Controlled Radical Homopolymerization of Representative Cationically Polymerizable Vinyl Ethers

Installing a Single Monomer within Acrylic Polymers Using Photoredox Catalysis

Incorporating exactly one monomer at a defined position during a chain polymerization is exceptionally challenging due to the statistical nature of monomer addition. Herein, photoinduced electron/energy transfer (PET) enables the incorporation of exactly one vinyl ether into polyacrylates synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Near-quantitative addition (>96%) of a single vinyl ether is achieved while retaining >99% of the thiocarbonylthio chain ends. Kinetic studies reveal that performing the reactions at 2 °C limits unwanted chain breaking events. Finally, the syntheses of diblock copolymers are reported where molecular weights and dispersities are well-controlled on either side of the vinyl ether. Overall, this report introduces an approach to access acrylic copolymers containing exactly one chemical handle at a defined position, enabling novel macromolecular architectures to probe structure-function properties, introduce sites for de/reconstruction, store information, etc.

Umpolung Isomerization in Radical Copolymerization of Benzyl Vinyl Ether with Pentafluorophenylacrylate Leading to Degradable AAB Periodic Copolymers

This study revealed that benzyl vinyl ether (BnVE) shows a peculiar isomerization propagation in its radical copolymerization with an electron-deficient acrylate carrying a pentafluorophenyl group (PFA). The co-monomer pair inherently exhibits the cross-over propagation feature due to the large difference in the electron density. However, the radical species of PFA was found to undergo a backward isomerization to the penultimate BnVE pendant giving a benzyl radical species prior to propagation with BnVE. The isomerization brings a drastic change in the character of the growing radical species from electrophilic to nucleophilic, and thus the isomerized benzyl radial species propagates with PFA. Consequently, the two monomers were consumed in the order AAB (A: PFA; B: BnVE) and the unique periodic consumption was confirmed by the pseudo-reactivity ratios calculated by the penultimate model: r11 =0.174 and r21 =6600 for PFA (M1 ) with BnVE (M2 ). The pentafluorophenyl ester groups of the resulting copolymers are transformed into ester and amide groups by post-polymerization alcoholysis and aminolysis modifications. The unique isomerization in the AAB sequence allowed the periodic introduction of a benzyl ether structure in the backbone leading to efficient degradation under acid conditions.

Statistical Copolymers of N-Vinylpyrrolidone and 2-Chloroethyl Vinyl Ether via Radical RAFT Polymerization: Monomer Reactivity Ratios, Thermal Properties, and Kinetics of Thermal Decomposition of the Statistical Copolymers

The radical statistical copolymerization of N-vinyl pyrrolidone (NVP) and 2-chloroethyl vinyl ether (CEVE) was conducted using the Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization technique, employing [(O-ethylxanthyl)methyl]benzene (CTA-1) and O-ethyl S-(phthalimidylmethyl) xanthate (CTA-2) as the Chain Transfer Agents (CTAs), leading to P(NVP-stat-CEVE) products. After optimizing copolymerization conditions, monomer reactivity ratios were estimated using various linear graphical methods, as well as the COPOINT program, which was applied in the framework of the terminal model. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the monomers' mean sequence lengths. Thermal properties of the copolymers were studied by Differential Scanning Calorimetry (DSC) and kinetics of their thermal degradation by Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG), applying the isoconversional methodologies of Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS).

Alternating Terpolymers through Cyclopolymerization and Subsequent Orthogonal Functionalization

A method for the synthesis of functionalized alternating copolymers by reversible deactivation radical polymerization was developed. Copolymerization by reversible addition-fragmentation chain transfer of hexenyl vinyl ether with a novel fluorinated divinyl monomer yields alternating cyclopolymers that can be chemoselectively modified by three distinct orthogonal functionalization reactions. Along the thiol-ene click reaction and amidation, a third functionalization was achieved via NHC-catalyzed transesterification or acylation resulting in a small library of ABC-type alternating terpolymers.

Radical Homopolymerization of Vinyl Ethers Activated by Li+-π Complexation in the Presence of CH3OLi and LiI

In this study, we develop a direct, thermally initiated radical homopolymerization of vinyl ethers mediated by lithium salts CH3OLi and LiI. In the case of vinyl ether monomers having a...

Synthesis and cationic polymerization of halogen bonding vinyl ether monomers

Halogen bonding is rapidly becoming recognized as a viable and useful intermolecular interaction in supramolecular chemistry. While various monomers amenable to radical polymerization methods containing halogen bonding donors have been developed, this study aims to expand the type of monomers that incorporate this intermolecular interaction to facilitate use of cationic polymerization by developing three novel vinyl ether monomers containing halogen bonding donor moieties: 2,3,5,6-tetrafluoro-4-iodophenoxyethyl vinyl ether (C2I), 2,3,5,6-tetrafluoro-4-iodophenoxybutyl vinyl ether (C4I), and 2-(2,3,5,6-tetrafluoro-4-iodophenoxyethoxy)ethyl vinyl ether (O3I). Well controlled cationic polymerization is achievable through the use of a proton trap, 2,6-di-tert-butylpyridine. The use of SnCl₄ as a co-Lewis acid was found to accelerate the reaction. Between the three monomers, the difference in the chain length is shown to influence the reaction rate, with the longest chain demonstrating the fastest polymerization. Initial studies of the halogen bonding ability shows that halogen bonding exists for all three monomers but is most pronounced in C4I. The polymerized vinyl ethers also exhibit halogen bonding. Due to the ease of synthesis and polymerization, these are promising new monomers to increase functionality available for polymers synthesized using cationic polymerization.

