Porous Poly(l-lactide)/Poly(d-lactide) Blend Film with Enhanced Flexibility and Heat Resistance via Constructing a Regularly Oriented Pore Structure

Developing eco-friendly polymers, such as poly(lactic acid) (PLA), is a hopeful strategy to reduce the dependence on petroleum-based polymers and alleviate the "white pollution" crisis. Nonetheless, the manufacture of high-performance biodegradable films remains a major challenge, which are lightweight, highly porous, and combine favorable flexibility with excellent thermal stability. Herein, brand-new porous PLA films with enhanced flexibility and heat resistance are successfully prepared via a simple combination of blade coating and thermally induced phase separation without damaging the environmental protection advantage. The elongation at break of the prepared pure poly(l-lactide) film can reach 45.5%. Thanks to enhanced crystallization ability of stereocomplex crystals, leaf vein-like-oriented pores are obtained, finally resulting in flexible poly(l-lactide)/poly(d-lactide) blend films (elongation at break of 10–40%) with improved mechanical properties and high porosity. For example, the 50/50 blend film has the elongation at break of 10.4%, tensile strength of 4.1 MPa, specific modulus of 328.2 MPa cm3 g–1, porosity of 90.1%, and pore size range of 0–10 μm. Additionally, the improved crystallinity significantly enhances the films' heat resistance, and the T5% and TMAX of the 50/50 blend film increased by 32 and 16 °C, respectively, compared with those of the pure film. This work will open up a new path for the use of PLA in microfiltration, packaging, and modified applications.