Tailoring polymer dispersity by mixing chain transfer agents in PET-RAFT polymerization†
Here we report a simple and versatile batch methodology to tailor polymer dispersity utilizing PET-RAFT polymerization. By mixing two chain transfer agents (CTAs) possessing different transfer constants (a higher and a lower transfer constant CTA) in different ratios, control over the dispersity (Đ = 1.08–1.82) can be achieved for a range of monomer classes including methacrylates, acrylates and acrylamides while maintaining monomodal molecular weight distribution. The high end-group fidelity of both low and high dispersity macroCTAs was confirmed by the synthesis of block copolymers. In contrast to previously developed photo-mediated methodologies, we show that PET-RAFT exhibits perfect temporal control for all targeted dispersities regardless of the percentage of the lower transfer constant CTA employed. Other benefits of the approach include the use of visible light irradiation, ppm concentrations of a photo-redox catalyst and the possibility to manipulate Đ in the absence of external deoxygenation methodologies, which significantly simplify the process.
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