Macromonomers grafting onto polymers

Grafting from is useful since many polymers can he used together with a range of reaction conditions (radical and ionic). Grafting through is also convenient but requires the synthesis of a macromonomer. Grafting onto is the least useful method since reactions between polymers are slow and there are relatively limited numbers of polymers with functional... 

Radical induced grafting may be carried out in solution, in the melt phase,292 29 or as a solid state process.296 This section will focus on melt phase grafting to polyolefin substrates but many of the considerations are generic. The direct grafting of monomers onto polymers, in particular polyolefins, in the melt phase by reactive extrusion has been widely studied. Most recently, the subject has been reviewed by Moad1 9 and by Russell.292 More details on reactive extrusion as a technique can be found in volumes edited by Xanthos," A1 Malaika and Baker et a 21 7 The process most often involves combining a frcc-radical initiator (most commonly a peroxide) and a monomer or macromonomer with the polyolefin as they are conveyed through the extruder. Monomers commonly used in this context include MAII (Section 7.6.4.1), maleimidc derivatives and malcate esters (Section 7.6.4.2), (meth)acrylic acid and (meth)acrylate esters (Section 7.6.43), S, AMS and derivatives (Section 7.6.4.4), vinylsilancs (Section 7.6.4.5) and vinyl oxazolines (Section 7.6.4.6). 

This model shows that the radius of polymer particle follows simple scaling relationships with the key parameters in the system x1/3, [comonomer]02/3, [macromonomer]01/2, and [initiator]0 1/2, where [ ]0 means initial concentration. These equations also predict that the particle size and stabilization are determined by the magnitude of In addition the surface area occupied by a hydrophilic (PEO) chain follows x 1/3 in the case of azeotropic copolymerization, x=Xj. This means that the PEO chain conformation for chains grafted onto the polymer particles change with grafting density. 

Graft (co)polymers are polymers with a linear backbone to which macromo-lecular side chains are connected. They can be prepared by three different methods grafting from , grafting onto , and (co)polymerization of macromonomers. 

A wide variety of polymer microspheres can be made by dispersion polymerization. A key component in all of these systems is the stabilizer (dispersant) both during particle formation and for the stability of the resulting colloidal particles. Functionality can be introduced into colloidal particles in various ways by copolymerization of functional monomers (like HEMA), or incorporation of functional dispersants, initiators, chain transfer agents, or macromonomers. Many different types of macromonomer are prepared and used to prepare functional microspheres. Amphiphilic macromonomers provide a particularly versatile component in these systems, being the source of both stabilizer and functional residue. They act as stabilizer because they are covalently grafted onto the particles surface by copolymerization with main monomers, and form tightly bound hairy shells on the particles surface. 

Additionally, graft copolymers can be prepared by a grafting onto method that involves coupling living polymers to reactive side groups on a prepolymer. An alternative approach to the preparation of graft copolymers involves the use of macromonomers. A macromonomer is a prepolymer with terminal polymerizable C=C bond. In this method, graft copolymers are produced by copolymerization of the macromonomer with another olefinic monomer as shown in Fig. 14.26. 

Randomly branched comb-shaped polymers can be prepared by three general synthetic methods the grafting onto , the grafting from , and the grafting through or macromonomer method.88... 

Figure 20 Modes of grafting dendrimers or dendrons onto polymer backbones. Shown here are (A) the graft-to route, (B) the graft-front method, and (C) the macromonomer route. Source From Ref. 106.

Branched polymers are macromoleailar structures composed of a main polymer chain (backbone) to which one or more side chains (branches) are covalendy attached. When the backbone and the branches are of the same chemical nature, these architectures are called comb polymers, whereas the term graft polymers is used when backbone and branches differ from their chemical nature and/or composition. So far, three methods have been developed for the synthesis of randomly branched grafted (co)polymers (1) the grafting to or grafting onto (2) the grafting from and (3) the grafting through, also called the macromonomer method. ... 

Cell-polymer interactions of fluorescent polystyrene (FPS) latex particles coated with thermosensitive PNIPAM and poly(N-vinylcaprolactam) or grafted with poly(ethylene oxide)-macromonomer were analyzed by Vihola et al. [131] by modifying the surface of the FPS particles with the thermosensitive polymer gels or with poly(ethylene oxide)-macromonomer grafts. In all the cases, the FPS were surface-modified by polymerization of both thermosensitive monomers and macromonomer onto the surface of the fluorescent particles. The final surface-coated particles have potential biotechnological applications in the form of either stealth-carrier behavior or enhanced cellular contact. 

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