Transport Properties of Commercial Cellulose Nanocrystalsin Aqueous Suspension Prepared from Chemical Pulp via Sulfuric AcidHydrolysis

摘要

A cellulose nanocrystal (CNC) sample prepared from chemical pulp via sulfuric acid hydrolysis procedures has been supplied by InnoTech Alberta Inc. in the shape of white dry powder as a prototype product. Some transport coefficients were precisely investigated for the CNC sample in aqueous suspensions at the room temperature of 25 °C such as the average rotational and translational diffusion coefficients (Dr and Dt) and viscoelastic relaxation times (τv) at dilute conditions. The determined values, Dr ≈ 2.3 × 10³ s^–1 and Dt ≈ 1.0 × 10^–11 m² s^–1, using depolarized and usual dynamic light scattering (DLS) techniques, respectively, proposed the consistent length and width of L ≈ 170 nm and W ≈ 7.6 nm via a theoretical model for monodisperse rigid rods dispersed in pure water. The viscoelastic behavior for aqueous CNC suspensions containing spherical probe particles was examined using DLS rheological techniques. The obtained value of τv = 1.0 × 10^–4 s fairly agrees with that of (6Dr)⁻¹ ≈ 7.4 × 10^–5 s. Because the theoretical modelfor monodisperse rods denotes the relationship τv = (6Dr)⁻¹, this observationstrongly confirms that the CNC sample behaves as approximately monodisperserigid rodlike particles. Transmission electron microscopy (TEM) imagesclearly demonstrated a bimodal distribution in rod length with majorand small minor peaks at ca. 150 and 240 nm, respectively. Then, thereason for the observed disagreement between the L values resulted from the transport coefficients and the major peakin TEM images is the presence of the small minor component with L ≈ 240 nm. Consequently, individual nanosize rodlikecrystalline particles in the CNC sample well disperse without forminglarge aggregations because of strong interactions and behave as isolatedindividual rods in dilute aqueous suspensions.