Polymer grafting functionalization

The anionic polymerization of methacrylates using a silyl ketene acetal initiator has been termed group-transfer polymerization (GTP). First reported by Du Pont researchers in 1983 (100), group-transfer polymerization allows the control of methacrylate molecular stmcture typical of living polymers, but can be conveniendy mn at room temperature and above. The use of GTP to prepare block polymers, comb-graft polymers, loop polymers, star polymers, and functional polymers has been reported (100,101). 

The consideration made above allows us to predict good chromatographic properties of the bonded phases composed of the adsorbed macromolecules. On the one hand, steric repulsion of the macromolecular solute by the loops and tails of the modifying polymer ensures the suppressed nonspecific adsorptivity of a carrier. On the other hand, the extended structure of the bonded phase may improve the adaptivity of the grafted functions and facilitate thereby the complex formation between the adsorbent and solute. The examples listed below illustrate the applicability of the composite sorbents to the different modes of liquid chromatography of biopolymers. 

Fig. 15. Schematic representation of the synthesis of hyperbranched, branched, and linear polymers grafted from functionalized silicon wafers SFM images and XPS spectra of the surface-grafted polymers. (Reproduced with permission from [48],Copyright 2001 American Chemical Society.)...

Y Okahata, H Noguchi, T Seki. Functional capsule membranes. 26. Permeability control of polymer-grafted capsule membranes responding to ambient pH changes. Macromolecules 20 15-21, 1987. 

For both kinds of polymer-grafted particles, flocculation was induced either by changing the temperature or by adding a nonsolvent for the stabilising polymer. In this way critical flocculation temperature (c.f.T) and critical flocculation vol. fractions of non-solvent (c.f.v.) values were obtained, in general as a function of . 

The A-B type iniferters are more useful than the B-B type for the more efficient synthesis of polymers with controlled structure The functionality of the iniferters can be controlled by changing the number of the A-B bond introduced into an iniferter molecule, for example, B-A-B as the bifunctional iniferter. Detailed classification and application of the iniferters having DC groups are summarized in Table 1. In Eqs. (9)—(11), 6 and 7 serve as the monofunctional iniferters, 9 and 10 as the monofunctional polymeric iniferters, and 8 and 11 as the bifunctional iniferters. Tetrafunctional and polyfunctional iniferters and gel-iniferters are used for the synthesis of star polymers, graft copolymers, and multiblock copolymers, respectively (see Sect. 5). When a polymer implying DC moieties in the main chain is used, a multifunctional polymeric iniferter can be prepared (Eqs. 15 and 16), which is further applied to the synthesis of multiblock copolymers. 

A number of different types of copolymers are possible with ATRP—statistical (random), gradient, block, and graft copolymers [Matyjaszewski, 2001]. Other polymer architectures are also possible—hyperbranched, star, and brush polymers, and functionalized polymers. Statistical and gradient copolymers are discussed in Chap. 6. Functionalized polymers are discussed in Sec. 3-16b. 

Grafting from involves a polymer with functional groups that initiate polymerization of... 

In a similar way, Mizota et al. grafted polymer chains functionalized with sulfonic sites over a polystyrene-type polymer. As observed above, the flexibility of the polymer chains allowed better accessibility of the catalytic sites and this solid acid catalyst was ten times more active than the conventionally used cross-linked resin in the hydrolysis of sucrose (Scheme 2) [27]. 

However, often it is difficult to produce suitable graft or block copolymers for important commercial applications. Alternatively, these compatibilizing copolymers can be generated in situ during the blend preparation through polymer-polymer grafting reactions using functionalized polymers (38). 

The use of reactive antioxidants containing two polymerisable polymer-reactive functions in the same antioxidant molecule is outlined here. Careful choice of the processing parameters, the type, and the amount of free radical initiator can lead to very high levels of antioxidant grafting [53, 57]. For example, melt grafting of concentrates (e.g. 5-20 wt%) of the di-acrylate hin-... 

Homogeneous ion-exchange membranes can be prepared by polymerization of monomers that contain a moiety that either is or can be made anionic or cationic, or by polymerization of a monomer that contains an anionic or a cationic moiety, or by introduction of anionic or cationic moieties into a polymer dissolved in a solvent by a chemical reaction, or grafting functional groups into a preformed polymer film [10]. 

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