Approach to the preparation of temperature‐sensitive poly(N‐isopropylacrylamide)/polyethylenimine microgel

Abstract

A novel route was developed to the preparation of temperature-sensitive poly(N-isopropylacrylamide)/polyethylenimine (PNIPAM/PEI) microgels by the radical copolymerisation of N-isopropylacrylamide with acryloylated PEI in aqueous media. Here, the acryloylated polyethylenimine (PEI), used as a macromonomer, was synthesised by a dehydration condensation reaction between PEI and acrylic acid. The as-prepared microgels exhibited well-defined core/shell structure with PNIPAM-rich core surrounded by PEI-rich shell. The microgels showed the volume phase transition temperature near physiological temperature, which can be easily regulated by the pH of microgel dispersion.

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“…The structure of dry microgels was studied by using FE-SEM (Figure S1D Further, PNIPAM grafting from PEI was confirmed by Fourier transform infrared (FTIR) spectroscopy, as shown in Figure 1B. Compared to pure PNIPAM, the spectra of PNIPAM-PEI showed broader peaks at 1645 cm −1 for amide I and 1541 cm −1 for amide II bands present in PNIPAM, 38 with an additional broad peak at 3300 cm −1 that corresponds to the N−H stretching of primary amine groups in PEI. 39 The temperature-based swelling behavior of PNIPAM-PEI microgels was investigated by dynamic light scattering (DLS).…”