Controlled Chain Branching by RAFT-Based Radical Polymerization

Abstract

Styrene radical polymerization was carried out in the presence of a polymerizable dithioester, benzyl 4-vinyldithiobenzoate, which possesses a dithioester group and a polymerizable double bond. Branched polystyrene was formed during the polymerization, as indicated by multimodal GPC curves of the products. The branched polystyrene contains a dithiobenzoate C(dS)S moiety at each branch point and thus can be analyzed by cleavage with amine. After cleavage, the GPC profiles became narrow. The molecular weight of the cleaved product increased linearly with monomer conversion, illustrating a living fashion of the polymerization. Solution property obtained by simultaneous online measurements of viscosity and light scattering indicates that the viscosity of the branched product decreased remarkably as compared to the linear polystyrene of equivalent molecular weight. The copolymerization behavior of styrene and benzyl 4-vinyldithiobenzoate was investigated by FT-IR monitoring during the polymerization. The results show that the latter was incorporated homogeneously into polystyrene chain. Therefore, branched polystyrene was synthesized with controlled architecture in the light of the length and narrow distribution of primary chains as well as the degree and the distribution of branching along the polymer chain.

Living Radical Polymerization by the RAFT Process

“…The potential of this chemistry to cleave end groups and decolourize polymers and produce polymers with thiol end groups was cited in our initial communication on RAFT polymerization. [13] Examples of end-group cleavage with nucleophiles such as amines, [15,96,198,199] hydroxide, [93] and borohydride [164,200] can be found in recent publications. Radical induced reduction with, for example, tri-n-butylstannane [15,201,202] can be used to replace the thiocarbonylthio group with hydrogen.…”

Thermolysis of RAFT-Synthesized Poly(Methyl Methacrylate)

“…[2] Thiocarbonylthio groups undergo reaction with nucleophiles and ionic reducing agents (e.g. amines, [8][9][10][11][12][13][14][15] hydroxide, [16,17] borohydride [18,19] ) to provide thiols. They also react with various oxidizing agents (including NaOCl, H 2 O 2 , Bu t OOH, peracids, ozone) [2,[20][21][22] and are sensitive to UV irradiation.…”

Effects of RAFT Agent on the Selective Approach of Molecularly Imprinted Polymers

“…To compare with other RDRP methods, such as atom transfer radical polymerization (ATRP), the RAFT technique does not involve any metal catalyst, hence, there is no trace of metal contaminants in the final products, unlike the ATRP method [19,33]. RAFT polymerization allows the synthesis of several functional polymeric materials and the design of hyperbranched polymers [34][35][36][37]. Due to its advantages, RAFT polymerization has been used to prepare cross-linked polymers, such as MIPs synthesis [20,38,39] and other homogeneous polymer networks [40,41].…”