The synthesis of high molecular weight star-shaped polymers comprising poly(1,3-cyclohexadiene) arms coupled to a divinylbenzene (DVB) core is reported. In-situ FTIR spectroscopy was used to verify first-order polymerization kinetics for 1,3-cyclohexadiene at 40 °C in cyclohexane with a 10 wt % monomer concentration using a tetramethylethylenediamine (TMEDA) to n-butyllithium (n-BuLi) ratio of 5/4. The propagation rate constant was determined to be 0.31 L mol-1 s-1. The degree of 1,2-addition (70%) vs 1,4-addition (30%) for 1,3-cyclohexadiene was determined using 1H NMR spectroscopy. The molecular weights of the preformed arms were 10 000 and 5000 g/mol, and the ratio of DVB to n-BuLi was systematically varied from 6:1 to 24:1. Gel permeation chromatography coupled with light scattering detection was utilized to detect the formation of star-shaped polymers and the presence of star−star coupling. In-situ spectroscopy and obvious color changes indicated that the addition of DVB to poly(1,3-cyclohexadienyllithium) was rapid. The molecular weight distribution (M w/M n) of the star polymers ranged from 1.4 to 1.9. The polymeric materials were thermally stable to 330 °C under a nitrogen environment. The refractive indices of both the homopolymers and star polymers were 1.572 at 600 nm and remained relatively constant from 1600 to 550 nm. The T g of the high molecular weight star-shaped polymers was 150 °C.

Adsorption of a model nitrogen vapor on a range of complex nanoporous carbon structures is simulated by grand canonical Monte Carlo simulation for a single subcritical temperature above the bulk freezing point. Adsorption and desorption isotherms, heats of adsorption, and three-dimensional singlet distribution functions (SDFs) were generated. Inspection of the SDFs reveals significant levels of solidlike adsorbate at saturation even in the most complex of the microporous solids considered. This strongly suggests that solidlike adsorbate will also occur for simple subcritical vapors adsorbed on real noncrystalline solids such as microporous carbons at temperatures above the bulk freezing point, supporting indirect experimental observations. The presence of significant levels of solidlike adsorbate has implications for characterization of microporous solids where adsorbate density is used (e.g., determination of pore volume from loading). Detailed consideration of the SDF at different loadings for a model microporous solid indicates solidlike adsorbate forms at distributed points throughout the pore space at pressures dependent on the nature of the local porosity. The nature of the local porosity also dictates the freezing mechanism. A local freezing/melting/refreezing process is also observed. Introduction of mesoporosity into the model causes hysteresis between the adsorption and desorption isotherms. Adsorption in the hysteresis loop occurs by a series of local condensation events. It appears as if the presence of adjacent microporosity and/or adsorbate within it affects the pressure at which these events occur. Reversal of the condensation during desorption occurs throughout the mesoporosity at a single pressure; this pressure is unaffected by the presence of adjacent microporosity or the adsorbate within it. It is also shown that the empirical concept of “pore size” is not consistent for describing adsorption in the complex solids considered here. A new concept is, therefore, proposed that seeks to account for the factors that affect local adsorption energy:  local geometry, microtexture, surface atom density, and surface chemistry.

Poly(1,3-cyclohexadiene) (PCHD) derivatives were synthesized via facile chemical modification reactions of the residual double bond in the repeat unit. The oxidation and degradation of PCHD was investigated to enable subsequent controlled epoxidation reactions. PCHD exhibited a 15% weight loss at 110°C in the presence of oxygen. The oxidative degradation, demonstrated by gel permeation chromatography (GPC) and 1 H NMR spectroscopy, was attributed to main-chain scission. Aldehyde and ether functional groups were introduced into the polymer during the oxidation process. PCHD was quantitatively epoxidized in the absence of deleterious oxidation with meta-chloroperoxybenzoic acid. 1 H and 13 C NMR spectroscopy confirmed that polymers with controlled degrees of epoxidation were reproducibly obtained. Epoxidized PCHD exhibited a glass-transition temperature at 154°C, which was slightly higher than that of a PCHD precursor of a nearly equivalent molecular weight. Moreover, GPC indicated the absence of undesirable crosslinking or degradation, and the molecular weight distributions remained narrow. The thermooxidative stability of the fully epoxidized polymer was compared to that of the PCHD precursor, and the epoxidized PCHD exhibited an initial weight loss at 250°C in oxygen, which was 140°C higher than the temperature for PCHD.

The design and use of microporous solids depends on having access to characteristics such as the pore volume and surface area. Comparison methods such as the alpha(s) method are one of the most widely used means of determining these parameters. An assessment of this group of methods was undertaken by comparing estimates obtained from them using adsorption isotherms generated by grand canonical Monte Carlo simulation on a selection of model nanoporous solids with exactly known surface areas and pore volumes. Conclusions are drawn from this absolute assessment in regard to the validity of the alpha(s) method for determining the micropore volume, the mesopore surface area, and the separation of pore groups based on the concept of primary and cooperative filling, the subtracting pore effect (SPE) method, and the required character of the reference surface.

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A series of poly(1,3-cyclohexadiene-alt-styrene)-containing block copolymers that exhibited predictable molecular weights and narrow molecular weight distributions were synthesized with various 1,3-cyclohexadiene contents (13-57 mol %). In situ FTIR spectroscopy in combination with the Mayo-Lewis graphical method was employed to determine the reactivity ratios for the anionic copolymerization of styrene and 1,3-cyclohexadiene. The reactivity ratios for 1,3-cyclohexadiene and styrene were 0.022 and 0.024, respectively, which indicated the formation of an alternating copolymer. The alternating copolymers served as suitable precursors for chemical modification and were either quantitatively aromatized or hydrogenated in a controlled fashion. The thermal stabilities of the modified copolymers were determined, and as expected, the hydrogenated copolymers exhibited improved thermal stability compared to that of poly(1,3-cyclohexadiene-alt-styrene)-containing block copolymers. However, the aromatized copolymers unexpectedly exhibited reduced thermal stability in both nitrogen and oxygen environments due to the introduction of labile benzylic hydrogens in the repeating unit.

Unmanned aerial vehicle (UAV) control stations feature multiple menu pages with systems accessed by keyboard presses. Use of speech-based input may enable operators to navigate through menus and select options more quickly. This experiment examined the utility of conventional manual input versus speech input for tasks performed by operators of a UAV control station simulator at two levels of mission difficulty. Pilots performed a continuous flight/navigation control task while completing eight different data entry task types with each input modality. Results showed that speech input was significantly better than manual input in terms of task completion time, task accuracy, flight/navigation measures, and pilot ratings. Across tasks, data entry time was reduced by approximately 40% with speech input. Additional research is warranted to confirm that this head-up, hands-free control is still beneficial in operational UAV control station auditory environments and does not conflict with intercom operations and intra-crew communications.