Abstract
Aqueous cationic polymerizations of vinyl ethers (isobutyl vinyl ether (IBVE), 2-chloroethyl vinyl ether (CEVE), and n-butyl vinyl ether (n-BVE)) were performed for the first time by a CumOH/B(C6F5)3/Et2O initiating system in an air atmosphere. The polymerization proceeded in a reproducible manner through the careful design of experimental conditions (adding initiator, co-solvents, and surfactant or decreasing the reaction temperature), and the polymerization characteristics were systematically tested and compared in the suspension and emulsion. The significant difference with traditional cationic polymerization is that the polymerization rate in aqueous media using B(C6F5)3/Et2O as a co-initiator decreases when the temperature is lowered. The polymerization sites are located on the monomer/water surface. Density functional theory (DFT) was applied to investigate the competition between H2O and alcohol combined with B(C6F5)3 for providing a theoretical basis. The effectiveness of the proposed mechanism for the aqueous cationic polymerization of vinyl ethers using CumOH/B(C6F5)3/Et2O was confirmed.
Highlights
Conventional cationic polymerizations of vinyl monomers, such as isobutylene (IB), vinyl ethers, and styrene, are usually achieved by using initiator/co-initiator systems primarily in chlorinated solvents under low-temperature and strict water-free conditions [1,2,3,4,5,6,7,8]
Because Yb(OTf)3 was first investigated as a water-tolerant co-initiator for its ability to induce the polymerization of p-methoxystyrene in 1999 [23], considerable attention has been paid to the utilization of aqueous cationic polymerization
We examined styrene polymerization in the aqueous suspension (Figure S2), and the characteristics were fully consistent with those in isobutyl vinyl ether (IBVE)
Summary
Conventional cationic polymerizations of vinyl monomers, such as isobutylene (IB), vinyl ethers, and styrene, are usually achieved by using initiator/co-initiator systems primarily in chlorinated solvents under low-temperature and strict water-free conditions [1,2,3,4,5,6,7,8]. Water is one of the most ideal polymerization solvents. Because Yb(OTf) was first investigated as a water-tolerant co-initiator for its ability to induce the polymerization of p-methoxystyrene (pMOS) in 1999 [23], considerable attention has been paid to the utilization of aqueous cationic polymerization. With the development of various water-tolerant Lewis acids (LAs), this new polymer synthesis technology has achieved remarkable breakthroughs [21]
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