Ionic Liquid Functionalized Polylactide by Cationic Polymerization: Synthesis and Stabilization of Carbon Nanotube Suspensions

Medium molecular weight poly(L,L-lactide)s (PLA) containing at one chain end ionic group derived from imidazolium ionic liquid (IL) were synthesized by cationic polymerization using hydroxylated IL as initiator. matrix assisted laser desorption/ionization time-of-flight analysis confirmed the structure of products (PLA-IL). Carbon nanotubes (CNT) were dispersed in solution of PLA-IL in 1,4-dioxane and significant improvement of stability of suspension was observed by measurements of suspension absorbance. Similar effect was, however, observed also for solutions of PLA which did not contain terminal IL group. CNT samples treated with PLA-IL and PLA were isolated, thoroughly washed with 1,4-dioxane and stability of suspensions was again measured. Sample treated with PLA after washing behave similarly to untreated CNT. Stability of suspension of CNT treated with PLA-IL after washing was considerably higher than that of untreated CNT and the presence of polymer bound to CNT was clearly detectable in scanning electron microscopy images. Results indicate that there is indeed an interaction between end-group derived from IL and CNT surface as postulated earlier but to observe solely this effect an excess of polymer should be removed, otherwise factors such as increase of viscosity of solution or weak interactions of PLA ester groups with CNT may obscure results. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 5239-5244, 2011