Dissolution dynamics of woven all-silk composites fabricated in the ionic liquid 1-ethyl-3-methylimidazolium acetate

Abstract

Single layer woven all-silk composites (ASCs) have been prepared using the ionic liquid 1-ethyl-3- methylimidazolium acetate ([C2mim][OAc]), with the dissolution carried out under various times and temperatures. Cross sectional images revealed the dissolved and coagulated silk matrix were formed along both fibre directions with thicker matrix layer observed along warp direction. Radial integration utilising the second Legendre polynomial function (P2) were conducted on the collected intensity distribution curves attained from WAXD azimuthal scans, enabling the quantitative measurement of the average orientation of crystals. A simple linear mixing rule was employed to correlate the coagulated matrix (Vm) with respective P2 values, leading to the calculation of Vm. Time–temperature superposition (TTS) was verified through the construction of master curves, from which the dissolution was found to have Arrhenius-like behaviour allowing the determination of dissolution activation energy (Ea). The three measured tensile properties were all found to follow TTS principle, thus yielding another two methods to determine Ea. Five different methods point to an average Ea value of 93±2 kJ/mol. Additionally, the dissolution rates and activation energies of single and woven silk were compared. The master curves constructed in this study may provide a guidance for future design of silk fibre reinforced composites with desired properties.