Mechanically strong and thermosensitive macromolecular microsphere composite poly(N-isopropylacrylamide) hydrogels

Macromolecular microsphere composite poly(N-isopropylacrylamide) (MMC-PNIPAAm) hydrogels with high mechanical strength and thermosensitive property are synthesized by using peroxidized macromolecular microspheres as polyfunctional initiating and crosslinking centers (PFICC). The synthesis conditions including pre-irradiation time, mixed solvent volume ratio, macromolecular microspheres content, reaction temperature, and monomer concentration, are optimized. Compression tests prove that the MMC-PNIPAAm hydrogels have high mechanical strengths. Hydrogels synthesized under the optimal conditions show compressive strengths higher than 10 MPa (at 95% strain) when the water content is about 60 wt.%. Deswelling tests and differential scanning calorimetry (DSC) characterizations indicate that the MMC-PNIPAAm hydrogels have thermosensitive properties and their phase transition temperatures varied with the macromolecular microspheres content and reaction temperature. This work demonstrates a new kind of hydrogel with both high mechanical strength and thermosensitivity, which may find practical applications in biomedical and some other fields, especially in load-bearing situations.