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Universidad Nacional de Colombia (National University of Colombia)
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Papers by daniela yañez
Applied Catalysis A: General, 2015
Polyethylene (PE) and polyethylene-octadecene (LLDPE) composites containing titanium dioxide nano... more Polyethylene (PE) and polyethylene-octadecene (LLDPE) composites containing titanium dioxide nanotubes were synthesized and applied to the inhibition of selected bacteria. It was found that polymerization rate of the polymerizations increased with the incorporation of the octadecene compared with bare ethylene, while with modified nanotubes (O-TiO 2-Ntbs) the catalytic activity showed a slight decrease compared with the pure polymer. Regarding physical properties, the melting temperature and cristallinity of PE was higher than LLDPE. LLDPE presented lower rigidity than PE and thus lower Young's modulus. On the other hand, with the incorporation of nanotubes, Young's modulus did not change significantly with respect to PE. After 2 h of contact, the PE/O-TiO 2-Ntbs composite showed a reduction of Escherichia coli of 36.7% under no UVA irradiations. In contrast, LLDPE/O-TiO 2-Ntbs showed 63.5%. The photocatalytic reduction (under UVA light) was much higher and after 60 min the LLDPE/O-TiO 2-Ntbs composites showed a bacterial reduction of 99.9%, whereas the PE/O-TiO 2-Ntbs showed 42.6% of catalytic reduction.
Journal of the Chilean Chemical Society, 2013
The copolymerization of styrene with cyclohexene, 1-methyl-1-cyclohexene and with norbornene at v... more The copolymerization of styrene with cyclohexene, 1-methyl-1-cyclohexene and with norbornene at various styrene/comonomer molar ratio, using cyclopentadienyltitanium trichloride and methylaluminoxane, CpTiCl 3-MAO, initiating system has been tested. Only the couple styrene-norbornene produce real styrenenorbornene copolymers, while comonomers cylohexene and 1-methyl-1-cyclohexene only yielded syndiotactic polystyrene, s-PS. The present paper also report results of exploratory experiments on the synthesis through in-situ polymerization of nanocomposites based on styrene/para-methylstyrene copolymer, S/p-MeS, including SiO 2 nanoparticles where nanocomposites with modified SiO 2 nanoparticles, showed a better dispersion of nanoparticles in the copolymer matrix.
Applied Catalysis A: General, 2015
Polyethylene (PE) and polyethylene-octadecene (LLDPE) composites containing titanium dioxide nano... more Polyethylene (PE) and polyethylene-octadecene (LLDPE) composites containing titanium dioxide nanotubes were synthesized and applied to the inhibition of selected bacteria. It was found that polymerization rate of the polymerizations increased with the incorporation of the octadecene compared with bare ethylene, while with modified nanotubes (O-TiO 2-Ntbs) the catalytic activity showed a slight decrease compared with the pure polymer. Regarding physical properties, the melting temperature and cristallinity of PE was higher than LLDPE. LLDPE presented lower rigidity than PE and thus lower Young's modulus. On the other hand, with the incorporation of nanotubes, Young's modulus did not change significantly with respect to PE. After 2 h of contact, the PE/O-TiO 2-Ntbs composite showed a reduction of Escherichia coli of 36.7% under no UVA irradiations. In contrast, LLDPE/O-TiO 2-Ntbs showed 63.5%. The photocatalytic reduction (under UVA light) was much higher and after 60 min the LLDPE/O-TiO 2-Ntbs composites showed a bacterial reduction of 99.9%, whereas the PE/O-TiO 2-Ntbs showed 42.6% of catalytic reduction.
Journal of the Chilean Chemical Society, 2013
The copolymerization of styrene with cyclohexene, 1-methyl-1-cyclohexene and with norbornene at v... more The copolymerization of styrene with cyclohexene, 1-methyl-1-cyclohexene and with norbornene at various styrene/comonomer molar ratio, using cyclopentadienyltitanium trichloride and methylaluminoxane, CpTiCl 3-MAO, initiating system has been tested. Only the couple styrene-norbornene produce real styrenenorbornene copolymers, while comonomers cylohexene and 1-methyl-1-cyclohexene only yielded syndiotactic polystyrene, s-PS. The present paper also report results of exploratory experiments on the synthesis through in-situ polymerization of nanocomposites based on styrene/para-methylstyrene copolymer, S/p-MeS, including SiO 2 nanoparticles where nanocomposites with modified SiO 2 nanoparticles, showed a better dispersion of nanoparticles in the copolymer matrix.