Photocontrolled lactide ROP by the light-regulated release of potassium acetate from an azobenzene-bridged crown ether

Abstract

An azobenzene-bridged 15-crown-5 ether (1) was successfully used as photoswitchable cocatalyst modulating the catalytic activity of potassium acetate (KOAc) in the ring-opening polymerization (ROP) of L-lactide (L-LA) when initiated from...

Recent advances in externally controlled ring-opening polymerisations

“…8). 100 The same group had pre- viously reported the use of crown ethers to accelerate the ROP of L-LA through the in situ generation of free ions. 101 The use of azobenzene as a bridge could allow a controllable system where more active species are generated "on-demand".…”

“…Fig.8A photoresponsive azobenzene incorporated bis(15-crown-5-ether) which transforms the K +− OAc ion pair like into free ions through a butterfly movement by E/Z isomerisation of the azo linkage resulting in increased polymerisation rates 100. Reproduced from ref 100. with permission from Royal Society of Chemistry.…”

Unexpected Quasi-Alternating Copolymerization of Oxiranes Driven by a Benign Acetate-based Catalyst

“…To meet the rising demand for sustainable and simple ROP systems, the organocatalytic polymerization approach has emerged as a powerful tool for polyether synthesis 19,20,21,22,23 . In this context, alkali metal carboxylate catalysts, eventually complexed by crown ethers 24,25 , have played a crucial role in the development of various (co)polymers due to their ability to be used in bulk, of their low cost and low toxicity. Our group has recently demonstrated the potential of an equimolar mixture of potassium acetate (KOAc) and 18crown-6 ether (18C6) as a robust and benign catalytic system for preparing PPO in a controlled fashion at room temperature and in solvent-free conditions 26 .…”

Recent developments in the UV-visible light-intervened ring-opening polymerization of cyclic esters

“…26 Practically speaking, it also provides excellent spatial or temporal control, allowing the polymerization process as well as the properties/compositions of the polymeric product to be controlled. 27–49 Moreover, photopolymerization frequently offers a rapid cure, allowing for quick processing and lower costs. 14 The primary driving forces behind this technique are not only the environmental and practical advantages it offers, but also the recent advancements in this field in terms of technology, 50,51 reactions, 15–19 and applications.…”

“…Light, in particular, is an ideal stimulus for controlling polymerization reactions because it has wavelength or intensity tunability and is easy to handle, non-invasive, highly versatile, chromophore selective, ubiquitous, and environmentally friendly. 27–49 Photosensitive substances contain a photochromic moiety that absorbs the incident light to produce active species that initiate polymerization. Hence, the utilization of different photosensitive substances such as photoacid generators (PAGs) 17,24 and photobase generators (PBGs) 24,66 for the polymerization techniques has been reported.…”