On the copolymerization of monomers from renewable resources: l-lactide and ethylene carbonate in the presence of metal alkoxides

Abstract

The copolymerization of l-lactide with ethylene carbonate carried out at 120 °C in the presence of organic derivatives of aluminum, zinc and tin as catalysts leads to the formation of linear polymers of relative molecular masses in the 10 000-30 000 range containing up to 12 mol. % of carbonate monomeric units (m.u.). A decrease in T g of copolymers down to 48 °C demonstrates the internal plasticization effect for polylactide matrix. In the first reaction step mainly lactide homopolymerization proceeds in the systems studied. Carbonate m.u. incorporate into the growing chain as a result of recurring transesterification processes. Backbiting type intramolecular transesterification reactions dominate in the system and macrocycle compounds containing 1 carbonate m.u. and 3-9 lactic acid m.u. are the main reaction products after prolonged time. On the basis of analysis of the low molecular weight products formed in the polymerization system and products of the model reaction of ethylene carbonate with metal alkoxides, the mechanism of elementary reactions leading to the incorporation of carbonate m.u. into the copolymer chains has been proposed.

Multi‐arm star polymers of lactide obtained in melt in the presence of hyperbranched oligoglycerols

“…Generally, the observed T g of the PLA phase in the systems initiated with PG 8 , MPG 8 and PG 18 was slightly lower (44-52 ∘ C) than that presented in the literature 15 for linear PLA homopolymers (approximately 62 ∘ C). This reflects the internal plasticization of PLA with flexible PG cores characterized by T g in the range −36 to −47 ∘ C. Moreover, in three cases, a second T g , characteristic for the PG domains, was determined, which suggests that oligoglycerols exhibit only partial miscibility with PLLA.…”

“…The thermal properties of the multi‐arm star PLLA crude products were characterized by means of DSC with respect to the glass transition temperatures ( T g ) and the presence of a crystalline fraction ( x ) (Table ). Generally, the observed T g of the PLA phase in the systems initiated with PG 8 , MPG 8 and PG 18 was slightly lower (44–52 °C) than that presented in the literature for linear PLA homopolymers (approximately 62 °C). This reflects the internal plasticization of PLA with flexible PG cores characterized by T g in the range −36 to −47 °C.…”

“…In this process, PGs were reacted with EC in the presence of K 2 CO 3 as a catalyst. It is known that the reaction of an alkoxide with five‐membered cyclic carbonate can proceed according to two reaction pathways. The alkoxide can attack at the carbonyl carbon atom leading to a linear carbonate or at alkyl carbon atom forming an ether linkage.…”

“…The common routes for modification of PLA properties are copolymerization and physical mixing including blending with other polymers. The first route leads to different kinds of block, graft and random copolymers with improved properties such as high elasticity and fast degradation. Some papers have reported the synthesis of PLA stars by ring opening polymerization (ROP) of lactide (LA) in the presence of simple polyols and branched initiators with various numbers of hydroxyl groups ranging from 6 to 71, obtaining polymers characterized by M n in the range 2–250 kg mol −1 .…”

Polymeric Materials Based on Carbon Dioxide: A Brief Review of Studies Carried Out at the Faculty of Chemistry, Warsaw University of Technology

“…It should be noted that the thermodynamic products of the reaction between CO 2 and epoxides are five-membered cyclic carbonates (1,3-dioxolan-2-ones) that are easily available in the presence of the appropriate catalysts. They cannot be applied as precursors for poly(alkene carbonates) due to the positive Gibbs free enthalpy of polymerization [12]; however, it has been found that some of them could undergo copolymerization with heterocyclic monomers [13,14]. Unfortunately, in most of the studied systems, the amount of carbonate units incorporated into the polymer chain was small.…”