In this work, we have obtained experimental cloud points, i.e., liquid-liquid equilibrium boundaries at constant composition, for the systems 'polybutadiene (PB) + n-pentane (C5)', 'PB + dimethyl ether (DME) + C5', 'polyethylene (PE) + DME + C5'. and 'PB + PE + DME + C5'. The temperature range of the experiments was from 50 to 184 degrees C. The maximum pressure was 303 bar. In all cases the overall polymer concentration was less than or equal to 4.1 wt%. At the ranges of conditions of the experiments we have found the following: (a) For PB + C5, the minimum pressure required to guarantee homogeneity is 140 bar. (b) For 'PB + C5 + DME', the cloud point pressure (CPP) curves lie in between the CPP curves of 'PB + DME' and 'PB + C5', and the maximum CPP was 226 bar. The CPP increases with the increase of the DME/C5 ratio in the solvent mixture. (c) For 'PE + DME + C5', there is a substantial decrease in the CPPs with the addition of C5 to the DME + C5 solvent mixture, and the maximum CPP was 303 bar. (d) The CPPs for 'PB + PE + DME + C5' are higher than the CPPs of 'PB + DME + C5' but lower than the CPPs of 'PE + DME + C5'. (C) 2012 Elsevier B.V. All rights reserved.