4-cyanopentanoic acid dithiobenzoate

RAFT polymerization of two anionic acrylamido monomers sodium 2-acrylamido-2-methylpropane-sulfonate, AMPS, and sodium 3-acrylamido-3-methyl-butanoate, AMBA, (Scheme 29) was conducted in water at 70 °C using 4,4/-azobis(4-cyanopentanoic acid) as the initiator and 4-cyanopentanoic acid dithiobenzoate as the RAFT chain transfer agent [80]. The synthesis was initiated either from one monomer or the other leading to narrow molecular weight distributions in both cases (Mw/Mn < 1.2). 

Spherical gold nanoparticles coated with poly(N-isopropylacrylamide) (PNIPAM) grafts have been synthesized by controlled radical polymerization. The polymerization of N-isopropylacrylamide was initiated from the surface of the nanoparticles modified with 4-cyanopentanoic acid dithiobenzoate for reversible addition-fragmentation chain-transfer polymerization. The mean diameter of the Au core was 3.2 nm, as observed by means of high-resolution transmission electron microscopy [90]. 

The RAFT homopolymerization was mainly applied to vinyUc suhbbe-taines, for the synthesis of homopolymers as well as of block copolymers. The synthesis of the latter proceeds mainly in two steps a macromolecular CTA of a monomer A is synthesized, which is subsequently employed in the polymerization of a monomer B. Polymers 49a, 49b, and 50 (Scheme 10) were prepared using 4-cyanopentanoic acid dithiobenzoate as CTA. Mw/Mn values between 1.04 and 1.08 at higher conversion were reported [154]. 

PSSA may also be prepared by sulfonation of polyst5rrene or by hydrolysis of poly(re-propyl p-vinylbenzenesulfonate). The latter cases allow preparation of tactic structures. Copol5uners can also be prepared by free-radical copolymerization of appropriate monomers or post-reaction. Poljuners are purified by precipitation of aqueous solutions with methanol, alkaline methanol, or other alcohols. Controlled structure PSSA homopolymers and block copolymers may also be prepared directly in aqueous media via RAFT using 4-cyanopentanoic acid dithiobenzoate as the CTA and V-501 as the radical source (48). NMP has been successfully... 

Other Sulfonic Acids. Extensive development work has been conducted on acrylic sulfonate-containing monomers. 2-Sulfoethyl methacrylate (SEM) monomer 5Ahas proved to be of limited commercial value owing to the hydrolytic instability of the ester linkage. However, recently well-defined homopolymers of 3-sulfopropyl methacrylate (SPMA) were prepared under aqueous RAFT conditions with 4-cyanopentanoic acid dithiobenzoate and V-501 as the CTA/initiator pair at 70°C (39). This same hydrolytic instability has been a serious problem with 3-sulfo-2-hydroxypropyl methacrylate. In contrast, 2-acrylamido-2-methylpropanesulfonic acid (AMPSA) 6A, prepared by the reactions of SO3 with isobutylene followed by the Ritter reaction with acrylonitrile (134), is quite hydrolytically stable. 

Scheme 1.5 Preparation of cationic glycopolymer-DTC derivatives. ACPA 4,4 -azobis (4-cyanovaleric acid) ACVA 4-cyanopentanoic acid dithiobenzoate and THF tetrahydrofuran. Reproduced with permission from M. Ahmed, S. Mamba, X-H. Yang, J. Darkwa, P. Kumar and R. Narain, Bioconjugate Chemistry, 2013,24, 979. 2013, American Chemical Society...

Albeitin L, Stenzel MH, Bamer-Kowollik C, Davis TP (2006) Effect of an added base on (4-cyanopentanoic acid)-4-dithiobenzoate mediated RAFT polymerization in water. Polymer 47(4) 1011-1019... 

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