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A high-pressure gravimetric apparatus using a quartz spring for measuring solubility and diffusivity of CO2 in ionic liquids (ILs) was established for the first time. The time-dependent amounts of CO2 were recorded with a telescopic cathetometer and analyzed by using a one-dimensional diffusion model to obtain diffusion coefficients of CO2 in two ILs, namely, 1-n-butyl-3-methyl imidazolium hexafluorophosphate ([bmim][PF6]) and 1-butyl-3-methyl imidazolium tetrafluoroborate ([bmim] [BF4]) at pressures up to 10 MPa. Solubility data of CO2 in the two ILs up to 20 MPa were also obtained from its equilibrium masses and compared with those reported in the literature. The Peng–Robinson equation of state with the van der Waals one-fluid mixing rules was employed to correlate the experimental solubility data, revealing satisfactory calculation results. The measured diffusion coefficients of CO2 in [bmim][PF6] and [bmim][BF4] separately increase from 3.550 × 10–10 to 6.064 × 10–10 m2/s and from 7.184 × 10–10 to 9.880 × 10–10 m2/s following the pressure increase from 2.0 to 10.0 MPa at 323.2 K, while those at 5.0 MPa and different temperatures follow the Arrhenius equation, providing the diffusion activation energies of 25.53 and 20.30 kJ/mol for the [bmim][PF6]–CO2 and [bmim][BF4]–CO2 systems, respectively.

The effect of temperature, pressure, time, solid ionic liquid (SIL) mass (here, the SIL used is tetra-n-heptyl-ammonium bromide, abbreviated as THepAmBr), reuse of THepAmBr, type of SIL, and additives on the solid–gas (Ca(OH)2–CO2) carbonation system was investigated. Results showed that conversion increased as the temperature increased from 25.0 °C up to 50.0 °C and then decreased thereafter; but increased consistently with increasing pressure. Similarly, conversion increased as the mass of THepAmBr increased, leading to complete conversion at a THepAmBr/Ca(OH)2 mass ratio of 0.1:1 with the production of rhombohedral calcites. Stability tests revealed that THepAmBr was active and stable. The effect of BmimBr and BmimCl indicated that they gave conversions of >96%. Furthermore, studies on polymorphic control to aragonite gave interesting results: 30.2% aragonite was synthesized with MgCl2 and 54.7% with PEG6000. Moreover, time-dependent conversion showed that the reaction mechanism for the system was self-catalytic. Consequently, the reaction rate equation that was derived described the experimental conversion satisfactorily.

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In atomistic molecular dynamics simulations, alkane oligomers (C50 or C100) rapidly form an oriented interface when placed in contact with a crystal slab of stretched periodic polyethylene chains. The oriented atoms in this interface have a similar order parameter to those of nematic atoms. After a quench below the melting point, we show that this oriented "nematic" interface thickens from around two to three layers thick and crystalline order nucleates from this layer onto the crystal-slab surface and spreads as a two-dimensional patch. Once a crystal patch is large enough, the oriented interface above it advances by forming a stable nematic patch three layers above the crystal nucleus which grows and eventually nucleates a crystal patch within it. Simulation snapshots and mean-first-passage time (MFPT) results prior to reaching steady-state growth suggest that the nematic-to-crystal transition is rate-determining, as it is much slower than the thickening of the induced oriented interface. After steady state is established, the rate of crystallization of C100 at 360 K is determined roughly equally by the rates of nucleation and of spreading of a new crystal patch to the size large enough to propagate the nematic growth front. These findings, along with those of Bourque and Rutledge (Bourque, A. J.; Rutledge, G. C. Macromolecules 2016, 49, 3956−3964) contrast sharply with the stem-bystem growth assumed in the Hoffman−Lauritzen theory of secondary nucleation, with the work reported here indicating the importance of the oriented "nematic" layer in the propagation of the crystalline front.