TY - JOUR
T1 - Size, concentration, and solvency effects on the viscosifying behavior of PEO-PS-PEO triblock copolymers in AOT oil-continuous microemulsions
AU - Lynch, I.
AU - Piculell, L.
PY - 2004
Y1 - 2004
N2 - The effect of changing the block lengths of triblock copolymers of poly(ethylene oxide)−polystyrene−poly(ethylene oxide) on the relative viscosity of AOT oil-continuous microemulsions, with cyclohexane as the oil, was investigated. Five different microemulsion compositions were used to have (a) a series of increasing droplet concentration at constant droplet size and (b) a series with increasing droplet size at constant droplet weight fraction. All polymer and microemulsion mixtures showed Newtonian viscosity, and in all cases the presence of a polymer in the microemulsion led to an increase in the viscosity. Results were presented at 40 °C, which is above the theta temperature of polystyrene in cyclohexane. With all polymers, the relative viscosity decreased with increasing droplet concentration (at constant droplet size) and, in general, increased with increasing droplet size (at constant droplet weight fraction), although there were some exceptions. Comparing the viscosifying behavior of the different triblock copolymers on the molar scale (moles of polymer/dm3) resulted in the emergence of trends that are significantly different from those of previous investigations of triblock copolymers in microemulsions. In particular, we show evidence that increasing the PS block length leads to increased viscosity enhancement. However, at high droplet concentration this increased viscosity enhancement with long PS blocks is lost as the system comes closer to the segregative phase-separation boundary.
AB - The effect of changing the block lengths of triblock copolymers of poly(ethylene oxide)−polystyrene−poly(ethylene oxide) on the relative viscosity of AOT oil-continuous microemulsions, with cyclohexane as the oil, was investigated. Five different microemulsion compositions were used to have (a) a series of increasing droplet concentration at constant droplet size and (b) a series with increasing droplet size at constant droplet weight fraction. All polymer and microemulsion mixtures showed Newtonian viscosity, and in all cases the presence of a polymer in the microemulsion led to an increase in the viscosity. Results were presented at 40 °C, which is above the theta temperature of polystyrene in cyclohexane. With all polymers, the relative viscosity decreased with increasing droplet concentration (at constant droplet size) and, in general, increased with increasing droplet size (at constant droplet weight fraction), although there were some exceptions. Comparing the viscosifying behavior of the different triblock copolymers on the molar scale (moles of polymer/dm3) resulted in the emergence of trends that are significantly different from those of previous investigations of triblock copolymers in microemulsions. In particular, we show evidence that increasing the PS block length leads to increased viscosity enhancement. However, at high droplet concentration this increased viscosity enhancement with long PS blocks is lost as the system comes closer to the segregative phase-separation boundary.
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-2942735191&partnerID=MN8TOARS
U2 - 10.1021/jp049147t
DO - 10.1021/jp049147t
M3 - Article
SN - 1089-5647
VL - 108
SP - 7515
EP - 7522
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 22
ER -