RESUMO
In this article, a new system employing an ultrasonic microreactor coupled with a tubular reactor is presented for the continuous generation of polymer nanoparticles. The continuous generation of cross-linked polymer nanoparticles utilizing the monomer butyl methacrylate and the cross-linker ethylene glycol dimethacrylate is demonstrated. Firstly, the miniemulsion polymerization of a monomer-in-water miniemulsion is studied in a batch system. Secondly, a coiled tubular reactor is employed for the continuous polymerization of the miniemulsion generated by an ultrasonic microreactor. Finally, the influence of monomer volume fraction and surfactant concentration on the synthesized polymer nanoparticles is studied. Polymer particles in a size range of 50-250 nm are synthesized and a high polymerization conversion is achieved utilizing the system demonstrated in this article.
RESUMO
The properties of poly(p-phenylene vinylene) (PPV) films depend on the degree of orientational order present in the films. Recently, Dermaut et al. reported a novel cold-stretching technique (Macromolecules 33, 5634-5637 (2000)) in which chain alignment can be introduced into PPV precursor films by uniaxially stretching them prior to the thermal elimination reaction that forms PPV. The two-dimensional direction exchange with correlation for orientation-distribution evaluation and reconstruction (DECODER) 13C NMR technique was applied to both unstretched PPV films and PPV films that were uniaxially cold stretched to a draw ratio lambda = l/l0 = 5. The unstretched films were found to be moderately ordered, comprised of a component present at 80% with a Gaussian distribution of 60 degrees fwhm, while the remaining 20% is isotropically distributed. A distribution of 9 degrees +/- 3 degrees fwhm was measured by NMR in good agreement with IR dichroism measurements for the uniaxially cold-stretched films, establishing that a high degree of orientational order can be introduced by cold stretching PPV films.