Structure, orientation, and dynamics of per- and polyfluoroalkyl substance (PFAS) surfactants at the air-water interface: Molecular-level insights.

Hypothesis: Understanding the intricate molecular-level details of toxic per- and polyfluoroalkyl substances (PFAS) partitioning to the air-water interface holds paramount importance in evaluating their fate and transport, as well as for finding safer alternatives for various applications, including aqueous film forming foams. The behavior of these substances at interfaces strongly depends on molecular architecture, chemistry, and concentration, which define molecular packing, self-assembly, interfacial diffusion, and the surface tension.

Simulations: Modeling of three PFAS surfactants, namely, longer-tail (perfluorooctanoate (PFOA)) and shorter-tail (perfluorobutanoate (PFBA) and 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy) propanoate (GenX)) has been conducted using atomistic molecular dynamics simulations.

Carboxymethyl hydroxypropyl guar gum physicochemical properties in dilute aqueous media.

We investigate carboxymethyl hydroxypropyl guar gum (CMHPG) solution properties in water and NaCl, KCl, and CaCl aqueous solutions. The Huggins, Kraemer, and Rao models were applied by fitting specific and relative viscosity of CMHPG/water and CMHPG/salt/water to determine the intrinsic viscosity [η]. The Rao models yielded better results (R = 0.

Effects of Ionic Liquids on the Cylindrical Self-Assemblies Formed by Poly(ethylene oxide)-Poly(propylene oxide)-Poly(ethylene oxide) Block Copolymers in Water.

Aiming at the fundamental understanding of solvent effects in amphiphilic polymer systems, we considered poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers in water mixed with an ionic liquid-ethylammonium nitrate (EAN), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF), or 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF)-and we investigated the hexagonal lyotropic liquid crystal structures by means of small-angle X-ray scattering (SAXS). At 50% polymer, the hexagonal structure (cylinders of self-assembled block copolymer) was maintained across the solvent mixing ratio. The effects of the ionic liquids were reflected in the characteristic length scales of the hexagonal structure and were interpreted in terms of the location of the ionic liquid in the self-assembled block copolymer domains.

Salt and Temperature Effects on Xanthan Gum Polysaccharide in Aqueous Solutions.

Xanthan gum (XG) is a carbohydrate polymer with anionic properties that is widely used as a rheology modifier in various applications, including foods and petroleum extraction. The aim was to investigate the effect of Na, K, and Ca on the physicochemical properties of XG in an aqueous solution as a function of temperature. Huggins, Kraemer, and Rao models were applied to determine intrinsic viscosity, [], by fitting the relative viscosity () or specific viscosity () of XG/water and XG/salt/water solutions.

Phase Behavior and Structure of Poloxamer Block Copolymers in Protic and Aprotic Ionic Liquids.

Ionic liquids are promising media for self-assembling block copolymers in applications such as energy storage. A robust design of block copolymer formulations in ionic liquids requires fundamental knowledge of their self-organization at the nanoscale. To this end, here, we focus on modeling two-component systems comprising a Poly(ethylene oxide)-poly (propylene oxide)-Poly(ethylene oxide) (PEO-PPO-PEO) block copolymer (Pluronic P105: EOPOEO) and room temperature ionic liquids (RTILs): protic ethylammonium nitrate (EAN), aprotic ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF), or 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF).