Gels are useful for a wide range of applications, including drug-delivery and environmental remediation. Because of this, it is important to control and optimize their properties for the desired application. Here, we report the manipulation of polyvinyl alcohol (PVA) organogels formed with boric acid (BA). We have found that the properties of PVA-BA organogels can be dramatically altered by introducing an additional crosslinker, 1,4-benzenediboronic acid (1,4-BDBA). While combinations of PVA and BA in DMSO often hold their weight upon inversion, these self-supporting PVA-BA materials are viscous dispersions rather than gels, having moduli that vary with frequency. However, exchanging as little as 10% of BA for 1,4-BDBA yields a stiff gel. Additionally, we found that the stiffness of these organogels increased with higher ratios of 1,4-BDBA, reaching a maximum at ~50:50 and leveling off. Notably the stiffness of the PVA organogels crosslinked with BA and 1,4 BDBA in a 50:50 ratio was significantly higher than PVA gels with each individual crosslinker alone at the same concentration. To this end, simply varying the ratios or identities of the BDBA crosslinker allows us to manipulate the properties of the PVA-BA materials. We attribute this increase to cooperative crosslinking between 1,4-BDBA and BA. That is, 1,4-BDBA is not only introducing new crosslinks, but also improving BA’s ability to function as a crosslinker. Because these gels are derived from commercially available materials and easily adjustable properties, they can be employed for a number of different applications. Furthermore, this cooperative crosslinking mechanism could be useful for triggered and controlled property adjustments.

Improving the crosslinking of boric acid in PVA organogels

ACS Spring Meeting 2021

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