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 (T_gel) 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 T_gel of ABC1 is lower than that of ABC2 since hydrophobic BA is copolymerized into block C1. Remarkably, the T_gel varies linearly within this temperature range by simply blending the two polymers, while the resultant gel strength (G′) remains almost unchanged. Therefore, the T_gel can be precisely adjusted by the mixing ratio of the two polymers. This method for straightforward manipulation of T_gel has great potential for various soft material applications such as biomaterials for tissue engineering, drug delivery systems, and injectable gels.