ABSTRACT We have synthesized novel acrylamide‐based copolymer microgels exhibiting a volume phase transition temperature (VPTT) well‐above the one of poly‐ N ‐isopropylacrylamide (pNIPAM). The high VPTT is achieved by copolymerization of three different main monomers N , N ‐propylacrylamide (NNPAM), NIPAM, and N ‐isopropylmethacrylamide (NIPMAM), with the hydrophilic comonomer NIPMAMol ( N ‐(1‐hydroxy‐2‐propyl)methacrylamide). Nuclear magnetic resonance spectroscopy (NMR) shows a high incorporation of NIPMAMol into the microgels, approaching 100 %. The swelling behavior of the microgels in solution has been studied by photon correlation spectroscopy and turbidity measurements, evidencing the increase in VPTT with NIPMAMol content. We determined an ideal VPTT of pNIPMAMol homopolymer microgels to be 85°C by extrapolation, highlighting the strong impact of this comonomer on the swelling behavior of the microgels. Finally, the microgel shape in the dried state has been studied via scanning electron microscopy. For high NIPMAMol contents a second, large species is observed, exhibiting a core‐shell structure. This sheds light on the polymerization mechanism in the presence of high VPTT comonomers.
Runge et al. (Wed,) studied this question.