PEG-based nanocomposite hydrogel: Thermoresponsive sol-gel transition controlled by PLGA-PEG-PLGA molecular weight and solute concentration

A PEG-based copolymer with a high PEG ratio was synthesized and the sol-gel transition temperature (T_gel) around the physiological temperature (25 °C–37 °C) was achieved. Specifically, we synthesized a triblock PEG copolymer of poly (_D,L-lactide-co-glycolide)-b-poly (ethylene glycol)-b-poly (_D,L-lactide-co-glycolide) (PLGA-PEG-PLGA) with different molecular weights and a high PEG/PLGA ratio of 0.80. By adding synthetic clay (laponite) to an aqueous solution of the PEG-based copolymer, it was found that the discriminating concentration combinations of the laponite (from 0.75 to 1.5 wt%) and the PLGA-PEG-PLGA (from 2.0 to 5.0 wt%) could effectively regulate the T_gel to fall between 25 °C and 37 °C (physiological temperature), simultaneously controlling the storage and the loss moduli of the specimens studied by the dynamic mechanical analyses (DMA). The structural analyses were also performed by the cryo-TEM and the high-resolution small angle X-ray scattering (SAXS) measurements at SPring-8, Japan.