Bio‐safe synthesis of linear and branched PLLA

Abstract

The catalytic activities of Bi(III) acetate (Bi(OAc) 3 ) and of creatinine towards the ring-opening polymerization of Llactide have been compared with those of a stannous (II) ethylhexanoate ((SnOct) 2 )-based system and with those of a system catalyzed by enzymes. All four were suitable catalysts for the synthesis of high and moderate molecular weight poly(L-lactide)s and the differences in reactivity and efficiency have been studied. Linear and branched poly(L-lactide)s were synthesized using these bio-safe initiators together with ethylene glycol, pentaerythritol, and myoinositol as coinitiators. The polymerizations were performed in bulk at 120 and 140 C and different reactivities and molecular weights were achieved by adding different amounts of coinitiators. A molecular weight of 105,900 g/mol was achieved with 99% conversion in 5 h at 120 C with a Bi(OAc) 3 -based system. This system was comparable to Sn(Oct) 2 at 140 C. The reactivity of creatinine is lower than that of Bi(OAc) 3 but higher compared with enzymes lipase PS (Pseudomonas fluorescens). A ratio of Sn(Oct) 2 M o /I o 10,000:1 was needed to achieve a polymer with a reasonable low amount of tin residue in the precipitated polymer, and a system catalyzed by creatinine at 140 C has a higher conversion rate than such a system.

Zwitterionic ring opening polymerization of lactide by metal free catalysts: Production of cyclic polymers

“…ROP of lactide can be catalyzed by the addition of organometallic compounds such as stannous octanoate [1][2][3] and zinc lactate 4 and high temperatures have to be applied. Such conditions induce side reactions such as transesterification and racemization, which hamper the control over the polymerization process.…”

Synthesis and characterization of polylactides with different branched architectures

“…One interesting aspect of the lactide ring‐opening reaction is the flexibility in designing different molecular architectures by employing multifunctional initiators. Different branched structures such as star‐shaped with arm numbers from 3 to 6, dendrimers, comb‐like, and barbell‐like molecules are synthesized by applying this strategy. An alternative procedure for the in situ synthesis of branched PLA is to use co‐monomers bearing initiation groups, such as 2,2‐ bis (hydroxymethyl) butyric acid in the presence of a tertiary amine, glycidol, and 5‐hydroxymethyl‐1,4‐dioxane‐2‐one .…”

A novel use of Ti‐POSS as initiator of L‐lactide ring‐opening polymerization

“…Among the metal salts and coordination compounds studied for the ROP of LA, also titanium‐based systems have been considered. Following the pioneering work of Kricheldorf et al9 on the use of titanium alkoxides as initiators of the polymerization of lactones, several types of Ti‐based complexes have been studied for the ROP of LA to produce PLA 10–25. Indeed, some of the above systems enable stereoselective polymerization reactions.…”