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Abstract We report the thermoresponsive assembly and rheology of an amphiphilic thermosensitive graft copolymer, poly(ethylene glycol)-graft-(poly(vinyl caprolactam)- co -poly(vinyl acetate)) (commercial name Soluplus ® ), which has been investigated for potential biomedical applications. It has received attention due to is ability to solubilize hydrophobic drugs and for its thickening behavior close to body temperature. Through use of the synchrotron at Brookhaven National Lab, and collaboration with the department of energy, the nanoscale structure and properties can be probed in greater detail. Soluplus ® undergoes two structural changes as temperature is increased; the first, a concentration independent change where samples become turbid at 32 °C. Increasing the temperature further causes the formation of physically associated hydrogels. This sol-gel transition is concentration dependent and occurs at 32 °C for 40 wt% samples, and increases to 42 °C for 10 wt% samples. From variable temperature SAXS characterization micelles of 20–25 nm in radius can be seen and maintain their size and packing below 32 °C. A gradual increase in the aggregation of micelles corresponding to a thickening of the material is also observed. Close to and above the gelation temperature, micelles collapse and form a physically associated 3D network. A model is proposed to explain these physical effects, where the poly(vinyl caprolactam) group transitions from the hydrophilic corona at room temperature to the hydrophobic core as temperature is increased. 

Significant research has been directed toward producing composites that mimic the micro‐ to nanoscale structure of bone tissue, and it remains a challenge to develop synthetic strategies to create cost‐effective biocomposite materials with nanoscale inorganic domains. In this paper, we report the synthesis of nanocrystalline calcium phosphate minerals in situ in gels of a commercially available block copolymer, Pluronic F127 (F127). Although solutions of F127 have previously been explored as a templating agent for calcium phosphate mineralization, here we demonstrate the synthesis of nano‐sized calcium hydrogen phosphate hydrate directly in F127 gels. Composites formed at pH 7 contained highly crystalline, millimeter‐scale crystals of brushite, while composites created at an initial pH of 11 contained nanoscale particles of a calcium hydrogen phosphate hydrate similar to natural bone apatite in morphology and size, with a mean particle diameter of 120 nm. The in situ composites have storage moduli of 15–25 kPa, which is comparable to mechanically processed hydrogel composites containing four times more inorganic material. We believe that our synthetic strategy may provide a new class of versatile and cost‐effective nanostructured biomaterials for use in understanding and replicating mineralized tissues.