Cationic Ring-Opening Polymerization of Five-Membered Cyclic Thiocarbonate Bearing an Adamantane Moiety via Selective Ring-Opening Direction

A novel five-membered cyclic thiocarbonate bearing adamantane moiety, 4,6-dioxatetracyclo[6.3.1.1. 3,10 0 3,7 ]tridecane-5-thione ( 1 ), was synthesized from 1,2-adamantanediol and thiophosgene in the presence of pyridine. Monomer 1 underwent cationic ring-opening polymerization initiated by triethyloxonium tetrafluoroborate (Et 3 OBF 4 ), methyl trifluoromethanesulfonate (TfOMe), trifluoromethanesulfonic acid (TfOH), and H 2 O with 2 mol % of boron trifluoride etherate (BF 3 OEt 2 ) in CH 2 Cl 2 at 30 °C to afford the polythiocarbonate by isomerization of the thiocarbonyl group into a carbonyl group with selective ring-opening direction. The number-average molecular weight and polydispersity of the polymer obtained by polymerization with H 2 O/BF 3 OEt 2 were 10 600 and 1.44, respectively. The temperature with 5% weight loss of the obtained polymer was 338 °C. Monomer 1 expanded as large as 14% during the polymerization.