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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 15: Poster Session I
CPP 15.52: Poster
Montag, 17. März 2025, 19:00–21:00, P4
Volume phase transition of NIPAM based copolymer microgels with non-thermoresponsive comonomers — •Jannis Krüger and Thomas Hellweg — Physical and Biophysical Chemistry, Bielefeld University
We conducted photon correlation spectroscopy (PCS) to obtain swelling curves of N-isopropylacrylamide
(NIPAM)-based copolymer-microgels with varying content of non-thermoresponsive N-tert-butylacrylamide
(NtBAM).
Increasing NtBAM content reduces the hydrodynamic radius
and broadens the volume phase transition (VPT).
We analyzed the thermoresponsive contribution
to the swelling curves with a cooperative
Hill-like model for the Flory-Huggins interaction parameter χHill(T) [1].
This model effectively describes the microgel swelling at various compositions.
The Hill parameter ν estimates the
number of water molecules leaving a polymer segment at
the phase transition.
A linear decrease of ν with BIS content
suggests that water stays adsorbed on BIS during the VPT due to the lack of an LCST [2].
We fitted PNIPAM-co-NtBAM microgel swelling curves [3] with a
hybrid model of χHill for NIPAM
and the original Flory-Huggins parameter χFH for NtBAM,
revealing an exponential decrease in ν
with xNtBAM, indicating that NtBAM inhibits water adsorption of neighboring NIPAM units.
Based on these results we propose a steric
mechanism, which qualitatively describes the observed inhibition of microgel hydration.
[1] D. C. Leite et al., Langmuir 34 (2018), 10943.
[2] S. Friesen et al., Gels 7 (2021), 42.
[3] J. Krüger et al., Colloid Polym. Sci. (2024).
Keywords: Microgels; Volume Phase Transition; Flory-Rehner; Smart Materials