Single molecule study of Polymer-Surfactant Interactions:
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Objectives:
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Monitor the association behavior of polymer in complex media by optical correlation technique.
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Measure the mobility of single polymer chain / micelle.
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Gelation behavior of polymer by single molecule method.
The association between polymers and surfactants has drawn much attention in the last decades. Water soluble polymer-surfactant systems are important for a variety of industrial applications in the areas of cosmetics, personal-care, food, pharmaceutics, detergents, and mineral processing. In particular complexes formed between non-ionic cellulose ethers and ionic surfactant in aqueous solution were investigated in the past. Among the various non-ionic cellulose ethers, methyl cellulose (MC) is the simplest and most well known. Commercial
MC is a heterogeneous polymer consisting of highly substituted hydrophobic zones and less substituted hydrophilic zones resulting in an amphiphilic multiblock copolymer. The amphiphilic nature of the polymer leads to weak inter and intra molecular hydrophobic interactions in aqueous environment. The addition of an anionic surfactant like sodium dodecyl sulfate (SDS) is expected to lead to aggregation in the hydrophobic zones of MC.
Methylcellulose-SDS interactions. At low SDS concentration (region I) we expect some hydrophobic interaction between the hydrophobic regions on the MC chains with barely any influence of the surfactant. In region II complexes are formed between SDS and the hydrophobic regions of MC leading to a significant strengthening of the physical network. Finally, at high enough SDS concentrations (region III) the hydrophobic regions of the MC molecules are saturated by SDS micelles and the physical network breaks down.
