A series of organogelator salts has been prepared from n-alkylamines by the rapid in situ and isothermal (at room temperature) uptake of a neutral triatomic molecule, CO2, NO2, SO2, or CS2. The organogels have been examined by differential scanning calorimetry, optical microscopy, and X-ray diffraction methods. The efficiency of each gelator has been assessed on the bases of the diversity of liquids it gelled, the minimum amount of it required for gelation, and the temporal and thermal stabilities of its gels. Thus, alkylammonium alkylcarbamates, amine-CO 2 adducts, are the most effective gelators and the amine-NO2 adducts are the least efficient. Salts from longer n-alkylamines are better gelators than those from shorter homologues. Some of the salts are reconverted to their amine and triatomic constituents by heating, while others are transformed into new compounds. In the case of the CS 2 adducts, H2S is expelled and the new species formed, N,N′-dialkylthioureas, are also gelators.

Rapid and isothermal (at room temperature) uptake of CO2 by solutions or, in some cases, organogels comprised of a primary or secondary aliphatic amine (1) and an organic liquid leads to in situ chemical transformation to the corresponding alkylammonium alkylcarbamate (2) based gels. Chemical reversibility is demonstrated by removal of CO2 from 2-based gels upon gentle heating in the presence of nitrogen. This is a general strategy for reversible self-assembly or disassembly of molecular aggregates relying on the initiation or termination of ionic interactions. The dependence of the amine structure and the nature of the liquid component on the formation and stability of the 1 and 2 organogels are examined by differential scanning calorimetry, optical microscopy, and X-ray diffraction methods. In most cases, the 2 gelators are more effective (based on the minimum gelator concentration required at room temperature, the gelation temperature, and the duration of time a gel persists without bulk phase separation) and more diverse (based on the classes of liquids gelled) than their corresponding amines. The differences are attributed to the presence of ionic interactions between molecular segments of the alkylammonium alkylcarbamates that are stronger than the hydrogen-bonding interactions available between molecules of amines. The initial stages of aggregation in the gel assemblies (i.e., changes in the degree of aggregation of sols of some 2 gelators) have been examined as a function of concentration and temperature by NMR techniques.

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.

The initial stages of aggregation of a series of organogelator salts, prepared from n-alkylamines by the rapid in situ and isothermal (at room temperature) uptake of the neutral triatomic molecule, CO2, have been probed by NMR spectroscopy in the nongelled liquid, chloroform-d. Evidence for specific interactions of the ionic headgroups in the aggregates is presented. The influences of concentration and temperature on the processes leading to pre-sol aggregates of decylammonium decylcarbamate (2b) have been investigated in detail. NMR spectra of selectively deuterated (at the R-methylene group) and selectively 13 C-enriched (at the carbonyl carbon) 2b demonstrate that CO2 is scrambled rapidly between the ammonium and carbamate parts of the molecule in chloroform solution. No scrambling of CS2 was detected in alkylammonium alkyldithiocarbamates under the same experimental conditions.