Hybrid Organic/Inorganic Dendritic Triblock Copolymers: Synthesis, Nanostructure Characterization, and Micellar Behavior

Abstract

A new class of amphiphilic dendritic ABA triblock copolymers, which is based on organic linear polyethylene oxide (PEO) and inorganic dendritic carbosiloxane (CSO) was synthesized. The strategy used in synthesizing these materials is based on divergent method using hydrosilylation-alcoholysis cycles. The reaction conditions and structural features of dendrimers were analyzed by different physicochemical techniques such as: GPC, NMR, UV spectroscopy, DSC, and viscometry. The generational limit of dendrimer after the first generation, OSC-D(G1)-PEO-D(G1)-CSO, forced us to employ HSiCl(2)CH(3) as branching reagent. Also further hydrosilylation of the third generation yielded an irregular structure species. Self-assembling and morphological studies of first, OSC-D(G1)-PEO-D(G1)-CSO, and second, OSC-D(G2)-PEO-D(G2)-CSO, generations in aqueous medium were monitored by using fluorescence, TEM and DLS techniques. However, the dendritic block copolymer with third generation, OSC-D(G3)-PEO-D(G3)-CSO, could not be dispersed in aqueous phase. The diameters of denderitic micelles had a narrow distribution in the ranges of 69 and 88 nm, respectively. Although the micelles were stable even in first generation, partition equilibrium constants of pyrene and critical micelle concentration in both of dendritic micelles imply that the micellar behaviors of the supramolecules strongly depend on the hydrophobic block's size in which increasing generation effectively promoted the micelle formation. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 1085-1094, 2010