Thiol reactive polymer chains

The ability of thiol-ene click chemistry to retain high efficiency under the most benign reaction conditions was exempHfied by Ritter and Bardts, in the preparation of hydrogels based on methacryhc acid [224]. In this study, poly(methacrylic acid) polymers were modified with cysteamine and aUyl amine to afford complementary thiol-ene reactive polymer chains. Solutions of the polymer pairs in water were mixed in the presence of a radical initiator, and the formation of a highly elastic gel was observed within only 2 h at room temperature. The authors noted that this approach might have broad application for a rapid and straightforward access to hydrogel materials for which the properties could easily be tailored by the choice of the amine modifiers. 

The lanthanocene initiators also polymerize EtMA, PrMA and BuMA in a well-controlled manner, although syndiotacticity decreases as the bulk of alkyl substituent increases. Reactivity also decreases in the order MMA EtMA > PrMA > BuMA. Chain transfer to provide shorter polymer chains is accomplished by addition of ketones and thiols.460 The alkyl complexes (190) and (191) also rapidly polymerize acrylate monomers at 0°C.461,462 Both initiators deliver monodisperse poly(acrylic esters) (Mw/Mn 1.07). An enolate is again believed to be the active propagating species since the model complex (195) was also shown to initiate the polymerization of MA. 

This type of modification process has been used to form sulfhydryl-reactive dextran polymers by coupling amine spacers with crosslinkers containing an amine reactive end and a thiol-reactive end (Brunswick et al., 1988 Noguchi et al., 1992). The result was a multivalent sulfhydryl-reactive dextran derivative that could couple numerous sulfhydryl-containing molecules per polymer chain. 

The concept of PO macroinitiators centers on the introduction of an initiation moiety into an olefinic polymer chain for polymerization. The most effective route for preparing PO macroinitiators is by employing functional polyolefins containing hydroxyl groups or other reactive groups. These functional POs are prepared by copolymerization of olefins with functional monomers and post-polymerization reaction, as mentioned above. In the case where an initiation moiety was at the chain-end of the polyolefins, a block type copolymer is produced. It has been reported that thiol-terminated PP was used as polymeric chain transfer agent in styrene and styrene/acrylonitrile polymerization to form polypropylene-b/odc-polystyrene (PP-b-PS) and polypropylene-btock-poly(styrene-co-acrylonitrile) (PP-b-SAN) block copolymer [19]. On the other hand, polymer hybrids with block and graft structures can be produced if initiation moieties are in the polymer chain. 

The polymers are apphed to the wool fibers or fabrics as solutions or emulsions. The polymers contain reactive side-chains, which form cross-links between the polymer chains during a curing process after apphcation and may form covalent links with the wool protein. For example, Hercosett 57 is a polyaminoamide with reactive azetidinium side-chains, which form cross-links between the polymer chains. They also form covalent links with amino and thiol groups in the wool protein. In the case of some polymers (e.g., Hercosett 57), it is necessary to give the wool a mild chlorination treatment to modify the surface of the fibers before applying the polymer. Such a treatment allows the polymer to spread evenly on the surface. 

Polymeric L-B films fabricated by spreading various polymers at the air/water interface are well-known [6-8], indieating the eapability to take a three-dimensional polymer eoil in dilute solution and form a quasi-two-dimensional array at the air-water interface. By analogy, the adsorption of polymers bearing ehemieally reactive side chains (e.g., thiols, disulfides or silanes) specific for certain interfacial sites, could take advantage of the same organizational principles to yield multipoint attached polymer... 

A polymer chain will be formed only if both the thiol and the olefinic compound contain at least two reactive functions, e.g. a diene plus a dithiol. With multifunctional monomers, such as a tetrathiol ([CRSHJ4) associated to a diene (CH2=CH-R -CH=CH2), a three-dimensional network is produced, in which the connecting chains are made of an alternating copolymer ... 

Thiol functionality Thiol-reactive functionality 000030 Polymer chain... 

A cation radical chain cycloaddition-polymerization catalysed by tris(4-bromophenyl)aminium hexachloroantimonate has been reported to afford polymers with an average molecular weight up to 150000. Both cyclobutanation and Diels-Alder polymers were obtained. " The reactivity of the phospine radical cation towards nucleophiles was studied. Tributylphosphine reacted with l,l-dimethyl-4,4-bipyridinium (methyl viologen, MV) in the presence of an alcohol or thiol (RXH X = O, S), which resulted in the gradual formation of the one-electron reduced form... 

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