Association between Nonionic Amphiphilic Polymer and Ionic Surfactant in Aqueous Solutions: Effect of Polymer Hydrophobicity and Micellization.

Samhitha Kancharla,Nathan A Zoyhofski,Lucas Bufalini,Paschalis Alexandridis,Boris F Chatelais

doi:10.3390/polym12081831

Samhitha Kancharla, Nathan A Zoyhofski + Show 3 more

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https://doi.org/10.3390/polym12081831

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Journal: Polymers	Publication Date: Aug 15, 2020
Citations: 45	License type: CC BY 4.0

Affiliation: University at Buffalo, State University of New York

Abstract

The interaction in aqueous solutions of surfactants with amphiphilic polymers can be more complex than the surfactant interactions with homopolymers. Interactions between the common ionic surfactant sodium dodecyl sulfate (SDS) and nonionic amphiphilic polymers of the poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO-PPO-PEO) type have been probed utilizing a variety of experimental techniques. The polymer amphiphiles studied here are Pluronic F127 (EO100PO65EO100) and Pluronic P123 (EO19PO69EO19), having the same length PPO block but different length PEO blocks and, accordingly, very different critical micellization concentrations (CMC). With increasing surfactant concentration in aqueous solutions of fixed polymer content, SDS interacts with unassociated PEO-PPO-PEO molecules to first form SDS-rich SDS/Pluronic assemblies and then free SDS micelles. SDS interacts with micellized PEO-PPO-PEO to form Pluronic-rich SDS/Pluronic assemblies, which upon further increase in surfactant concentration, break down and transition into SDS-rich SDS/Pluronic assemblies, followed by free SDS micelle formation. The SDS-rich SDS/Pluronic assemblies exhibit polyelectrolyte characteristics. The interactions and mode of association between nonionic macromolecular amphiphiles and short-chain ionic amphiphiles are affected by the polymer hydrophobicity and its concentration in the aqueous solution. For example, SDS binds to Pluronic F127 micelles at much lower concentrations (~0.01 mM) when compared to Pluronic P123 micelles (~1 mM). The critical association concentration (CAC) values of SDS in aqueous PEO-PPO-PEO solutions are much lower than CAC in aqueous PEO homopolymer solutions.

Highlights

We present the interactions of sodium dodecyl sulfate (SDS) with Pluronic F127 first, followed by the interactions of SDS with Pluronic P123
In the SDS + 0.01% Pluronic F127 system, a change in the slope is observed at 8.5 mM SDS, a concentration that likely corresponds to the surfactant concentration (Cm ) where free SDS micelles form in the aqueous solution
12, 1831 in the2020, slope is observed at 8.5 mM SDS, a concentration that likely corresponds to the surfactant concentration (Cm) where free SDS micelles form in the aqueous solution

Summary

Introduction

Surfactant molecules interact with polymers above a certain concentration called the critical association (or aggregation) concentration (CAC), which is typically much lower than the critical micellization concentration (CMC) of surfactants in the absence of a polymer [1,2,9]. Polymers 2020, 12, 1831 surfactant micelles begin to form above a certain polymer saturation point (PSP). In the case of mixed systems comprising amphiphilic polymer and surfactant, the surfactant–polymer interactions can be rather different from those in the case of non-amphiphilic homopolymers [2,10,11,12,13]; the surfactant molecules can participate in amphiphilic polymer assemblies to form mixed micelles [2,13,14]

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