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The influences of channel size and structure on the molecular dynamics of polyethylene at 300K have been studied using the inclusion complex of n;tetracontane with perhydrotriphenylene. The diameter of the channel in the real physical system is enlarged by 1 or2 A to provide alternative sizes.rhe content ofgauche (G) states rises from almost nil in the real physical channel to a value in the channel enlarged by 2 A that is nearly half of the result seen with the free unperturbed chain.The population of G*TG+ triplets is much larger than the population of G*TG* triplets (T denotes the trans state).Translation of the center of mass along the channel shows that I-tetracontane senses the molecular structur? of the perhydrotriphenylene in the walls when the channel is enlarged by 1 A, but not when the channel is enlarged by 2 A. Rotation of the n-tetracontane as a rigid body about its long axis is primarily responsible for the decay of the orientation autocorrelation functions for the C-C and C-H bonds.

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The adsorption of diblock copolymers from a nonselective solvent onto a surface that attracts one of the two blocks has been simulated on a cubic lattice. The simulation uses periodic boundary conditions in two directions and places the surface at the edges of the box in the third direction. The diblock copolymers are ANABNB with 6≤NA≤20 and 10≤NB≤30, where A is the anchoring block and B does not adsorb. This report describes the adsorption isotherms and the kinetics of adsorption in the simulation. Good approximations to a Langmuir adsorption isotherm are observed only at small values of NA and the adsorption energy per segment. The kinetics observed in the isotherm has an initial stage that depends on √I, followed by a second stage that depends on [1−exp(−I/constant)], where I is the number of iterations. These results are in agreement with expectations based on previous experimental and theoretical results in the situation. The internal structure of the adsorbed layer is addressed in the following paper.

The formation and the structure of a polymer thin film have been studied by molecular dynamics simulations. A poly(l,4-trans-butadiene) chain with a degree of polymerization of 180 and terminated by methyl groups was initially constructed so that all dihedral angles at the skeletal bonds are in the tram state. The model film, exposed to vacuum on both sides, was formed by a transition of the fully extended chain to a coil at a temperature of 300 K, with the use of periodic boundary conditions in two dimensions. A collapse transition of the extended chain to a globule was also simulated as a comparison. Simulations have been performed for a duration of 1500 ps. The conformations of the chains in the film and in the globule were examined. The collapse process of the chains can be divided into two regions for the transition to both the coil and the globule. In the first region the chain size shows a dramatic drop, while in the second region it decreases slowly with fluctuations. The density near its center of mass is close to the bulk density of amorphous poly(l,4-trans-butadiene). The coil that is the parent chain for the film exhibits a very loose structure, and its density at the center of mass is close to zero. The radius of gyration for the coil from the simulation is very close to the estimated value from rotational isomeric state theory. The local density of the film follows a sigmoidal profile at the free surfaces. The maximum thickness of the polymer/vacuum interface is about 10 A, as judged by the density profile. The backbone bonds exhibit a tendency for parallel orientation in the vicinity of the free surfaces. The trans conformation is favored in the equilibrium distribution of the dihedral angles at the CHz-CHz bonds within the film.