The hierarchical surface structure of polymer materials leads to unique properties which are of both academic and commercial interest. In this work we explore the ability to replicate the well-defined surface structure of anodic aluminum oxide (AAO) templates by in situ polymerization of methyl methacrylate. When the reaction is conducted inside the templates, the rate of polymerization was significantly higher and molecular weight was reduced, as compared to the reaction in bulk. These observations were explained using a mathematical model to describe the polymerization based on free-volume theory and confinement effects. As the dimensions of the template are reduced, a catalytic effect on the rate of initiator decomposition leads to a faster polymerization rate in the early stages of polymerization. In addition, due to the confined reaction volume, the rate of termination is increased in the latter stages of the reaction. The two confinement effects combine to lead to lower molecular weight polymers of reduced dispersity in comparison to the reaction conducted in bulk.