Ethylcellulose Colloids Incubated in Dilute Solution.

This study revealed, for the first time, that dilute solutions made of a representative series of commercial ethylcellulose (EC; molecular weights 77-305 kDa, provided by the manufacturer) and four distinct organic solvents (α-terpineol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (TPIB), tetrahydrofuran (THF), and benzene) can be used to foster stabilized, nearly monodisperse, nanoscale (pure) polymer colloid, with no isolated chains present. Using combined light-scattering (dynamic light scattering, static form factor, and Zimm/Berry plots) and intrinsic viscosity (Tanglertpaibul-Rao, Huggins, and Kraemer plots) analyses, the structural features of colloidal EC aggregates, ρ = ⟨Rg ⟩/⟨Rh ⟩ = 0.67-0.83, were first shown to be described rather well by the theory on colloidal spheres (⟨Rg ⟩ and ⟨Rh ⟩ being the mean radius of gyration and the hydrodynamic radius, respectively). An empirical scaling law relating the intrinsic viscosity to the mean colloid size can thus be established: [η]H = (1.7 ± 0.2) ×10-3 ⟨Rh ⟩(2.1±0.3) ([η]H and ⟨Rh ⟩ in units of mL/g and nm, respectively), which may be contrasted with the Zimm model for isolated Gaussian coils, [η]H ∼ ⟨Rh ⟩1 , and the Einstein equation for isolated solid spheres, [η]H ∼ ⟨Rh ⟩0 . Optical microscopy images of thin films cast from different EC solutions clearly revealed the abundance of micron EC agglomerates, contrary to the uniform thin-film morphology produced from a dilute polystyrene solution, which serves as a reference solution composed of isolated chains. These observations point to new features and applications of EC dispersions.