Multilayer Polymeric Nanoparticles Based on Specific Interactions in Solution: Polystyrene-block-poly(methacrylic acid) Micelles with Linear Poly(2-vinylpyridine) in Aqueous Buffers

Abstract

Polymeric micelles of polystyrene-block-poly(methacrylic acid) with the shell containing various amounts of poly(2-vinylpyridine) chains were prepared by dialysis from 1,4-dioxane-rich mixtures into alkaline aqueous solutions. The structure of the polymeric nanoparticles was studied by light scattering, atomic force microscopy, fluorometry, and capillary zone electrophoresis. The presence of both weak polyacid and weak polybase in the corona allows the micelles to form fairly stable solutions in a broad pH range. Poly(methacrylic acid) blocks are dissociated in basic buffers, while poly(2-vinylpyridine) chains stabilize the micelles in acidic solutions. Besides the water-swollen shell, the inner parts of the micelles consist of the kinetically frozen polystyrene core and relatively rigid layer of poly(methacrylic acid) and poly(2-vinylpyridine) segments. An insufficient number of stabilizing polymer chain segments results in the aggregation of the micelles into clusters.

Keywords:

• Atomic force microscopy
• Capillary zone electrophoresis
• Copolymer micelles
• Fluorescence spectroscopy
• Interpolymeric complexes
• Light scattering
• Polymeric nanoparticles
• Pyrene
• Self-assembly

ACKNOWLEDGMENTS

P. M. would like to acknowledge the financial support of the Grant Agency of the Czech Republic (grant No. 203/06/P138), and Mil. Š. the support of the Grant Agency of the Academy of Sciences of the Czech Republic (grant No. A400500505). P. M., M. U., Mir. Š., and K. P. thank the Marie Curie Research and Training Network (No. 505 027, POLYAMPHI) and long term research plan of the Ministry of Education of the Czech Republic (No. MSM 0021620857). Software provided by www.nanotec.es was used for the imaging of AFM scans.