Merging CO2-Based Building Blocks with Cobalt-Mediated Radical Polymerization for the Synthesis of Functional Poly(vinyl alcohol)s

Mechanically triggered on-demand degradation of polymers synthesized by radical polymerizations

Polymers that degrade on demand have the potential to facilitate chemical recycling, reduce environmental pollution and are useful in implant immolation, drug delivery or as adhesives that debond on demand. However, polymers made by radical polymerization, which feature all carbon-bond backbones and constitute the most important class of polymers, have proven difficult to render degradable. Here we report cyclobutene-based monomers that can be co-polymerized with conventional monomers and impart the resulting polymers with mechanically triggered degradability. The cyclobutene residues act as mechanophores and can undergo a mechanically triggered ring-opening reaction, which causes a rearrangement that renders the polymer chains cleavable by hydrolysis under basic conditions. These cyclobutene-based monomers are broadly applicable in free radical and controlled radical polymerizations, introduce functional groups into the backbone of polymers and allow the mechanically gated degradation of high-molecular-weight materials or cross-linked polymer networks into low-molecular-weight species.

Synthesis of Polymeric Mimics of Ice-Binding Proteins

Cobalt-mediated radical polymerization (CMRP) enables the preparation of both short and long polymers from acrylic and vinyl ester monomers with low dispersity. Here we describe the synthesis, purification, and characterization of polymeric mimics of ice-binding proteins based on the water-soluble polymer poly(vinyl alcohol) by CMRP. Block copolymers of poly(vinyl alcohol) and poly(acrylic acid) were prepared from the precursor copolymers poly(vinyl acetate)-b-poly(acrylonitrile) upon hydrolysis. Copolymers comprising up to hundreds of monomers and dispersities Mw/Mn < 1.3 were produced by this method.

Exovinylene Cyclic Carbonates: Multifaceted CO2 -Based Building Blocks for Modern Chemistry and Polymer Science

Carbon dioxide is a renewable, inexhaustible, and cheap alternative to fossil resources for the production of fine chemicals and plastics. It can notably be converted into exovinylene cyclic carbonates, unique synthons gaining momentum for the preparation of an impressive range of important organic molecules and functional polymers, in reactions proceeding with 100 % atom economy under mild operating conditions in most cases. This Review summarizes the recent advances in their synthesis with particular attention on describing the catalysts needed for their preparation and discussing the unique reactivity of these CO₂ -based heterocycles for the construction of diverse organic building blocks and (functional) polymers. We also discuss the challenges and the future perspectives in the field.

Multi-responsive γ-methylene-γ-butyrolactone/N-vinyl caprolactam copolymers involving pH-dependent reversible lactonization

Copolymerization of γ-methylene-γ-butyrolactone with N-vinyl caprolactam leads to a peculiar multi-responsive NVCL-based system involving a unique reversible pH-dependent ring opening/closure of the pendant lactones.

Organo-Cobalt Complexes in Reversible-Deactivation Radical Polymerization

Cobalt complexes have played an essential role in different chemical reactions. One of them that has attracted substantial attention in polymer science is cobalt mediated radical polymerization (CMRP), which is famous for its remarkable efficiency in controlling the radical polymerization of vinyl acetate (VAc) and other less active monomers (LAMs). Two pathways, reversible termination (RT) and degenerative transfer (DT), were recognized to control the polymerization in CMRP and could be further used to rationalize the mechanism of other RDRP methods. These control mechanisms were then found to be correlated to the redox potential of cobalt complexes and thus could be judged more quantitatively. The control of polymer composition and tacticity could also be achieved by using CMRP. The hybridization of CMRP and atom transfer radical polymerization (ATRP) could directly synthesize the vinyl acetate/methyl methacrylate and vinyl acetate/styrene block copolymers in one pot. The copolymer of acrylates and 1-octene could be obtained by visible-light-induced CMRP. With the addition of bulky Lewis acid, CMRP of N,N-dimethylacrylamide (DMA) showed high isotacticities with the contents of meso dyads (m) and meso triads (mm) up to 94 % and 87 %, respectively, and generated the crystalline PDMA with T_m as high as 276 °C. This personal account reviewed the development of CMRP with the mechanistic understanding, the control of composition and stereoselectivity of the polymeric products, and its perspective.

