Non‐transition metal‐catalyzed living radical polymerization of vinyl chloride initiated with iodoform in water at 25 °C

Abstract

Non‐transition metal‐catalyzed living radical polymerization (LRP) of vinyl chloride (VC) in water at 25–35 °C is reported. This polymerization is initiated with iodoform and catalyzed by Na2S2O4. In water, S2O dissociates into SO that mediates the initiation and reactivation steps via a single electron transfer (SET) mechanism. The exchange between dormant and active propagating species also includes the degenerative chain transfer to dormant species (DT). In addition, the SO2 released from SO during the SET process can add reversibly to poly(vinyl chloride) (PVC) radicals and provide additional transient dormant ∼SO radicals. This novel LRP proceeds mostly by a combination of competitive SET and DT mechanisms and, therefore, it is called SET‐DTLRP. Telechelic PVC with a number‐average molecular weight (Mn) = 2,000–55,000, containing two active ∼CH2CHClI chain ends and a higher syndiotacticity than the commercial PVC were obtained by SET‐DTLRP. This PVC is free of structural defects and exhibits a higher thermal stability than commercial PVC. SET‐DTLRP of VC is carried out under reaction conditions related to those used for its commercial free‐radical polymerization. Consequently, SET‐DTLRP is of technological interest both as an alternative commercial method for the production of PVC with superior properties as well as for the synthesis of new PVC‐based architectures. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6267–6282, 2004

Impact of Competitive Processes on Controlled Radical Polymerization

“…[44][45][46][47] In light of the theory proposed here it may be as a result of the reduced transient radical lifetime that defects, which for vinyl chloride polymerization are largely caused by transfer to polymer, are reduced. In addition, similar polymerizations conducted in aqueous media suggested that chain transfer to the poly(vinyl alcohol) stabilizer employed does not occur.…”

“…In addition, similar polymerizations conducted in aqueous media suggested that chain transfer to the poly(vinyl alcohol) stabilizer employed does not occur. 47,48 Given that chain transfer to PVA in conventional radical polymerization of PVC is extensive and leads to a characteristic skin of the resulting particles, it is clear that the imposition of controlled polymerization conditions significantly diminishes the extent of transfer in this case. 48 Extending further it has been shown that in general, copper(0) mediated polymerization has excellent end group fidelity in comparison to other atom transfer processes.…”

Thermal characterization of poly(vinyl chloride) samples prepared by living radical polymerization: Comparison with poly(vinyl chloride) prepared by free radical polymerization

“…Because sodium dithionate is not able to form growing radicals and start the polymerization, as happens for example when peroxides are used (common DCT systems), a better control over the polymerization is achieved. The outstanding structural properties of the PVC that resulted from this LRP method were already assessed by nuclear magnetic resonance 10 (NMR) carried out to very lowmolecular weight PVC samples that could not be prepared without a living mechanism. The new PVC-LRP prepared by SET-DTLRP demonstrated to have high crystallinity, 10 to be free of structural defects, 9,10 and to require more than twice the time to burn completely in the discoloration tests by using the standard discoloration tests used in the industry.…”

“…5 Nevertheless, the stringent conditions associated to some of these methods have limited the perspectives for widespread of commercial products. After several years of the development, Percec et al discovered a new strategy to polymerize-activated [6][7][8] and nonactivated monomers, [9][10][11] under controlled/ living mechanism in aqueous medium. In addition, this method requires only industrially consumed compounds and lead to a polymer that does not need to be purified.…”

“…It provides the reversible activation-deactivation step required to accomplish LRP by the combination of competitive single-electron-transfer (SET) and degenerative-chain transfer (DT). 10 The SET-DTLRP allows the synthesis of PVC free of internal allyl and tertiary alkyl chloride structural defects, which result from inevitable side reactions that are present in the FRP process. Apart form that, the use of iodoform allows each polymer chains to grow in two directions at the same time.…”