The interplay between hydrophobically associated polymers and ionic surfactants gives rise to complex microstructures that govern the macroscopic rheological properties of the resulting composite systems. This study focuses on the structural evolution and viscoelastic response of a PAAC-sodium dodecyl sulfate (SDS) system as a function of composition, salt concentration, and temperature. By systematically varying the mass ratio of polymer to surfactant, it is demonstrated that a critical balance exists at a 15:1 ratio, where maximum viscosity and network integrity are achieved. At this point, dynamic light scattering (DLS) reveals a significant increase in hydrodynamic radius, indicating the formation of large, stable aggregates with average sizes exceeding 500 nm—consistent with Cryo-TEM observations.
Fluorescence spectroscopy using pyrene as a polarity probe provides molecular-level insight into the microenvironment within the composite. The I₁/I₃ ratio initially decreases with increasing surfactant content, reflecting the creation of more hydrophobic, less polar microdomains due to enhanced association between polymer and surfactant chains. However, beyond the optimal ratio, the ratio increases again, signaling a transition toward a more polar environment caused by structural disintegration and reduced hydrophobic packing. This dual behavior underscores a non-monotonic evolution of microstructure: initial network growth followed by destabilization upon over-surfactant addition.
Rheological analysis confirms the presence of a well-defined viscosity plateau under dynamic shear, which is absent in pure polymer or surfactant solutions. This plateau indicates the existence of a percolated network capable of resisting deformation. The storage modulus (G′) exceeds the loss modulus (G″) at low frequencies, confirming elastic dominance and solid-like behavior. As frequency increases, the crossover point shifts to higher values with increasing polymer concentration, suggesting longer relaxation times and stronger structural integrity. The composite exhibits pronounced shear-thinning, attributed to the alignment and disruption of the entangled network under applied stress.Estrogen Receptor-β Antibody Purity & Documentation
Salt plays a pivotal role in modulating the interaction strength.55-98-1 Molecular Weight Viscosity peaks at 20,000 mg/L NaCl, consistent with the screening of electrostatic repulsions between surfactant headgroups and the promotion of hydrophobic aggregation. The pH remains nearly constant (7.23–7.31), ruling out acid-base effects as a major factor. Notably, even at high salt levels, no phase separation occurs, indicating robust solubility and colloidal stability. This contrasts sharply with other polymer-surfactant systems that undergo demixing at elevated concentrations, highlighting the unique stability conferred by the synergistic hydrophobic and electrostatic interactions in this system.PMID:34716094
Temperature-dependent measurements reveal that while both the composite and pure polymer solutions experience viscosity reduction with rising temperature, the composite maintains significantly higher viscosity across the tested range (25–70 °C). The lower activation energy for viscous flow (24.61 kJ/mol vs. 34.92 kJ/mol) confirms enhanced thermal resilience. These findings collectively demonstrate that the composite’s performance stems from a self-assembled, hierarchical structure stabilized by mixed micelle formation and physical entanglement points, enabling high viscoelasticity without reliance on wormlike micelles. This work offers a rational design strategy for next-generation functional fluids with tunable mechanical properties and environmental adaptability.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
