Bismuth(III) Alkoxide Catalysts for Ring‐Opening Polymerization of Lactides and ϵ‐Caprolactone

Abstract

Homoleptic bismuth alkoxide complexes, Bi(OR) 3 [R = i Pr ( 1 ), t Bu ( 2 ), and CMe 2 i Pr ( 3 )], are used as catalysts in the ring-opening polymerization (ROP) of lactides. In contrast to 1 , two bulkier bismuth alkoxides, 2 and 3, show high activity in the ROP of lactides in toluene at 75 ° C. Notably, Bi III alkoxides 2 and 3 are more active in lactide ROP than Sn II octoate activated with n -butanol under identical reaction conditions. Bismuth alkoxides 2 and 3 exhibit a living behavior in the ROP of lactides that is demonstrated both in homopolymerization and in a polymerization resumption experiment. Polymerization of rac -lactide using 2 and 3 yields polylactide with a slight heterotactic bias. In addition, 2 is an effi cient initiator for the ROP of ε -caprolactone in bulk at 120 ° C. Variation of the monomer-to-catalyst ratio yielded poly( ε -caprolactone) with M n s up to 120 000 g mol − 1 in corrected gel-permeation chromatography (GPC) data.

Bismuth subsalicylate, a low-toxicity catalyst for the ring-opening polymerization (ROP) ofl-lactide (l-LA) with aliphatic diol initiators: synthesis, characterization, and mechanism of initiation

“…Our interest in the use of bismuth-based catalysts is further motivated by the fact that Mexico produces the second most bismuth in the world (825 metric tonnes). 21 A number of bismuth compounds have been reported to catalyze ROP processes, including inorganic derivatives such as BiX 3 (X ¼ Cl, Br, I), 22 the homoleptic acetate, 23 2-ethyl hexanoate, 24 hexanoate, 25 triate, [26][27][28] alkoxides, 29 the heteroleptic subsalicylate, 25,30,31 (salen)bismuth alkoxides, 32 and the diphenyl bismuth bromide. 33,34 Bismuth(III) compounds have proven to be versatile catalysts for a variety of organic transformations.…”

“…The simple formulation, low toxicity, and high activity of Bi(III) alkoxides make them very attractive catalyst candidates. 48 BiSS (Scheme 1) has recently been demonstrated to be a less toxic catalyst for the ROP of cyclic esters, [46][47][48][49][50][51][52][53] and as a catalyst/ initiator for homo-and copolymerizations of lactones and lactides. [53][54][55] An exciting result was the discovery that BiSS favored the presence of less blocky sequences than copolyesters prepared with SnOct 2 under identical conditions.…”

Preparation of stiffer ternary blends of polypropylene/polyamide 6/biodegradable polymers with improved interfacial adhesion

“…Table I presents the properties of the biodegradable polyesters used in the blend. Both copolymers contain 15 mol% of ε‐caprolactone 28 …”

Bismuth complex catalysts for the in situ preparation of polycaprolactone/silicate bionanocomposites

“…The attractiveness of bismuth‐based catalysts is highlighted by the fact that most, if not all, polyurethane‐producing chemical companies have replaced the toxic tin catalysts by bismuth salts despite their lower reactivity. Systematic research on bismuth‐based catalysts or initiators for the ROP of cyclic esters was pioneered by Kricheldorf and co‐workers …”