Cascade (Dithio)carbonate Ring Opening Reactions for Self‐Blowing Polyhydroxythiourethane Foams

Abstract

Polyurethane (PU) foams are very common materials that have found many applications over the years. Their use is constantly improving due to their unique physical properties and easy blowing which does not require the addition of a blowing agent. Greener routes have been explored in the recent years to replace isocyanates. One of the most promising routes is leading to polyhydroxyurethanes (PHU). However, with PHUs, external blowing agent are usually required to obtain a foam. Thus, the work focuses on PHU foam synthesis using in situ reaction to produce NIPU foam. Hence, the aminolysis of thiocyclic carbonate triggers Pearson reaction between released thiols and cyclic carbonates which serves as a chemical blowing agent.

Reprocessable, Bio-Based, Self-Blowing Non-Isocyanate Polyurethane Network Foams from Cashew Nutshell Liquid

“…The NC-514 foams were immersed in DMF for 3 days at room temperature; swelling of the foams was observed, confirming cross-linking. The gel contents ranged from 82 to 85%, comparable with self-blowing PHU foams in the literature. , FTIR studies confirm the hydroxyurethane linkages, indicated by the presence of the hydroxyl stretch at 3100–3500 cm –1 and the urethane carbonyl stretch at 1700–1730 cm –1 . For all PHU foams in different compositions, some levels of unreacted cyclic carbonate remain in the foam, evident in the residual carbonate carbonyl stretch at 1790 cm –1 .…”

“…The temperature at 5% mass loss (T 95% ), a proxy for thermal stability, increases with increasing hydroxythioether linkage concentration (Figure S12). With T 95% values of 268−275 °C, the thermal stability of our NC-514 foams is the highest among self-blowing PHU foams made from a cyclic carbonate aminolysis−decarboxylation route, 19,21,28,45,55 further highlighting the excellent performance of bio-based NIPU arising from the aromatic cardanol structure.…”

A review of fatty epoxide ring opening reactions: Chemistry, recent advances, and applications

“…An important aspect of NIPUs is that volatiles are not released during their production, rendering them suitable for coatings applications but not for foams. Therefore, a disadvantage to NIPUs is that foams are not easily obtained without the aid of external physical or chemical blowing agents (Coste et al, 2022). A recent review discusses the chemistry of blowing agents, including innovative synthetic pathways for generation of volatile gases to expand PUs into foams (Coste et al, 2020).…”

“…Relatedly, NIPU foams of varying crosslink density and viscosity were prepared from carbonated LSO, SBO, and MAO via aminolysis with diamines in the presence of ammonium bicarbonate as an external blowing agent (Dong et al, 2021). An analogous approach to carbonation is the production of thiocarbonates by ring expansion of epoxides with carbon disulfide (CS 2 ) at 60 C for 90 h in the presence of F I G U R E 2 8 (a) Polyhydroxyurethanes from cyclic carbonates, (b) polyhydroxythioethers from Pearson reaction of carbonates with diamines, and (c) thiocarbonates from ring expansion of an epoxide with carbon disulfide catalytic LiBr (Figure 28c) (Coste et al, 2022). Lastly, a side reaction may occur between diamines and the ester group of the carbonated oil or alkyl ester, resulting in the formation of amide groups, especially at higher temperatures (e.g., 100 C), which may affect the structure and properties of the resulting polymer (Javni et al, 2008).…”

Influence of Phosphorus Structures and Their Oxidation States on Flame-Retardant Properties of Polyhydroxyurethanes

“…Indeed, its global production in 2020 was nearly 25 Mt, ranking 5th among all polymers, with a global market valued at $71 billion [ 1 , 2 , 3 ]. PUs are synthetized by the polyaddition reaction of a polyol and a diisocyanate [ 4 ]. They are composed of hard and soft segments, which confer their unique properties and structuring [ 5 , 6 ].…”