High Performance Star Block Aliphatic Polyester Thermoplastic Elastomers Using PDLA-b-PLLA Stereoblock Hard Domains

Stereocomplexed Functional and Statistical Poly(lactide-carbonate)s via a Simple Organocatalytic System

The stereocomplexation of polylactide (PLA) has been widely relied upon to develop degradable, sustainable materials with increased strength and improved material properties in comparison to stereopure PLA. However, forming functionalized copolymers of PLA while retaining high crystallinity remains elusive. Herein, the controlled ring-opening copolymerization (ROCOP) of lactide (LA) and functionalized cyclic carbonate monomers is undertaken. The produced polymers are shown to remain crystalline up to 25 mol % carbonate content and are efficiently stereocomplexed with homopolymer PLA and copolymers of opposite chirality. Polymers with alkene and alkyne pendent handles are shown to undergo efficient derivatization with thiol-ene click chemistry, which would allow both the covalent conjugation of therapeutic moieties and tuning of material properties.

Microscopic Origins of the Distinct Mechanical Response of ABA and ABC Block Copolymer Nanostructures

It has been commonly believed that the ordered thermoplastic elastomers formed by the ABC triblock copolymer should have better mechanical performance than that by the ABA counterpart due to the higher bridging fraction. However, the thermoplastic elastomer of ABA was often observed to perform better than that of ABC. To compare the performance of two kinds of thermoplastic elastomers and unveil the underlying microscopic mechanism, we have calculated their stress-strain curves using coarse-grained molecular dynamics simulations in conjunction with self-consistent field theory. It is revealed that the stretching degree of the bridging blocks and the network connectivity play important roles in determining the mechanical properties in addition to the bridging fraction. The higher degree in the stretching of bridging blocks and network connectivity of the structure formed by the ABA triblock copolymer enables its superior mechanical performance over the ABC block copolymer.