Synthesis of Ultrahigh Molecular Weight PLAs Using a Phenoxy-Imine Al(III) Complex

Abstract

l - and d -lactide polymerization kinetics using phenoxy-imine ligands of the type Me 2 Al[O-2- tert- Bu-6-(C 6 F 5 N=CH)C 6 H 3 ] in the presence of n -butanol and benzyl alcohol by ring-opening polymerization into polylactide are investigated. Effects of initiator concentration, catalyst concentration, polymerization temperature, and time on the molecular weight of poly- l -lactide are also investigated. Purification and drying of l -lactide are found to significantly influence the polymerization kinetics and the final molecular weight achieved. Ultrahigh molecular weight poly( l -lactic acid) PLLA ( M w = 1.4 × 10 6 g/mol with Đ = 1.8) and ultrahigh molecular weight poly( d -lactic acid) PDLA ( M w = 1.3 × 10 6 g/mol with Đ = 2.0) are obtained when polymerization is performed with a molar ratio of monomer to catalyst (LA/Al) of 8000 for 72 h at 120 °C in the presence of benzyl alcohol with conversions of 96 and 91%, respectively. We report for the first time the synthesis of ultrahigh molecular weight poly- l - and d -lactide using the Me 2 Al[O-2- tert -Bu-6-(C 6 F 5 N=CH)C 6 H 3 ] catalyst. The identified catalyst is found to be suitable for the synthesis of a broad range of molecular weights.

On the Influence of the cis/trans Stereochemistry of Limonene Oxides toward the Synthesis of Biobased Thermosets by Crosslinking with Anhydrides

“…This could be explained by the amount of IMI used, 2.5 wt %, corresponding to a molar ratio [ cis -LO]/[IMI] or [GA/IMI] of 10. The theoretical molar mass would thus be calculated according to eq : − …”

Thermo-Rheological and Shape Memory Properties of Block and Random Copolymers of Lactide and ε-Caprolactone

“…The ROP of racemic mixture of D and L lactide (D,L-LA or rac-LA), in the absence of a stereoselective catalysts, will produce instead an amorphous polymer, the poly-(D,L-lactide), with a glass transition temperature close to 50 °C [ 10 ]. Unfortunately, the brittle nature of isotactic PLA limits its application [ 11 ]. For instance, for biomedical applications, because the glass transition temperature of poly-(D,L-lactide) (PDLLA) and poly(L-lactide) (PLLA) is well above the human body temperature, these materials are too stiff [ 6 ].…”

Crystallization behavior analysis and reducing thermal shrinkage of poly(lactic acid) miscibilized with poly(butylene succinate) film for food packaging

“…In other words, PLA is a chiral polymer, containing asymmetric carbon atoms which form the helical structures for crystallization. When the optical purity of L‐lactide was lower than 90% by contamination of D‐ or DL‐lactide, the crystallization of L‐lactide‐rich PLA will be lost, and consequently the low X c of PLA strongly affected on low thermal stability 3–6 . Theoretically, the thermal shrinkage of semi‐crystalline polymer easily occurs above T g because amorphous chains relax and deform, driven by elevating temperature and strain 7,8 …”

“…When the optical purity of L-lactide was lower than 90% by contamination of D-or DL-lactide, the crystallization of L-lactide-rich PLA will be lost, and consequently the low X c of PLA strongly affected on low thermal stability. [3][4][5][6] Theoretically, the thermal shrinkage of semi-crystalline polymer easily occurs above T g because amorphous chains relax and deform, driven by elevating temperature and strain. 7,8 Previously, the formation of a crystalline PLA network through strain-or thermal-induced crystallization and blending with highly crystalline molecules have been reported to restrict the free movement of amorphous PLA chains with a consequent enhancement of thermal dimensional stability.…”