Structure of solid dispersions in the system polyethylene glycol-griseofulvin with additions of sodium dodecyl sulphate

Abstract

Solid dispersions of polyethylene glycol (PEG) 3000 and 10% w/w griseofulvin were prepared by the melting method. Samples were also prepared with 10% w/w of the anionic surfactant sodium dodecyl sulphate (SDS) added to the melt. Phase analysis was performed by X-ray powder diffraction and investigation of the short-range structure by 13C-CP/MAS solid-state NMR. In the samples without the added surfactant, a solid particulate dispersion of griseofulvin in PEG is obtained. The periodic structure of the pure phases is retained and so is the local structure as seen by NMR. When a surfactant is added to the dispersion a solid molecular dispersion i.e., a solid solution, is formed. The interaction between the environment and certain carbons in griseofulvin and SDS is evident. Both hydrophilic and hydrophobic parts of the molecules are influenced in a significant way. The solid solution of griseofulvin in PEG obtained on addition of SDS seems to depend on an interaction between the polymer and SDS in aggregates (micelles). These aggregates can bind griseofulvin in a molecular form at the surface or in the interior of the aggregate.