Polymer-based coatings often incorporate fillers or inclusions into the polymer matrix to tune application-specific physical and chemical properties. Furthermore, the presence of specific solvents can either promote or impede dispersal of the inclusions and polymer chains. Here, all-atom molecular dynamics (MD) simulations are performed to probe the formation of interfacial regions in metal-organic framework (MOF)-polymer composites by including nanoscale crystallites of UiO-66 in a binder of a polyurethane or polyhydroxyurethane solvated with hexane or hexanol. We study the effect of different surface chemistries on the metal oxide nodes (hydroxyl, formate, or acetate groups), calculating polymer and solvent densities and interaction energies. We report secondary trends in chain adsorption (depletion) near the MOF surface as a function of different surface chemistries, while the polymer-solvent and solvent-solvent interactions appear as the primary factors controlling the interfacial uniformity. The simulations show that chain penetration into the MOF can be either entirely impeded by the choice of the blending solvent or promoted by the particular surface functionalization. Energetic barriers from the MD are directly extracted to quantify chain interpenetration of the MOF and reveal that interpenetration is a stabilizing process during interface formation and strongly dependent upon solvent presence and surface chemistry.
Polymer-grafted nanoparticles (PGNPs) provide a model platform for investigating the interplay between polymer solvation and interfacial assembly. However, the behavior of PGNPs bearing hydrophilic chains at liquid-air interfaces remains poorly understood due to their strong affinity for aqueous subphases. In this work, we examine the interfacial assembly of polyethylene glycol (PEG)-grafted gold nanoparticles (AuNP@PEG) under conditions where polymer solubility is modulated by Hofmeister ions. By systematically varying the identity and concentration of kosmotropic anions, we demonstrate that ion-specific regulation of PEG hydration significantly alters nanoparticle-subphase interactions, leading to a transition from dissolution-dominated behavior to stable interfacial retention and monolayer formation. The dependence of this transition on PEG molecular weight reveals the critical role of chain length in governing desolvation and interfacial free energy. In addition, PEG/polystyrene (PS) co-functionalized nanoparticles are employed to further tune interfacial affinity, providing a comparative framework for disentangling the contributions of polymer solubility and ligand hydrophobicity. These results establish a mechanistic picture in which ion-mediated changes in polymer hydration control nanoparticle residence and assembly at interfaces. This study provides insight into the coupling between polymer solvation and interfacial behavior in PGNP systems and offers a basis for extending interfacial assembly to hydrophilic polymer-grafted nanomaterials.
Viscosity of porous liquids (PLs) is a critical factor for their processability and transportation, yet controlling their viscosity without compromising pore volume remains a significant challenge. In this work, we present a strategy to modulate the viscosity of type I PLs by varying surface functionality. A series of star-shaped PLs was synthesized by coordinating 12 equiv of soft polymer chains to isostructural rhodium metal-organic polyhedra (RhMOPs) as central cores with different surface groups (nonsubstituted, hydroxy, tert-butyl, or dodecyloxy groups). The functional groups on the RhMOP surface were found to significantly affect the conformation of polymer chains, thereby resulting in different rheological behavior and pore accessibility. The use of RhMOPs with dodecyloxy surface groups yielded a closely compact conformation of polymer chains on the MOP surface. The obtained PLs have a viscosity as low as 1.8 × 101 Pa·s and exhibit a temperature-dependent gating effect; CO2 uptake increases with increasing temperature. By contrast, the hydroxyl group afforded PLs with a loosely stretched polymer conformation, resulting in a dramatically high viscosity of 3.0 × 109 Pa·s and high gas accessibility to the inner RhMOP pores. This work provides a feasible way to adjust PLs' rheological properties without altering pore volume to meet the requirements of different practical applications.