Functional Polyethylenes by Organometallic-Mediated Radical Polymerization of Biobased Carbonates

Partly or fully renewable (co)polymers are gaining interest in both academia and industry. Polyethylene is a widely used polymer, classically derived from fossil fuels, with a high versatility stemming from the introduction of comonomers altering the mechanical properties. The introduction of renewable functionalities into this polymer is highly attractive to obtain functional, tunable, and at least partially renewable polyethylenes. We herein report the introduction of biosourced cyclic carbonates into polyethylene using organometallic-mediated radical polymerization under mild conditions. Molecular weights of up to 14 600 g mol^-1 with dispersities as low as 1.19 were obtained, and the cyclic carbonate content could be easily tuned by the ethylene pressure during the polymerization. As a proof of concept, the hydrolysis of the cyclic carbonates of a representative copolymer was explored, and it provided polyethylene-bearing vicinal diols, with a hydrolysis degree of 71%. Given the multitude of chemoselective modifications possible on cyclic carbonates as well as the fact that many allylic- and alkylidene-type cyclic carbonates are accessible from renewable resources, this work opens up an avenue for the design of functional and more sustainable polyethylenes.

Progress Toward Sustainable Reversible Deactivation Radical Polymerization

The recent focus of media and governments on renewability, green chemistry, and circular economy has led to a surge in the synthesis of renewable monomers and polymers. In this review, focussing on renewable monomers for reversible deactivation radical polymerizations (RDRP), it is highlighted that for the majority of the monomers and polymers reported, the claim to renewability is not always accurate. By closely examining the sustainability of synthetic routes and the renewability of starting materials, fully renewable monomers are identified and discussed in terms of sustainability, polymerization behavior, and properties obtained after polymerization. The holistic discussion considering the overall preparation process of polymers, that is, monomer syntheses, origin of starting materials, solvents used, the type of RDRP technique utilized, and the purification method, allows to highlight certain topics which need to be addressed in order to progress toward not only (partially) renewable, but sustainable monomers and polymers using RDRPs.

Reversible deactivation radical (co)polymerization of dimethyl methylene oxazolidinone towards responsive vicinal aminoalcohol-containing copolymers

Well-defined oxazolidinone-containing copolymers produced by controlled radical polymerization give access to multi-responsive vicinal amino-alcohol functional poly(vinyl alcohol)s.

Polymers Based on Cyclic Carbonates as Trait d'Union Between Polymer Chemistry and Sustainable CO2 Utilization

Given the large amount of anthropogenic CO₂ emissions, it is advantageous to use CO₂ as feedstock for the fabrication of everyday products, such as fuels and materials. An attractive way to use CO₂ in the synthesis of polymers is by the formation of five-membered cyclic organic carbonate monomers (5CCs). The sustainability of this synthetic approach is increased by using scaffolds prepared from renewable resources. Indeed, recent years have seen the rise of various types of carbonate syntheses and applications. 5CC monomers are often polymerized with diamines to yield polyhydroxyurethanes (PHU). Foams are developed from this type of polymers; moreover, the additional hydroxyl groups in PHU, absent in classical polyurethanes, lead to coatings with excellent adhesive properties. Furthermore, carbonate groups in polymers offer the possibility of post-functionalization, such as curing reactions under mild conditions. Finally, the polarity of carbonate groups is remarkably high, so polymers with carbonates side-chains can be used as polymer electrolytes in batteries or as conductive membranes. The target of this Review is to highlight the multiple opportunities offered by polymers prepared from and/or containing 5CCs. Firstly, the preparation of several classes of 5CCs is discussed with special focus on the sustainability of the synthetic routes. Thereafter, specific classes of polymers are discussed for which the use and/or presence of carbonate moieties is crucial to impart the targeted properties (foams, adhesives, polymers for energy applications, and other functional materials).