High-pressure viscosity and density of poly (epsilon-caprolactone) (PCL) (Mw = 14,300; Mw/Mn = 2.34) solutions in acetone and in acetone + CO2 mixtures have been determined over a temperature range from 323 to 398 K and a pressure range from 7 to 35 MPa. The effect of adding CO2 on viscosity was investigated for the 5 wt% solutions at CO2 concentrations of 1, 2, 4 and 40 wt%. The effect of phase separation on viscosity was studied for the 5 wt% polymer solution in the binary fluid mixture with high (40 wt%) carbon dioxide content. The solution viscosities ranged from 0.2 to 0.6 mPa.s with flow activation energies in the range 7-9 kJ mol(-1) and flow activation volumes in the range from 12 to 29 cm(3) mol(-1). Close-packed volumes estimated from correlation of the data to Doolittle equation were in the range 0.5-0.6 cm(3)/g. In ternary solutions containing carbon dioxide, solution densities were higher, reflecting the higher density of compressed CO2 compared to that of acetone, but viscosities were lowered. A viscosity reduction of about 50% was observed with 40 wt% CO2 addition. The density and viscosity data for the PCL solutions have been compared with data for solutions of poly (methyl methacrylate) (PMMA) with similar molecular weight in acetone + CO2. The results show that the acetone + CO2 binary mixtures are "better" solvents for PCL than PMMA. (c) 2006 Elsevier B.V. All rights reserved.