Xiangmei Xiang, Zaoming Wang, Masataka Yamashita et al.· Journal of the American Chem...· 0 citations
The increasing interest in the development of intrinsically stretchable electronic devices based on polymer semiconductors (PSCs) necessitates a comprehensive understanding of the interfacial chemistry of these PSC films, alongside facile processing methods to modify these properties, which dictate layer compatibility. Solvent-mediated functionalization provides a scalable, controllable, and tunable method to target and modulate several key interfacial properties. Herein, we aim to understand the influence of solvent exposure on a blended polymer film. This is achieved through small molecule modification of a poly-thieno[3,2-b]thiophene-diketopyrrolopyrrole (DPPTT) and low molecular weight polybutadiene (BA)-blended elastomer film. We investigated solvent-mediated film functionalization on blended films by incorporating 1H,1H,2H,2H-perfluorodecanethiol (PFDT), as the highly fluorinated small molecule provided excellent measurement contrast throughout several characterization techniques. By comparing solvent environments that differentially swell the blended polymer films, we show programming of PFDT incorporation from uniform, through-thickness functionalization to surface-enriched gradients. Quartz crystal microbalance with dissipation monitoring (QCM-D) measurements and further corroborated with X-ray photoelectron spectroscopy (XPS) depth profiles quantified the estimated apparent mass uptake of PFDT. In a non-swelling/compacting solvent environment, QCM-D reflected a diffusion-governed uptake of PFDT with a distinct thickness-dependent concentration gradient. In contrast, swelling films with methoxyperfluorobutane (MPFB) opened diffusion pathways that facilitated PFDT penetration throughout the entire polymer network and resulted in more uniform functionalization across the entire film thickness. Collectively, these results establish a broader understanding of solvent-mediated film functionalization and further the understanding of molecular diffusion through PSC film systems.
Max Schrock, L. Michalek, Qun-Gao Chen et al.· ACS Applied Materials and In...· 0 citations
Ceramic nanoparticles incorporated into solid polymer electrolytes have been reported to both enhance and suppress ionic conductivity, but the origins of these effects remain unclear due to difficulties in isolating interfacial phenomena in disordered bulk systems. Here, we characterize ion transport in ultrathin films of poly(ethylene oxide)–lithium bis(trifluoromethanesulfonyl)imide on silica and employ analytical modeling to elucidate how interfaces might control thickness-dependent behavior. Ionic conductivity is suppressed for the thinnest films at all salt concentrations and temperatures, though modest enhancement appears in some films at low salt concentration. The extent of modulation, however, varies with concentration alone. A modified Vogel–Fulcher–Tammann model incorporating both substrate and free-interface effects on polymer dynamics best captures the observed behavior, outperforming models based on nonconducting layers, interfacial salt partitioning, or substrate-only interface effects. This indicates that both inorganic surfaces and free interfaces can substantially influence polymer mobility and conductivity, suggesting that strategies to optimize composite polymer electrolytes should address the coupled behavior of interfacial polymer dynamics.
Shannon Zhang, Ohad Bouni, Daniel Sharon et al.· ACS Macro Letters· 0 citations
Polymer adsorption at solid/liquid interfaces plays a crucial role in many applications, yet the molecular pathway of adsorption remains difficult to resolve experimentally. Here, we investigated the adsorption of poly(methyl methacrylate) (PMMA) and polystyrene (PS) from solution onto silica using in situ, real-time sum frequency generation vibrational spectroscopy. PMMA adsorption proceeds through multiple steps accompanied by changes in molecular orientation. Ester side chains first adsorb onto silica via hydrogen-bonding interactions with silanol groups and adopt a preferred interfacial orientation. This is followed by adsorption and reorientation of chain-end methyl groups and backbone methylene groups, revealing a sequential, functional-group-specific adsorption pathway. In contrast, PS, which lacks hydrogen-bonding interactions with silica, exhibits markedly slower adsorption under otherwise comparable conditions. These results demonstrate that interfacial hydrogen-bonding determines both adsorption kinetics and the molecular structure of the adsorbed layer. This study provides a functional-group-resolved view of polymer adsorption from solution and offers molecular-level insight into the design of polymer interfaces.
Tatsuki Abe, Tieyi Lu, John S. Andre et al.· Langmuir· 0 citations
Type II porous liquids that exhibit host-guest properties derived from molecular cages are of potential utility in liquid-liquid separations; however, those with metal-organic cages (MOCs) as pore hosts are extremely rare due to the limited solubility of MOCs in cavity-excluded solvents. Here, we report the use of polyvinylpyrrolidone (PVP) to deliver polyoxovanadate-organic hybrid cages (HD) in polyethylene glycol (PEG) for a concentrated type II porous liquid (HDPVP/PEG). Structural characterizations and modeling studies collectively confirm that the PVP-PEG compatibility and the HD-PVP interaction enable the high HD concentration in PEG. The minimal loading of PVP coupled with the steric hindrance of PVP and PEG ensure the permanent porosity and room-temperature fluidity. HDPVP/PEG exhibits high uptake and selectivity toward C5–C7 n-alkanes over their branched isomers due to the host-guest interactions between HD and n-alkanes. The design strategy of HDPVP/PEG was successfully extended to other typical MOCs and commonly-used cavity-excluded solvents.
Shuaibo Yang, Y. Han, M. Cui et al.· Science Advances· 0 citations
