Controlled/Living Ring-Closing Cyclopolymerization of Diallyldimethylammonium Chloride via the Reversible Addition Fragmentation Chain Transfer Process

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Assem, Yasser ; Chaffey-Millar, Hugh ; Barner-Kowollik, Christopher ; Wegner, Gerhard ; Agarwal, Seema:
Controlled/Living Ring-Closing Cyclopolymerization of Diallyldimethylammonium Chloride via the Reversible Addition Fragmentation Chain Transfer Process.
In: Macromolecules. Bd. 40 (2007) Heft 11 . - S. 3907-3913.
ISSN 1520-5835
DOI: https://doi.org/10.1021/ma0629079

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Abstract

For the first time, controlled/living free-radical polymerization of a cyclopolymerizing monomer, that is diallyldimethylammonium chloride (DADMAC), was achieved via reversible addition fragmentation chain transfer (RAFT) chemistry in the presence of both trithiocarbonate and xanthate RAFT/macromolecular design via the interchange of xanthate (MADIX) agents in aqueous solution at 60, 80, and 90 °C. The structural characterization of the polymers was achieved via nuclear magnetic resonance spectrometry, indicating that during the RAFT polymerization of DADMAC, identical to its equivalent conventional free radical polymerization, five-membered rings are formed almost exclusively. In the case of the trithiocarbonate agent, there was excellent agreement between the theoretical and experimental number average molecular weights, Mn, with narrow polydispersities (approaching polydispersity index (PDI) ≈ 1.10) being observed (2100 g mol-1 < Mn < 51 000 g mol-1). Chain extension was carried out by sequential batchwise addition of the monomer, confirming the living character of the system. However, the increase in Mn with respect to conversion was not linear in the case of the xanthate agent, yet the PDIs were as low as 1.12, indicating that control was achieved. The inclusion of NaCl into the reaction mixture reduces of the rate of polymerization for both RAFT agents. Such an observation supports the hypothesis that electrostatic repulsion is crucial to fragmentation of the primary propagating radicals from the adduct RAFT radical; that is, it appears that an electrostatic interaction is affecting the (chemical) RAFT equilibrium.