Synthesis and characterization of pH‐sensitive crosslinked (NIPA‐co‐AAC) nanohydrogels copolymer

Abstract

A thermoresponsive polymeric nanohydrogels has been synthesized by inverse microemulsion polymerization of N-isopropylacrylamide (NIPA) and acrylic acid (AAc) using Aerosol (AOT) as a surfactant, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, and 2,2 0 -azobisisobutyronitrile (AIBN) as initiator. The effect of concentration of AIBN, EGDMA, and NIPA/AAc weight ratio was investigated. The lower critical solution temperature (LCST) of poly (NIPA-co-AAC) can be manipulated to be 40 C and 45 C which was correlated to amount of AAc that was copolymerized with NIPA. FTIR, 1H NMR, TEM, and DSC characterized the nanohydrogels.

Temperature- and pH-Sensitive Nanohydrogels of Poly(N-Isopropylacrylamide) for Food Packaging Applications: Modelling the Swelling-Collapse Behaviour

“…For instance, the addition of ionic hydrophilic comonomers, such as acrylic, methacrylic or itaconic acid, to the PNIPA polymer leads to an increase in the overall polymer hydrophilicity, strengthening polymer–water interactions and increasing the LCST [10] , [12] – [14] . In addition the introduction of ionizable groups (–COO − ) in the polymeric matrix results in pH-sensitive hydrogels that swell at pH values above the pK a of the hydrophilic comonomers, and collapse below the pK a [14] , [15] . Additionally PNIPA is non-toxic [16] and its temperature-controlled on/off release mechanism has been has been widely investigated in biomedicine, and many other fields, for application in drug delivery systems [17] – [19] , enzyme immobilization [20] , [21] or gene carrier systems [22] , [23] .…”

In situ synthesis of magnetic poly(N-tert-butyl acrylamide-co-acrylic acid)/Fe3O4 nanogels for magnetic resonance imaging

“…26,27 The characteristic bands at 1627-1636 cm À1 and 984-994 cm À1 assigned to C]C of AA and TBA, which could not be found in the spectra of the P(TBA-co-AA) and P(TBA-co-AA)/Fe 3 O 4 nanogels, indicating that the AA and TBA monomers totally formed the P(TBA-co-AA) and P(TBA-co-AA)/Fe 3 O 4 nanogels in the process of polymerization. 28,29 Two characteristic bands for Fe-O stretching observed at 587-593 cm À1 and 464-467 cm À1 were found in the Fe 3 O 4 spectra. Moreover, the two characteristic bands of Fe 3 O 4 were found in the P(TBA-co-AA)/Fe 3 O 4 nanogels spectra but didn't appear in the P(TBA-co-AA) nanogels spectra which conrmed presence of Fe 3 O 4 in the magnetic P(TBA-co-AA)/Fe 3 O 4 nanogels.…”

Responsive Systems in Food Packaging

“…Without the presence of AA, no effect of pH can be observed. Degree of Collapse was higher at low pH for obvious reason [17]. PNIPAM alone can be used as thermoresponsive material whereas PNIPA/AA responds to both temperature and pH.…”