Bulk and solution properties of model PS-b-PDMS copolymers

MARIO D. NINAGO; ANGEL J. SATTI; DANIEL A. VEGA; ENRIQUE M. VALLÉS; MARCELO A. VILLAR; ANDRÉS E. CIOLINO

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Encuentro; Annual Meeting of the Belgian Polymer Group (BPG 2011); 2011

Model linear poly(styrene-b-dimethylsiloxane) PS-b-PDMS copolymers were synthesized by using sequential addition of monomers and anionic polymerization (high-vacuum techniques). The model diblock copolymers obtained were characterized by analytical techniques, such as size exclusion chromatography (SEC), 1H nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FTIR). The PS-b-PDMS copolymers obtained showed narrow molar mass distribution and variable PDMS content, ranging from 2 up to 55 wt. Compacted powder samples were investigated by small angle X-ray scattering (SAXS) to reveal their structure and morphology changes on thermal treatment in the range of 30 to 200 °C. The sample with the highest PDMS content exhibits, in bulk, a lamellar morphology, whereas two other samples show hexagonally packed cylinders of PDMS in a PS matrix. For the lowest PDMS content samples, the SAXS pattern corresponds to a disordered morphology and did not show any changes on thermal treatment. Detailed information about the morphology of scattering domains was obtained by fitting the SAXS scattering curves1. The internal structure of polystyrene(PS)-shell micelles having a core-forming block of polydimethylsiloxane (PDMS) was determined in detail by accessing the multilevel structural organization using static and dynamic light scattering and small-angle X-ray scattering techniques. Model PS-b-PDMS diblock copolymers were dispersed in cyclohexane, dimethylacetamide, or dimethylformamide. Colloidal nanoparticles exhibiting either swollen core with a large surface area per corona chain that enables the PS chains to assume a random coil conformation with Gaussian statistics, or compact core and slightly stretched PS chains in the corona were obtained. These results provide an interesting alternative allowing for precise control of the core and corona properties of PS-b-PDMS in selective solvents