Dithiolane

Abstract: The use of dithiolane-containing polymers to construct responsive and dynamic networks is an attractive strategy in material design. Here, we provide a detailed mechanistic study on the self-assembly and gelation behavior of a class of ABA triblock copolymers containing a central poly(ethylene oxide) block and terminal polycarbonate blocks with pendant 1,2-dithiolane functionalities. In aqueous solution, these amphiphilic block copolymers self-assemble into bridged flower micelles at high concentrations. The addition of a thiol initiates the reversible ring-opening polymerizations of dithiolanes in the micellar cores to induce the cross-linking and gelation of the micellar network. The properties of the resulting hydrogels depend sensitively on the structures of 1,2-dithiolanes. While the methyl asparagusic acid-derived hydrogels are highly dynamic, adaptable, and self-healing, those derived from lipoic acid are rigid, resilient, and brittle. The thermodynamics and kinetics of ring-opening polymerization ...

Abstract: Some chemical and photochemical observations of 1,2-dithiolane and its derivatives are reported with particular reference to the possible mode of function of the naturally occurring system, 6-thioctic acid Experimental evidence is presented to demonstrate that the strain energy in this 5-membered ring is not less than 65 Kcals and probably larger Reagents which both oxidize and reduce this ring are described together with the conditions required for its reformation from the corresponding dithiol Evidence is adduced to indicate that the primary product of photolysis of this ring in acetic media is very likely a thiol and sulfenic acid or derivative thereof

Abstract: Lipoic acid (LA) has gained attention in the late 1940’s as a growth factor for micro-organisms In 1951 Reed and co-workers [1] isolated 30 mg of this factor form 100 kg of liver and later on the molecular structure of LA (chemical name: 1,2-dithiolane-3-pentanoic acid) was elucidated The compound has a chiral center at the C3 carbon atom (Fig 1) Naturally occurring LA has the R configuration LA is present in most pro– and eukaryotic cells In our diet it can be found in several products such as meat, liver and heart LA is considered not to be a vitamin because of possible biosynthesis in man The physiological function of LA as a component in the pyruvate dehydrogenase complex is now textbook knowledge In the enzyme complexes LA is linked by an amide bound to the γ-amino group of a lysine residue of the protein, giving the so-called lipoyl group In this way the dithiolane ring is attached to the enzyme by a relatively long and flexible chain, which makes it possible for this group to react with the catalytic center of other enzymes in the enzyme complexes

Abstract: The design and generation of adaptable materials derived from structurally dynamic polymers provides a strategy for generating smart materials that can respond to environmental stimuli or exhibit self-healing behavior. Herein we report an expedient organocatalytic ring-opening polymerization of cyclic carbonates containing pendant dithiolanes (trimethylene carbonate/dithiolane, TMCDT) from poly(ethylene oxide) diols to generate water-soluble triblock (ABA) copolymers containing a central poly(ethylene oxide) block and terminal dithiolane blocks. Hydrogels generated from the triblock copolymers and a cross-linking dithiol exhibited dynamic behavior as a result of the reversible ring opening of the pendant 1,2-dithiolanes. These materials exhibit self-healing behavior, can be injected through a syringe, and rapidly recover their mechanical properties after a severe strain deformation. The dynamic properties of these gels can be modulated with the number of dithiolane units, pH, and temperature.