title: Poly(N-isopropylacrylamide)-clay based hydrogels controlled by the initiating conditions: evolution of structure and gel formation.
abstract: The formation of the hydrogel poly(N-isopropylacrylamide)-clay (LAPONITE®) by redox polymerization was investigated, and the main factors governing the gel build-up were determined. The significant effect of the redox initiating system ammonium peroxodisulfate (APS) and tetramethylethylenediamine (TEMED) on gel formation and structure was established, making it possible to control the structure of the gel. Moreover, the pre-reaction stage involving the quality of the clay exfoliation in an aqueous suspension and the interaction of reaction components with the clay play a role in controlling the polymerization and gel structure. The molecular and phase structure evolution during polymerization was followed in situ by the following independent techniques: Fourier transform infrared spectroscopy (FTIR), chemorheology, small-angle X-ray scattering (SAXS) and ultraviolet-visible spectroscopy (UV/Vis). The combination of these methods enabled us to describe in detail particular progress stages during the gel formation and determine the correlation of the corresponding processes on a time and conversion scale. The mechanism of gel formation was refined based on these experimental results.
authors.affiliation: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic. matejka@imc.cas.cz.
authors.forename: Beata
authors.initials: B
authors.lastname: Strachota
authors.affiliation: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic. matejka@imc.cas.cz.
authors.forename: Libor
authors.initials: L
authors.lastname: Matějka
authors.affiliation: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic. matejka@imc.cas.cz.
authors.forename: Alexander
authors.initials: A
authors.lastname: Zhigunov
authors.affiliation: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic. matejka@imc.cas.cz.
authors.forename: Rafał
authors.initials: R
authors.lastname: Konefał
authors.affiliation: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic. matejka@imc.cas.cz.
authors.forename: Jiří
authors.initials: J
authors.lastname: Spěváček
authors.affiliation: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic. matejka@imc.cas.cz.
authors.forename: Jiří
authors.initials: J
authors.lastname: Dybal
authors.affiliation: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic. matejka@imc.cas.cz.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Puffr