High molar mass cyclic poly(l-lactide) via ring-expansion polymerization with cyclic dibutyltin bisphenoxides. (August 2018)

• Record Type: Journal Article
• Authors: Kricheldorf, Hans R.; Weidner, Steffen M.
• Is Part Of: European polymer journal. Volume 105(2018)
• Page Start: 158
• Page End: 166
• Publication Date: 2018-08
• Subjects: Polylactide -- Ring-opening polymerization -- Cyclization -- Catalysts -- MALDI-TOF MS; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; Polymerization; Polymers; Periodicals; Electronic journals; 547.705
• DOI: 10.1016/j.eurpolymj.2018.05.036
• Languages: English
• ISSNs: 0014-3057

Abstract

Graphical abstract: The purpose of this work is to demonstrate the suitability of a new class of cyclic tin catalysts for a potential racemization-free, technical production of high molar mass cyclic pol(l -lactide). Furthermore, an experimental evidence for the assumed ring-expansion polymerization is elaborated. Highlights: New cyclic tin catalysts allow for preparation of high molar mass cyclic poly(l -lactide)s. Experimental evidence for ring-expansion polymerization has been elaborated. The new catalysts allow for easy upscaling of the polymerization process. Abstract: Two new catalysts (SnNa and SnBi) were prepared from dibutyltin oxide and 2, 2′-dihydroxybiphenyl or 2, 2′dihydroxy(1, 1′-binaphtyl). These catalysts enabled rapid polymerizations of l -lactide at 160 or 180 °C in bulk, whereby almost exclusively cyclic polylactides were formed. These polymerizations were free of racemization and yielded pol(l -lactide)s having weight average molecular weights (Mw's) up to 140 000 g mol −1 . The Mw's varied little with the Lac/Cat ratio as expected for a ring expansion polymerization (REP). Polymerizations performed in bulk at 140, 120 and 102 °C yielded cyclic polylactides with lower molecular weights. At 102 °C a strong predominance of even-numbered cycles was found with SnNa as catalyst. SnNa can also catalyze alcohol-initiated ROPs yielding linear poly(l -lactide) free of cyclics.