Lyotropic Behaviour of Nitrocellulose

Abstract

Recent work on the ternary system nitrocellulose (NC)/tetrahydrofuran (THF)/ethanol (EtOH) has yielded the room temperature section through the phase diagram. Separation into isotropic and anisotropic phases is observed within limits qualitatively in agreement with Flory's theory for the phase separation of rigid rod/solvent/non-solvent systems. The equilibrium arrangement of molecules in the mesophase favours a layered structure, consistent with their chiral nature. Given sufficient time, a crystallosolvate of NC and EtOH is formed by some ternary solutions; this confirms our choice of EtOH as a non-solvent with a significant effect on the polymer-environment interaction parameter. Aligned reconstituted NC can be produced from single-phase anisotropic solutions or from two-phase isotropic + anisotropic solutions in THF/EtOH. In the latter case, nematic-like order may be induced in the isotropic phase by a suitably high shear. The reconstituted fibres do not contain any detectable amount of crystallosolvate. Considerable local reinforcement between chains in the solid polymer may arise from the formation of “non-periodic layer” crystallites.