The polydispersity effect of distributed oxyethylene chains on the cloud points of nonionic surfactants

Abstract

The cloud points of aqueous solutions containing polyoxyethylene surfactant molecules with a distribution of chain lengths were studied for several nonionic surfactants Experimentally the cloud points Increased as the oxyethylene chain lengths Increased with a linear or logarithmic relation of the number of oxyethylates as proposed by Schott An experimental scale the p - Po scale was previously developed to correspond to the cloud points where p is the average number of oxyethylene units per molecule and Po is the shortest chain length reference However no previous prediction methods of cloud point addressed systems containing a range of chain lengths In this work we propose a rescaling of the representative chain length as s - Po where s is the cloud point-weighted mean ethylene oxide chain below p and approximated as (p - Po)/PDI where PDI is the polydispersity index Using the rescaled length the experimental data for C(12)Es (lauryl alcohol ethoxylate LAE) NPE 10 (nonyl phenol ethoxylate) and TDE-10 (tridecyl alcohol ethoxylate) were successfully predicted with no additional parameters such as {(p - Po)/(PDI)}/CP = a + b{(p - Po)/(PDI)} where PDI indicates the Broadness of the chain length distribution (C) 2010 Elsevier Inc All rights reserved