Amphiphilic triblock copolymer based on poly(p-dioxanone) and poly(ethylene glycol):: Synthesis, characterization, and aqueous dispersion

Amphiphilic triblock copolymers composed of poly(p-dioxanone) (PPDO) and poly(ethylene glycol) (PEG) were synthesized by ring opening polymerization of PDO initiated through dihydroxyl-terminated PEG in the presence of stannous 2-ethylhexanoate [Sn(oct)(2)] as a catalyst. Polymeric nanoparticles were prepared in an aqueous medium (triple distilled water and phosphate buffer pH 7.4) by cosolvent evaporation technique at room temperature (25 degrees C). Stability of nanoparticles was significantly enough in triple distilled water when compared with the phosphate buffer. Core-shell geometry of polymeric nanoparticles was characterized by H-1-NMR spectroscopy and further confirmed by spectrophotometric analysis using pyrene as a probe. Variation in physicochemical characteristics of polymeric nanoparticles with the fraction of PPDO was investigated through the analysis of microscopic, spectroscopic, and light scattering techniques. Critical micelle concentration of polymer in triple distilled water decreased from 2.3 x 10(-3) to 4.7 x 10(-3). Atomic force microscopic observation revealed that polymeric nanoparticles were spherical and uniform with smooth textured of around 50-68 nm diameter. Dynamic light scattering and electrophoretic light scattering measurements showed a mono-disperse size distribution of around 113-171 nm hydrodynamic diameters and negative zeta zeta-potential (-4.00 to -5.87 mV), respectively. The investigation showed a significant effect of polymeric composition on the physicochemical characteristic of polymeric nanoparticles. (c) 2006 Wiley Periodicals, Inc.