Copolymers, amphiphilic grafted

AJ Dualeh, CA Steiner. Bulk and microscopic properties of surfactant-bridged hydrogels made from an amphiphilic graft copolymer. Macromolecules 24 112-116, 1991. 

Recently this grafting methods has been used to synthesize amphiphilic graft copolymers in which hydrophilic grafts are linked to a hydrophobic backbone. Partly chloromethylated polystyrene is used to deactivate either monofunctional "living" polyethylene oxide or monofunctional "living" polyvinylpyridine. In the latter case subsequent quaternization yields polyelectrolyte grafts. ... 

Such hydrophilic macromonomers (DPn=7-9) were radically homopolymer-ized and copolymerized with styrene [78] using AIBN as an initiator at 60 °C in deuterated DMSO in order to follow the kinetics directly by NMR analysis. The macromonomer was found to be less reactive than styrene (rM=0.9 for the macromonomer and rs=1.3 for styrene). Polymerization led to amphiphilic graft copolymers with a polystyrene backbone and poly(vinyl alcohol) branches. The hydrophilic macromonomer was also used in emulsion polymerization and copolymerized onto seed polystyrene particles in order to incorporate it at the interface. 

Amphiphilic graft copolymers are conveniently synthesized by copolymerization of a hydrophobic monomer with a hydrophilic macromonomer and vice versa. The resulting copolymers are of great interest from the point of view of their surface active properties. 

Finally, amphiphilic graft copolymers will be reviewed and compared to the linear block copolymer structures of the same composition and it will be shown that micellization depends not only on composition, pH, and ionic strength, but also significantly on the topology of the polymer molecule. 

Special attention was granted to amphiphilic graft copolymers in which hydrophilic grafts are attached to a hydrophobic backbone (or vice versa). Such materials can be used as emulsifiers, compatibilizers, surface modifiers, adhesives, etc. and they may play a role in many industrial developments. 

The macromonomer method (C) has also been adopted in cationic polymerization. For instance, amphiphilic graft polymers of vinyl ethers are synthesized by the cationic polymerization of a vinyl ether-capped macromonomer (26) with a block copolymer chain consisting of IBVE and AcOVE segments, followed by alkaline hydrolysis of the latter part into the HOVE units [165], This graft polymer also undergoes a host-guest interaction similar to those with amphiphilic star block copolymers [220]. 

In all instances of the dispersion polymerization, amphiphilic graft copolymers produced in a selective solvent for the branches play a crucial role. Schematically, a microsphere obtained by copolymerization in this way with a small amount of macromonomer has a core-shell structure as given in Fig. 2, with the core occupied by the insoluble substrate polymer chains and the shell by the soluble, graft-copolymerized macromonomer chains. The backbone chains of the graft copolymers, which must be insoluble in the medium, serve as the anchors into the core. The following section presents general criteria for the size control of polymeric microspheres by dispersion copolymerization... 

Partially chloromethylated or bromomethylated anionically prepared polystyrenes have been used for the preparation of several graft copolymers containing PS backbones and PI,43 P2VP,45 139 P4VP,140 PtBuMA,45 and PEO141142 branches. Some of these copolymers are precursors for amphiphilic graft copolymers (Scheme 64). 

Berlinova IV, Amzil A, Tsvetkova S, Panayotov IM. Amphiphilic graft copolymers with poly(oxyethylene)side chains synthesis via activated ester intermediates—properties. J Polym Sci Part A Polym Chem 1994 32 1523-1530. 

Xie HQ, Wu XD, Guo JS. Synthesis and properties of two kinds of amphiphilic graft copolymers with well-defined structure. J Appl Polym Sci 1994 54 1079-1086. 

A particularly interesting example of graft copolymers produced via active ester synthesis is that of the comb structure (25, Fig. 19) with a hydrophobic backbone and hydrophilic grafts. A series of these amphiphilic graft copolymers have been produced by partial displacement of the trichlorophenoxyl groups... 

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