Evaporative crystallization of Poly(ethylene oxide)-b-Poly(L-lactic acid) on water surface

Evaporative crystallization on water surface (ECWS) provides a unique approach to tuning polymer crystallization pathways. Recent studies have shown that poly( l -lactic acid) (PLLA) forms biphasic one-dimensional (1D) and two-dimensional (2D) crystals upon ECWS. In this work, we report on the ECWS behavior of poly(ethylene oxide)- b -(poly( l -lactic acid) (PEO- b -PLLA). Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) were used to track the structural and morphological evolution of the block copolymer assembly. 1D filaments were exclusively observed, and the formation process was systematically studied. ECWS conditions, such as polymer concentration, evaporation rate, and temperature, were varied to understand the formation mechanism and tune the structure. Rotational flow was introduced to control the 1D filament packing. Quasi-2D liquid crystalline films were obtained. • ECWS alters the crystallization pathway of PLLA- b -PEO. • 1D crystalline filaments were obtained. • Crystallization-driven particle merging leads to 1D filaments. • Rotational flow controls 1D filament size and packing.