Random and Diblock Thermoresponsive Oligo(ethylene glycol)-Based Copolymers Synthesized via Photo-Induced RAFT Polymerization.

Ksenia Otopkova,Alexey Sivokhin,Olga Sivokhina,Michael Smirnov,Oleg Kazantsev,Rostislav Karpov,Sergey Orekhov,Dmitry Orekhov,Denis Kamorin

doi:10.3390/polym14010137

Ksenia Otopkova, Alexey Sivokhin + Show 7 more

Open Access

https://doi.org/10.3390/polym14010137

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Abstract

Amphiphilic random and diblock thermoresponsive oligo(ethylene glycol)-based (co)polymers were synthesized via photoiniferter polymerization under visible light using trithiocarbonate as a chain transfer agent. The effect of solvent, light intensity and wavelength on the rate of the process was investigated. It was shown that blue and green LED light could initiate RAFT polymerization of macromonomers without an exogenous initiator at room temperature, giving bottlebrush polymers with low dispersity at sufficiently high conversions achieved in 1–2 h. The pseudo-living mechanism of polymerization and high chain-end fidelity were confirmed by successful chain extension. Thermoresponsive properties of the copolymers in aqueous solutions were studied via turbidimetry and laser light scattering. Random copolymers of methoxy- and alkoxy oligo(ethylene glycol) methacrylates of a specified length formed unimolecular micelles in water with a hydrophobic core consisting of a polymer backbone and alkyl groups and a hydrophilic oligo(ethylene glycol) shell. In contrast, the diblock copolymer formed huge multimolecular micelles.

Highlights

In the last decade, methods of controlled photopolymerization induced by visible light have attracted great interest
The low-temperature process without a thermal initiator allows the use of water as a green solvent in preparing thermoresponsive polymers at temperatures below LCST [5]
Amphiphilic random and diblock thermoresponsive OEGMA-based bottlebrushes were successfully synthesized via photoiniferter RAFT polymerization

Summary

Introduction

Methods of controlled photopolymerization induced by visible light have attracted great interest. The simplicity of the experimental setup, lack of high temperatures, and cheap household light source coupled with good control of the reaction made this process quite popular among researchers. An essential advantage of photoRAFT polymerization is high chainend fidelity [6,7], making it one of the best tools for precision polymer synthesis. The use of continuous flow reactors for photoRAFT polymerization, in addition to the mentioned advantages, makes it possible to significantly reduce reaction times and achieve high conversions while maintaining good control over the molecular weight distribution [8]

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