Phase segregation of diblock copolymers in nanopore geometries

The self-assembly of a diblock copolymer melt in a confined regular geometry with a given pore size is studied using self-consistent field theory. For a particle in a polymer domain, we obtain the interaction potential as a function of the distance from the polymer interface. For a given concentration of particles of a certain size and separation, we find that microphase segregation is sensitive to the characteristic length scales of the geometry. In particular, novel polymer morphologies arise when the size of the pores and the distance between them are comparable to the diblock polymer radius of gyration Rg. Confinement can result in morphologies not allowed in the bulk. However, if the pore size is much larger than Rg, the effects are then limited to the vicinity of the pore surface

INVESTIGATION OF THE HYDROGEN STORAGE CAPACITY OF HYDRATES WITH MONTE CARLO SIMULATIONS

In the present work Grand Canonical Monte Carlo simulations are implemented in order to evaluate the hydrogen storage capacity of hydrates under a wide range of conditions. Hydrates of sII and sH type with or without promoter have been examined. Concerning hydrates of pure H2, our results show that sII hydrates can store up to 3.3 wt. % H2 and sH up to 3.6 wt. % in the pressure range examined (up to 500 MPa). The small cavities of the sII hydrate as well as the small and medium cavities of the sH hydrate are occupied by one H2 molecule at most. The occupancy of the large cavities of both types of hydrates highly depends on pressure. At 400 MPa, the average occupancy of the large cavity of the sII hydrate is 2.8 while the respective value for the sH hydrate is 5.5. Binary hydrates of H2 and promoter present a reduced H2 uptake (less than 1.1 wt. % for sII and less than 1.4 wt. % for sH hydrates). There rather limited values are attributed to the single occupancy of the cavities that are not occupied by the promoter molecules. Furthermore, the results of our simulations do not support the suggestion that the H2 uptake of the binary (sII) H2-THF hydrate can be “tuned” by adjusting the THF concentration in the equilibrium solution. Finally, binary sH hydrates with the promoter occupying the medium instead of the large cavities could be an alternative approach to increase hydrogen uptake.Non UBCUnreviewe

Storage of Methane in Clathrate Hydrates: Monte Carlo Simulations of sI Hydrates and Comparison with Experimental Measurements

Extensive grand canonical Monte Carlo simulations are performed for the calculation of the amount of methane gas that can be stored inside the hydrate structure sI focusing on temperature and pressure conditions that are of interest to practical applications (e.g., methane storage/transportation, methane hydrates in nature). Langmuir-type “absorption isotherms” are used in order to present the results for methane in the cages of the hydrate structure. In particular, the methane content inside the different type of hydrate cages is given as a function of pressure, where the parameters of this function are temperature-dependent. A comparison between available experimental data for cage occupancies and calculated values resulted in good agreement. The correlation between chemical potential and pressure is determined through <i>NVT</i> Monte Carlo simulations. Simulations are performed for the TIP4P/Ice water model and two methane models (United–Atom and All–Atom). The calculations of the current study can be utilized during the process of refining the estimates of methane gas “in-place”, in hydrate deposits, when pressure and temperature conditions at the hydrate reservoirs are known. A discussion on the implication to geologic media containing hydrates is also presented

Using clathrate hydrates for gas storage and gas-mixture separations: experimental and computational studies at multiple length scales

<p>Clathrate hydrates have characteristic properties that render them attractive for a number of industrial applications. Of particular interest are the following two cases: (i) the incorporation of large amounts of gas molecules into the solid structure has resulted in considering hydrates as possible material for the storage/transportation of energy or environmental gases, and (ii) the selective incorporation of guest molecules into the solid structure has resulted in considering hydrates for gas-mixture separations. For the proper design of such industrial applications, it is essential to know accurately a number of thermodynamic, structural and transport properties. Such properties can either be measured experimentally or calculated at different scales that span the molecular scale-up to the continuum scale. By using clathrate hydrates as a particular case study, we demonstrate that performing studies at multiple length scales can be utilised in order to obtain properties that are essential to process design.</p