Effect of methyl position on the dynamic mechanical and shape-memory properties of cresol-based polybenzoxazines

Three difunctional benzoxazines were synthesized from cresol isomers (o-, m-, and p-methylphenols), 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and formaldehyde. The ring-opening polymerization temperature decreases in the order of ortho-, para-, and meta-positions of methyl group for the benzoxazine monomers, whereas the glass transition temperature increases in the order of ortho-, para-, and meta-positions of methyl group for the resultant polybenzoxazines. In addition, the polybenzoxazines exhibit one-way dual-shape-memory behavior in response to changes in temperature, and the shape-memory effects are evaluated by tensile and bending tests with a temperature program based on glass transition temperature. The o- and p-cresol-based polybenzoxazines exhibit higher shape-memory performance than their m-cresol-based analogue/counterpart. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45443.