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Influence of TMAO as co‐solvent on the gelation of silica‐PNIPAm core‐shell nanogels at intermediate volume fractions
Author(s) -
Frenzel Lara,
Lokteva Irina,
Koof Michael,
Narayanan Suresh,
Grübel Gerhard,
Lehmkühler Felix
Publication year - 2020
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202000114
Subject(s) - nanogel , dynamic light scattering , colloid , aqueous solution , chemistry , solvent , micelle , hydrodynamic radius , trimethylamine n oxide , poly(n isopropylacrylamide) , hydrogen bond , chemical engineering , trimethylamine , oxide , polymer chemistry , nanoparticle , molecule , organic chemistry , polymer , copolymer , drug delivery , engineering
We study the structure and dynamics of poly(N‐isopropylacrylamide) (PNIPAm) core‐shell nanogels dispersed in aqueous trimethylamine N‐oxide (TMAO) solutions by means of small‐angle X‐ray scattering and X‐ray photon correlation spectroscopy (XPCS). Upon increasing the temperature above the lower critical solution temperature of PNIPAm at 33 °C, a colloidal gel is formed as identified by an increase of I ( q ) at small q as well as a slowing down of sample dynamics by various orders of magnitude. With increasing TMAO concentration the gelation transition shifts linearly to lower temperatures. Above a TMAO concentration of approximately 0.40 mol/L corresponding to a 1 : 1 ratio of TMAO and NIPAm groups, collapsed PNIPAm states are found for all temperatures without any gelation transition. This suggests that reduction of PNIPAm‐water hydrogen bonds due to the presence of TMAO results in a stabilisation of the collapsed PNIPAm state and suppresses gelation of the nanogel.