Acyclic Diene Metathesis (ADMET) Polymerization of 2,2,6,6‐Tetramethylpiperidine‐1‐sulfanyl (TEMPS) Dimers

Abstract

of polymers with functional groups containing heteroatoms within the main chain. This reaches from carbon-oxygen bonds (e.g., ethers, esters, and carbonates) to carbon-nitrogen (e.g., imines, [3] hydrazones, [4] and oximes [5] ). Interestingly, their sulfur-containing analogues, [6] have been underestimated for long time, although the intrinsic characteristics of these polymers are offering a myriad of superior properties (e.g., degradation, flame retardancy, film-forming ability, good solubility in polar solvents, and high refractivity with small chromatic dispersions amongst other) compared to the carbon-derivatives. This is particularly the case for sulfurnitrogen based polymers. The distinctive characteristics of the sulfur-nitrogen based polymers result from the unique chemical properties of the sulfur-nitrogen bond (e.g., its polar character and the multiple valence states of sulfur). As one of the most intriguing dynamic covalent bonds featuring a simple redox chemistry, the disulfide bond has a crucial importance in organic and polymer chemistry. [7] On the contrary, the amino-and diaminodisulfide functional groups (-S-S-N-and -N-S-S-N-, respectively) are rarely studied in organic chemistry, and the respective polymers are very much in their infancy. At the same time, diaminodisulfide and its derivatives represented with the formula -N-S-S-N-, are known for their low S-S bond dissociation energies (e.g., BDE of 180 kJ mol −1 for the simplest diaminodisulfide H 2 N-S-S-NH 2 ) in reference to diaryl and dialkyl disulfide bonds (190-230 and 250-290 kJ mol −1 , respectively). In spite of this, diaminodisulfides are stable and readily handled at ambient temperature as a result of the high stability of the respective thiyl radicals that are formed via catalyst freethermally induced reversible dissociation. Literature survey also clearly depicts that polymers with sulfur-nitrogen bond (particularly, poly(sulfenamide)s, poly(diaminosulfide)s, and poly(diaminodisulfide)s [8,9] ) could be considered as sleeping beauties and (re)appear to be promising for new materials that combine the advantages of sulfur and nitrogen solely. While, the first synthesis of organic molecules decorated with disulfidediamine dates back to 1895, [10] it took almost a century until a pioneering study on polymeric diaminodisulfide derivatives was reported in 1991. [11] Whilst the study failed to provide any complementary characterization of the reported poly(diaminodisulfide) derivatives, the first report dealing with the in-depth characterization of this polymer class dates back to 2012. [12] In a recent study, Otsuka and co-workers, [13] The preparation of polymers containing sulfur-nitrogen bond derivatives, particularly 2,2,6,6-tetramethylpiperidine-1-sulfanyl (TEMPS) dimers (i.e., BiTEMPS), has been limited to free-radical or conventional step-growth polymerization as result of the inherent thermal lability of the BiTEMPS unit. Accordingly, a novel poly(diaminodisulfide) possessing the BiTEMPS functional group is synthesized via acyc...

Ring-chain equilibria of dynamic macrocycles with a bis(hindered amino)disulfide linker

“…[31][32][33][34][35] The BiTEMPS structure can exchange its disulfide bonds above 80 °C via the generation of relatively stable sulfide radicals (Scheme 1a), providing a dynamic polymer system. [36][37][38][39] Macrocyclic monomers (MMs) with desired structures and one BiTEMPS unit can be synthesized via selective and efficient cyclodepolymerization 31 of linear polymers containing BiTEMPS units in their repeating units, i.e., ring-chain equilibria with low concentrations. Isolated MMs can be polymerized by heating in highly concentrated conditions, whereupon they are converted to cyclic polymers (CPs), 32 mechanically interlocked CPs (MICPs), 33 or enddefined LPs 34 (Scheme 1b).…”

“…31–35 The BiTEMPS structure can exchange its disulfide bonds above 80 °C via the generation of relatively stable sulfide radicals (Scheme 1a), providing a dynamic polymer system. 36–39 Macrocyclic monomers (MMs) with desired structures and one BiTEMPS unit can be synthesized via selective and efficient cyclodepolymerization 31 of linear polymers containing BiTEMPS units in their repeating units, i.e. , ring-chain equilibria with low concentrations.…”

Synthetic Strategy for Mechanically Interlocked Cyclic Polymers via the Ring-Expansion Polymerization of Macrocycles with a Bis(hindered amino)disulfide Linker

“…Recently, exploiting the dynamic nature of bis­(2,2,6,6-tetramethylpiperidin-1-yl) disulfide (BiTEMPS), − we were able to selectively isolate some macrocyclic monomers (MMs) with one BiTEMPS unit (S-S linkage) in their cyclic structure . The BiTEMPS structure allows the exchange of disulfide bonds above 80 °C via relatively stable radicals (Scheme a).…”

A thermally driven rotaxane–catenane interconversion with a dynamic bis(hindered amino) disulfide

“…Recently, we have developed a method for the selective isolation of macrocycles that contain bis(2,2,6,6-tetramethylpiperidin-1-yl) disulfide (BiTEMPS [25][26][27] ) units in their cyclic structure. 28 The BiTEMPS unit is a dynamic moiety, whose disulfide linker can exchange with other disulfides merely upon heating to ∼100 °C.…”