Chain grafting polymeric side

Modification of Collagenous Surfaces by Grafting Polymeric Side Chains to Collagen and Soft and Hard Tissues... 

Graft (polymeric side chain different) -graft-or -g- Poly A-graft-poly B poly(A-g-B) AAAAA (g-BBB)AAAAAAA... 

Graft Polymeric side chain —AAAAAAAAAAAA— -graft- Polybutadiene-gra/i - gm -Copoly(butadiene/... 

Remember from Sec. 1.3 that graft copolymers have polymeric side chains which differ in the nature of the repeat unit from the backbone. These can be prepared by introducing a prepolymerized sample of the backbone polymer into a reactive mixture—i.e., one containing a source of free radicals—of the side-chain monomer. As an example, consider introducing polybutadiene into a reactive mixture of styrene ... 

Macromers are then short polymers, which contain an active end group. This end group can be a site of unsaturation, heterocycle, or other group that can further react. Macromers are usually designed as intermediates in the complete synthesis of a polymeric material. These macromers can be introduced as side chains (grafts) or they may serve as the backbones (comonomer) of polymers. The macromers can also act as separate phases. 

Another variation for both pseudopolyrotoxanes and polyrotoxanes is the placement of the cyclic component on linear side chains during a graft polymerization process. 

The variability and potential of the graft polymerization technique is best discussed in terms of the various parameters involved. The graft reaction is, to a large extent, controlled by the structure of the backbone prepolymer. The temperature at which grafting can take place and the number of grafted chains can be controlled via the type and concentration of the azo functions. Additionally, the molar mass of the backbone prepolymer has an influence on the number of azo groups per polymer chain and thus on the number of side chains. The comonomer for the backbone can be freely chosen unless quantitative conversions are required. In this case a comonomer should be used which copolymerizes ideally with the azo monomer. 

Photolysis of this polymer gives radicals on which side chains can be formed, giving graft polymerization 122, 123, 153). Similarly the polymerization of styrene (152) or vinyl acetate (157) in the presence of bromotrichloromethane gives telomers carrying terminal bromine atoms and trichloromethyl groups. By ultraviolet irradiation (3500 A) in the presence of methyl methacrylate the carbon-bromine links are broken and block copolymers are formed. The telomerization of acrylonitrile and acrylic acid with bromoform is based on the same technique the end groups of both polyacrylonitrile and polyacrylic acid were photolyzed in the presence of acrylamide and afforded polyacrylamide blocks linked to polyacrylonitrile or polyacrylic acid blocks (164, 165). 

In full agreement with this explanation it was recognized that by a certain side reaction very strong cross links are formed during the polymerization. If a polymide was used as cocatalyst (a polymer styrene-methacryloyl caprolactam) the grafted polyamide side chains were joined in the very beginning of the polymerization and a crosslinked polymer resulted (92). 

Grafting of Polymeric Side Chains to Collagenous Surfaces Reaction Times 3 hours Temperature 37°C... 

There are in general two ways to synthesize side chain polymers, polymerization of peptide-functional monomers or introduction of the peptide moiety afterwards, by grafting. The latter technique is based on the synthesis of polymers containing some form of functionality in the side chain, normally an activated ester moiety, which can further react with a peptide. The most commonly used method for the polymerization of monomers containing active esters is free radical polymerization. In particular many activated acrylate esters have been polymerized in this manner [12] (Table 1) for use in a wide variety of applications, from the preparation of polymer drug conjugates [13,14] to supports for solid phase peptide synthesis [15,16]. 

Starch thiols can have the SH group directly on the pyranose ring or in a side chain. There are several methods of synthesizing starch thiols of the first type. One of them is based on the pyrolysis of starch xanthates (32), but the reaction proceeds in two parallel routes one producing thionates (35) and the other producing thiols (37).2675,2677 Reduction of starch xanthates with NaBPU in alkali is another approach to thiols. Thiols prepared in this manner were subjected to graft polymerization with vinyl polymers. Nucleophilic substitution of the chlorine... 

TABLE 13.1 Various In-Chain or Side-Chain Type II Photoinitiators for Graft Polymerization... 

High Impact Polystyrene (HIPS) HIPS is a heterogeneous material produced by continuous bulk or bulk-suspension processes, in which a butadiene-based elastomer (polybutadiene (PB), or a block copolymer of styrene-butadiene) is first dissolved in styrene monomer (St) and the resulting mixture is then heated so that the polymerization proceeds either thermally or with the aid of a chemical initiator. At the molecular level, the product is a mixture of free polystyrene (PSt) chains and elastomer chains grafted with PSt side chains. The process yields a continuous (free) PSt matrix containing... 

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