Phase Separation of Mixtures of Colloidal Boehmite Rods and Flexible Polymer

✍ Scribed by Johan Buitenhuis; Liesbeth N. Donselaar; Paul A. Buining; Alain Stroobants; Henk N.W. Lekkerkerker

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 714 KB
• Volume: 175
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1995.1427

✦ Synopsis

Phase separation experiments have been performed on mixtures of colloidal polyisobutene grafted boehmite rods and flexible polymers. Two systems of rods have been studied, one with an average length and diameter of (71 \mathrm{~nm}) and (11.1 \mathrm{~nm}), and the other with an average length and diameter of (253 \mathrm{~nm}) and (\mathbf{9 . 4}) (\mathrm{nm}). The polymers used have molecular weights varying from 35 to (186 \mathrm{~kg} \mathrm{~mol}^{-1}), leading to radii of gyration of 5.9 to (20 \mathrm{~nm}). Bi- and triphasic equilibria involving a dilute isotropic phase, a concentrated isotropic phase, and a nematic phase are observed. The phase belavior is compared to a recent theory, which is an extension of the treatment for sphere/polymer mixtures (H. N. W. Lekkerkerker et al., Europhys. Lett. 20, 559 (1992)). The main features of the phase behavior can be understood on the basis of this simple theory. There remain significant discrepancies between theory and experiment which are attributed to the limitations of the theory on the one hand and to the polydispersity of the colloidal rods and the formation of metastable and nonequilibrium states such as colloidal gels and glasses on the other hand. 1995 Academic Press, Inc.

Key Words: boehmite; polymer; phase separation; colloidal rods; nematic phase.