Reprocessing and shape recovery of polybenzoxazine-polydimethylsiloxane networks enabled with incorporation of dynamic diselenide bonds

Abstract

In this contribution, we reported the synthesis of linear polybenzoxazine-polydimethylsiloxane (PBZ-PDMS) multiblock copolymers with diselenide bonds (Se–Se) in the main chains. First, bis(4-aminophenyl)diselenide (BAPDS) was synthesized via the reaction of p-bromoaniline with selenium, which was catalyzed with copper (II) oxide nanoparticles. The aromatic diamine bearing a diselenide bond was used for Mannich polycondensation with 4,4′-dihydroxyldiphenylisopropane and para-formaldehyde to obtain the linear PBZ. To synthesize the multiblock copolymer, α,ω-diaminopropyl-terminated polydimethylsiloxane (denoted NH2-PDMS-NH2) was used as a macromolecular diamine and added to perform the Mannich copolycondensation. It was found that the PBZ-PDMS multiblock copolymers readily underwent the self-curing (or crosslinking) at elevated temperature. Compared to linear PBZ only bearing static covalent bonds, the introduction of diselenide bonds significantly decreased the activation energy (Ea) of curing reaction. For the curing of the PBZ-PDMS multiblock copolymers, the Ea's increased with raising the contents of PDMS. The morphological investigation showed that the PBZ-PDMS networks were microphase-separated. Depending on the contents of PDMS, the PBZ-PDMS networks displayed the thermomechanical properties from glassy to rubbery polymers. The introduction of PDMS component endowed the networks with enhanced surface hydrophobicity compared to the control PBZ network. More importantly, the PBZ-PDMS networks are reprocessable. The exchange of the dynamic covalent bonds (viz. diselenide bonds) is responsible for the reprocessing behavior. In addition, the PBZ-PDMS networks displayed shape memory properties, which can be modulated with the contents of PDMS. Furthermore, the original shapes were re-configurable by taking advantage of the metathesis of dynamic diselenide bonds.