title: A confocal microscopy study of micron-sized poly(N-isopropylacrylamide) microgel particles at the oil-water interface and anisotopic flattening of highly swollen microgel.
abstract: OBJECTIVE
  Responsive poly(N-isopropylacrylamide) microgel (PNIPAM microgel) stabilized Pickering emulsions were investigated in this study. A recent theoretical study of other researchers has suggested that large soft particles at the oil/water interface are less deformable than their small counterparts. Therefore, we expected that our micron-sized microgel particles might not significantly deform at the oil/water interface.
  
  
  METHODS
  We applied confocal laser scanning microscopy (CLSM) to examine the structure of soft PNIPAM-based microgel particles at the decane-water interface in a microgel-stabilized emulsion. Using micron-sized microgel particles with better labelling techniques, we could compensate the weakness in resolution of using CLSM. Seven PNIPAM-based microgel samples with various softness values and morphologies were examined at different pH values.
  
  
  RESULTS
  Our results demonstrate that the deformation of ordinary micron-sized microgel samples was not significant if they were not in the pH-swollen state. Nevertheless, the soft, pH-swollen microgel particles exhibited anisotropic deformation at the decane-water interface. Such flattening was not reported in previous studies. The studies of microgel particles at the oil-water interface with different imaging techniques and their comparison are valuable to help to elucidate the particles' roles in stabilizing the Pickering emulsions.
authors.affiliation: Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong.
authors.forename: Man-Hin
authors.initials: MH
authors.lastname: Kwok
authors.affiliation: Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong; Shenzhen Municipal Key Laboratory of Chemical Synthesis of Medicinal Organic Molecules, Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen 518057, China. Electronic address: tongai@cuhk.edu.hk.
authors.forename: To
authors.initials: T
authors.lastname: Ngai
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D016880:Anisotropy; D004655:Emulsions / Q000737:chemistry; D005782:Gels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D018613:Microscopy, Confocal; D009821:Oils / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; D004655:Emulsions; D005782:Gels; D009821:Oils; D014867:Water; C052970:poly-N-isopropylacrylamide
keywords: Confocal laser scanning microscopy; Micron-sized microgel; PNIPAM