Microstructure Development and Process Pathway Effects In Glassy Polymer Networks

The ability to track network formation of epoxide/amine polymer matrices in real time through Fourier Transform Infrared Spectroscopy (FT-IR) has resolved the cure path dependency of these glassy material\u27s formation. However, the dependency of epoxy system\u27s morphologies and properties on network formation and cure path remains undetermined, impeding the usage of cure path optimization for improving part performance. In the subsequent work, systems consisting of the difunctional epoxide monomer diglycidyl ether of bisphenol F (DGEBF), the tetra functional epoxide monomer tetraglycidyl 4,4\u27-diaminodiphenylmethane (TGDDM), and a mixture of the two crosslinked with the diamine curing agent 4,4\u27-diaminodiphenylsulphone (44DDS) in stoichiometric and non-stoichiometric epoxide to reactive proton ratios were studied. The network formation of each system was monitored in-situ through near infrared (NIR) FTIR for various cure profiles consisting of isotherms at 120 °C, 150 °C, and 180 °C chosen to elicit altered network formation. Then the relation between network formation and morphologies was studied through atomic force microscopy (AFM), scanning electron microscopy (SEM), and nanoscale IR analysis (AFM-IR). The cure path dependent network formation of each system was determined through NIR analysis indicating an enhanced secondary amine to primary amine reactivity (RS/P) for the systems cured at 150 °C that resulted in a distinct nodular morphology; however, upon post-curing for one hour at 220 °C each system exhibited similar features. This work begins to connect the dependence of epoxy system\u27s properties on cure path through the investigation of morphology development

Bioinspired Design Rules from Highly Mineralized Natural Composites for Two-Dimensional Composite Design

Discoveries of two-dimensional (2D) materials, exemplified by the recent entry of MXene, have ushered in a new era of multifunctional materials for applications from electronics to biomedical sensors due to their superior combination of mechanical, chemical, and electrical properties. MXene, for example, can be designed for specialized applications using a plethora of element combinations and surface termination layers, making them attractive for highly optimized multifunctional com- posites. Although multiple critical engineering applications demand that such composites balance specialized functions with mechanical demands, the current knowledge of the mechanical perfor- mance and optimized traits necessary for such composite design is severely limited. In response to this pressing need, this paper critically reviews structure–function connections for highly mineralized 2D natural composites, such as nacre and exoskeletal of windowpane oysters, to extract fundamental bioinspired design principles that provide pathways for multifunctional 2D-based engineered sys- tems. This paper highlights key bioinspired design features, including controlling flake geometry, enhancing interface interlocks, and utilizing polymer interphases, to address the limitations of the current design. Challenges in processing, such as flake size control and incorporating interlocking mechanisms of tablet stitching and nanotube forest, are discussed along with alternative potential solutions, such as roughened interfaces and surface waviness. Finally, this paper discusses future per- spectives and opportunities, including bridging the gap between theory and practice with multiscale modeling and machine learning design approaches. Overall, this review underscores the potential of bioinspired design for engineered 2D composites while acknowledging the complexities involved and providing valuable insights for researchers and engineers in this rapidly evolving field

Orientation Sensing with Color Using Plasmonic Gold Nanorods and Assemblies

Colorimetric analysis of broadband illumination scattered from isolated gold nanorods and reduced symmetry Dolmen structures provide a visible measure of the local nanoscale orientation of the nanostructures relative to the laboratory frame of reference. Polarized dark-field scattering microscopy correlated with scanning electron microscopy of low and high aspect ratio gold nanorods demonstrated accuracies of 2.3 degrees, which is a 5-fold improvement over photothermal and defocused imaging methods. By assigning the three color channels of the imaging detector (red, green, and blue) to the plasmon resonance wavelengths of the nanostructure, the quantitative display of orientation improved by 200%. The reduced symmetry of a gold nanorod Dolmen structure further improved the sensitivity of colorimetric orientation by a factor of 2 due to the comparative intensities of the resonances. Thus the simplicity, high accuracy, and sensitivity of visual colorimetric sensing of local nanoscale orientation holds promise for high throughput, inexpensive structure and dynamics studies in biology and material science

Engineering the Optical Properties of Gold Nanorods: Independent Tuning of Surface Plasmon Energy, Extinction Coefficient, and Scattering Cross Section

The future integration of plasmonic nanoparticles, such as gold nanorods (Au NRs), into applications requires the ability to tune the components of their optical properties to optimize performance for the underlying technology. Verifying techniques that model the resonance energy and associated extinction, scattering, and absorption cross sections necessitate experimental data from series of Au NRs where structural features are independently tuned. Here, the extinction cross section and scattering efficiency are presented for Au NR series with high compositional and structural purity where effective volume, aspect ratio, length, and diameter are independently varied by factors of 25, 3, 2, and 4, respectively. The extinction cross sections quantitatively agree with prior calculations, confirming that the volume of the rod is the dominant factor. Comparisons of the scattering efficiency however are less precise, with both quantitative and qualitative differences between the role of rod volume and aspect ratio. Such extensive experimental data sets provide a critical platform to improve quantitative structure–property correlations, and thus enable design optimization of plasmonic nanoparticles for emerging applications

Control over Position, Orientation, and Spacing of Arrays of Gold Nanorods Using Chemically Nanopatterned Surfaces and Tailored Particle-Particle-Surface Interactions

The synergy of self- and directed-assembly processes and lithography provides intriguing avenues to fabricate translationally ordered nanopartide arrangements, but currently lacks the robustness necessary to deliver complex spatial organization. Here, we demonstrate that interparticle spacing and local orientation of gold nanorods (AuNR) can be tuned by controlling the Debye length of AuNR in solution and the dimensions of a chemical contrast pattern. Electrostatic and hydrophobic selectivity for AuNR to absorb to patterned regions of poly(2-vinylpyridine) (P2VP) and polystyrene brushes and mats was demonstrated for AuNR functionalized with mercaptopropane sulfonate (MS) and poly(ethylene glycol), respectively. For P2VP patterns of stripes with widths comparable to the length of the AuNR, single- and double-column arrangements of AuNR oriented parallel and perpendicular to the P2VP line were obtained for MS-AuNR. Furthermore, the spacing of the assembled AuNR was uniform along the stripe and related to the ionic strength of the AuNR dispersion. The different AuNR arrangements are consistent with predictions based on maximization of packing of AuNR within the confined strip