Hydrophobically modified associative polymers: Solution rheology and applications in electrospinning

Hydrophobically modified associative polymers are generating considerable research interest owing to their ability to be used in a variety of applications ranging from paints and coatings to drug delivery. These polymers have pendant hydrophobic groups that form a reversible physical network in an alkaline solution comprising of both intra- and inter-molecular hydrophobic junctions resulting in a unique thickening mechanism. The present study can essentially be divided into two parts. In the first part, we discuss how nonionic surfactants, both individually and in binary surfactant mixtures, can be effectively used to modify the rheology of associative polymers via formation of free as well as bound micelles incorporating polymer hydrophobes. We also demonstrate the applicability of nonionic surfactants in modulating hydrophobic associations in these polymers in the presence of inclusion compounds called cyclodextrin.;Electrostatic spinning or electrospinning of nanofibers has drawn considerable research attention in recent years. It involves the application of an electric filed to a polymer solution or melt to facilitate production of fibers in the sub-micron range. The scope and utility of associative polymers can be broadened further by incorporating them in precursor electrospinning solutions due to their ability to alter solution rheology. In the second part of this study, we focus on gaining insights into the role of rheology on fiber formation by including associative polymers in electrospinning solutions. We further illustrate how the concept of using surfactants to control viscoelasticity of these polymers can be extended to fabricate electrospun nanofibers. Finally, we establish the utility of associative polymers in improving the morphology of electrospun fibers through significant changes in viscosity and viscoelasticity of precursor solutions. This concept of using associative polymers is extended further to other associative polymers that interact via mechanisms other than hydrophobic associations.