Publications

Influence of cross-link density on the thermal properties of thin polymer network films

Lenhart, Joseph L.; Wu, Wen I.

X-ray reflectivity was used to characterize the thermal expansion of thin cross-linked polymer films. Changing the molecular mass of the hardener varied the cross-link density of the network. When the smaller-molecular-mass hardener was used, no changes in the apparent glass transition temperature (CTE) were observed in the thin films. When the larger-molecular-mass hardener was used, a transition from bulk to confined expansion occurred near 200 Å, where thinner films exhibit smaller rubbery expansion coefficients. For the lower cross-link density network, the thermal expansion behavior of the films was independent of the substrate surface treatment.