Semiempirical condensed structure analysis and quantification of disorder for extrusion-printed polylactide filaments

Polylactide (PLA) is applied as a structural biomaterial for fabrication of wearable electronics and tissue regenerative devices. Yet it remains challenging to rationalize the processing parameters for PLA-based materials and devices for desired properties. Comprehensive understanding on the condensed structure and its evolution with processing conditions for PLA materials may be the key. This work developed a semiempirical quantitative model to analyze the condensed structure of PLA filaments extrusion-printed from fused deposition modelling (FDM) and cold crystallization. We applied differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) to acquire quantitatively the melting enthalpy and glass transition tan δ of PLA filaments. The structure order and disorder information can be derived based on a framework of group interaction modelling (GIM). A three-phase condensed structure model including order, disorder and metaorder was proposed for PLA filaments. Based on this model, we revealed the condensed structure evolution upon the effect of printing speed for FDM processing of PLA filaments. Additional wide-angle X-ray scattering (WAXS) further revealed the intricate crystalline characteristics. Such quantitative structure modelling may be extended to rationalize the processing of other biopolymers for precision-demanding biomedical applications.