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 G 1 -PEO-D G 1 -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 G 1 -PEO-D G 1 -CSO, and second, OSC-D G 2 -PEO-D G 2 -CSO, generations in aqueous medium were monitored by using fluorescence, TEM and DLS techniques. However, the dendritic block copolymer with third generation, OSC-D G 3 -PEO-D G 3 -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.

Side-by-side comparison of dendritic-linear hybrids and their hyperbranched analogs as micellar carriers of chemotherapeutics

“…Although the synthesis is facile, it requires the time consuming stepwise synthesis of the dendritic part. Many of the more advanced applications of DL hybrids, such as in drug delivery, have been hampered by the complex, and time‐consuming synthesis, limiting the scale, and availability of these very promising materials …”

PEG-dendritic block copolymers for biomedical applications

“…20 The tendency of amphiphilic PEGdendritic block copolymers to selfaggregate in aqueous media was already revealed in the early reports by the groups of Fre´chet 4 and Chapman. 22 Similar studies on the aggregation of AB and ABA block copolymers with carbosilane, 10 triazine, and carbosiloxane dendrons 14 have also been performed. 21 Shortly after, again the group of Fre´chet prepared related starshaped (A 4 B 4 ) copolymers and studied their aggregation behaviour as a function of solvent.…”

“…This was the strategy followed by Fre´chet and coworkers in their pioneering preparation of PEG-dendritic block copolymers of the types AB and ABA with poly(benzyl ether) dendrons of generations 3 and 4 (G3 and G4). 14 (c) Dendron-first: in this approach, copolymers are obtained by polymerization of the linear block using a dendritic macroinitiator. This strategy was first described by Chapman and coworkers in 1994 for the preparation of amphiphilic AB type copolymers incorporating N-Boc protected poly-Llysine (PLL) dendrons (up to G4).…”

Invitro Photo-Controlled Drug Release System Based on Amphiphilic Linear-Dendritic Diblock Copolymers; Self-Assembly Behavior and Application as Nanocarrier

“…The same synthetic method was applied to afford the polymer containing two allyloxy (PEOM-All, 2) groups by using methydichlorosilane as branching agent. A modified literature procedure was employed (25). The operations were carried out in an inert argon atmosphere.…”

“…The solutions were prepared by a reported literature procedure (25). Briefly, the PEOM-Azo, 2 and PEOM-Azo, 6 systems were dissolved in a few drops of THF.…”