Cross-linking density and temperature effects on the self-assembly of SiO2 - PNIPAAm core-shell particles at interfaces

Kadriye Özlemnazli, Christian Pester, Artjom Konradi, Alexander Böker, Patrick Vanrijn

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

SiO2-PNIPAAm core-shell microgels (PNIPAAm=poly(N- isopropylacrylamide)) with various internal cross-linking densities and different degrees of polymerization were prepared in order to investigate the effects of stability, packing, and temperature responsiveness at polar-apolar interfaces. The effects were investigated using interfacial tensiometry, and the particles were visualized by cryo-scanning electron microscopy (SEM) and scanning force microscopy (SFM). The core-shell particles display different interfacial behaviors depending on the polymer shell thickness and degree of internal cross-linking. A thicker polymer shell and reduced internal cross-linking density are more favorable for the stabilization and packing of the particles at oil-water (o/w) interfaces. This was shown qualitatively by SFM of deposited, stabilized emulsion droplets and quantitatively by SFM of particles adsorbed onto a hydrophobic planar silicon dioxide surface, which acted as a model interface system. The temperature responsiveness, which also influences particle-interface interactions, was investigated by dynamic temperature protocols with varied heating rates. These measurements not only showed that the particles had an unusual but very regular and reversible interface stabilization behavior, but also made it possible to assess the nonlinear response of PNIPAAm microgels to external thermal stimuli. Softness matters: SiO2-PNIPAAm core-shell microgels with various internal cross-linking densities and different degrees of polymerization were used to investigate the effects of stability, packing, and static/dynamic temperature responsiveness at polar-apolar interfaces (see figure). These particles displayed an unusual but very regular and reversible interface stabilization behavior and a nonlinear particle response to heat. PNIPAAm=poly(N- isopropylacrylamide)

Original languageEnglish (US)
Pages (from-to)5586-5594
Number of pages9
JournalChemistry - A European Journal
Volume19
Issue number18
DOIs
StatePublished - Apr 26 2013

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Organic Chemistry

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