Graft polymerization features

Block and Graft Polymerization. These two t3rpes of polymerization have one feature in common, namely, that more or less extended sequences of monomer Mi are joined to prepolymerized sequences of monomer Mi. 

Bottlebmsh copolymers are a class of shape-persistent macromolecules that possess a highly branched comblike architecture. Steric repulsion between densely grafted polymeric branches causes the backbone to adopt an extended conformation. By combining this feature with grafts that are... 

In the same context, a critical review discusses the recent advances in graft polymerization techniques involving cellulose and its derivatives [137]. The study summarizes some of the features of cellulose structure and cellulose reactivity and describes the various techniques for grafting synthetic polymers from the cellulosic substrate. In addition to the traditional grafting techniques, the recent developments in polymer synthesis that allow increased control over the grafting process and permit the production of functional celluloses with improved physical and chemical properties, are highlighted. 

The success of the multifunctional initiators in the preparation of block and graft copolymers depends critically on the kinetics and mechanism of radical production. In particular, the initiator efficiency, the susceptibility to and mechanism of transfer to initiator, and the relative stability of the various radical generating functions. Each of these factors has a substantial influence on the nature and homogeneity of the polymer formed. Features of the kinetics of polymerizations initiated by multifunctional initiators have been modeled by O Driscoll and Bevington 64 and Choi and Lei.265... 

Highly branched polymers, polymer adsorption and the mesophases of block copolymers may seem weakly connected subjects. However, in this review we bring out some important common features related to the tethering experienced by the polymer chains in all of these structures. Tethered polymer chains, in our parlance, are chains attached to a point, a line, a surface or an interface by their ends. In this view, one may think of the arms of a star polymer as chains tethered to a point [1], or of polymerized macromonomers as chains tethered to a line [2-4]. Adsorption or grafting of end-functionalized polymers to a surface exemplifies a tethered surface layer [5] (a polymer brush ), whereas block copolymers straddling phase boundaries give rise to chains tethered to an interface [6],... 

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. 

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