Three novel vinyl ether monomers containing halogen bonding moieties were synthesized, polymerized via cationic polymerization and exhibited clear halogen bonding.

Vinyl mercaptoethanol as a reactive monomer for the preparation of functional homo- and copolymers with (meth)acrylates

Vinyl mercaptoethanol is a scalable vinyl thioether monomer, which can readily be polymerized in a free radical process or by controlled methods. It tends to form alternating copolymers if copolymerized with acrylates and methacrylates.

Anthranilamide-protected vinylboronic acid: rational monomer design for improved polymerization/transformation ability providing access to conventionally inaccessible copolymers

We designed a vinyl-boronic-acid protected by anthranilamide as a “transformable” monomer in radical polymerization to synthesize conventionally inaccessible copolymers, such as poly(vinyl alcohol-co-styrene) and poly(ethylene-co-acrylate).

Recent Advances in Living Cationic Polymerization with Emerging Initiation/Controlling Systems

While the conventional living cationic polymerization (LCP) provided opportunities to synthesizing well-defined polymers with predetermined molecular weights, desirable chemical structures and narrow dispersity, it is still important to continuously innovate new synthetic methods to meet the increasing requirements in advanced material engineering. Consequently, a variety of novel initiation/controlling systems have be demonstrated recently, which have enabled LCP with spatiotemporal control, broadened scopes of monomers and terminals, more user-friendly operations and reaction conditions, as well as improved thermomechanical properties for obtained polymers. In this work, recent advances in LCP is summarized with emerging initiation/controlling systems, including chemical-initiated/controlled cationic reversible addition-fragmentation chain transfer (RAFT) polymerization, photoinitiated/controlled LCP, electrochemical-controlled LCP, thionyl/selenium halide-initiated LCP, organic acid-assisted LCP, and stereoselective LCP. It is hoped that this summary will provide useful knowledge to people in related fields and stimulate new ideas to promote the development and application of LCP in both academia and industry.

UV-Assisted Li+-Catalyzed Radical Grafting Polymerization of Vinyl Ethers: A New Strategy for Creating Hydrolysis-Resistant and Long-Lived Polymer Brushes as a "Smart" Surface Coating

A facile synthetic route was developed to prepare a surface-grafted brush layer of poly(vinyl ethers) (PVEs) directly by a radical mechanism, with the "naked" Li⁺ acting as a catalyst. Density functional theory calculations suggested that complexation of naked Li⁺ to VEs significantly reduced the highest unoccupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gap from 5.08 to 0.68 eV, providing a better prospect for electron transfer. The structure, morphology, and surface properties of grafted polymer layers were characterized using attenuated total reflection Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and dynamic water contact angle (DCA). Moreover, ellipsometry data indicated that the thickness of the polymer brushes was in the range of 20-60 nm, which corresponds to the grafting densities of 0.65-1.15 chain/nm², and DCA decreased from 84.4 to 45.3°. Most importantly, no hydrolysis was observed for the modified surface after 30 days of exposure to phosphate-buffered saline solution, 0.1 mol/L NaOH(eq) and 0.1 mol/L HCl(eq), demonstrating excellent hydrolysis resistance with long service life. In addition, as a proof of concept, the side hydroxyl groups of grafted PVEs provide active sites for efficient fixation of bioactive molecules, e.g., glycosaminoglycan and serum protein.

Continuous-Flow Synthesis of Pyrylium Tetrafluoroborates: Application to Synthesis of Katritzky Salts and Photoinduced Cationic RAFT Polymerization

Katritzky salts have emerged as effective alkyl radical sources upon metal- or photocatalysis. These are typically prepared from the corresponding triarylpyrylium ions, in turn an important class of photocatalysts for small molecules synthesis and photopolymerization. Here, a flow method for the rapid synthesis of both pyrylium and Katrizky salts in a telescoped fashion is reported. Moreover, several pyrylium salts were tested in the photoinduced RAFT polymerization of vinyl ethers under flow and batch conditions.

Highly 2,3-selective and fast living polymerization of alkyl-, alkoxy- and phenylallenes using nickel(ii) catalysts

A novel Ni(ii) catalyst was developed to initiate the polymerization of various allene monomers efficiently in a fast and living/controlled manner, and the thermodynamic and crystallization properties of the polymers were investigated.

Synthesis of Well-Defined Alternating Copolymer Composed of Ethylmaleimide and Hydroxy-Functionalized Vinyl Ether by RAFT Polymerization and Their Thermoresponsive Properties

Here we report the controlled synthesis of alternating copolymers by reversible addition-fragmentation chain transfer (RAFT) polymerization of hydroxy-functionalized vinyl ether (DEGV) and ethylmaleimide (EtMI) using dithiocarbonate derivative (CPDB) as the RAFT reagent. The resulting alternating copolymer poly[ethylmaleimide-alt-(diethylene glycol mono vinyl ether)] (poly(MalMI-alt-DEGV)) had a relatively narrow molecular weight distribution (M_w/M_n < 1.4). These polymers are fully soluble in cold water (5 °C) and an aqueous solution of poly(MalMI-alt-DEGV) became turbid upon heating (using an incident wavelength of 600 nm and 1.0 mg mL⁻¹ (0.1 wt %) polymer concentration), indicating phase separation above the cloud point temperature (T_cp). The T_cp of the polymer solution ranged from 15–35 °C, depending on the molecular weight and molecular weight distribution of the polymer.