Comonomer effect: Switching the lower critical solution temperature to upper critical solution temperature in thermo-pH sensitive binary graft copolymers |
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Authors: | Victor H Pino-Ramos Gerardo Cedillo Eduardo López-Barriguete Emilio Bucio |
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Affiliation: | 1. Depto. de Química de Radiaciones y Radioquímica, Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, CDMX, 04510 Mexico;2. Instituto de Investigación en Materiales, Universidad Nacional Autónoma de México, Avenida Universidad, Ciudad Universitaria, CDMX, 04510 Mexico |
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Abstract: | Hydrophilic biocompatible surfaces can be obtained by grafting stimuli-sensitive polymers onto commercially available medical devices. Thermo and pH-responsive polymers are two of the most studied materials due to their potential application as drug delivery systems. Poly(N-vinylcaprolactam) has a lower critical solution temperature (LCST) near to physiological temperature. However, when it is grafted with pH-sensitive moieties its LCST it is affected undergoing remarkable displacements. We studied the effect of acrylic acid (AAc), 4-vinylpyridine (4VP), and 1-vinylimidazole (Vim) on the LCST of N-vinylcaprolactam (NVCL) grafted onto silicone rubber (SR), and SR-g-NVCL (32.5 °C). The binary graft copolymers were obtained by ionizing grafting radiation using the simultaneous technique; the samples were characterized by Fourier transform infrared attenuated total reflectance (FTIR-ATR), cross-polarization magic angle spinning nuclear magnetic resonance (CP/MAS 13C-NMR), and thermogravimetrical analysis (TGA). LCST value was dramatically affected by the comonomer content; even it was observed the switching from LCST to upper critical solution temperature (UCST) for (SR-g-NVCL)-g-AAc and (SR-g-NVCL)-g-4VP samples. The observed behavior is rarely reported for binary graft copolymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48170. |
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Keywords: | graft copolymers gamma radiation LCST stimuli-responsive materials surface modification |
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