One‐Pot Synthesis of PTFEMA‐b‐PMMA‐b‐PTFEMA by Controlled Radical Polymerization with a Difunctional Initiator in Conjugation with Photoredox Catalyst of Ir(ppy)₃ Under Visible Light

Abstract

Visible-light-induced free radical polymerization of methyl methacrylate (MMA) and 1,1,1-trifl uoroethyl methacrylate (TFEMA) with a difunctional initiator, dimethyl 2,6-dibromoheptanedioate (DMDBHD), conjugated with a photoredox catalyst, tris(2-phenylpyridinato)iridium(III) ( fac -[Ir(ppy) 3 ]), is investigated. Kinetic studies demonstrate that homopolymerizations of both MMA and TFEMA are controlled radical polymerizations. The linear increase of mole cular weights with monomer conversion and the narrow PDIs (1.2-1.4) reveal a good living character. In addition, PTFEMA-b -PMMA-b -PTFEMA triblock copolymer is prepared by a one-pot process with sequential monomer addition. The M n of the triblock copolymers increases linearly with monomer conversion and the PDI of block copolymers is still maintained around 1.2-1.4. Experimental data confi rm that the products are pure block polymers. Furthermore, the molar fraction of the TFEMA monomeric unit in the block copolymer is about 21.96%, close to the theoretical value 21.00% calculated from the monomer conversion. elemental reactions, such as the initiation, propagation, and termination, of free radical polymerization take place in the order of 1 s, roughly the average lifetime of a propagating chain. Thus, it is impossible to control the molecular weight and its distribution, notwithstanding the macromolecular architecture. Inspired by the achievements of living ionic polymerization, polymer chemists made a great effort twoard the development of controlled radical polymerization (CRP). Otsu et al. [ 2 ] rightly pointed out that a stepwise chain growth would likely lead to control of the molecular weight in radical polymerization. They successfully developed a CRP system mediated by small stable radicals known as iniferter. Since then, several CRP methods, such as nitroxide-mediated polymerization (NMP), [ 3,4 ] atom-transfer radical polymerization (ATRP), [ 5 ] transitional metal-catalyzed CRP, [ 6 ] addition-fragmentation

Visible light‐induced thiol‐ene reaction: A new strategy to prepare Α,ω‐dithiol and Α,ω‐divinyl telechelic polythiolether oligomers

“…More importantly, the corresponding molar ratios of DEGVE segment to BDMT segment in obtained copolymers were 1/1.2 and 1/1.5 as well. For each oligomer, the M n determined by 1 H NMR (M n,NMR ) was 1798 (DEGVE/BDMT52/1), 1810 (DEGVE/BDMT51/ 1.2), and 826 (DEGVE/BDMT 5 1/1.5) g mol 21 .…”

“…The solution was purged with argon for 2 h while stirring. After the addition of a solution of NPM in DMF (2 mL, 5 mg mL 21 ), the Pyrex flask (50 mL) was sealed ARTICLE with a rubber septum. Then this solution was allowed to reaction for 24 h. Then, the reaction mixture was passed through a basic alumina column prior to fluorescence measurement.…”

“…In a vial, 2 mg of oligomer was dissolved in 1 mL of acetone. The solution for MALDI-TOF MS analysis was obtained by mixing 2,5-dihydroxybenzoic acid matrix (10 mg mL 21 ), and oligomer solution in a 1/1 volumetric ratio.…”

“…Some studies have already focused on the synthesis of linear oligomers and polymers through step-growth and addition/chain polymerizations of diolefins with dithiols. For instance, in 1998, radical polyadditions of diolefins with several dithiols were carried out at 60 8C for 20 h in the presence of 3 mol% 2,2'-azobis-isobutyronitrile in N,N-dimethylformamide by Koyama et al Linear polymers with M n of 20000-75700 g mol 21 were successfully prepared. 34 Thereafter, the formation of linear polymer on the surface of silica nanoparticles using thiol-ene photopolymerizations was also investigated by Khire et al 35 In their research, 1,6-hexanedithiol and triethylene glycol divinyl ether were photopolymerized on the thiol-terminated surfaces with 0.1 wt % 2,2-dimethoxy-2-phenylacetophenone as photoinitiator under UV irradiation.…”

“…Lluch et al 37 developed an efficient and versatile "one-pot" method for the preparation of well-defined telechelic polymers via two sequential thiolene click processes in 2010. At first, alkene-functionalized linear polymers with different molecular weights (M n,theo 5 1000, 2000, 3000 g mol 21 ) were prepared by allyl ester of 10-undecenoic acid and 3,6-dioxa-1,8-octanedithiol. Then, these end-functional polymers were employed as precursors to prepare block copolymers.…”