Deuterium oxide solutions of schizophyllan, a triple-helical polysaccharide, undergoing an order-disorder transition centered at 17℃, were studied by optical rotation (OR) and heat capacity (Cp) to elucidate the molecular mechanism of the transition and water structure in the solution and frozen states. The ordered structure at low temperature consisted of the side chains and water in the vicinity forming an ordered hydrogen-bonded network surrounding the helix core and was disordered at higher temperature. In the solution state appeared clearly defined transition curves in both the OR and Cp data. The results for three samples of different molecular weights were analyzed theoretically, treating this transition as a typical linear cooperative transition from the ordered to disordered states and explained quantitatively if the molecular weight polydispersity of the ample was considered. The excess heat capacity Cp EX defined as the Cp minus the contributions from schizophyllan and D2O was estimated. In the frozen state it increased with raising temperature above 150 K until the mixture melted. This was compared with the dielectric increment observed in this temperature range and ascribed to unfreezable water. From the heat capacity and dielectric data, unfreezable water is mobile but more ordered than free water. In the solution state, the excess heat capacity originates from the interactions of D2O molecules as bound water and structured water, and so forth. Thus the schizophyllan triple helix molds water into various structures of differing orders in solution and in the solid state.

Grand canonical Monte Carlo and configurational-bias Monte Carlo techniques were employed to simulate the adsorption of binary mixtures of C4-C7 alkane isomers in ISV and MOR zeolites at 300 K, and the results were compared to that in MFI. Unlike in MFI, the amount of adsorption of the linear and branched alkanes all increases with pressure increasing in ISV and MOR for 0.5-0.5 gas-phase mixtures. The location of alkane isomers is astatic, and it does not exhibit obvious orientation in ISV and MOR. The interaction energy of 2-methylpropane-zeolite is obviously higher than that of n-butane-zeolite in MFI. As to ISV and MOR, the interaction energy between 2-methylpropane and zeolite is a little lower than that between n-butane and zeolite. It can be found that the zeolite MFI behaves quite differently in adsorption from ISV and MOR.

Heat capacity of the halogen-bridged mixed-valence complex Pt2(dta)4I (dta) CH3CS2-) has been measured in the temperature region between 6 and 386 K. The complex exhibited a phase transition of order-disorder type at Ttrs) 373.4 K, from being arranged in an ordered helical form of four dta ligand planes around the central Pt-Pt axis to dynamically jumping between two orientations. Neither latent heat nor distinct thermal hysteresis was observed for the phase transition, suggesting that the phase transition is of higher-order rather than of first-order. The transition enthalpy and entropy were determined to be

The adsorption equilibria of ternary and quaternary mixtures of short linear alkanes, involving methane, ethane, propane, and n-butane, were simulated by using the configurational-bias Monte Carlo technique in grand canonical ensemble in MFI zeolite. The simulation results are in good agreement with the experimental data. The adsorption isotherms in MFI zeolite show that the longer chain component is preferentially adsorbed at low pressures. Its adsorption increases and then decreases as the pressure increases. But the shorter chain component is adsorbed at higher pressures and its adsorption increases as the pressure increases. The selectivity of ISV and MFI is much higher than that of MOR. The selectivity increases rapidly as the mole fraction of methane in the gas phase increases, but the change of selectivity of MOR is not obvious in an methane-ethane-propane mixture. The adsorbed amount in mixtures is in the order of ISV>MFI>MOR.

The density profiles and the diffusion behavior of fluid argon confined in micropores were studied by molecular-dynamics simulations. The effects of pore size width!, temperature and number density on the density profiles and the self-diffusion coefficients in micropores were simulated with pore widths from 0.6 to 4.0 nm. The density profiles are greatly affected by the pore size. Strong inhomogeneities in the channel direction and vapor-liquid phase separation in the micropores were observed when initial conditions were chosen in the coexistence region of the fluid. The self-diffusion coefficient in the channel direction in the pores was found to be much lower than in the bulk, and decreasing with decreasing pore size, decreasing temperature, and increasing density.