ABSTRACT
Literature values show considerable scatter, with a preferred value of about 20 MPa1/2. Burrell 1 reported the determination from solubility/swelling studies of δ = 21.1 MPa1/2 for N22 ethyl cellulose. Soon after, Moore, Epstein, Brown, and Tidswell 2 determined χ values from osmotic pressures of solutions of ethyl cellulose (48.2% ethoxyl, M n = 58,000) and estimated Hildebrand parameters from observation of the initial phase separation (χ = 0.5) in systems of ethyl cellulose, solvent, and hexane, with the assumption that χS = 0–12 (Table 1). The mean values were 19.0 MPa1/2 in polar liquids and 20.5 MPa1/2 in nonpolar liquids. Kent and Rowe 3 determined the Hildebrand parameter solubility profile of N50 (49.9% ethoxyl content) and N7 (47.9% ethoxyl content) ethyl cellulose from Hercules Powder Co. (Wilmington, DE), observing maxima as follows:
about 20 MPa1/2 for poorly hydrogen-bonding liquids
about 21 MPa1/2 for moderately hydrogen-bonding liquids
no clear maximum for strongly hydrogen-bonding liquids
Polymer-Liquid Interaction Parameters from Osmotic Pressures and Hildebrand Parameter Values from Initial Phase Separation for Ethyl Cellulose at 25°C, as Reported by Moore et al.Liquid, i
j δ/MPa1/2
χ
j δ/MPa1/2
Acetone
20.0
0.46
19.4
Methyl ethyl ketone
18.7
0.42
19.1
Methyl n-propyl ketone
18.1
0.37
19.0
Methyl n-amyl ketone
17.3
0.38
18.8
Methyl acetate
19.5
0.41
19.3
Ethyl acetate
18.5
0.40
19.1
n-Propyl acetate
17.9
0.33
18.8
n-Butyl acetate
17.5
0.24
18.7
n-Amyl acetate
17.3
0.28
18.7
Trichloromethane
19.0
0.34
18.6
Tetrachloromethane
17.6
0.46
20.6
Benzene
18.7
0.48
20.6
Toluene
18.2
0.47
20.4
Polar liquids, mean
19.0
Nonpolar liquids, mean
20.5
