Polylactones, 29. Preferentially syndiotactic poly(β‐(R,S)‐butyrolactone) obtained by ring‐opening polymerization with triphenyltin methoxide or diphenyltin dimethoxide

Triphenyltin methoxide (Ph3SnOMe) and diphenyltin dimethoxide (Ph2Sn(OMe)2)‐initiated polymerizations of β‐(R,S)‐butyrolactone were conducted in bulk at 50 and 75°C. The low catalytic reactivity of the initiator prevented lower temperatures. The stereosequences of the isolated poly(β‐(R,S)‐butyrolactones) were analyzed by 13C NMR spectroscopy and characterized by the ratio of isotactic and syndiotactic diads (i/s‐ratios down to 0,4/1,0 were found). With Ph3SnOMe relatively high molecular weights (ηinh = 0,3 dL/g, M̄w ≈ 25 000−30000) were obtained but the stereoselectivity of the polymers obtained with both Ph3SnOMe and Ph2Sn(OMe)2 is not higher than that with Bu3SnOMe (published previously). Selected poly(β‐(R,S)‐butyrolactone) samples were characterized by IR spectra, WAXS powder patterns and DSC measurements.