Controlled/“Living” Radical Ring-Opening Polymerization of 5,6-Benzo-2-Methylene-1,3-Dioxepane Based on Reversible Addition-Fragmentation Chain Transfer Mechanism

Abstract

ABSTRACT:The radical ring-opening polymerization of 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) was performed in the presence of 1-(ethoxycarbonyl)prop-1-yl-dithiobenzoate (EPDTB) and dicumyl peroxide (DCP). The completely ring-opening polymerization of BMDO via reversible addition-fragmentation transfer mechanism was proved to be controlled by the following experimental evidences: the straight line of ln ([M] 0 /[M] t ) vs. polymerization time; linear increase of molecular weight with increasing conversion and relatively narrow molecular weight distribution. The mechanism of the polymerization was discussed. The complete ring-opened structure of the PBMDO was characterized by 1 H and 13 C NMR spectroscopies as well as gel permeation chromatography (GPC). KEY WORDS Controlled Polymerization / Radical Ring-Opening Polymerization / Reversible Addition-Fragmentation Chain Transfer (RAFT) / 5,6-Benzo-2-Methylene-1,3-Dioxepane / Free radical ring-opening polymerization has been an attractive subject because it produces polymers with various functional groups (such as ethers, esters, amides, and carbonates) in their backbone. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Addition of unsaturated heterocycles into polymerization system of commercial monomers will improve the properties of the polymers obtained. For example, when 2-methylene-4-n-decyl-1,3-dioxolane was copolymerized with vinyl chloride, the thermal stability and flexibility of the polymer obtained improved. 15 However, free radical ring-opening polymerization of the unsaturated heterocycles yields polymers with low molecular weight and broad molecular weight distribution. For instance, the radical ring-opening polymerization of 2-methylene-4-phenyl-1,3-dioxolane proceeds via chain radicals 1 and 2 as shown in Scheme 1. [16][17][18] The chain radicals 1 and 2 are stabilized respectively by two oxygens and phenyl group. The former radical is more active than the later one. The low molecular weight polymer with broad polydispersity index may be due to the transfer reaction during the polymerization.Recently, significant progress has been made in the field of living free radical polymerization including nitroxide-mediate stable free radical polymerization (SFRP); 19-23 atom transfer radical polymerization (ATRP); 24-26 and reversible addition-fragmentation transfer (RAFT) process. 27,28 In these polymerizations, there is a fast equilibrium between propagating radiScheme 1. cals and dormant chains, which is prerequisite for the synthesis of controlled polymers. 29 When the methods apply in the polymerization of unsaturated heterocycles, the termination of propagating radicals must be affected. To produce polymers with controlled molecular weights and architectures, Wei et al. 30 reported the study on nitroxide-mediated stable free radical polymerization of 2-methylene-1,3-dioxepane, which underwent quantitative ring-opening polymerization to afford a polyester with polydispersity less than 1.5. Jia et al. 31 presented the first example of a controlled free r...

Controlling the synthesis of degradable vinyl polymers by xanthate-mediated polymerization

“…33,34 However, with the exception of less activated monomers (LAMs) such as VAc, the reactivity ratios for these copolymerizations indicate that final polymer compositions are more gradient-like or blocky, not statistical. 17,25,29,35 Control of polymerizations incorporating CKAs has also been attempted through reversible-deactivation radical polymerization (RDRP) techniques such as Nitroxide-Mediated Polymerization (NMP), 19,36 Atom Transfer Radical Polymerization (ATRP), [37][38][39] and Reversible Addition-Fragmentation Chain-Transfer Polymerization/Macromolecular Design by Interchange of Xanthates (RAFT/MADIX) 40 but there are only a handful of examples where these techniques have been used to control copolymerizations with MDO. Using BlocBuilder MA alkoxyamine initiator (SG1) to mediate the copolymerization of PEGMA or MMA, AN, and MDO, Delplace et al have demonstrated control with final dispersities, Đ M , <1.4.…”

Mapping the characteristics of the radical ring‐opening polymerization of a cyclic ketene acetal towards the creation of a functionalized polyester

“…Radical polymerization of MDO in the presence of a stable free radical (TEMPO) was shown to yield a ring‐opened aliphatic polyester with narrow molecular weight distributions 21, 22. The cyclic ketene acetal 5,6‐benzo‐2‐methylene‐1,3‐dioxepane has been homopolymerized by reversible addition‐fragmentation chain transfer polymerization23 and homo‐24, 25 and copolymerized with vinyl monomers26, 27 by atom transfer radical polymerization.…”

Living Radical Polymerization by the RAFT Process

“…BMDO [76] -20 [44] S, [14,44,46,77] MA, [44] BA, [13,44] S-b-DMA, [14,77] S-b-SMe, [14,77] MMA-b-S, [9] (MMA), [44] DMA, [14] S-MAH, [51,79,80] (AMS-MAH) [51] NIPAM, [78] S, [9,14] MMA [9] (continued) …”