensitivity to radiation ionization is reflected in its G value, which represents the number of radicals in a specific type (e.g., peroxy or allyl) produced in the material per 100 eV of energy absorbed. For example, the G value of poly(vinyl chloride) is 10-15, of PE is 6-8, and of polystyrene is 1.5-3. Regarding monomers, the G value of methyl methacrylate is 11.5, of acrylonitrile is 5.6, and of styrene is >0.69. 

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. 

Radiation Induced Reactions. Graft polymers have been prepared from poly(vinyl alcohol) by the irradiation of the polymer-monomer system and some other methods. The grafted side chains reported include acrylamide, acrylic acid, acrylonitrile, ethyl acrylate, ethylene, ethyl methacrylate, methyl methacrylate, styrene, vinyl acetate, vinyl chloride, vinyl pyridine and vinyl pyrrolidone (13). Poly(vinyl alcohols) with grafted methyl methacrylate and sometimes methyl acrylate have been studied as membranes for hemodialysis (14). Graft polymers consisting of 50% poly(vinyl alcohol), 25% poly(vinyl acetate) and 25% grafted ethylene oxide units can be used to prepare capsule cases for drugs which do not require any additional plasticizers (15). 

Graft polymerization of monomers such as acrylic acid on core particles consisting of magnetic iron oxide embedded in cross-linked poly (vinyl alcohol) (PVA) has been described previously (2). 

The synthetic methods and chemical characterization data for the various polymeric materials to be discussed in this work have been reported elsewhere [6-8]. In some cases copolymerization of the unchlorinated oxazolidinone monomer with other common monomers such as acrylonitrile, vinyl chloride, styrene, and vinyl acetate, using potassium persulfate as an initiator, was performed. In other cases the unchlorinated oxazolidinone monomer was grafted onto polymers such as poly(acrylonitrile), poly(vinyl chloride), poly(styrene), poly(vinyl acetate), and poly(vinyl alcohol), again using potassium persulfate as an initiator. 

Here we discuss dispersion polymerizations that are not related to vinyl monomers and radical polymerization. The first one is the ring-opening polymerization of e-caprolactone in dioxane-heptane (30). A graft copolymer, poly(dodecyl acrylate)-g-poly(e-caprolactone), is used as a stabilizer. The polymerization proceeds via anionic or pseudoanionic mechanism initiated by diethylaluminum ethoxide or other catalysts. The size of poly(caprolactone) particles depends on the composition of stabilizer, ranging from 0.5 to 5 i,m. Lactide was also polymerized in a similar way. Poly(caprolactone) and poly(lactide) particles with a narrow size distribution are expected to be applied as degradable carriers of drugs and bioactive compounds. 

The results suggests that the copolymer has a graft structure and that the mastication medium involves three kinds of domains. The first is the inner domain of poly(vinyl chloride) which is only slightly penetrated by monomer. Polymerization is initiated by macroradicals created in the PVC domain causing the formation of a true copolymer. Short radical segments arising from transfer reactions migrate into the third external domain which consists practically entirely of pure monomer and there initiate polymerization. The second domain is the surface of the resin particle which is swollen by monomer. The free radicals created by bond rupture appear in this second domain. 

The idea of the preparation of porous polymers from high internal phase emulsions had been reported prior to the publication of the PolyHIPE patent [128]. About twenty years previously, Bartl and von Bonin [148,149] described the polymerisation of water-insoluble vinyl monomers, such as styrene and methyl methacrylate, in w/o HIPEs, stabilised by styrene-ethyleneoxide graft copolymers. In this way, HIPEs of approximately 85% internal phase volume could be prepared. On polymerisation, solid, closed-cell monolithic polymers were obtained. Similarly, Riess and coworkers [150] had described the preparation of closed-cell porous polystyrene from HIPEs of water in styrene, stabilised by poly(styrene-ethyleneoxide) block copolymer surfactants, with internal phase volumes of up to 80%. 

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