The static properties of a homopolymer melt between energetically neutral walls are studied as a function of the degree of confinement (plate spacing) and polymer molecular weight. The cooperative motion lattice model is used and allows all calculations to be performed at full occupancy (i.e., at a volume fraction of 1); chain lengths varying from 384 to 24 are examined. Properties investigated include the magnitude of the end-to-end vector, the radius of gyration, and components of the end-to-end vector. In addition, orientation effects and the distribution of chain ends are also calculated. As the chains are confined, the end-to-end vectors align parallel to the walls beginning at a value of about twice the unconstrained value of the radius of gyration, regardless of the molecular weight. For values less than this, chain conformations are distorted and the magnitude of the average end-to-end vector and radius of gyration increase. The components of the end-to-end vector parallel and perpendicular to the walls are considered; in the cases of confinement, it is seen that there is a universal scaling relationship between the parallel component of the end-to-end vector and the plate spacing. The parallel component increases with the decreasing plate spacing according to approximately a one-sixth power (〈r 2〉∥ 1/2 ∼ L -1/6). Chain ends are most likely to be in the vicinity of one of the walls due to entropic constraints.

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Relative permittivity measurements of 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), 1,1,1,2,3,3-hexafluoropropane (HFC-236ea), and 1,1,1,3,3-pentafluorobutane (HFC-365mfc) in the liquid phase are reported. Measurements were performed by using a direct capacitance method at temperatures from 223 K to 303 K and pressures up to 16 MPa for HFC-227ea and HFC-236ea and at temperatures from 263 K to 303 K up to 16 MPa for HFC-365mfc. The uncertainty of the relative permittivity measurements is estimated to be better than ±1.1·10-2. The theory developed by Vedam et al., and adapted by Diguet, and the Kirkwood modification of the Onsager were applied to obtain the apparent dipole moment of HFC-227ea, HFC-236ea, and HFC-365mfc in the liquid state, found to be 2.356 D for HFC-227ea, 2.624 D for HFC-236ea, and 4.917 D for HFC-365mfc. The effective dipole in the liquid state of HFC-236ea predicted by the Kirkwood−Frölich theory is 2.065 D. Density functional and density functional self-consistent calculations (SCIPCM) of the electronic distribution and of the dipole moment are reported for HFC-227ea.

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