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Ionic (Co)Organocatalyst with (Thio)Urea Anion and Tetra‑ n ‑butyl Ammonium Cation for the Polymerization of γ‐Butyrolactone
Author(s) -
Fang Ge,
Zhe Wang,
Yanyun Zhu,
Xiaowu Wang
Publication year - 2020
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.202000172
Subject(s) - chemistry , thio , polymerization , polymer chemistry , benzyl alcohol , ammonium hydroxide , thiourea , hydroxide , molar mass distribution , catalysis , inorganic chemistry , polymer , organic chemistry
An effective ionic organocatalyst system is developed for the challenging ring‐opening polymerization (ROP) of γ‐butyrolactone (GBL) at low temperature. The catalysts are prepared by dehydration reaction between tetra‐ n ‐butyl ammonium hydroxide (TBAOH) and (thio)ureas at ambient temperature, and utilized with or without extra benzyl alcohol (BnOH) initiator. The solid‐state structure of TUA‐3 comprising thiourea anion is characterized by X‐ray diffraction analysis. Typically, a mixture of cyclic and linear poly(GBL) with low molecular weights (5000–1600 g mol −1 ) and slightly narrow molecular distribution Ð (1.2–1.4) is obtained by single base with/without combination with (thio)ureas. Interestingly, solely linear high‐molecular‐weight poly(GBL) (10 400 g mol −1 ) can be achieved by a synergistic effect of TBAOH/ N,N ′‐isopropylthiourea in the presence of BnOH. The obtained poly(GBL) is characterized with NMR spectroscopy and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy (MALDI‐TOF MS). Mechanistic studies reveal different polymerization initiation steps in this reported catalyst system, which leads to poly(GBL) with divergent end groups.