Preparation of PLLA/PDLA stereocomplexes using a novel initiator based on Mg(II) and Ti(IV) alkoxides

Abstract

Herein we describe the obtention of polylactide stereocomplexes using a novel initiator system comprising Mg(II) and Ti(IV) centers. The stereocomplexes were successfully prepared using two different routes: by PDLA and PLLA co-precipitation from chloroform solutions and two-step diblock copolymerization. For the PDLA/PLLA mixing procedure, individual homochiral polymers were prepared in solution at different monomer/initiator ratios; whereas, the PLA stereoblock was prepared employing one-pot sequential polymerization of both chiral monomers. The products analyzed by WAXD showed the characteristic stereocrystal reflections while the high melting temperatures found in the DSC runs confirmed the formation of PLA stereocomplexes in both cases. Surprisingly, one of the stereocomplexes showed a second endothermic event at 250.1 C and to our knowledge this is the highest melting temperature reported for PLA stereocomplexes till date. These results point to the discovery of an effective initiator based on low toxicity metals for the preparation of biodegradable materials with interesting thermal properties.

Preparation of blends of oligo([R,S]-3-hydroxybutyrate) and poly([R]-3-hydroxybutyrate): Thermal properties and molecular dynamic studies

“…Due to the presence of low cytotoxic Mg(II) and Ti(IV) centers in its composition, the hypothesis that Catylen ® S200 could be an excellent candidate for ROP of [R,S]-b-butyrolactone for potential application in biomedical devices came to our attention. One of us has already reported the use of Catylen ® S200 as initiation system for the polymerization of cyclic esters [23,24].…”

Ring Opening Polymerization of L-Lactide With Two Different Zinc(ii) Phenoxy-Imine Complexes as Initiators

“…Each mixture containing the desired amount of initiator and L-lactide (about 2 g) was prepared in a Schlenk flask under N 2 . Each polymerization reaction was conducted at 180 °C for 2 h. 3,4 After this period, the reaction was quenched by cooling to room temperature. Then, the solid residue was dissolved in chloroform, and the polymer was precipitated from ethanol.…”

“…1,2 In effect, metal-initiated ROP of lactides offers large degree of reaction and polymer tacticity controls as well as generates high molecular weight polymers. [2][3][4] ROP initiators generally affect the properties of the final polymers in different ways. 5,6 When metal complexes are used as initiators, the structure and properties of the final polymers are dictated by the type of the metal and the stereochemical attributes of the ancillary ligands.…”

Influence of graphene nanosheets on stereocomplex crystallization behaviors of star‐shaped poly (D(L)‐lactide) stereoblock copolymer

“…Stereocomplex poly (lactic acid) (sc-PLA) consisting of both enantiomer segments of poly (L-lactic acid) (PLLA) and poly (D-lactic acid) (PDLA) has been extensively interesting due to its excellent thermal stability and mechanical properties compared to PLLA homopolymer. [1][2][3][4][5][6][7][8][9][10][11][12][13] Those properties of sc-PLA implied that it could be applied in totally biodegradable engineering plastics. However, usually the crystallinity of sc-PLA is less about 20%.…”