Graft copolymer synthesis mechanisms

The synthesis of block and graft copolymers by mechanical forces has bear earlier reviewed by many authors (4-10). This review is thus not intended to be exhaustive and a different approach has thus been takea The material is organized by state of matter rather than by the instruments used. Thus the authors hope to provide a descriptive mosaic for the parallel studies developing in different countries and in different facets of the field. Some of the original references may be difficult to procure so that more general secondary references are cited in some cases. 

Over last decades the synthesis of block and graft copolymers by mechanical forces has been studied by various researchers, and the recent development in this field has been reviewed by Casale and Porter (S). Pioneer works of ESR studies on low temperature reactions of the mechano-radicals were reported by Butyagin and his collaborators 34, 100). In this review presentation will be limited to ESR studies on polymerization initiated by the PTFE mechano-radical at low temperatures 101). 

SCHEME 3.3 Mechanism of graft copolymer synthesis of polyacrylamide chains-grafted agar backbone by microwave-assisted technique. 

Casale, A. and Porter, R. Mechanical Synthesis of Block and Graft Copolymers. Vol. 17, pp. 1-71. 

The purpose of this review is to report on the recent developments in the macromolecular engineering of aliphatic polyesters. First, the possibilities offered by the living (co)polymerization of (di)lactones will be reviewed. The second part is devoted to the synthesis of block and graft copolymers, combining the living coordination ROP of (di)lactones with other living/controlled polymerization mechanisms of other cyclic and unsaturated comonomers. Finally, several examples of novel types of materials prepared by this macromolecular engineering will be presented. 

The mechanical synthesis of block and graft copolymer is a method of sizable versatility. It can be performed (as already stated) during polymer processing and in standard equipment. The reaction, also, can be carried out by subjecting a mixture of two or more polymers to mechanical degradation in either the solid, elastic-melt, or solution states. It is, also, possible to induce reaction mechanically between polymers and monomers. 

The picture of mechanical synthesis is much more complex if the segments of block and graft copolymers can undergo rupture to polymeric free radicals forming multisegment block copolymers, gelled and crosslinked structures. Baramboim in his book (if) describes 14 different possibilities of block ami graft reactions. 

The mechanical synthesis of block and graft copolymers by vibromilling a polymer-monomer blend has been performed by many researchers. Natural polymers (14,17) vinyl polymers (18—27), and heterochain polymers (18, 28-34) have been formed during polymer mechanochemical degradation. Importantly, Simionescu, Vasiliu-Oprea and Neguleanu studied the possibility of carrying out mechanically-induced polycondensations starting from polyesters and diamines (33,35-37). 

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