Fabrication and optical properties of transparent PMMA/BPEF blend films via reactive melt extrusion with catalysis of Mg(TFSI)2

This study utilized a straightforward one-step method, melt extrusion , to blend polymethyl methacrylate (PMMA) with 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (BPEF) to fabricate optically transparent polymer blends , utilizing Mg(TFSI) 2 as the catalyst for the ester exchange reaction. All polymer blends demonstrated excellent mechanical and optical properties , achieving high transparency (≥90 %) in the visible spectrum. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results indicated that the blends formed a thermodynamically homogeneous system. Additionally, gel permeation chromatography (GPC) confirmed the occurrence of ester exchange reactions between PMMA and BPEF in both salted and unsalted blends. Very interestingly, without Mg(TFSI) 2 one hydroxyl group of BPEF is linked to PMMA side group through transesterification reaction, leading to a zero birefringence . Nonetheless, the inclusion of Mg(TFSI) 2 appears to facilitate the ester exchange reaction between both hydroxyl groups of BPEF and a single PMMA chain, which causes a cyclic ring structure. Such cyclic ring structure orients parallel to the planar plan, which then increases n // and also Δn.