Poly mercapto groups

In recent years there has been a growing interest in the use of polymeric herbicides, pesticides and drugs. Several reviews have appeared on this general area (69-71) and we earlier noted several examples of such potential behavior with poly(vinyl alcohol) modifications. These included modifications containing 6-methylthiopurine (an antileukemia drug) (55), 2,6-dichloro-benzaldehyde (a herbicide) (56), various enzymes (52,53), aspirin (analgesic)(51) and mercapto groups (46-49). 

Mercapto groups in poly(caprolactam) fibers having disulfide and alkalene sulfide cross-links have been determined by swelling the sample with methanol and titrating the suspended strips with an alcoholic silver nitrate solution [1,33]. 

Poly(vinylbenzene) or polystyrene containing mercapto groups may have the degree of proximity assessed by iodine oxidation to disulphide. "... 

Poly-L-cysteine (XXXIV) was prepared by polymerization of S-carbobenzoxy-N-carboxy-L-cysteine anhydride (XXXIII), followed by reduction with sodium in liquid ammonia 47). The reactivity of the thiol groups in this polymer toward iodoacetic add indicated that quantitative liberation of mercapto groups had beat effected but selective reactivity was observed with methyl mercuric nitrate in the presence of sodium nitroprusside, an internal indicator. These reactivity differences result from sterk exclusion of the nitroprusside dye from about one third of the available mercaptan moities. Thus the concept of sluggish-SH groups in a protein has been demonstrated with a synthetic homopolymer. 

Di- and poly-fimctional mercaptans have been used for many years to crosslink polymers with labile halogens (chlorine or bromine). 2,5-Dimercapto-l,3,4-thiadiazole (DMTD) is one such crosslinker that displays relatively fast cures but poor scorch safety. Improved scorch safety can be achieved by derivatising one or both mercapto groups. Several derivatives of DMTD have been developed recently for this purpose. Proper selection of the thiadiazole derivative and associated accelerator is often a key to successftil use in a given halogen-containing polymer compound. The various... 

Modifications with Thiol Groups. Mercapto or thio groups often have powerful physiological activity and have been claimed to be useful as radiation protective groups. These groups have been introduced into poly(vinyl alcohol) in a variety of ways. 

Scheme 3. Idealized sketch of a gold surface modified with a multilayered assembly prepared by (a) alternate deposition of layers of poly(acryhc acid) and poly-L-lysine on a positively charged cystamine SAM (the multilayer assembly is stabilized by electrostatic interactions between adjacent layers, [136]) and by (b) covalent attachment of a layer of G4 poly(amidoamine) dendrimer to a 11-mercapto-l-undecanoic acid SAM after activation of the surface-bound cEirboxylic groups with pentafiuorophenol and EDC. The dendrimer monolayer is afterwards biotinylated by covalent binding of desthiobiotin amidocaproate (not shown) to assemble an overlayer of avidin by affinity interactions [133].

The carbojylation of unsaturated PHA has been performed through reactions that involved the conversion of the double bonds to thioethers via the free-radical addition of 11-mercaptoundecanoic acid or (R)-3-mercaptopropionic acid. Transesterification reactions of poly(3-hydro y butyrate) were carried out under reflux of 1,2-dichlorobenzene in the presence of 1,4-butane diol, poly(ethylene glycol) bis(2-aminopropyl ether) with molecular weights of 1000 and 2000, poly(ethylene glycol)methactylate or glycerol at 180 °C. Addition reactions of bromine and the -SH groups of 3-mercaptopropionic acid to the double bond of poly(3-hydro)y-10-undecenoate) were also carried out. The molecular weights of the modified polymers (despite the addition of mercapto acids to the double bonds) remained almost constant. " ... 

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