Controlling the dynamics of elastomer networks with multivalent brush architectures

A method for lowering the activation energy of melting while improving the mechanical robustness of an elastomer was achieved using bottlebrush topologies. This system has the potential to realize self-healing materials with enhanced processability.</jats:p

Design and Synthesis of Quick Setting Nonswelling Hydrogels via Brush Polymers

Brush polymers have emerged as components of novel materials that show huge potential in multiple disciplines and applications, including self-assembling photonic crystals, drug delivery vectors, biomimetic lubricants, and ultrasoft elastomers. However, an understanding of how this unique topology can affect the properties of highly solvated materials like hydrogels remain under investigated. Here, it is investigated how the high functionality and large overall size of brush polymers enhances the gelation kinetics of low polymer weight percent gels, enabling 100-fold faster gelation rates and 15-fold higher stiffness values than gels crosslinked by traditional star polymers of the same composition and polymer chain length. This work demonstrates that brush polymer topology provides a useful means to control gelation kinetics without the need to manipulate polymer composition or crosslinking chemistry. The unique architecture of brush polymers also results in restrained or even nonswelling behavior at different temperatures, regardless of the polymer concentration. Brush polymers therefore are an interesting tool for examining how high-functionality polymer building blocks can affect structure-property relationships and chemical kinetics in hydrogel materials, and also provide a useful rapidly-setting hydrogel platform with tunable properties and great potential for multiple material applications

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 (<i>T</i>_gel) of a physically cross-linked hydrogel by blending two kinds of ABC triblock terpolymers. Well-defined triblock terpolymers including thermosensitive <i>N</i>-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 <i>n</i>-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 <i>T</i>_gel of ABC1 is lower than that of ABC2 since hydrophobic BA is copolymerized into block C1. Remarkably, the <i>T</i>_gel varies linearly within this temperature range by simply blending the two polymers, while the resultant gel strength (∼<i>G</i>′) remains almost unchanged. Therefore, the <i>T</i>_gel can be precisely adjusted by the mixing ratio of the two polymers. This method for straightforward manipulation of <i>T</i>_gel has great potential for various soft material applications such as biomaterials for tissue engineering, drug delivery systems, and injectable gels