Preparation and performance of poly(AM/NVCL) temperature-sensitive composite hydrogels enhanced by laponite

Temperature-sensitive hydrogels with high mechanical strength are widely used in biomedical and environmental fields. In this work, a series of high-strength temperature-sensitive composite hydrogels, i.e., laponite-modified poly(acrylamide-co-N-vinylcaprolactam) [poly(AM-co-NVCL)] were prepared by aqueous solution polymerization and characterized by Fourier-transform infrared (FTIR), thermogravimetric (TG-DTG), X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The swelling kinetic showed that the swelling ratio of the gels increased rapidly in the first 120 min, and then the increase slowed down. All samples reached swelling equilibrium after 1000 min. The equilibrium swelling ratio of the composite hydrogels was affected by the monomers ratio and amount of laponite. When AM:NVCL = 1:1 and the dosage of laponite was 10 wt%, the swelling ratio of the composite hydrogel was the highest, which was 594 g/g. The compressive strength of the composite hydrogels increased while the elongation-at-break values increased first and then decreased with the increase of laponite content. The hydrogel with 15 wt% laponite has the best comprehensive mechanical properties. Its elongation-at-break value was 820%, and compressive strength was 48.83 MPa. The volume phase transition of the composite hydrogels occurred at 30.1-35 degrees C. SEM micrographs showed that the number of pores in the gels increased with the addition of laponite but the pore size decreased.