The phase behavior and optical- and selected mechanical properties of the binary system consisting of isotactic polypropylene (i-PP) and a new sorbitol-based nucleating and clarifying agent, 1,2,3-trideoxy4,6:5,7-bis-O-[(4-propylphenyl) methylene]-nonitol (TBPMN), were investigated. Temperature/composition diagrams of the binary were found to be of the simple monotectic type, similar to those of, among others, the previously investigated i-PP/1,3:2,4-bis(3,4-dimethyldibenzylidene)sorbitol (DMDBS). Liquid-liquid phase separation was observed in binaries comprising more than similar to 5% w/w TBPMN, indicative of enhanced miscibility of the new additive with i-PP when compared with that of DMDBS. At TBPMN contents >= 0.1% w/w the optical properties haze and clarity progressively improved to remarkable levels with increasing concentration of the nucleating agent up to the onset of liquid-liquid phase separation, above which they deteriorated. The enhanced solubility in i-PP of the new clarifying agent on the one hand required uneconomically higher concentrations than previous members of the sorbitol family to be effective, but on the other, the superior optical properties of the system may permit manufacturing of clarified products of increased thickness. (C) 2009 Elsevier Ltd. All rights reserved.