Comonomer effect: Switching the lower critical solution temperature to upper critical solution temperature in thermo‐pH sensitive binary graft copolymers

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.

Highly Crosslinked Agar/Acrylic Acid Hydrogels with Antimicrobial Properties

“…Hydrogels presented a similar electrolytic behavior, despite different applied radiation doses ( Figure 9 b); they showed the same critical pH value, 5.2, as they have the same amount of ionizable groups. However, this value differs from that commonly observed for PAAc of 4.6 [ 40 ]; this signifies that the inclusion of agar causes a slight displacement in pH of the pH-sensitive polymer. This property can be used to control the desorption of a drug or nanoparticle previously loaded on the hydrogel through swell-contraction kinetics [ 10 ].…”

The Effect of Absorbed Dose and Chemical Composition On the Ionic Conductivity of 1-Vinylimidazole-Grafted PVDF Membranes Made Via Y-Ray Induced Grafting

“…Additionally, PVI-containing imidazole groups was used as a model polyelectrolyte to investigate the adsorption characteristics of different minerals due to their complexation with catalytic divalent metallic ions such as Co2+ and Cu2+ [22]. Copolymerization of VIm was obtained via the comonomer effect Zor binary graft copolymers by ionizing grafting radiation using the simultaneous technique [23]. PVDF and VIm can graft via γ-ray induced grafting.…”

Multi-responsive γ-methylene-γ-butyrolactone/N-vinyl caprolactam copolymers involving pH-dependent reversible lactonization

“…29,[37][38][39] For example, copolymerizing NVCL with ionizable monomers imparted dual pH-and thermo-sensitivity to the final copolymers. [40][41][42][43][44][45][46] Typical ionizable comonomers which have been associated with NVCL in order to fabricate dual responsive microgels of interest for drug delivery applications are acrylic acid (AA), 42,46 methacrylic acid (MAA) 27,43,44 and itaconic acid (IA). 27,45 At physiological pH, the ionized carboxylate groups predominated, increasing the hydrophilicity of the copolymer and its LCST.…”