Grafting reactive

Malkovsky M, Edwards AJ, Hunt R et al. (1983) T-cell-mediated enhancement of host-versus-graft reactivity in mice fed a diet enriched in vitamin A acetate. Nature 24-30 302(5906) 338-340... 

Of major interest is the development of combinatorial methodologies for the discovery of novel catalysts [45]. The DCCA CL scheme may be applied towards the same goal by grafting reactive groups to the basic components so as to generate DCLs of potentially catalytic constituents. The self-assembly of an inorganic catalyst represents a case in point [46]. 

Low-density polyethylene (LDPE) is commonly used biomaterial which possesses fairly good grafting reactivity compared to other common polymeric materials. A number of plasma modification and plasma polymerization systems have been employed in order to incorporated oxygen-containing functional groups onto polyethylene surfaces for biomaterial applications. i Tiie aim of this work was to introduce acidic sulfur-containing functional groups onto LDPE surfaces by plasma treatment and to assess the potential blood compatibility of the modified materials. 

Incompatibility problems with organic and inorganic spherical fillers in plastics may be overcome by grafting reactive groups on their surface or adding coupling agents. 

Table 2 Ultraviolet embrittlement times (EMT) of PP films containing different grafted reactive photostabilizers, based on HALS and UVA functions, when used alone and in combination with other stabilizers (extraction in dichloromethane)...

It is important to point out here that there are different approaches to the grafting of antioxidants on polymers, each with its set of advantages and disadvantages. However, the behavior of grafted reactive antioxidants is similar to that... 

Grafting Reactive Functional Molecules onto Lignin. 51... 

Silane crosslinking works by first grafting reactive groups onto the PE molecule by addition of silanes and very small amounts of peroxide, in a one- or two-stage extrusion process. The crosslinking is effected by moisture or water and is accelerated by a tin catalyst [36]. 

Good adhesion between the dispersed rubber phase and the continuous polystyrene phase is one requirement for improving the impact strength of rubber modified blends. Adhesion can be improved by compatibilization. There are several ways that this can be done. One way is to add molecules to the resin mixture that interact with, or have molecular similarities to, both phases. These are called compatibilizers. Another way to improve adhesion is to graft reactive substituents onto the molecules of one or both phases. Properly chosen, these grafted units interact with... 

Moreover, the chemist has the possibility to graft reactive functional groups on the blocks to promote chemical reactions between the blocks and the surrounding chains of the hosting polymer to improve adhesive strength by covalent bonding. 

Remember from Sec. 1.3 that graft copolymers have polymeric side chains which differ in the nature of the repeat unit from the backbone. These can be prepared by introducing a prepolymerized sample of the backbone polymer into a reactive mixture—i.e., one containing a source of free radicals—of the side-chain monomer. As an example, consider introducing polybutadiene into a reactive mixture of styrene ... 

Reactive Flame Retardants. Reactive flame retardants become a part of the polymer by either becoming a part of the backbone or by grafting onto the backbone. Choice of reactive flame retardant is more complex than choice of an additive type. The reactive flame retardant can exert an enormous effect on the final properties of the polymer. There are also reactive halogenated compounds used as iatermediates to other flame retardants. Tables 8 and 9 Hst the commercially avaHable reactive flame retardants and iatermediates. 

Brominated Styrene. Dibromostyrene [31780-26 ] is used commercially as a flame retardant in ABS (57). Tribromostyrene [61368-34-1] (TBS) has been proposed as a reactive flame retardant for incorporation either during polymerization or during compounding. In the latter case, the TBS could graft onto the host polymer or homopolymerize to form poly(tribromostyrene) in situ (58). 

Although there is no rehable method as of this writing for induction of Ag-speciftc unresponsiveness, some degree of tolerance has been observed by use of nonspecific immunosuppressive therapy. This conclusion is supported by a decrease in the frequency of precursor T-ceUs reactive with graft HLA Ags in long-term recipients of organ transplants. 

Moreover, commercially available triblock copolymers designed to be thermoplastic elastomers, not compatihilizers, are often used in Heu of the more appealing diblock materials. Since the mid-1980s, the generation of block or graft copolymers in situ during blend preparation (158,168—176), called reactive compatibilization, has emerged as an alternative approach and has received considerable commercial attention. 

Miscellaneous Copolymers. VP has been employed as a termonomer with various acryUc monomer—monomer combinations, especially to afford resins usehil as hair fixatives. Because of major differences in reactivity, VP can be copolymerized with alpha-olefins, but the products are actually PVP grafted with olefin or olefin oligomers (151,152). Likewise styrene can be polymerized in the presence of PVP and the resulting dispersion is unusually stable, suggesting that this added resistance to separation is caused by some grafting of styrene onto PVP (153). The Hterature contains innumerable references to other copolymers but at present (ca 1997), those reviewed in this article are the only ones known to have commercial significance. 

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