Photopatterned Multidomain Gels: Multi-Component Self-Assembled Hydrogels Based on Partially Self-Sorting...

We report a multicomponent self-assembling system based on 1,3:2,4-dibenzyldene-D-sorbitol (DBS) derivatives which form gels as the pH is lowered in a controlled way. The two DBS gelators are functionalized with carboxylic acids: the first in the 4-position of the aromatic rings (DBS-CO2H), the second having glycine connected through an amide bond and displaying a terminal carboxylic acid (DBS-Gly). Importantly, these two self-assembling DBS-acids have different pKa values, and as such, their self-assembly is triggered at different pHs. Slowly lowering the pH of a mixture of gelators using glucono-δ-lactone (GdL) initially triggers assembly of DBS-CO2H, followed by DBS-Gly; a good degree of kinetic self-sorting is achieved. Gel formation can also be triggered in the presence of diphenyliodonium nitrate (DPIN) as a photoacid under UV irradiation. Two-step acidification of a mixture of gelators using (a) GdL and (b) DPIN assembles the two networks sequentially. By combining this approach with a mask during step b, multidomain gels are formed, in which the network based on DBS-Gly is positively patterned into a pre-existing network based on DBS-CO2H. This innovative approach yields spatially resolved multidomain multicomponent gels based on programmable low-molecular-weight gelators, with one network being positively "written" into another.