Precise Tuning of Micelle, Core, and Shell Size by the Composition of Amphiphilic Block Copolymers Derived from ROMP Investigated by DLS and SAXS

• Published in: Macromolecules Vol. 39; no. 17; pp. 5865 - 5874
• Main Authors: Stubenrauch, Kurt, Moitzi, Christian, Fritz, Gerhard, Glatter, Otto, Trimmel, Gregor, Stelzer, Franz
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 22.08.2006
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Solution and gel properties; Hydrodynamic radius; Norbornene derivative copolymer; Light scattering; Composition effect; Small angle X ray scattering; Experimental study; Dimension spectrum; Complex catalyst copolymerization; Functional polymer; Hydrolysis; Polyelectrolyte; Monodispersed polymer; Chemical modification; Dynamical scattering; Metathesis polymerization; Preparation; Diblock copolymer; Unsaturated copolymer; Acid copolymer; Alcoholic solution; Micellar solution; Ring opening copolymerization; Amphiphilic polymer; Ruthenium complex
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma060451p

Self-assembly of well-defined block copolymers in solution has gained attention not only for its scientific value but also for its potential application in nanotechnology. In this study, we present a comprehensive series of synthesized block copolymers that allows conclusions to be drawn how to design micelles by ROMP with defined core−shell geometry and controlled size. We used a general route for the preparation of well-defined block copolymers by ring opening metathesis polymerization (ROMP) with “Grubbs first generation catalyst” RuCl2(PCy3)2(CHPh) (Cy = cyclohexyl). In a first step, we sequentially polymerized endo,exo[2.2.1]bicyclo-2-ene-5,6-dicarboxylic acid dimethylester with endo,exo[2.2.1]bicyclo-2-ene-5,6-dicarboxylic acid di-tert-butyl ester, to obtain a high control of polymerization and complete characterization of the block copolymers. The polymers were characterized by 1H- and 13C NMR spectroscopy, FT-IR spectroscopy, by GPC, and by DSC. By cleavage of the tert-butyl group, the polymer was transformed into an amphiphilic block copolymer. In two series of polymers, we investigated the micelle formation in ethanol by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS). In the first series, the influence of the block ratio on the size of the micelle, the aggregation number, and the core−shell dimensions were investigated while the overall polymer length was kept constant. In the second series, the block ratio was fixed to 1:1 and the overall polymer length was varied, leading to direct proportionality of the micelle size to the polymer length, while the core-to-shell ratio was constant.