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Abstract Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a versatile surface-sensitive technique for characterizing both hard and soft matter. Its chemical and molecular specificity, high spatial resolution, and superior sensitivity make it an ideal method for depth profiling polymeric systems, including those comprised of both inorganic and organic constituents (i.e., polymer nanocomposites, PNCs). To best utilize ToF-SIMS for characterizing PNCs, experimental conditions must be optimized to minimize challenges such as the matrix effect and charge accumulation. Toward that end, we have successfully used ToF-SIMS with a Xe+ focused ion beam to depth profile silica nanoparticles grafted with poly(methyl methacrylate) (PMMA-NP) in a poly(styrene-ran-acrylonitrile) matrix film by selecting conditions that address charge compensation and the primary incident beam angles. By tracking the sputtered Si+ species and fitting the resultant concentration profile, the diffusion coefficient of PMMA-NP was determined to be D = 2.4 × 10−14 cm2/s. This value of D lies between that measured using Rutherford backscattering spectrometry (6.4 × 10−14 cm2/s) and the value predicted by the Stokes–Einstein model (2.5 × 10−15 cm2/s). With carefully tuned experimental parameters, ToF-SIMS holds great potential for quantitatively characterizing the nanoparticles at the surfaces and interfaces within PNC materials as well as soft matter in general. 

Because 3D batteries comprise solid polymer electrolytes (SPE) confined to high surface area porous scaffolds, the interplay between polymer confinement and interfacial interactions on total ionic conductivity must be understood. This paper investigates contributions to the structure-conductivity relationship in poly(ethylene oxide) (PEO)–lithium bis(trifluorosulfonylimide) (LiTFSI) complexes confined to microporous nickel scaffolds. For bulk and confined conditions, PEO crystallinity decreases as the salt concentration (Li+:EO (r) = 0.0.125, 0.0167, 0.025, 0.05) increases. For pure PEO and all r values except 0.05, PEO crystallinity under confinement is lower than in the bulk, whereas glass transition temperature remains statistically invariant. At 298 K (semicrystalline), total ionic conductivity under confinement is higher than in the bulk at r = 0.0167, but remains invariant at r = 0.05; however, at 350 K (amorphous), total ionic conductivity is higher than in the bulk for both salt concentrations. Time–of–flight secondary ion mass spectrometry indicates selective migration of ions towards the polymer–scaffold interface. In summary, for the 3D structure studied, polymer crystallinity, interfacial segregation, and tortuosity play an important role in determining total ionic conductivity and, ultimately, the emergence of 3D SPEs as energy storage materials. 

This study investigates the interplay between film thickness and the surface and internal morphologies in polymer nanocomposite (PNC) films. The PNC is 25 wt.% poly(methyl methacrylate)-grafted silica nanoparticles (NPs) in poly(styrene-ran-acrylonitrile) annealed in the two-phase region. At greatest confinement (120 nm), NP surface density remains constant and lateral phase separation is inhibited upon annealing. For thicker films (240 nm to 1400 nm), surface density increases with time before approaching ca. 740 NP/μm2, consistent with 2D random close packing. Moreover, lateral domain growth exhibits a dimensional crossover as thickness increases from 𝑡 to , consistent with domain coalescence. Water contact angles 1/2 𝑡1/3 decrease upon annealing in agreement with the lateral domain composition. For thickest films (1400 nm to 4000 nm), a morphology map summarizes the distinct internal arrangements of NPs: disordered aggregates, continuous vertical pillars, discrete vertical pillars, isolated domains, and random networks. This study of PNC films provides guidance for controlling surface and bulk structure which can lead to improved barrier, mechanical and transport properties. 

Because surface-grafted polyelectrolyte brushes (PEBs) are responsive to external stimuli, such as electric fields and ionic strength, PEBs are attractive for applications ranging from drug delivery to separations technologies. Essential to PEB utilization is understanding how critical parameters like grafting density (σ) impact PEB structure and the dynamics of the PEB and counterions. To study the effect of σ on PEB and counterion structure and dynamics, we fine-tune a coarse-grained model that retains the chemical specificity of a strong polyelectrolyte, poly[(2-(methacryloyloxy)ethyl) trimethylammonium chloride] (PMETAC), using the MARTINI forcefield. Using “salt-free” conditions where the counterion concentration balances the charge on the brush, we build coarse-grained (CG) molecular dynamics simulations for MARTINI PMETAC brushes (N=150 monomers; MW = 31.2 kg/mol) at experimentally relevant values of σ = 0.05, 0.10, 0.20, and 0.40 chains/nm2. Using 5 µs simulations, we investigate the effects of grafting density on PEB structure, ion dissociation dynamics, polymer mobility, and counterion diffusivity. Results show that competition between electrostatic interactions, steric hindrance, and polymer mobility controls counterion diffusivity. The interplay of these factors leads to diffusivity that depends non-monotonically on σ, with counterion diffusivity peaking at an intermediate σ = 0.10 chains/nm2. 

Titanium dioxide (TiO2)/nitrogen-doped graphene (NG) nanocomposite is prepared via a solvent-free hydrothermal reaction. The resulting TiO2/NG materials exhibit a reduction of the band gap energy compared to pristine TiO2 from 3.27 eV to 2.69 eV. These materials are characterized by scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). To prepare biopolymer films with photocatalytic properties, TiO2 and NG are mixed with biodegradable chitosan and spin-coated on a silicon wafer. Film roughness and thickness are evaluated by atomic force microscopy (AFM). These films are then tested for ciprofloxacin photodegradation by irradiating with visible light. In comparison to the TiO2/chitosan films, the addition of NG substantially enhances photodegradation efficiency by up to 34% upon the addition of 5% w/w of NG. Furthermore, this film is shown to be a good substrate for biomarker detection using laser desorption ionization mass spectrometry (LDI-MS). In summary, this nanocomposite-biopolymer film provides good photocatalytic activity towards ciprofloxacin degradation and enhances the ionization efficiency of peptide biomarkers in LDI-MS owing to high efficiency of laser absorption/desorption. This nanocomposite film might be useful for environmental-related and medical application. 

Polymer infiltrated nanoporous gold is prepared by infiltrating polymer melts into a bicontinuous, nanoporous gold (NPG) scaffold. Polystyrene (PS) films with molecular weights (Mw) from 424 to 1133 kDa are infiltrated into a NPG scaffold (∼120 nm), with a pore radius (Rp) and pore volume fraction of 37.5 nm and 50%, respectively. The confinement ratios (Γ=RgRp) range from 0.47 to 0.77, suggesting that the polymers inside the pores are moderately confined. The time for PS to achieve 80% infiltration (τ80%) is determined using in situ spectroscopic ellipsometry at 150 °C. The kinetics of infiltration scales weaker with Mw, τ80%∝Mw1.30±0.20, than expected from bulk viscosity Mw3.4. Furthermore, the effective viscosity of the PS melt inside NPG, inferred from the Lucas–Washburn model, is reduced by more than one order of magnitude compared to the bulk. Molecular dynamics simulation results are in good agreement with experiments predicting scaling as Mw1.4. The reduced dependence of Mw and the enhanced kinetics of infiltration are attributed to a reduction in chain entanglement density during infiltration and a reduction in polymer–wall friction with increasing polymer molecular weight. Compared to the traditional approach involving adding discrete particles into the polymer matrix, these studies show that nanocomposites with higher loading can be readily prepared, and that kinetics of infiltration are faster due to polymer confinement inside pores. These films have potential as actuators when filled with stimuli-responsive polymers as well as polymer electrolyte and fuel cell membranes.