Probing Hydrophobic Interactions between Polymer Surfaces and Air Bubbles or Oil Droplets: Effects of Molecular Weight and Surfactants

Metal-Phenolic Networks Enable Biomimetic Antioxidant Interfaces Through Nanocellulose Engineering

Metal-phenolic networks (MPNs) integrated with functionalized cellulose nanofibers present a promising platform for stabilizing oxidation-sensitive compounds. Here, a novel antioxidant pickering emulsion system utilizing MPN-decorated carboxyl-functionalized pulp cellulose nanofibers (MPN-PCNF) is demonstrated. The system exhibits exceptional interfacial stability through synergistic effects of MPN coating and alkyl functionalization, validated by DLVO theoretical modeling and rheological characterization. MPN-PCNF demonstrates remarkable antioxidant efficacy, achieving 94% α-tocopherol retention over 50 days and 80% reduction in cellular reactive oxygen species. In reconstructed human skin models, the system significantly attenuates UV-induced oxidative stress, evidenced by preserved stratum corneum integrity and suppressed matrix metalloproteinase-1 expression. This biocompatible platform represents a versatile solution for protecting oxidation-sensitive compounds across pharmaceutical, cosmetic, and food applications, offering a sustainable alternative to conventional synthetic antioxidant systems.

Both nanoplastic and iron mineral types determine their heteroaggregation: Aggregation kinetics and interface process

Nanoplastics (NPs) inevitably interact with iron minerals (IMs) after being released into aquatic environments, changing their transport and fate. In this study, batch heteroaggregation kinetics of four types of NPs, i.e., polymethyl methacrylate (PMMA), polystyrene (PS-Bare), amino-polystyrene (PS-NH2), and carboxyl-polystyrene (PS-COOH), with two different IMs (hematite and magnetite) were conducted. We found that the heteroaggregation of NPs and IMs and the associated interfacial interaction mechanisms are both NPs-dependent and IMs-dependent. Specifically, the NPs had stronger heteroaggregation with hematite than magnetite; the heteroaggregation order of two IMs with NPs was PMMA > PS-NH2 > PS-Bare > PS-COOH. Moreover, hydrogen bond, complexation, hydrophobic, cation-π, and electrostatic interaction were involved in the interfacial reaction between NPs and hematite, and electrons were transferred from the NPs to the hematite, causing the reduction of Fe3+ into Fe2+. Furthermore, we first revealed that both pre-homoaggregation of NPs and IMs could affect their subsequent heteroaggregation, and the homoaggregates of IMs could be interrupted by PMMA or PS-COOH NPs introduction. Therefore, the emerging NPs pollution is likely to generate an ecological effect in terms of elemental cycles such as iron cycle. This work provides new insights into assessing the environmental transfer and ecological effects of NPs in aquatic environments.

Charge-Dipole Attraction as a Surface Interaction between Water Droplets Immersed in Organic Phases

The dynamic behavior of emulsion droplets during their interactions with one another or with solid surfaces plays a paramount role in their ultimate stability in various applications. While the interaction of oil droplets through a surrounding aqueous phase is well understood, recent studies on the interaction of water droplets through a surrounding pure organic phase showed the presence of an unexplained attraction between water droplets at relatively long ranges. In this research study, we propose fixed-surface-charge-bulk-dipole attraction as a new interaction force between water-in-oil droplets and then derive an equation for its disjoining pressure. The behavior of water droplets in the presence and absence of this charge-dipole interaction was numerically quantified using the Stokes-Reynolds-Young-Laplace model and compared to the experimental data. Numerically calculated net force curves are in excellent agreement with experimental data from the literature when charge-dipole attraction is included, while they deviate in its absence. In addition, the water droplet and thin oil film profiles in the presence and absence of charge-dipole attraction were calculated and compared. This research indicates that charge-dipole attraction can adequately explain the mysterious force observed in some studies, which demonstrates its unexplored potential to capture the physical properties and dynamic behavior of water droplets in organic phases with useful implications to unravel unidentified interactions between emulsion droplets in different industries.