Abstract
In this study, we investigated direct-controlled/living cationic polymerization and copolymerization of 4-vinylguaiacol (4VG), i.e., 4-hydroxy-3-methoxystyrene, which can be derived from naturally-occurring ferulic acid, to develop novel bio-based amphiphilic polystyrenes with phenol functions. The controlled/living cationic polymerization of 4VG was achieved using the R–OH/BF3·OEt2 initiating system, which is effective for the controlled/living polymerization of petroleum-derived 4-vinylphenol in the presence of a large amount of water via reversible activation of terminal C–OH bond catalyzed by BF3·OEt2, to result in the polymers with controlled molecular weights and narrow molecular weight distributions. The random or block copolymerization of 4VG was also examined using p-methoxystyrene (pMOS) as a comonomer with an aqueous initiating system to tune the amphiphilic nature of the 4VG-derived phenolic polymers. The obtained polymer can be expected not only to be used as a novel styrenic bio-based polymer but also as a material with amphiphilic nature for some applications.
Highlights
Living or controlled polymerization is one of the most facile methods for preparing various well-defined macromolecular architectures with functional groups, including amphiphilic block copolymers that consist both of hydrophilic and hydrophobic segments [1]
The living cationic polymerization has been conducted using a binary initiating system containing a protonic acid or its adduct of monomer and a metal-based Lewis acid, which has been applied for the synthesis of a series of amphiphilic polymers that consist of functional vinyl ether or styrene [2,3,4,5,6,7]
Approximately 20 years ago, controlled/living cationic polymerization in a water system was realized with BF3 ·OEt2 as the Lewis acid, which possibly induced selective activation of a stable carbon-oxygen bond (R–OH) that was generated by the reaction between the carbocation and water [8,9,10,11,12,13,14]
Summary
Living or controlled polymerization is one of the most facile methods for preparing various well-defined macromolecular architectures with functional groups, including amphiphilic block copolymers that consist both of hydrophilic and hydrophobic segments [1]. The reaction is generally performed in a rigorously-dried medium. This is because a small amount of water could be an initiator, namely, a so-called “cationogen”, when coupled with a strong Lewis acid. Approximately 20 years ago, controlled/living cationic polymerization in a water system was realized with BF3 ·OEt2 as the Lewis acid, which possibly induced selective activation of a stable carbon-oxygen bond (R–OH) that was generated by the reaction between the carbocation and water [8,9,10,11,12,13,14]. The R–OH/BF3 ·OEt2 system was applicable even for the direct controlled/living cationic polymerization of p-hydroxystyrene (pHS) or 4-vinylphenol
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