Anionic Polymerization of Oxadiazole-Containing 2-Vinylpyridine by Precisely Tuning Nucleophilicity and the Polyelectrolyte Characteristics of the Resulting Polymers

Abstract

Anionic polymerization is one of the most powerful techniques for preparation of well-defined polymers. However, this well-known and widely employed polymerization technique encounters major limitations for the polymerization of functional monomers containing heteroatoms. This work presents the anionic polymerization of 2-phenyl-5-(6-vinylpyridin-3-yl)-1,3,4-oxadiazole (VPyOzP), a heteroatom monomer that contains both oxadiazole and pyridine substituents within the same pendant group, using various initiating systems based on diphenyl­methyl potassium (DPM-K) and triphenyl­methyl potassium (TPM-K). Remarkably, well-defined poly­(2-phenyl-5-(6-vinylpyridin-3-yl)-1,3,4-oxadiazole) (PVPyOzP) polymers having predicted molecular weights (MW) ranging from 2200 to 21 100 g/mol and polydispersity indices (PDI) ranging from 1.11 to 1.15 were prepared with TPM-K, without any additional additives, at −78 °C. The effect of temperature on the polymerization of PVPyOzP was also studied at −78, −45, 0, and 25 °C, and it was observed that increasing the polymerization temperature produced materials with unpredictable MW’s and broader molecular weight distributions. Furthermore, the nucleophilicity of PVPyOzP was investigated through copolymerization with methyl methacrylate and acrylonitrile, where only living poly­(methyl methacrylate) (PMMA) prepared by DPM-K/VPPy and in the absence of additives such as lithium chloride (LiCl) and diethyl zinc (ZnEt2) could be used to produce the well-defined block copolymer of PMMA-b-PVPyOzP. It was also demonstrated by sequential monomer addition that the nucleophilicity of living PVPyOzP is located between that of living PMMA and polyacrylonitrile (PAN). The pyridine moiety of the pendant group also allowed for quaternization and produced PQVPyOzP homopolymer using methyl iodide (CH3I) and bis­(trifluoro­methyl­sulfonyl)­amide [Tf2N–]. The resulting charged polymer and counterion complexes were manipulated and investigated for potential use as membranes for carbon dioxide (CO2) capture.

Precise Synthesis of Functional Block Copolymers by Living Anionic Polymerization of Vinyl Monomers Bearing Nitrogen Atoms in the Side Chain

“…Kang and co‐workers made well‐defined polymers of para‐substituted pyridine derivatives containing oxadiazole units, 2‐phenyl‐5‐(6‐vinylpyridin‐3‐yl)‐1,3,4‐oxadiazole (VPyOzP) . During anionic polymerization, VPyOzP is vulnerable to attack from active nucleophilic carbanions on the pyridine and oxadiazole units.…”

“…SEC curves of PVPyOzP initiated by (B) DPM‐K, (C) DPM‐K/2VP, and (D) DPM‐K/VPPy. Reproduced with permission . Copyright 2016, American Chemical Society.…”

Syntheses of Rare-Earth Metal Alkyl Complexes Bearing a Dianionic α-Iminopyridyl Ligand and Their Catalytic Activities toward Polymerization of 2-Vinylpyridine

“…Poly­(2-vinylpyridine) (P2VP) is an important nitrogen polar polymeric material, which has been widely applied in membrane technology, self-assembly, and ion-exchange resin materials . In contrast to radical polymerization, anionic polymerization, and Lewis pair polymerization, coordination polymerization of 2-VP afforded stereoregular polymers which exhibited excellent mechanical and physical properties . Bis­(phenolato) rare-earth metal alkyl complexes have been demonstrated as highly efficient catalysts for 2-VP polymerization to afford highly isotactic and high molecular weight P2VP through coordination–insertion mechanisms .…”