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Abstract
Qualitative and quantitative solubility studies of ethyl cellulose, Type N-10, in 112 and 36 solvents respectively are reported. The relative contribution of dispersive, polar and hydrogen bonding intermolecular forces are depicted on two-dimensional and triangular solubility graphs. Phase separation phenomena may be explained in terms of the differences in both the solubility parameter (δ) and the polymer-solvent interaction parameter (χc) values between ethyl cellulose and each solvent. Coacervation occurs in very poor solvents with δ values just outside the solubility spectrum of ethyl cellulose
A mean value for the solubility parameter and critical interaction parameter (χc) for ethyl cellulose obtained from turbidity titration measurements were 9.39 ± 0.17 (cal/cm3)½ and 0.38 ± 0.04 respectively. Gelation occurs with nonsolvents with δ values significantly outside the solubility spectrum and with correspondingly larger χc values. Flocculation was observed only in polar solvents in which large χc values occur
Theoretical values for the ethyl cellulose-solvent interaction parameters were calculated for 112 solvents. It is proposed these parameters can identify potentially useful solvents or solvent-nonsolvent systems for the preparation of microcapsules using coacervation