Copolymes, graft properties

An effective method of NVF chemical modification is graft copolymerization [34,35]. This reaction is initiated by free radicals of the cellulose molecule. The cellulose is treated with an aqueous solution with selected ions and is exposed to a high-energy radiation. Then, the cellulose molecule cracks and radicals are formed. Afterwards, the radical sites of the cellulose are treated with a suitable solution (compatible with the polymer matrix), for example vinyl monomer [35] acrylonitrile [34], methyl methacrylate [47], polystyrene [41]. The resulting copolymer possesses properties characteristic of both fibrous cellulose and grafted polymer. 

However, no indications are given of the molecular weights nor of the compositional heterogeneity of the graft copolymers, their properties or potential applications. The existence of a microphase separation was evidenced however on methyl metha-crylate/polyisobutene graft copolymers by means of DSC measurements. Two glass transitions were observed at —68 °C (polyisobutene) and at 102 °C (PMMA), i.e. at the same temperatures at which they occur in the corresponding hono-polymers. 

Selected blends of styrene-acrylonitrile copolymer (30 to 55%), a styrene-butadiene copolymer grafted with styrene and acrylonitrile (45 to 70%), and a coal-tar pitch (0 to 25%), were prepared. Physical properties of the experimental blends were determined and statistical techniques were used to develop empirical equations relating these properties to blend composition. Scheff canonical polynominal models and response surfaces provided a thorough understanding of the mixture system. These models were used to determine the amount of coal-tar pitch that could be incorporated into ABS compounds that would still meet ASTM requirements for various pipe-material designations. ... 

FIG. 6 Emulsion type diagram of ra-dodecane-water emulsions ( = 0.5) stabilized with hydrophobically modified poly(sodium acrylate)s effect of changing the degree of grafting and type of the graft (single versus twin-tailed). Salt is used as a tool to estimate the copolymer HL properties. (From Ref. 152.)... 

Enzymes are perfectly equipped to convert substrates into products in high enantio-, regio-, or chemoselectivity, a property that is commonly used in industry to prepare optically active fine-chemical intermediates [5]. More specifically, lipases appeared as ideal catalysts as a result of their high enantioselectivity, broad substrate scope and stability. In addition, lipases are powerful catalysts for the preparation of polyesters, polycarbonates and even polyamides, as is reviewed in Chapters 4 and 5 of this book. Moreover, a variety of different polymer architectures such as block copolymers, graft copolymers etc have been prepared using lipases as the catalyst (see Chapter 12). 

The synthesis and bulk and solution properties of block copolymers having nonlinear architectures are reviewed. These materials include star-block copolymers, graft copolymers, mik-toarm star copolymers, and complex architectures such as umbrella polymers and certain dendritic macromolecules. Emphasis is placed on the synthesis of well-defined, well-characterized materials. Such polymers serve as model materials for understanding the effects of architecture on block copolymer self-assembly, in bulk and in solution. 

Acrylonitrile-butadiene-styrene copolymers (ABS) are random styrene-acrylonitrile copolymers grafted to butadiene, which are amorphous, opaque, and process easily. The properties depend on the ratios of the comonomers used. ABS is used in cosmetics packaging, and has been used in margarine tubs. 

PAT Patrizi, M.L., Piantanida, G., Coluzza, C., and Masci, G., ATRP synthesis and association properties of temperature responsive dextian copolymers grafted with poly(A-isopropylacrylamide), Eur. Polym. J., 45, 2779, 2009. 

R171 B. S. Kaith, H. Mittal, J. K. Bhatia and S. Kalia, Polysaccharide Graft Copolymers - Synthesis, Properties and Applications , in Biopolymers Biomedical and Environmental Applications, eds. S. Kalia and L. Averous, Scrivener Publishing, Salem, Mass., 2011, p. 35. 

The major forte of anionic polymerization has been the ability to prepare polydlene and polystyrene polymers and copolymers with control over the major variables affecting polymer properties. Researchers continue to exploit this method for the preparation of model block copolymers, graft copolymers, and branched copolymers, and homopolymers with controlled, well-defined structures. The ability to prepare well-defined polymers and copolymers with functionalized end groups, especially ionic or ionizable groups, is also generating considerable current interest. Methods are also being explored to anionically pol)rmerize and copolymerized a variety of polar monomers with controlled structures. The current interest in blends and... 

ABS comprises the dispersed phase of styrene/acrylonitrile copolymer grafted on polybutadiene rubber and the continuous phase of styrene/acry-lonitrile copolymer. The use of SAN grafted on polybutadiene rubber provides high impact strength, processability, chemical resistance, staining property, etc., as the characteristics peculiar to ABS resins. 

Two types of investigations are essential to explain the behavior of block and graft copolymers (1) properties in a solvent in which both the A and B blocks are soluble—this gives information on their conformation (2) Properties in a solvent that is a nonsolvent for one of the blocks but a good solvent for the other block. 

Other acrylonitrile copolymers have found specialty applications with good gas-barrier and chemical-resistant properties. An example is BP Chemicals Barex resins which are acrylonitrile-methyl acrylate copolymers grafted on a nitrile rubber. Barex resins are unique barrier resins with the combinations of excellent oxygen barrier, good chemical resistance, and antiscalping properties. 

G. Giirdag and S. Sarmad, Gellulose graft copolymers Synthesis, properties, and applications, in Polysaccharide based graft copolymers. Chapter 2, S. Kalia and M. W. Sabaa (Eds.), pp. 15-57, Springer-Verlag, Berlin Heidelberg. (2013). 

Cunliffe, D., De Las Heras Alarcon, C., Peters, V., Smith, J. R., Alexander, C. (2003). Thermoresponsive surface-grafted poly(N-isopropylacrylamide) copolymers surface-properties and effect of phase transitions on protein and bacterial attachment langmuir, 19, 2888-2899. 

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