Hybridization of Step‐/Chain‐Growth and Radical/Cationic Polymerizations Using Thioacetals as Key Components for Triblock, Periodic and Random Multiblock Copolymers with Thermoresponsiveness

Abstract

A novel strategy for synthesizing a series of multiblock copolymers is developed by combining radical/cationic step‐growth polymerizations of dithiols and divinyl ethers and chain‐growth cationic degenerative chain‐transfer (DT) polymerizations of vinyl ethers using thioacetals as key components. The combination of radical step‐growth polymerization and a cationic thiol‐ene reaction or cationic step‐growth polymerization enables the synthesis of a series of macro chain‐transfer agents (CTAs) composed of poly(thioether) and thioacetal groups at different positions. The resulting products are 1) bifunctional macro CTAs with thioacetal groups at both chain ends, 2) periodic macro CTAs periodically having thioacetal groups in the main chain, and 3) random macro CTAs randomly having thioacetal groups in the main chain. Subsequently, the obtained macro CTAs are used for chain‐growth cationic DT polymerization of methoxyethyl vinyl ether (MOVE) to result in 1) triblock, 2) periodic, and 3) random multiblock copolymers consisting of poly(thioether) and poly(MOVE) segments. All these triblock and multiblock copolymers composed of hydrophobic poly(thioether) and hydrophilic poly(MOVE) segments show an amphiphilic tendency to form characteristic micelles in aqueous solutions. In addition, due to the thermoresponsive poly(MOVE) segments, the obtained copolymers exhibit lower critical solution temperatures that depend on the segment sequences and lengths.

A straightforward and rapid synthesis of polydithioacetals in the presence of chlorodimethylsilane

“…32 After these preliminary studies, PDTA synthesis has been overlooked for a long time, but it has started to attract attention again in the last decade in parallel with the developments in polymer science. [33][34][35][36][37][38] More recently, Yang and coworkers reported monomer-polymer recycling of PDTA. 39 The authors prepared PDTA from 3,4,5-trimethoxybenzaldehyde and a variety of alkyl dithiols in acetonitrile catalyzed by p-toluenesulfonic acid (PTSA) at 50 °C for 24 h. Next, the authors described that the PDTA showed depolymerizability via ring-closing depolymerization into macrocycles, followed by entropy-driven ring-opening polymerization to reassemble the pristine PDTAs.…”

“…42,43 Therefore, PDTAs have found extensive applications in bio-related fields where controlled degradation is desired, such as targeted drug delivery and tissue engineering. 26,37,[44][45][46][47][48][49][50] In particular, all these recent studies indicate the huge potential and the increasing importance of PDTA in terms of synthetic polymer chemistry.…”

Synthesis and Degradation of Vinyl Polymers with Evenly Distributed Thioacetal Bonds in Main Chains: Cationic DT Copolymerization of Vinyl Ethers and Cyclic Thioacetals

“…In addition, we previously reported that main‐chain thioacetal bonds of polythioacetals, which are prepared by step‐growth cationic thiol‐ene polymerization of dithiol and divinyl ether, can serve as macro‐chain‐transfer agents for cationic polymerization of vinyl ethers to form copolymers. [ 82 , 83 ] However, the total polymer chain lengths cannot be controlled due to the step‐growth mechanism for the formation of polythioacetals in the first step.…”

Synthesis and Degradation of Vinyl Polymers with Evenly Distributed Thioacetal Bonds in Main Chains: Cationic DT Copolymerization of Vinyl Ethers and Cyclic Thioacetals

“…However, trithiocarbonate bonds are labile and can generate products with color and odor. In addition, we previously reported that main‐chain thioacetal bonds of polythioacetals, which are prepared by step‐growth cationic thiol‐ene polymerization of dithiol and divinyl ether, can serve as macro‐chain‐transfer agents for cationic polymerization of vinyl ethers to form copolymers [82, 83] . However, the total polymer chain lengths cannot be controlled due to the step‐growth mechanism for the formation of polythioacetals in the first step.…”