Bulk Polymerization of (L,L)-Lactide Using Non-Organometallic Triazolium Carbene: Limited Advantages

Abstract

The ring-opening polymn. (ROP) of L,L-lactide (L-LA) has been studied in bulk using alc. (either methanol or benzyl alc.) and 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene carbene, 1, resp. as initiator and non-organometallic catalyst, over a range of temp. and alc.-to-1 molar ratios. Although 1 is known to perfectly control the polymn. of L-LA in soln. at 90°C, its efficiency in bulk is drastically decreased since its thermal instability limits the possibility to reach high mol. wt. poly(L-lactide) (PL-LA). Under optimum conditions, PL-LA chains with av. mol. wt. up to 10,000 g.mol-1 have been obtained within 15 min and interestingly characterized by very narrow polydispersity indexes. Compared to PL-LA conventionally prepd. with stannous octoate as catalyst, the thermal stability proved remarkably enhanced when the ROP was promoted by 1. [on SciFinder(R)]