Thermal-Responsive and 3D Printable Hydrogel Based on an Acylhydrazine-Terminated Dynamic Covalent Bond and Pluronic F127

Abstract

Constructing hydrogels, which exhibit ultrastretchable and energy dissipation ability, are suitable for engineering. However, the hydrogel exhibited both ultrastretchable and flowable properties, which were usually contradictory in hydrogel design. It remains a challenge to achieve a hydrogel with a high-strength property and a 3D printable capacity. Herein, hydrogel tPEG-az-F127 was prepared by condensation of acylhydrazine-terminated three-armed PEG and benzaldehyde-terminated Pluronic F127, exhibiting high stretchability and 3D printable capability. These outstanding performances of hydrogel resulted from dynamic reversible covalent-bond of acylhydrazone bond and hydrophilicity–hydrophobicity transformation of Pluronic F127 moiety. Furthermore, the technical conditions for preparing the hydrogel, such as solid concentrations and gelation time, were optimized by the optical rheometer experiment. The principles of the switch-mode hydrogel, which can switch between high-stretchability and printability, have been comprehensively studied with dynamic light scattering (DLS), swelling, tensile and rheological tests. Furthermore, as the temperature increases from 10 to 25 °C, the hydrogel tPEG-az-F127-20 exhibits a rapid storage modulus (G′) change from 1 and 40 kPa, which is attributed to the thermal-driven increasing hydrophobicity of Pluronic F127 moiety. According to the thermosensitive switch-mode hydrogel, a pneumatical-type 3D printing was conducted to fabricate constructs of good shape and stability within human body temperature, which will be a potential candidate for 3D printable ink in the fields of tissue engineering.