Characterisation of the dispersion stability of a stimulus responsive core-shell colloidal latex

Reis, Bruno M., Armes, Steven P., Fujii, Syuji and Biggs, Simon (2010) Characterisation of the dispersion stability of a stimulus responsive core-shell colloidal latex. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 353 2-3: 210-215. doi:10.1016/j.colsurfa.2009.11.015


Author Reis, Bruno M.
Armes, Steven P.
Fujii, Syuji
Biggs, Simon
Title Characterisation of the dispersion stability of a stimulus responsive core-shell colloidal latex
Journal name Colloids and Surfaces A: Physicochemical and Engineering Aspects   Check publisher's open access policy
ISSN 0927-7757
1873-4359
Publication date 2010-01-15
Year available 2010
Sub-type Article (original research)
DOI 10.1016/j.colsurfa.2009.11.015
Open Access Status
Volume 353
Issue 2-3
Start page 210
End page 215
Total pages 6
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Language eng
Abstract Light scattering, electrokinetic measurements and flow rheology have been used to characterise the dispersion behaviour a responsive core-shell latex particle system. The system of choice is polystyrene latex which has a stimulus responsive steric polymeric layer at its surface: the responsive polymer used here is a block copolymer of poly(N,N-dimethylaminoethyl methacrylate)-b-poly(methylmethacrylate) [pDMAEMA-b-pMMA], where the pMMA block acts as an anchor to the latex particle and the pDMAEMA block projects into solution. pDMAEMA is a weakly basic polymer and its solubility is therefore dependent upon the pH, it also has a lower critical solution temperature (LCST) of around 40-50 °C in water. Zeta potential measurements showed an iso-electric point (iep) at between pH 7.5 and 8.2, dependent on the background salt concentration, with the core-shell particles having a positive charge at low pH as a result of the strong protonation of the weakly basic pDMAEMA shell. The dimensions of the pDMAEMA shell as a function of pH were measured using dynamic light scattering. At low pH, the steric pDMAEMA shell was seen to extend strongly from the surface of the core PS latex as a result of charge repulsions within this layer. Near to the iep, the steric polymer shell was seen to shrink as a result of the discharging of the weakly basic amine functionalities, finally collapsing back to the latex particle surface close to the iep. Flow rheology data indicated a significant shear-thinning behaviour at all measured particle volume fractions and at all pH. High shear rate data of the viscosity as a function of pH correlated directly with changes in the hydrodynamic volume of the particles; the measured viscosity decreasing as the apparent size of the core-shell particles decreased due to shell collapse. Evidence for the aggregation of the dispersion at high pH near to and above the iep were also seen.
Keyword Core-shell particles
Latex particles
pH responsive
Poly(methylmethacrylate)
Poly(N,N-(dimethylamino)ethyl methacrylate)
Rheology behaviour
Stimulus responsive polymers
Temperature responsive
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID 18004
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Faculty of Engineering, Architecture and Information Technology Publications
 
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