Sugar-based low-molecular-weight gelators are an interesting new class of compounds that are important in supramolecular chemistry and for the preparation of advanced materials. Previously, we synthesized a series of ester and carbamate derivatives of 4,6-O-benzylidene methyl-alpha-D-glucopyranoside and found that monosubstituted alkynyl esters with five to seven carbons and monosubstituted carbamates with saturated five- and seven-carbon chains are good gelators. To understand the structural requirement for the gelation of the carbamate derivatives (O-linked carbamates), a diverse series of analogs, including alkynyl, aryl, and alkyl halide derivatives, were prepared and analyzed. We found that for gelation the O-linked carbamate derivatives have different structural preferences than the ester derivatives. To exhibit gellation, the ester analogs favor alkyl-containing terminal acetylene groups and the carbamoyl derivatives prefer saturated hydrocarbons. Both the esters and the carbamates showed good gelation properties when they were functionalized with aryl side chains. We also synthesized and screened a new series of carbamates (N-linked carbamates) in which the nitrogen atom of the carbamate group is directly attached to the sugar ring. The N-linked carbamates are good gelators for aqueous DMSO and ethanol solutions, and two of the compounds are also able to form gels in pure water. Optical microscopy and scanning electron microscopy were used to characterize several representative gels. In general, long, narrow, uniform fibrous networks were observed for effective gelators. The structure-gelation correlation obtained here can be used in the design of new sugar-based low-molecular-weight gelators.

Diacetylene-containing glycolipids are a unique class of compounds that are able to self-assemble and form ordered supramolecular structures. Polymerizable diacetylene glycolipids that can function as low molecular weight gelators are particularly interesting molecules which can lead to stimuli-responsive smart materials. To discover efficient organogelators with built-in functionality that may be useful in sensing local environmental changes, we have synthesized a series of novel diacetylene-containing amide and urea derivatives using D-glucosamine as the starting material. Both amphiphilic and dipolar glycolipids were synthesized, and these compounds are effective gelators for several organic solvents and aqueous solutions. The resulting gels can be cross-linked under 6 W UV light to produce blue or purple polydiacetylene gels. The cross-linked gels obtained from urea derivatives are generally dark blue and exhibit blue to red color transitions upon heating. Compared to the urea derivatives, the analogous diacetylene amides produced blue to deep purple polymerized gels, depending on the structures of the gelators. The morphologies of the gels were characterized by optical microscopy and scanning electron microscopy. Typically, self-assembled fibrous networks were observed. The synthesis and characterization of these polymerizable gelators and their UV-vis absorption upon polymerization are reported.

No abstract

No abstract

No abstract