Metal-Free Polymethyl Methacrylate (PMMA) Nanoparticles by Enamine "Click" Chemistry at Room Temperature

"Click" chemistry has become an efficient avenue to unimolecular polymeric nanoparticles through the self-crosslinking of individual polymer chains containing appropriate functional groups. Herein we report the synthesis of ultra-small (7 nm in size) polymethyl methacrylate (PMMA) nanoparticles (NPs) by the "metal-free" cross-linking of PMMA-precursor chains prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization containing beta-ketoester functional groups. Intramolecular collapse was performed by the one-pot reaction of beta-ketoester moieties with alkyl diamines in tetrahydrofurane at r.t. (i.e., by enamine formation). The collapsing process was followed by size exclusion chromatography and by nuclear magnetic resonance spectroscopy. The size of the resulting PMMA-NPs was determined by dynamic light scattering. Enamine "click" chemistry increases the synthetic toolbox for the efficient synthesis of metal-free, ultra-small polymeric NPs.

Transformaciones en el retablo mayor de San Miguel Arcángel de Lazkao (Gipuzkoa): del Barroco al Neoclasicismo

[ES] El retablo mayor de la localidad guipuzcoana de Lazkao fue realizado por Juan de Ursularre en 1683, siguiendo los parámetros de la retablística barroca. Queriendo engrandecer su aspecto, fue paulatinamente transformado durante el siglo XVIII. Por ello se concibió un nuevo cascarón con pinturas enviadas desde Madrid y más tarde se adecuó a los nuevos gustos neoclásicos mediante una radical reforma realizada en 1791 que consistió en eliminar todo atisbo de decoración barroca.