Benzoyl Peroxide/2-Vinylpyridine Synergy in RAFT Polymerization: Synthesis of Poly(2-vinylpyridine) with Low Dispersity at Ambient Temperature

Theoretical investigations of 2-vinylpyridine stereoselective polymerization catalyzed by cationic yttrium complexes with different ancillary ligands

The polymerization mechanism of 2-vinylpyridine catalyzed by cationic yttrium complexes with diverse ancillary ligands, specifically [L1Y(CH2SiMe3)(THF)]+ [L1 = (2,6-Et2C6H3)NC(Me)CHC(Me)N(2,6-Et2C6H3)] (Y-1), [L2Y(CH2SiMe3)(THF)]+ [L2 = (2,6-Cl2C6H3)NC(Me)CHC(Me)N(2,6-Cl2C6H3)] (Y-2), and [L3Y(CH2SiMe3)(THF)]+ [L3 = (2,6-C6H5)NC(Me)CHC(Me)N(2,6-iPr2C6H3)] (Y-3), was studied using density functional theory (DFT) calculations. Having achieved an agreement between theory and experiment, it is found that isotactic selectivity induced by Y-1 or Y-2 results from a combination of smaller deformation of the catalyst and stronger electronic effects. Conversely, the Y-3 complex exhibits comparable energy barriers for proceeding via either isotactic or syndiotactic pathways, aligning with the production of atactic polymers as seen experimentally. To examine the steric effects on the kinetic and thermodynamic properties, a computational model of an analogue complex [L4Y(CH2SiMe3)(THF)]+ [L4 = (2,6-Cl2C6H3)NC(Me)CHC(Me)N(iPr2C6H3)] (Y-4), featuring increased steric hindrance, was analyzed. Distortion-interaction and topographic steric map analyses further affirmed that steric hindrance significantly influences stereoselectivity. A direct relationship was identified between the energy barriers of isotactic insertion transition states and the bulkiness of ancillary ligands; greater distortion energy of the catalyst correlates with higher barriers for isotactic polymerization. These findings enhance the mechanistic comprehension of 2-vinylpyridine polymerization and are expected to contribute valuable insights for the improvement of catalytic polymerization systems of 2-vinylpyridine.

RAFT Copolymerization of Styrene and Maleic Anhydride with Addition of Ascorbic Acid at Ambient Temperature

A novel method for RAFT copolymerization of styrene (St) and maleic anhydride (MAh) at ambient temperature using ascorbic acid (Asc) as an initiator is reported. Various experimental conditions including reaction component, monomer composition, the amount of Asc, and temperature were investigated in terms of monomer conversion, molecular weight, and molecular weight distribution. In this system, the copolymer of styrene/maleic anhydride (SMA) with well-regulated molecular weight and low molecular weight distribution (Mw/Mn=1.30) was obtained, and the conversion of monomer was 70.4% after 12 hours at 25°C. The NMR spectra demonstrated that the copolymer synthesized possesses a strictly alternating structure. Furthermore, the proposed mechanism adapted to the RAFT copolymerization of St and MAh initiated by Asc at ambient temperature is presented. Using this new methodology, it is possible to achieve well-defined SMA under mild conditions by RAFT copolymerization.

Catalyst free removal of trithiocarbonate RAFT CTAs from poly(vinylpyridine)s using tris(trimethylsilyl)silane and light

Trithiocarbonate end groups on various polymers, including polyvinylpyridines, are reduced rapily and quantitatively using only tris(trimethylsilyl)silane and light.

Synthesis of Poly(3-vinylpyridine)-Block-Polystyrene Diblock Copolymers via Surfactant-Free RAFT Emulsion Polymerization

In this work, we present a novel synthetic route to diblock copolymers based on styrene and 3-vinylpyridine monomers. Surfactant-free water-based reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization of styrene in the presence of the macroRAFT agent poly(3-vinylpyridine) (P3VP) is used to synthesize diblock copolymers with molecular weights of around 60 kDa. The proposed mechanism for the poly(3-vinylpyridine)-block-poly(styrene) (P3VP-b-PS) synthesis is the polymerization-induced self-assembly (PISA) which involves the in situ formation of well-defined micellar nanoscale objects consisting of a PS core and a stabilizing P3VP macroRAFT agent corona. The presented approach shows a well-controlled RAFT polymerization, allowing for the synthesis of diblock copolymers with high monomer conversion. The obtained diblock copolymers display microphase-separated structures according to their composition.

Controlled iso-specific polymerization of 2-vinylpyridine catalyzed by arylamide-ligated rare-earth metal aminobenzyl complexes

Arylamide rare-earth metal aminobenzyl complexes were employed as highly active catalysts for iso-specific polymerization of 2-vinylpyridine.

Perfectly isoselective polymerization of 2-vinylpyridine promoted by β-diketiminato rare-earth metal cationic complexes

Highly isotactic poly(2-vinylpyridine)s were produced with rare-earth metal complexes supported by a symmetric β-diketiminate ligand in the presence of borate.

Stereospecific catalytic precision polymerization of 2-vinylpyridine via rare earth metal-mediated group transfer polymerization with 2-methoxyethylamino-bis(phenolate)-yttrium complexes

C ₁-Symmetric 2-methoxyethylamino-bis(phenolate)-yttrium complexes for the stereospecific polymerization of 2-vinylpyridine.