Ambient Temperature Reversible Addition-Fragmentation Transfer Radical Polymerization Of N-Butyl Acrylate Under Solar Radiation

Controlled radical polymerization has witnessed a revolutionary development during the past decade, among all these"living"/controlled methodologies, Reversible Addition-Fragmentation Transfer (RAFT) polymerization has arguably the most promising industry prospect for its wild monomer selections, mild conditions during polymerization, low molecular weight distribution and accuracy in architecture design. However, for the intrinsic retardation of RAFT polymerization, recent RAFT approaches are mainly realized via thermal activation or initiation which was detrimental to thermally biodegradable materials and thermally responsive architectures. This paper cultivates an environment friendly continuous activation resource---Solar Radiation (SR), under which"living"/controlled RAFT polymerization was realized rapidly and efficiently at ambient temperature;also this paper studies the influence of a continuous- and a separated-spectroscopic-emission radiation resource to photo-activated RAFT polymerizations.Based on our previous researches, S-dodecyl-S′-(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (DDMAT) and S,S′-bis (α,α′-dimethyl-α″-acetic acid) trithio- carbonate (BDMAT) were selectively synthesized as Chain Transfer Agents (CTAs) in our research, (2,4,6-trimethyl-benzoyl) diphenylphosphine oxide (TPO) was utilized as photo-initiator, and focuses its research on ambient temperature RAFT polymerization of n-Butyl Acrylate (nBA) in solutions under SR. we found BAMAT is a more applicable CTA for the better well-controlled properties it conferred to the polymerizations.UV-vis spectrophotometry revealed that, for BDMAT mediated ambient temperature RAFT polymerization of nBA, the CTA moiety photolysis and initialization period can be evidently influenced under different radiation wavelength and intensity. A visible SR of lower intensity rendered a prolonged initialization period while an apparent decrease in CTA moiety photolysis to the polymerization.Kinetic studies indicated that a visible SR with intensity of I_365nm=3～10μW/cm², I_420nm=250～300μW/cm² yielded high conversion and exerted first-order polymerization kinetic to the BDMAT mediated ambient temperature RAFT polymerization of nBA.For further understanding of the BDMAT mediated ambient temperature RAFT polymerization of nBA, the living characteristics of polymerization under different SR wavelength, intensity and initial CTA concentration were investigated. As can be anticipated, polymerizations of all initial CTA concentrations carried out under visible SR with intensity of I_365nm=3～10μW/cm～2, I_420nm=250～300μW/cm～2 showed the best living characteristics evidenced by well-controlled molecular weight, linear increase of molecular weight with increasing conversion, narrow molecular weight distribution, and fine macro-CTA's chain-extension properties: narrow polydispersity and ideally symmetrical GPC traces for both self-block and hetero-block copolymers.Based on our realization in BDMAT mediated ambient temperature RAFT polymerization of nBA, analogous experiments were carried out under radiation of high pressure mercury vapor lamp. By comparison, we found that RAFT polymerization carried out under a continuous-spectroscopic-emission radiation (SR) has noticeably favorable living characteristics than that under separated- spectroscopic-emission high pressure mercury vapor lamp radiation.