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Non‐Thermoresponsive Decanano‐sized Domains in Thermoresponsive Hydrogel Microspheres Revealed by Temperature‐Controlled High‐Speed Atomic Force Microscopy
Author(s) -
Nishizawa Yuichiro,
Matsui Shusuke,
Urayama Kenji,
Kureha Takuma,
Shibayama Mitsuhiro,
Uchihashi Takayuki,
Suzuki Daisuke
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201903483
Subject(s) - materials science , polymerization , atomic force microscopy , thermoresponsive polymers in chromatography , microsphere , chemical engineering , core (optical fiber) , precipitation , self healing hydrogels , polymer chemistry , nanotechnology , polymer , chemistry , composite material , phase (matter) , organic chemistry , physics , reversed phase chromatography , meteorology , engineering
Despite the tremendous efforts devoted to the structural analysis of hydrogel microspheres (microgels), many details of their structures remain unclear. Reported in this study is that thermoresponsive poly( N ‐isopropyl acrylamide) (pNIPAm)‐based microgels exhibit not only the widely accepted core–shell structures, but also inhomogeneous decanano‐sized non‐thermoresponsive spherical domains within their dense cores, which was revealed by temperature‐controlled high‐speed atomic force microscopy (TC‐HS‐AFM). Based on a series of experiments, it is concluded that the non‐thermoresponsive domains are characteristic for pNIPAm microgels synthesized by precipitation polymerization, and plausible structures for microgels prepared by other polymerization techniques are proposed.