Monte Carlo simulations of the effect of confinement geometry on the lowering of the glass transition temperature

Abstract An off lattice simulation of the effect of confinement geometry on the glass transition temperature has been conducted using Monte Carlo techniques. The resulting change in volume fraction of occupied space, a measure of density, is monitored to detect the glass transition temperature Tg. Simulations have been conducted on freely jointed polymer chains which have been spatially confined by one dimension (between parallel plates), by two dimensions (in a tube) and by three dimensions (in a sphere). For all three constraint environments the value of Tg decreases as the confining dimension decreases in length. The onset of the decrease occurs first when the confinement is three-dimensional (3D) and the magnitude of the effect is largest for 3D confinement. The effect occurs at values of the confining lengths in 3D confining spheres which are about 33% larger than the value for comparable effects in 2D (tubes) constraining systems. Similarly, the 2D tubes show constraint effects at larger values of the constraint length than 1D plates. The results agree with the trends observed in a recent experimental on the relative effects of constraint geometries.