Synthesis of Catechol-Containing ABA Triblock Elastomer via Anionic Polymerization

Anionic polymerization of a catechol-containing diene monomer, 1-bis(3,4-tert-butyldimethylsilyloxy)phenyl-1,3-butadiene (1-TBDMS), was performed in tetrahydrofurane (THF) and benzene using sec-butyllithium as the initiator. The corresponding polymer was obtained quantitatively, and the anionic polymerization in THF proceeded well even at low temperatures. In addition, the results of block copolymerization with isoprene (Isp) showed that 1-TBDMS has a relatively high anionic polymerizability to Isp. Further, a triblock copolymer composed of poly(1-TBDMS)–poly(Isp)–poly(1-TBDMS) was prepared by anionic polymerization using a difunctional initiator in benzene at 50 °C. The quantitative cleavage of the tert-butyldimethylsilyloxy protecting group using Bu₄NF rendered catechol units, however, the catechols aggregated with increasing concentrations and yielded insoluble elastomers owing to chemical cross-linking. The deprotected poly(1-OH)-b-PIsp-b-poly(1-OH) film exhibited a maximum stress of 2.20 MPa and strain at break of 1170% in tensile tests, indicating a relatively higher toughness than polystyrene (PS)–poly(Isp)–PS prepared with a similar composition and conditions.