Stable dispersions of nanofibers are virtually unknown for synthetic polymers. They can complement analogous dispersions of inorganic components, such as nanoparticles, nanowires, nanosheets, etc as a fundamental component of a toolset for design of nanostructures and metamaterials via numerous solvent-based processing methods. As such, strong flexible polymeric nanofibers are very desirable for the effective utilization within composites of nanoscale inorganic components such as nanowires, carbon nanotubes, graphene, and others. Here stable dispersions of uniform high-aspect-ratio aramid nanofibers (ANFs) with diameters between 3 and 30 nm and up to 10 μm in length were successfully obtained. Unlike the traditional approaches based on polymerization of monomers, they are made by controlled dissolution of standard macroscale form of the aramid polymer, i.e. well known Kevlar threads, and revealed distinct morphological features similar to carbon nanotubes. ANFs are successfully processed into films using layer-by-layer (LBL) assembly as one of the potential methods of preparation of composites from ANFs. The resultant films are transparent and highly temperature resilient. They also display enhanced mechanical characteristics making ANF films highly desirable as protective coatings, ultrastrong membranes, as well as building blocks of other high performance materials in place of or in combination with carbon nanotubes.

Natural nanowires (NWs) of cellulose obtained from a marine animal tunicate display surprisingly high uniformity and aspect ratio comparable with synthetic NWs. Their layer-by-layer assembled (LBL) films show strong antireflection (AR) properties having an origin in a novel highly porous architecture reminiscent of a "flattened matchsticks pile", with film-thickness-dependent porosity and optical properties created by randomly oriented and overlapping NWs. At an optimum number of LBL deposition cycles, light transmittance reaches nearly 100% (lambda approximately 400 nm) when deposited on a microscope glass slide and the refractive index is approximately 1.28 at lambda = 532 nm. In accordance with AR theory, the transmittance maximum red-shifts and begins to decrease after reaching the maximum with increasing film thickness as a result of increased light scattering. This first example of LBL layers of cellulose NWs can be seen as an exemplary structure for any rigid axial nanocolloids, for which, given the refractive index match, AR properties are expected to be a common property. Unique mechanical properties of the tunicate NWs are also a great asset for optical coatings.

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Composite thin films containing cellulose nanocrystal (cellN) polyanions embedded between either poly(diallyldimethylammonium chloride) (PDDA) or chitosan were fabricated using the layer-by-layer (LBL) deposition technique. The in-plane and out-of-plane elastic constants of the composites were measured using Brillouin light scattering as a function of film thickness and cellulose content. Compared to the pure cast polymer films, the addition of cellN raises the elastic constants within the growth plane by a factor of 2 and 3 for [chitosan/cellN] and [PDDA/cellN] films, respectively, while in the growth direction the elastic constant increases by 50% for [PDDA/cellN] and not at all for [chitosan/cellN]. With increasing amounts of cellN in the films, the stiffness increases in the growth plane at a higher rate than in the growth direction. These trends reflect the contribution of the cellulose nanocrystals within and cross layers to load transmission. The results are interpreted in terms of processes that occur during film deposition and the resulting spatial arrangements of the nanocrystals.

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In this study, the cure kinetics of dicyclopentadiene was investigated using a combination of inelastic light scattering measurements and molecular-scale simulations. Concurrent Brillouin and Raman scattering served to monitor the structural evolution of the curing network as a function of time, both in terms of network connectivity and the concentration of chemical species present. Density functional theory calculations were used to interpret the measured Raman spectra. Comparison of the measured elastic moduli as a function of the degree of cure with those of structures generated using reactive molecular dynamics simulations provides insight into the reaction mechanism. An unexpected dependence of the reaction rate on the catalyst concentration was found.

The cure kinetics of dicyclopentadiene was investigated using a combination of inelastic light scattering measurements and molecular-scale simulations. Concurrent Brillouin and Raman scattering served to monitor the structural evolution of the curing network as a function of time, both in terms of network connectivity and the concentration of chemical species present. Density functional theory calculations were used to interpret the measured Raman spectra. Comparison of the measured elastic moduli as a function of the degree of cure with those of structures generated using reactive molecular dynamics simulations provide insight into the reaction mechanism. An unexpected dependence of the reaction rate on the catalyst concentration was found.