New hydrogels were synthesized based on free radical polymerization of N-isopropylacrylamide (NiPAAm) and macromonomers of 2-oxazolines in presence of clay Laponite XLS (synthetic hectorite). The used macromonomers were statistical copolymers of 2-(2-methoxycarbonylethyl)- and 2-methyl-2-oxazoline, with a polymerization degree of 20 and 24 units and a content of 23 and 49 mol-% of 2-(2-methoxycarbonylethyl)-2-oxazoline, respectively, and had a vinyl group at the chain end. The hydrogel synthesis was carried out using ammonium persulfate (APS) and N,N,N,N-tetramethylethylendiamine (TEMED) as initiating system and Laponite XLS as crosslinker. After polymerization, the esters groups of the obtained hydrogels were hydrolized in situ to obtain carboxylic acids groups. Finally, hydrogels were obtained with high mechanical stability, transparency, and responsivity to temperature and pH. The hyd...

New graft copolymers were synthesized from the free radical polymerization of N-isopropylacrylamide (NIPAAm) and 2-methyl-2-oxazoline (MM) macromonomers initiated by 2,2'-azobisisobutyronitrile in dimethylformamide. The macromonomers, with polymerization degrees 31 and 62, were synthesized by ring-opening cationic polymerization of 2-methyl-2-oxazoline initiated by chloromethylstyrene in the presence of sodium iodide. The grafted macromonomers and copolymers were characterized by proton nuclear magnetic resonance spectrometry (1H-RMN) and the conformational transition temperature was determined by turbidimetric measurements and 1H-RMN spectroscopy. The NIPAAm / MM molar ratio in the copolymer, determined by 1H-RMN, was higher than in the feed to the reactor due to the higher reactivity of the NIPAAm due to its greater diffusivity in the reacting medium due to its lower molecular weight. ...

En años recientes, una de las áreas de los polímeros más ampliamente investigadas, por las importantes aplicaciones tecnológicas a que pueden dar lugar, es la síntesis de macromoléculas conmutables o sensibles a cambios en el medio ambiente tales como; por ejemplo, temperatura, pH, luz, y campo eléctrico o magnético. Este tipo de polímeros, conmutables o sensibles, tienen alto potencial para aplicaciones en biomateriales, en microsistemas, sensores y catálisis, entre otros. Entre los polímeros conmutables que más se han investigado se encuentran los polímeros termosensibles Se pueden obtener polímeros con respuesta térmica usando los homopolímeros y copolímeros de N-isopropilacrilamida, N-vinilcaprolactama, y vinilmetiléter. Sin embargo, en años recientes, se descubrió que también algunos polímeros de 2-oxazolinas tienen la propiedad de tener sensibilidad térmica,...

In this research was studied the feasibility of making gold nanoparticles within thermosensitive hydrogels which were made from N-isopropylacrylamide and macromonomers of 2-oxazolines. The hydrogels contained carboxylic acid groups, which were transformed into thiol groups which were later complexed with auric ions. The auric ions were reduced and gold nanoparticles (NP-Au) were obtained. In hydrogels, with and without NP-Au, was determined that the water-absorbing capacity of the hydrogel increases with the increase of macromonomer content in its structure. Likewise, both hydrogels showed sensitivity to temperature, contracting its volume as it increased. As the macromonomer content in the hydrogel increases this contraction is obtained at higher temperatures and at higher intensity. The UV/Visible spectroscopy characterization of the Hydrogels with NP-Au showed a absorption at 520 nm, ...