Consequences of Composition on Morphological and Mechanical Properties in Fully Renewable Poly(lactide)-poly(farnesene) Block Copolymers

Abstract

Reliance on non-renewable fossil resources, sluggish degradability, and limited recycling opportunities encourage the implementation of more sustainable materials and manufacturing practices in society. Poly(lactide) (PLA), an FDA-approved biobased polymer with biodegradable properties, has long been studied as a promising alternative. However, there is a need to overcome the inherent brittleness associated with PLA, thereby drastically improving its applicability. We explored the incorporation of hydroxyl-telechelic poly(beta-farnesene) (PF)-a biobased, hydrophobic polymer derived from terpenes-as a soft midblock in a PLA-PF-PLA triblock system. The effect of molecular weight and weight fraction of PLA on morphology was studied using SAXS and TEM. Lower molecular weight polymers assembled into a lamellar morphology at high PLA weight fractions, while high molecular weight polymers adopted a hexagonally packed cylinder morphology and exhibited relatively elastomeric behavior. Tensile studies revealed that mechanical properties can be tuned by altering the PLA composition, with higher weight fractions increasing the tensile modulus to 22.1 MPa. Additionally, a comprehensive E-factor analysis was performed on the block copolymer synthesis in order to highlight the importance of process optimization in the design of complex sustainable polymers.