Chain Conformations of Poly(γ-benzyl-L-glutamate) Pre and Post an Electrospinning Process

In order to reveal mechanisms for the electrospinning of proteins, this study focuses on the polymer chain conformation, which is considered to be a critical factor for successful electrospinning. Poly(γ‐benzyl‐L‐glutamate) (PBLG) is employed and the relationships between the chain conformations of the pre‐spun PBLG molecules and the morphologies of the post‐spun PBLG fibers are investigated. By combining viscosity measurements, and circular dichroism and FT‐IR spectroscopies, chain conformations of the pre‐ and post‐spun PBLG are characterized. The chain conformations of the pre‐spun PBLG changes from an α‐helix to a random coil upon changing the solvent ratios of dichloromethane (CH2Cl2) and trifluoroacetic acid (CF3COOH) from 100:0 to 0:100. In an α‐helix conformation, the morphology of PBLG fibers is relatively thick, while that of the random coil is thin and homogenous. The mean fiber diameters decrease when the chain conformations change from an α‐helix to a random coil. FT‐IR spectroscopy and wide‐angle X‐ray diffraction measurements reveal that electrospinning predominantly induces an α‐helical conformation in post‐spun PBLG fibers, and more highly crystallized fibers are generated as the α‐helical content in the pre‐spun solution increases. SEM images of the electrospun PBLG fibers ($\overline {DP}$ = 1 200) at DCM/TFA ratios of a) 100:0, b) 90:10, c) 80:20, and d) 0:100 (magnification: ×1 000, scale bars: 20 µm).