We used differential scanning calorimetry (DSC) to study the effect of confinement on the glass transition temperature (T-g) of poly(methyl methacrylate) (PMMA) nanotubes supported in anodic aluminum oxide (AAO) templates. We created nanotubes by wetting templates with polymer melts and developed a design equation relating tube thickness (t(tube)) with bulk radius of gyration (R-g): (t(tube) approximate to 2 R-g + 9 nm). The results indicate that t(tube) depends on overall conformation and size of the polymer coils and can be tuned at the nanoscale by polymer molecular weight. The T-g of AAO template-supported PMMA nanotubes increases with decreasing t(tube), with T-g,T-tube - T-g,T-bulk = 12 K in 18-nm-thick nanotubes; we attribute the T-g increase to hydrogen bonds between PMMA ester side groups and hydroxyl groups on the surface of the gamma-Al2O3 templates. Using ellipsometry, we characterized T-g-confinement effects for PMMA films supported on Si/SiOx, sputtered Al2O3 and sapphire (alpha-Al2O3). Films supported on substrates with higher concentrations of surface hydroxyl groups (alpha-Al2O3 > sputtered-Al2O3 > Si/SiOx) exhibit larger T-g-confinement effects. The DSC-determined T-g enhancements for nanotubes supported in gamma-Al2O3 templates fall between the ellipsometry-determined T-g enhancements determined for PMMA films on alpha-Al2O3 and those for films on sputtered-Al2O3. These results show that molecular weight provides for tunability of polymer nanotube thickness in AAO templates, that there is excellent agreement in confinement effects measured by DSC and by ellipsometry, and that T-g can be tuned by modulating the levels of interfacial, polymer-substrate interactions by using surfaces with different chemical or crystallographic properties. (C) 2015 Elsevier Ltd. All rights reserved.