Precisely Tunable Sol–Gel Transition Temperature by Blending Thermoresponsive ABC Triblock Terpolymers

Here, we report a facile methodology to control the sol–gel transition temperature (Tgel) of a physically cross-linked hydrogel by blending two kinds of ABC triblock terpolymers. Well-defined triblock terpolymers including thermosensitive N-isopropylacrylamide (NIPAAm), ABC1, and ABC2, were prepared by sequential reversible addition–fragmentation chain transfer polymerization. The chemical structure as well as the molecular weight of the A and B blocks for both polymers are identical, whereas the C blocks are different. The C block of ABC1 (C1) is a statistical copolymer of NIPAAm with hydrophobic n-butyl acrylate (BA), while that of ABC2 (C2) is a PNIPAAm homopolymer. Independently prepared ABC triblock terpolymer solutions exhibit well-defined sol–gel transitions. The Tgel of ABC1 is lower than that of ABC2 since hydrophobic BA is copolymerized into block C1. Remarkably, the Tgel varies linearly within this temperature range by simply blending the two polymers, while the resultant gel strength (∼G′) remains almost unchanged. Therefore, the Tgel can be precisely adjusted by the mixing ratio of the two polymers. This method for straightforward manipulation of Tgel has great potential for various soft material applications such as biomaterials for tissue engineering, drug delivery systems, and injectable gels.