The recent interest in bent core liquid crystal has shown many unique physical properties, such the anomalous behaviour of the elastic constants (SplayK1, Twist K2, and BendK3). In bent core liquid crystals it is observed that K3K1). Such behaviour is analogous to calamitic liquid crystals but is in contrast to all other bent-core nematic materials reported to date. Such a result questions some of the current explanations for the elastic behaviour of bent-core materials. Using molecular field theory and atomistic modelling the different elastic behaviour predicted is again in excellent agreement with experimental results. The bend angle is again shown to be an important part in determining the physical properties of bent-core nematic liquid crystals. In a mixture from an oxadiazole dopant and calamitic host liquid crystal, it was found that a filament structure appears in the nematic phase. The filaments appear to interfere with the measurements for elastic constants. In order to understand the filament structure many methods were used including SAXS, dielectric permittivity, and DSC. It was found that the mixture had formed a gel - like phase. The gel is composed of a liquid crystal network and a liquid crystal background, not seen before in any gel system. Due to the liquid crystalline properties both the network and the background can be aligned and manipulated. The new gel phase can possess many new unique properties which warrant further studies understand further into how fundamentally the phase is forming.

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<p dir="ltr">Smart energetics are energetic materials (propellants, explosives, and pyrotechnics) with on/off capabilities or in real time modification of combustion behavior. Solid propellants are known for many positive qualities such as their simplicity and low cost but also their glaring lack of active burning rate control. Previous proposed methods of active control of solid propellants include pintle valve actuation and electronically controlled solid propellants, however there is a need for improved methods. Surface area modification is one proposed method and can be employed in real time to affect the burning behavior of solid propellants. To this end, derivations were conducted regarding a slot adjacent to a solid propellant strand and the pressure and slot width threshold conditions that allow for burning to occur inside of the adjacent slot. The derivations considered different modes of combustion (convective and conductive) and combustion threshold conditions. The derivations resulted in five equations that were curve fit to existing literature for validation resulting in high R squared values. A demonstration of the creation of an adjacent slot with a piezoelectric actuator, a mini case study of the adjacent slot proposal, and a discussion of methods to create an adjacent slot as well as the effect of propellant selection on convective burning in slots were all done to follow up on the promising results of the theoretical work. </p><p dir="ltr">Furthermore, flexoelectricity is the coupling between strain gradient and charge generation and has been considered to modify the combustion characteristics of energetic materials. This work measured the flexoelectric properties of polymers and their associated energetic composites including polyvinylidene fluoride (PVDF), micron aluminum (μAl)/PVDF, nano aluminum (nAl)/PVDF, poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)), nAl/P(VDF-TrFE), poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)), μAl/P(VDF-HFP), hydroxylterminated polybutadiene (HTPB), ammonium perchlorate (AP)/HTPB, μAl/AP/HTPB, polytetrafluoroethylene (PTFE), and polydimethylsiloxane (PDMS). The measurements made on PVDF, μAl/PVDF, P(VDF-TrFE), P(VDF-HFP), PTFE, and PDMS were all within or near to the range of measurements from the literature. Novel measurements were made on nAl/PVDF, nAl/P(VDF-TrFE), μAl/P(VDF-HFP), HTPB, AP/HTPB, and μAl/AP/HTPB. Additionally, the effect of porosity, particle additions (μAl, nAl, or AP), and manufacturing method (3D printing, casting, different 3D printers, etc.) on the flexoelectric performance of these samples was investigated. It was found that large pores (millimeter scale) added via the infill pattern of 3D printed PVDF and Al/PVDF samples decreased the effective flexoelectric effect relative to the near full density control samples. This contrasts with previous work showing that adding small (micron scale) pores increases the flexoelectric performance of various polymers and energetic materials. Mixed results were found with respect to the effect of particle additions (μAl, nAl, or AP) on the flexoelectricity of a variety of materials. This may be explained by the competing effect of particle additions adding extra local strain gradients which amplify flexoelectricity but also replace some polymer binder material (PVDF, P(VDF-TrFE), P(VDF-HFP), and HTPB) with the particle additions (μAl, nAl, and AP) which are typically less flexoelectric. Our work demonstrates that manufacturing method does affect the flexoelectric properties of polymers and energetic composites. Lastly, our flexoelectric measurements of P(VDF-HFP) and PTFE may help explain accidents related to Magnesium-Teflon®-Viton® (MTV) flare systems that have, in many cases, been attributed to electrostatic discharge.</p>

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