Green Polymer Chemistry: Investigating the Mechanism of Radical Ring-Opening Redox Polymerization (R3P) of 3,6-Dioxa-1,8-octanedithiol (DODT)

Molecules

Emily Q. Rosenthal-Kim¹  Judit E. Puskas¹ 

关键词: disulfide;    poly(disulfide)s;    thiol oxidation;    radical polymerization;    ring polymers;    cyclic polymers;    oxidation-reduction;    reducible polymers;   

DOI  :  10.3390/molecules20046504

来源: mdpi

【 摘 要 】

The mechanism of the new Radical Ring-opening Redox Polymerization (R3P) of 3,6-dioxa-1,8-octanedithiol (DODT) by triethylamine (TEA) and dilute H₂O₂ was investigated. Scouting studies showed that the formation of high molecular weight polymers required a 1:2 molar ratio of DODT to TEA and of DODT to H₂O₂. Further investigation into the chemical composition of the organic and aqueous phases by ¹H-NMR spectroscopy and mass spectrometry demonstrated that DODT is ionized by two TEA molecules (one for each thiol group) and thus transferred into the aqueous phase. The organic phase was found to have cyclic disulfide dimers, trimers and tetramers. Dissolving DODT and TEA in water before the addition of H₂O₂ yielded a polymer with M_n = 55,000 g/mol, in comparison with M_n = 92,000 g/mol when aqueous H₂O₂ was added to a DODT/TEA mixture. After polymer removal, MALDI-ToF MS analysis of the residual reaction mixtures showed only cyclic oligomers remaining. Below the LCST for TEA in water, 18.7 °C, the system yielded a stable emulsion, and only cyclic oligomers were found. Below DODT/TEA and H₂O₂ 1:2 molar ratio mostly linear oligomers were formed, with <20% cyclic oligomers. The findings support the proposed mechanism of R3P.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.