RESUMEN
Polymerization-induced self-assembly (PISA) was employed to compare the self-assembly of different amphiphilic block copolymers. They were obtained by emulsion polymerization of styrene in water using hydrophilic poly(N-acryloylmorpholine) (PNAM)-based macromolecular RAFT agents with different structures. An average of three poly (ethylene glycol acrylate) (PEGA) units were introduced either at the beginning, statistically, or at the end of a PNAM backbone, resulting in formation of nanometric vesicles and spheres from the two former macroRAFT architectures, and large vesicles from the latter. Compared to the spheres obtained with a pure PNAM macroRAFT agent, composite macroRAFT architectures promoted a dramatic morphological change. The change was induced by the presence of PEGA hydrophilic side-chains close to the hydrophobic polystyrene segment.
RESUMEN
Charging of nanoparticles through electrospray has scarcely been explored. Spherical nanometer-sized amphiphilic block copolymer nanoparticles with diameters ranging from â¼65 to â¼150 nm were electrosprayed and analysed by charge detection spectrometry. Herein, we explore the charging of these micellar nano-objects by conducting a thorough study in different solvents, including pure water, and upon the addition of "supercharging" agents. The charge (z) of micellar nanoparticles electrosprayed from water solution is compared to the Rayleigh's limiting charge (z(R)) of a charged water droplet of the same dimensions. An average ratio (z/z(R)) of 0.6-0.65 is observed for the micellar macro-ions, supporting the charge residue mechanism, where the number of charges available to the micellar macro-ion is limited by the number of charges on the nanodroplet, which is a function of the surface tension of the solvent. Also we show the possibility of increasing the charging of micellar nanoparticles in the negative mode by adding organic bases (in particular piperidine) to water/methanol solutions.
RESUMEN
The syntheses of amphiphilic block copolymers are successfully performed in water by chain extension of hydrophilic macromolecules with styrene at 80 °C. The employed strategy is a one-pot procedure in which poly(acrylic acid), poly(methacrylic acid) or poly(methacrylic acid-co-poly(ethylene oxide) methyl ether methacrylate) macroRAFTs are first formed in water using 4-cyano-4-thiothiopropylsulfanyl pentanoic acid (CTPPA) as a chain transfer agent. The resulting macroRAFTs are then directly used without further purification for the RAFT polymerization of styrene in water in the same reactor. This simple and straightforward strategy leads to a very good control of the resulting amphiphilic block copolymers.