Abstract
Structural details of thermoresponsive, cationically poly(N-iso-propylacrylamide-co-methacrylamido propyl trimethyl ammonium chloride) microgels and the influence of the anionic electrolyte polystyrene sulfonate (PSS) on the internal structure and dynamics of the cationic microgels have been studied with a combination of small angle neutron scattering (SANS) and neutron spin echo (NSE) spectroscopy. While SANS can yield information on the overall size of the particles and on the typical correlation length inside the particles, studying the segmental polymer dynamics with NSE gives access to more internal details, which only appear due to their effect on the polymer motion. The segmental dynamics of the microgels studied in this paper is to a large extent suppressed by the PSS additive. Possible scenarios of the influence of the polyanions on the microgel structure and dynamics are discussed.
Highlights
Microgels are made of chemically cross-linked polymer chains; the typical size of the microgel is of the order of 100–1000 nm.[1,2] A widely studied class of microgels are thermoresponsive, i.e., the solvent properties change from good to bad solvent when the temperature rises above the volume phase transition temperature (VPTT)
A rather recent topic is the measurement of polymer chain dynamics at the solid–liquid interface with grazing incidence neutron spin echo spectroscopy (GINSES), the dynamic extension to GISANS
An experiment with small angle neutron scattering is essential to understand whether the addition of the polyanions has caused any structural modification of the microgel
Summary
Microgels are made of chemically cross-linked polymer chains; the typical size of the microgel is of the order of 100–1000 nm.[1,2] A widely studied class of microgels are thermoresponsive, i.e., the solvent properties change from good to bad solvent when the temperature rises above the volume phase transition temperature (VPTT) Such microgels possess large potential for application in, for example, drug delivery systems, responsive switches, and functional coatings.[3] Neutron scattering has been used to investigate the structure of microgels with small angle neutron scattering (SANS), where the density profile of microgels with a dense core and a shell with decreasing polymer density has been determined.
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