Grafting onto method

Grafting from method, 7 652-653 Grafting onto method, 7 654 Grafting process, 73 537 Grafting through method, 7 653 Graft polymerization. See also Graft copolymerization ABS, 7 419, 421 acrylic ester monomers, 7 386 of methacrylic ester polymers, 76 289-290... 

Recently, Quirk and Mathers [264] performed LASIP of isoprene on silicon wafers. A chlorodimethylsilane-functionalized diphenylefhene (DPE) was coupled onto the surface and lithiated with n-BuLi to form the initiating species. The living poly(isoprene) (PI) was end- functionalized with ethylene oxide. A brush thickness of 5 nm after two days of polymerization (9.5 nm after four days) was obtained in contrast to a polymer layer thickness of 1.9 nm by the grafting onto method using a telechelic silane functionahzed PI. 

In a recent review, Spange et al. [271] compiled LCSIP systems on inorganic substrates as well as grafting onto methods involving carbocations in the grafting reaction and gave a detailed account on the extensive work of his group in the field of LCSIP employed directly on the sihca surface. 

In general, in the field of materials or condensed matter, the preparation of polymer brushes on solid surfaces is of great interest for surface modification and composite material preparation [4-6]. A number of model surface grafting techniques have been used on planar surfaces and particles and have been the subject of previous reviews. While a munber of polymer brush preparation methods have been reported using physisorption or chemisorption or so-called grafting onto methods, the emphasis of this review is on surface-initiated polymerization (SIP) methods or grafting from methods. 

The synthesis of graft copolymers can be achieved either by "grafting from or by grafting onto processes.— The former method seems more versatile, but it does not allow an adequate structure control, and it often yields rather polydisperse samples. On the contrary "grafting onto" methods allow a precise control of the size and of the nunber of grafts, but it is only applicable to a limited number of systems. 

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. 

The grafting onto method was used to prepare graft copolymers by deactivation reaction onto a backbone fitted with nucleophilic sites. Franta et al. (134) used this technique to synthesize graft copolymers of poly(THF) with nucleophilic backbones poly( -dimethylaminostyrene) and poly(2-vinylpyridine). 

Microwave irradiation Grafting onto method Various catalysts are used [4,4 -Azobis (4-cyanovaleric acid)] Telechelic polymers, polyethylene glycol, poly-dimethyl siloxane... 

Figure 30.9 Schematic representation of the generation-based synthesis of dendrigraft polymers by a divergent grafting-onto method. (See insert for the color representation of the figure.)...

Graft copolymers by cationic polymerization may be obtained by the grafting from , and grafting onto methods and by (co)polymerization of macromonomers. 

Scheme 30.8 Preparation of macromolecular brushes via the grafting-onto method, using a combination of ATRP and CuAAC click chemistry. Reproduced with permission from Ref [85] 2007, American Chemical Society.

In conclusion, graft copolymers of various chemical natures and grafting densities are accessible via various polymerization methods by grafting onto methods. However, until recently the control of the spacing between branch points combined with backbones of well-controlled molecular weight was rather difficult to achieve. 

There exist two approaches to the synthesis of rod-coil block copolymers first, the grafting from approach where one component is used as a macroinitiator for the preparation of the other, and, secondly, the grafting onto method where the second component is covalently attached to a suitably end-functionalised first component. The first approach was used to prepare block copolymers of polystyrene (PS) with PPP 207 (Scheme 95) by Francois and coworkers [304-308] and by Advincula and coworkers [309]. In this synthesis, cyclohexadiene was added to living polystyrene to give a precursor polymer 208, which was then aromatised to 207 using chloranil in refluxing xylene. 

Scheme 97 PPP-based rod-coU copolymers by grafting onto method...

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