The behavior of poly(ethylene oxide)-block-poly(N,N-dimethylacrylamide) (PEO-b-PDMA) in aqueous solution at dilute concentrations was studied by laser light scattering. Even though water was a nonselective solvent for both PEO and PDMA blocks, PEO-b-PDMA formed a certain loose associate in aqueous solutions. Different from the micellization of block copolymers in selective solvents, the association of PEO-b-PDMA in aqueous solution showed weak concentration and temperature dependence as well as opposite salt effect. At 4.0 M NaCl, the association was completely suppressed and PEO-b-PDMA existed as individual polymer chains. This opposite “salting out” effect revealed the association mechanism of block copolymers in nonselective solvent: the solubility of PEO block in aqueous solution was unique, and it exhibited a better hydrophilicity and thick hydration shell than other water-soluble polymers. This inequality or weak incompatibility drove the block copolymer to associate into loose structures containing multidomains rich of either blocks. The dependence of the association on the block ratio also supported our conclusions.

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A reactive azobenzene based super organogelator was found to rapidly and reversibly transform a range of hydrophobic solvents from gels to solutions upon changes in temperature, light and shear force. More specifically they formed gels at concentrations as low as 0.08 wt%. Upon heating, exposure to UV light, or application of shear, the π-π bonding was disrupted which resulted in a rapid drop of both modulus and viscosity. This was confirmed by (1)H NMR, SAXS, and rheological measurements. Although many examples of organogelators are known in the literature, this is the first time that a reactive group, a benzoyl chloride, has been incorporated in a supramolecular organogel structure. Moreover, this group is available for subsequent synthetic modifications. The presence of benzoyl chloride groups showed a remarkable effect on the formation and properties of the gels. Compared with other approaches, this strategy is advantageous in terms of structural design since it not only produces a multi-responsive soft material but also allows facile modifications which may expand the applications of organogels to other fields.