[Soft Matter Café] Dynamical Behaviour of Interpenetrated Polymer Network microgels

The novel class of responsive microgels has recently become very popular since their smart responsivity to external stimuli makes them very attractive for industrial applications and excellent model systems for exploring the exotic behaviours emerging in soft colloids since their softness allows to explore high density states well beyond random close packing. In the last years we have deeply investigated a dual responsive Interpenetrated Polymer Newtork (IPN) microgel composed of poly(N-isopropylacrylamide) (PNIPAM), a temperature sensitive polymer, and poly(acrylic acid) (PAAc), a pH sensitive polymer [1]. The system, with multi-stimuli responsiveness and rationally designed properties, can be finely controlled through different experimental parameters. PNIPAM-PAAc IPN microgels is investigated as a function of sample concentration [2], temperature and PAAC content [3] that permit to tune ad hoc the formation of arrested states. In this talk we will focus on the dynamical behaviour of PNIPAM-PAAc IPN microgels through Dynamic Light Scattering and X-ray Photon Correlation Spectroscopy [2,4] varying concentration, temperature and PAAC content. The slowing down of the dynamics approaching the glassy state has common feature with many glass-formers.

[1] V. Nigro et al., Polymers 13, 1353 (2021).
[2] V. Nigro et al., Soft Matter 13, 5185 (2017).
[3] V. Nigro et al., J. Colloid Interface Sci. 545, 210 (2019).
[4] V. Nigro et al., Macromolecules 53, 1596 (2020).