Polylactones. LXI. Polymerization of β‐D,L‐Butyrolactone Initiated with 1,3‐Diacetoxy‐1,1,3,3‐tetrabutyldistannoxane and with 1,3‐Dichloro‐1,1,3,3‐tetrabutyldistannoxane

Abstract

Commercial 1,3‐dichlorotetrabutyl distannoxane (DCTSO) and 1,3‐diacetoxy‐tetrabutyl distannoxane (DATSO) were used as initiators for the ring‐opening polymerization of β‐D,L‐butyrolactone (β‐D,L‐BL). These polymerizations were conducted in bulk and in concentrated solutions at 50°C or 100°C. Regardless of initiator and reaction medium, no polymerization took place at 25°C. When the monomer/initiator (M/I) ratio was varied from 100:1 to 2000:1, polymerization was observed up to M/I ratios of 600:1 or 800:1, but never at higher ratios, and the number average molecular weights did not parallel the M/I ratios. The stereosequences were evaluated by means of ¹³C NMR spectroscopy and a predominance of syndiotactic dyads was found. The highest percentage of syndiotactic dyads (around 75%) was found at the lower reaction temperature, and as a result, the consequence that semicrystalline polylactones with higher melting temperatures were formed than in the case of 65% or 55% syndiotactic dyads.

Keywords:

• β‐D,L‐Butyrolactone
• Ring‐opening polymerization
• Distannoxanes
• Syndiotactic stereosequences
• Enantioselectivity