Regioselective and Alternating Copolymerization of Carbonyl Sulfide with Racemic Propylene Oxide

Abstract

We report the first example of a regioregular and fully alternating poly (propylene monothiocarbonate) (PPMTC) from the well-controlled copolymerization of two asymmetric monomers, carbonyl sulfide and racemic propylene oxide, using (Salen)CrCl in conjunction with bis(triphenylphosphoranylidene)ammonium chloride. The maximum turnover of frequency of this catalyst system was 332 h −1 at 25°C. The contents of monothiocarbonate and tail-to-head linkages of PPMTC were up to 100% (based on 1 H NMR spectra) and 99.0% (based on 13 C NMR spectra), respectively. PPMTC samples have number-average molecular weight (M n ) up to 25.3 kg/mol with polydispersity index of 1.41. The very low decomposition temperature of 137°C and high refractive index of 1.63 of PPMTC make it a potential scarifying optical adhesive.

Sulfur Chemistry in Polymer and Materials Science

“…Since, carbonyl sulfide (COS) is a structural analogue of CO 2 (and CS 2 ), scientist were strongly motivated to convert COS into polymers, in a way similar with the CO 2 –epoxide copolymerization, producing poly(thiocarbonate) directly from the selective and completely alternating copolymerization of COS with epoxides via metal catalysis (Scheme D) . A recent report focused on the catalytic synthesis of poly(trimethylenethiocarbonate), a sulfur‐containing crystalline copolymer, from the completely alternating copolymerization of COS with oxetane (OX) . The analogous copolymerization reaction of COS with the asymmetric monomer, propylene oxide, occurred via the sulfur anion selectively ring‐opening at the methylene position of propylene oxide in the presence of binary (Salen)CrCl/[PPN]Cl catalyst system.…”

Alternating and regioregular copolymers with high refractive index from COS and biomass-derived epoxides

“…terminated epoxide, which has been well demonstrated in our previous study. 18 The effect of the reaction time on the EGE/COS copolymerization by using the binary (salen)CrCl/[PPN]Cl catalyst were investigated and the results are listed in entries 2-6 in Table 1. The conversion of EGE was up to 89% within only 6 min at 40 C, thus showing a high catalytic activity with a TOF of up to 8930 h À1 .…”

“…It was proposed that the solvent may facilitate the backbiting route of the sulfur anion to produce cyclic monothiocarbonate. 18 The type of the cocatalysts also had a strong inuence on the EGE/COS copolymerization (entries 13-17 in Table 1). The binary (salen)CrCl/1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) system presented a highly catalytic activity (TOF: 7460 h À1 ) towards the copolymerization, while two relatively strong bases, 4-dimethylaminopyridine (DMAP) and 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD), combined with the (salen)CrCl complex presented a low catalytic activity (580 and 1060 h À1 , respectively), as shown in the results in entries 14 and 15 in Table 1.…”

“…S3 †), indicating the occurrence of O/S ER reaction to a slight extent. 18 However, the a-Cl, u-OH copolymer could be minimized as shown in Fig. 4B.…”

“…16,17 The abovementioned biomass-derived compounds, guaiacol and eugenol, could be converted to the epoxides by reacting them with epichlorohydrin (ECH), as shown in Scheme 1. On the other hand, recently, our group has discovered a sulfurcontaining one-carbon (C1) building block, carbonyl sulde (COS), which could copolymerize with various epoxides to afford poly(monothiocarbonate)s. 18,19 Thus, we were inspired to synthesize sulfur-containing copolymers from COS with epoxides derived from guaiacol and eugenol. It would be a sustainable pathway for making polymeric materials because ECH can also be obtained from biomass 20 and COS can be produced from the reaction of CO with sulfur that is exceptionally rich in nature and is the main by-product of the renery.…”