DOI: 10.1021/la102780y 16791 Langmuir 2010, 26(22), 16791–16800 Published on Web 10/13/2010 pubs.acs.org/Langmuir © 2010 American Chemical Society Polystyrene-block-polyglycidol Micelles Cross-Linked with Titanium Tetraisopropoxide. Laser Light and Small-Angle X-ray Scattering Studies on Their Formation in Solution Melanie Siebert, †,§ Artur Henke, †,§ Thomas Eckert, ‡ Walter Richtering, ‡ Helmut Keul,* ,† and Martin M€ oller* ,† † DWI and Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Pauwelsstrasse 8, 52056 Aachen, Germany, and ‡ Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany. § Both authors contributed equally to this work Received July 12, 2010. Revised Manuscript Received September 24, 2010 Hybrid micelles from polystyrene-block-polyglycidol (PS-b-PG) copolymers with chemically cross-linked cores by titanium tetraisopropoxide (Ti(OC 3 H 7 ) 4 ) were prepared in toluene solution. Additionally, micellization of PS-b-PG copolymers with different mass fractions of polyglycidol (x PG ), was studied by static and dynamic light scattering as well as small-angle X-ray scattering. It was observed that copolymers with x PG smaller than 0.5 self-assembled in toluene into spherical core-shell micelles with hydrodynamic radii R h between 12 and 23 nm. On the other hand, copolymers with larger PG content formed particles with R h = 50-70 nm and aggregation numbers of several thousands. The presence of these aggregates in solution was attributed to the nonequilibrated form of block copolymers upon dissolving, most probably due to hydrogen bonding. In the following, spherical PS-b-PG micelles were loaded in toluene with hydrochloric acid and titanium tetraisopropoxide. Confined hydrolysis of Ti(OC 3 H 7 ) 4 induced by HCl in the micellar core was confirmed by small-angle X-ray scattering experiments. The subsequent condensation of the precursor with hydroxyl groups of polyglycidol chains led to covalently stabilized hybrid organic-inorganic particles. The presence of cross-linked PS-b-PG micelles was proven in two ways. First, micelles with “frozen” core showed stable hydrodynamic size in time upon dilution below critical micellization concentration while non-cross-linked PS-b-PG micelles underwent disintegration under the same conditions within several hours. Second, light scattering experiments revealed the presence of stable, swollen particles in N,N-dimethylformamide, which is a good solvent for both blocks. 1. Introduction Amphiphilic block copolymers are an intriguing class of soft matter. Their unique behavior in solution or in bulk results from the presence of unlike types of monomers within the same poly- mer chain. 1-6 As a consequence, copolymers can self-assemble in thermodynamically poor solvents for one of the blocks into spherical, rodlike, or vesicular particles. 1,2 In the melt, on the other hand, incompatibility between blocks induces arrangement of the copolymer chains into lamellar or cylindrical types of structures, among others. 5 The intensive studies on amphiphilic block copolymers within the last 40 years brought many potential applications of these systems, especially in the fields of nanotechnology and biomedi- cine. 7,8 For example, there is a growing demand for new and versatile strategies for fabrication of nanostructured materials with potential application in microelectronics, sensors, catalysis, or optical fields. 9-11 In this particular case block copolymers show promising properties for controlled preparation of metallic or semiconductor nanoparticles. 7,12,13 This follows from the fact that the growth of those nanoparticles can be limited in size to nanoscopic dimensions. 7 There are four main procedures used to fabricate nanostructured materials by means of self-assembly strategy. 14 Precursor and block copolymers can be co-self- assembled or associated through cooperative processes. Further- more, the metal precursor either can be chemically linked to the copolymer chains (inorganic-organic hybrid) or can be immobi- lized within already formed micelles. 7,14 The latter method offers a fast and reliable route for preparation and controlled ordering of the particles by using block copolymers based on polystyrene and poly(2-vinylpyridine), poly(ethylene oxide), or poly- (methacrylic acid). 14-16 When dissolved in nonpolar solvents, for example, toluene, these copolymers undergo inverse micellization with the hydrophilic block forming the core. In the following, the inner micellar compartment can be selectively loaded with metal salts/alkoxides and thus act as a nanoreactor for a reduction/ hydrolysis process of the precursor. 17 It was shown that the formed *Correspondence authors. H.K., keul@dwi.rwth-aachen.de; M.M., moeller@ dwi.rwth-aachen.de. 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