Browsing by Author "Müller, Alejandro J."

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    Efecto de la incorporación de nanopartículas de lignina iónica en la cristalización de polióxido de etileno
    (2020-04) Taverna, María E.; Olmedo, Jorge; Busatto, Carlos Alberto; Zubitur, Manoli; Nicolau, Verónica V.; Estenoz, Diana; Müller, Alejandro J.
    El polióxido de etileno (POE) es un poliéter semicristalino cuya cinética de cristalización ha sido ampliamente estudiada tanto en el componente puro como en sus mezclas con otros polímeros amorfos y semicristalinos. Se han investigado materiales compuestos basados en mezclas de POE y lignina (polímero natural, amorfo, abundante y de bajo costo). La mezcla eficiente de estos polímeros depende en gran medida de la compleja estructura de la lignina. Se ha reportado la cinética de cristalización de la mezcla de POE y lignina proveniente de procesos de aislamiento Alcell y/o Kraft.2 En este trabajo se estudia la síntesis de nanopartículas de lignina de origen iónico y su empleo en la obtención de mezclas con POE. Específicamente, se evalúa la influencia de nanopartículas en la cinética de cristalización del POE.
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    Supernucleation dominates lignin/poly(ethylene oxide) rystallization kinetics
    (2022-08) Taverna, María E.; Altorbaq, Abdullah S.; Kumar, Sanat K.; Olmedo-Martínez, Jorge L.; Busatto, Carlos Alberto; Zubitur, Manuela; Mugica, Agurtzane; Nicolau, Verónica V.; Estenoz, Diana; Müller, Alejandro J.
    The effect of lignin nanoparticles (LNPs) on the crystallization kinetics of poly(ethylene oxide) (PEO) is examined. Lignin from spruce and ionic isolation was used to prepare LNPs with a number-averaged diameter of 85 nm (with a relatively large polydispersity) by an ultrasonication method. PEO-based nanocomposites with four different LNP contents (5, 10, 15, and 20 wt %) were prepared and subject to isothermal and nonisothermal crystallization protocols in a series of experiments. Scanning electron microscopy (SEM) images showed welldispersed LNPs in the crystallized PEO matrix. The incorporation of LNPs exponentially increases nucleation density at moderate loadings, with this trend apparently saturating at higher loadings. However, the spherulitic growth rate decreases monotonically with LNP loading. This is attributed to the substantial PEO/LNP affinity, which impacts chain diffusion and induces supernucleation effect (with efficiencies in the order of 200%), but leads to slower growth rates. The overall crystallization kinetics, measured by the DSC, shows faster nanocomposite crystallization rates relative to the neat PEO at all LNP contents examined. This indicates that the supernucleation effect of LNPs dominates over the decrease in the growth rates, although its influence slightly decreases as the LNP content increases. The strong hydrogen-bonded interactions between the LNPs and the PEO are thus reminiscent of confinement effects found in polymer-grafted NP nanocomposites (e.g., PEO-g-SiO2/ PEO) in the brush-controlled regime.