Graft copolymers structure

Figure 3. Graft copolymer structures. Numbers refer to the equation...

Three other copolymer structures are known alternating, block, and graft copolymer structures (Fig. 1.1). In the alternating copolymer the two mers alternate in a regular fashion along the polymer chain ... 

Radiation-induced grafting is a process where, in a first step, an active site is created in the preexisting polymer. This site is usually a free radical, where the polymer chain behaves like a macroradical. This may subsequently initiate the polymerization of a monomer, leading to the formation of a graft copolymer structure where the backbone is represented by the polymer being modified, and the side chains are formed from the monomer (Fig. 1). This method offers the promise of polymerization of monomers that are difficult to polymerize by conventional methods without residues of initiators and catalysts. Moreover, polymerization can be carried out even at low temperatures, unlike polymerization with catalysts and initiators. Another interesting as-... 

Polycondensation techniques have been employed for the synthesis of macromonomers. Depending on the nature of the functional end group the copolymerization with comonomers can be performed with addition polymerization techniques, giving rise to very interesting graft copolymer structures. 

The products of polyethylene modification are mixed block and graft copolymer structures (with acrylic acid, methacrylamide, and acrylonitrile) or linear structures (acenaphthylene and maleic anhydride). This is again consistent with the nature of the monomers and the activity of their radicals. 

Narayan, R. (1988) Synthesis of Controlled Cellulose - Synthetic Polymer Graft Copolymer Structures in Cellulose Wood Chemistry and Technology, C. Schuerch (ed), John Wiley Sons New York, p.945. 

Based on a combination of dimethyl silicone fluid with organic wax side chains. The unique grafted copolymer structure of GP-7102 provides a special range of lubrication and compatibility characteristics, suggesting uses in mold release agents, waxes and polishes, textiles and plastic lubricants, and as an ingredient in oil based metal working fluids. 

Surface active agents are important components of foam formulations. They decrease the surface tension of the system and facilitate the dispersion of water in the hydrophobic resin. In addition they can aid nucleation, stabilise the foam and control cell structure. A wide range of such agents, both ionic and non-ionic, has been used at various times but the success of the one-shot process has been due in no small measure to the development of the water-soluble polyether siloxanes. These are either block or graft copolymers of a polydimethylsiloxane with a polyalkylene oxide (the latter usually an ethylene oxide-propylene oxide copolymer). Since these materials are susceptible to hydrolysis they should be used within a few days of mixing with water. 

The structure of PP-g-polystyrene was studied by wide and narrow angle x-ray diffractometry. The polystyrene component formed discrete amorphous structures, which were identified after chloromethylation [143]. Structure of Rayon-Styrene graft copolymer was characterized by IR, wide angle x-ray, and SEM, grafting occurred mainly in the amorphous regions of rayon [1441. 

Polymers are classified according to their chemical structures into homopolymers, copolymers, block copolymers, and graft copolymers. In a graft copolymer, sequences of one monomer are grafted onto a backbone of the other monomer and can be represented as follows ... 

It is well known that block copolymers and graft copolymers composed of incompatible sequences form the self-assemblies (the microphase separations). These morphologies of the microphase separation are governed by Molau s law [1] in the solid state. Nowadays, not only the three basic morphologies but also novel morphologies, such as ordered bicontinuous double diamond structure, are reported [2-6]. The applications of the microphase separation are also investigated [7-12]. As one of the applications of the microphase separation of AB diblock copolymers, it is possible to synthesize coreshell type polymer microspheres upon crosslinking the spherical microdomains [13-16]. 

Generally, the number of the shell chains in a microsphere ranges from a few hundred to a few thousand. The range of the diameter of the core is from 10-100 nm. Such a core-shell structure is very similar to the (AB)n type star block copolymers, which have many arms and spherical polymer micelles of the block or graft copolymers formed in selective solvents that are good for the corona sequence and bad for the core sequence. In fact, many theoretical investigations of the chain con-... 

The structure-property relationship of graft copolymers based on an elastomeric backbone poly(ethyl acry-late)-g-polystyrene was studied by Peiffer and Rabeony [321. The copolymer was prepared by the free radical polymerization technique and, it was found that the improvement in properties depends upon factors such as the number of grafts/chain, graft molecular weight, etc. It was shown that mutually grafted copolymers produce a variety of compatibilized ternary component blends. 

Compatibility and various other properties such as morphology, crystalline behavior, structure, mechanical properties of natural rubber-polyethylene blends were investigated by Qin et al. [39]. Polyethylene-b-polyiso-prene acts as a successful compatibilizer here. Mechanical properties of the blends were improved upon the addition of the block copolymer (Table 12). The copolymer locates at the interface, and, thus, reduces the interfacial tension that is reflected in the mechanical properties. As the amount of graft copolymer increases, tensile strength and elongation at break increase and reach a leveling off. 

In terms of structural control, block copolymers have considerable advantages over graft copolymers. The segment length and sequence are generally more easily controlled for block copolymers than for graft copolymers. 

Problem 31.7 1 Irradiation of poly(-l,3-butadiene), followed by addition of styrene, yields a graft copolymer that is used to make rubber soles for shoes. Draw the structure of a representative segment of this styrene-butadiene graft copolymer. 

Using 4,4,-bis(4-hydroxyphenyl)pentanoic acid (BHPA)196 197 as comonomer, some polysulfones with pendent carboxylic groups were successfully synthesized.198199 Table 6.1 shows the structure of BHPA. The functional groups can be used for the preparation of graft copolymers. 

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