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A Born–Green–Yvon integral equation approach is used to study the structure and phase behavior of a fluid of fused square-well-sphere dimers. We compute site–site distribution functions for dimers with bond lengths of L50.6s , 0.8s, and 1.0s ~where s is the hard-sphere diameter! and square-well diameters ranging from l51.25s to 2.0s over a wide range of… (More)

- J. Stephen Higgins, J . E . G . Lipson, Ronald P. White
- Philosophical transactions. Series A…
- 2010

Polymeric mixtures are important materials, but the control and understanding of mixing behaviour poses problems. The original Flory-Huggins theoretical approach, using a lattice model to compute the statistical thermodynamics, provides the basic understanding of the thermodynamic processes involved but is deficient in describing most real systems, and has… (More)

Recent observations using fluorophore probes of local dynamics in polymer films have provided new insight into the glass transition. Using a percolation model, we predict the local Tg in a polymer film, as a function of distance from a substrate or a free surface. Our predictions are in good agreement with the observed elevation of Tg near a substrate,… (More)

Using our simple lattice-based equation of state, we capture the effect of deuterium substitution in polystyrene (PS), predicting both the pure component melt properties and the remarkable shift in the coexistence curve when hPS is replaced by dPS in forming a blend with poly(vinyl methyl ether) (PVME). Taking advantage of a rare opportunity to compare with… (More)

In the companion paper to this we presented a quantitative theory for the suppression of the glass transition in a thin polymer film. Our Delayed Glassification (DG) model follows a proposal by de Gennes that free volume can be transmitted from surface to film interior via kinks transported along molecular strands or loops. In this paper we use the DG model… (More)

- Ronald P. White, J . E . G . Lipson
- Physical review. E, Statistical, nonlinear, and…
- 2011

We propose a new, simple, thermodynamically based model in order to study the effect of film thickness on the glass transition of a polymer. The model equation of state incorporates the effect of a free surface by accounting for missing interactions, and is parametrized using experimental data for bulk samples, leaving no freely adjustable parameters. To… (More)

- James A. Porter, J . E . G . Lipson
- The Journal of chemical physics
- 2005

We incorporate density dependence into continuum Born-Green-Yvon (BGY) theory through calculation of the end-to-end intramolecular correlation function. Whereas in previous studies we had only performed this calculation for the case of an isolated (zero-density) square-well chain of m segments (3</=m</=7), here we consider this single chain to have been… (More)

- Ronald P. White, J . E . G . Lipson
- The Journal of chemical physics
- 2009

In this work we compare lattice and continuum versions of the same theory, as derived in the previous paper (Paper I), to predict the behavior of simple alkane mixtures. In the course of doing this we use characteristic parameters obtained for the pure alkane fluids; no fits of mixture properties are involved. Our two sets of predictions are tested against… (More)

Suppression of the glass transition by some tens of degrees within a few tens of nanometers of a free surface in a polymer film is a technologically important, commonly observed, as-yet poorly understood phenomenon. We construct a quantitative theory of the influence of the free surface via transmission of “kinks” or “free volume” along the backbone of… (More)

Phase separation in mixtures of polymers and alkanes is investigated with the aid of a recently developed lattice model, based on the Born-Green-Yvon (BGY) integral equation approach to fluids. The system-dependent parameters of the BGY lattice model for binary mixtures are deduced from those of its pure components, which in turn are determined from a… (More)