Functional initiators for the ring‐opening polymerization of polyesters and polycarbonates: An overview

Abstract

Functional ring‐opening polymerization (ROP) initiators can instill a wide array of chemical, physical, and biological effects into a polymeric chain. Highlighting the versatility of this “active” initiator approach, a broad range of characteristics can be achieved through the use of initiators with chemistries spanning from drugs and dyes (key in the case of drug delivery or nanoparticle applications) through to radically active monomers, polymerization transfer agents, and catalysts. The selection of a suitable “active” initiator (monomers for tandem reactions, dyes, drugs, stereo‐catalysts, etc.) can not only provide the final polymers with interesting application potential but also facilitate the implementation of ROP reactions in tandem with other polymerization techniques. Overall, this review will highlight that functionalities and properties can be effectively tuned by exploiting simple chemistry approaches, allowing readers to identify how these approaches could be of benefit to their own work in a range of applications including drug/gene delivery, amphiphilic bio/degradable carriers, drug/scent controlled release, and stereo‐controlled polymers.

Preformed Biodegradable Zwitterionic Nanoparticles as Tunable Excipients for the Formulation of Therapeutics Directly at the Point of Care

“…33 These macromonomers are produced via ring opening polymerization (ROP) of lactones (e.g., caprolactone or lactide) in the presence of a primary alcohol comprising a vinyl group (e.g., hydroxyethyl methacrylate, HEMA). 34,35 In addition, these macromonomers can be provided with a charged functional moiety by exploiting the reactivity of their hydroxyl end-group. 36 We now exploit these latest advances in the synthesis of highly controllable colloids to produce biodegradable zwitterionic NPs that, with minimal effort, can be adapted for the efficient loading and controlled release of different drugs.…”

“…However, the advent of the reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization has allowed the production of highly tunable NPs composed of block copolymers directly in aqueous media. , To make these NPs biodegradable, oligoester-based macromonomers can be adopted to synthesize the hydrophobic portion of the copolymers and hence to drive their simultaneous self-assembly . These macromonomers are produced via ring opening polymerization (ROP) of lactones (e.g., caprolactone or lactide) in the presence of a primary alcohol comprising a vinyl group (e.g., hydroxyethyl methacrylate, HEMA). , In addition, these macromonomers can be provided with a charged functional moiety by exploiting the reactivity of their hydroxyl end-group …”

Graft Copolymers of N-Isopropylacrylamide with Poly(d,l-lactide) or Poly(ε-caprolactone) Macromonomers: A Promising Class of Thermoresponsive Polymers with a Tunable LCST

“…Moreover, very limited information is available in the literature on the synthesis of NIPAM copolymers with caprolactone-based macromonomers or macromonomers based on other biodegradable polymers. It should also be noted here that conventional radical polymerization was routinely applied for the synthesis of the above-mentioned copolymers of NIPAM with polylactide or polycaprolactone macromonomers that resulted in the preparation of ill-defined copolymers. − , In addition, polylactide or polycaprolactone macromonomers were typically prepared via Sn­(Oct) 2 - or NaOCH 3 -catalyzed ring-opening polymerization (ROP), − , which may be complicated by the transesterification reaction leading to obtaining ill-defined macromonomers. , …”

“…[22][23][24][25][26]33 In addition, polylactide or polycaprolactone macromonomers were typically prepared via Sn(Oct) 2 -or NaOCH 3 -catalyzed ringopening polymerization (ROP), [22][23][24][25][26]33 which may be complicated by the transesterification reaction leading to obtaining ill-defined macromonomers. 34,35 In this study, we synthesized a series of well-defined polylactide and polycaprolactone macromonomers (M n of ∼ 600 and ∼1200 Da) bearing a (meth)acrylate group at one side of the chain and either a hydrophobic nonpolar butyl group or a hydrophilic polar hydroxyl group at the other side of the chain via 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU)catalyzed ROP of D,L-lactide (LA) and methanesulfonic acid (MSA)-catalyzed ROP of ε-caprolactone, respectively. These macromonomers were copolymerized with NIPAM via controlled radical polymerization using 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid (DMP) as a RAFT agent to prepare a series of random graft copolymers with different contents of the macromonomers in a copolymer (the NIPAM content varying from 83.3 to 100 wt %).…”

Polyphosphonate-Based Macromolecular RAFT-CTA Enables the Synthesis of Well-Defined Block Copolymers Using Vinyl Monomers

“…This strategy involved the use of 2-bromo-isobutyryl groups as functional initiators or as part of the cyclic monomer (CH 2 O) 2 P­(O)­OR to form macroinitiators for ATRP via ROP of cyclic phosphates followed by the preparation of block or graft copolymers (Scheme A,B). − In contrast, no PPE-containing block copolymers have been reported previously using a RAFT protocol. Besides the well-known PEGylated macro-CTAs, , other CTAs used mostly hydrophobic polyesters, polyethers, and polycarbonates from ROP to prepare block copolymers. − A water-soluble PPE macro-CTA opens up the possibilities of replacing commercial PEGylated CTAs in a broad range of applications, such as drug encapsulation or polymerization-induced self-assembly, for example. , …”