Low Molecular-Mass Gelators with Diyne Functional Groups and Their Unpolymerized and Polymerized Gel Assemblies

Abstract

A series of low molecular-mass organogelators (LMOGs) with conjugated diyne units, R-CtCsCtC-R′, has been synthesized from 10,12-pentacosadiynoic acid. R is a long alkyl chain and R′ is a short or long alkyl chain containing an amide or ester group. The gelation efficiencies of these LMOGs and the parent acid (as assessed by the variety of liquids gelled, the amount of gelator needed for gelation, and the temporal and thermal stabilities of the gels) differ widely according to the nature of the substituents. An LMOG with an amide substituent is much more efficient than the corresponding molecule with an ester group, and LMOGs with longer R′ chains are more efficient than those with shorter ones. When irradiated, some gel networks polymerize. In most cases, the polymerized aggregates phaseseparate microscopically, but maintain the gel structure macroscopically. These gels are irreversibly photo-and thermo-chromic, and the thermal stabilities of some of the colored polymerized organogel networks are similar to those of the monomeric assemblies. The molecular packing of the LMOGs as neat powders and in gels before and after polymerization has been examined by X-ray diffraction techniques. This and analyses of IR, UV, and CD (in the case of a chiral diyne LMOG) data allow the nature of the aggregate assemblies before and after irradiation to be assessed. These monomeric organogels and their treatment with light and heat afford an approach to the synthesis of microheterogeneous polymerized networks from relatively simple molecules.

Structure and Behavior of Polydiacetylene‐Based Micelles

“…The symmetric and asymmetric stretching of CH 2 bands was present at 2 855 and 2 926 cm À1 . The CH 2 stretching band positions suggests that the CH 2 in the alkyl chains are disorganized, contrary to the reported CH 2 stretching bands at 2 848 and 2 915 cm À1 in crystalline forms [30][31] or in films and vesicles, where polydiacetylenes are highly organized and polymerized with a blue color.…”

Urea and Thiourea Derivatives as Low Molecular‐Mass Organogelators

“…Chiral fibrils have been observed in the strands of several optically-active LMOGs with complex structures. [72][73][74][75][76] With the exception of the tartrate gelators explored by Oda and co-workers, [77] it is difficult to pinpoint the relationship between molecular and strand asymmetry. [73,74] By using a series of alkylated ureas and thioureas with only one center of chirality and in which that center can be moved systematically along the alkyl chain, it should be possible to determine the relationship between molecular and aggregate chiralities.…”

Functional, Hierarchically Structured Poly(diacetylene)s via Supramolecular Self‐Assembly

“…[38][39][40][41][42][43][44] However, only few examples of diacetylene polymerizations carried out in hydrogenbonded organogels and supramolecular polymers are known to date. [45][46][47][48][49][50] Supramolecular self-assembly in solution and topochemical diacetylene polymerizations are ''a perfect couple''. While the latter offer an advantageous way of covalent capture which produces well-defined, optoelectronically active polymers, self-assembly would ideally provide the required order without being confined to single-crystalline monomers and include a self-healing of structural defects.…”