TY - JOUR
T1 - Poly(methyl methacrylate) nanotubes in AAO templates
T2 - Designing nanotube thickness and characterizing the Tg-confinement effect by DSC
AU - Tan, Anthony W.
AU - Torkelson, John M.
N1 - Funding Information:
This work made use of the EPIC facility (NUANCE Center-Northwestern University), which has received support from the MRSEC program (NSF DMR-1121262) at the Materials Research Center, the International Institute for Nanotechnology (IIN), and the State of Illinois, through the IIN. We also thank Lanhe Zhang for conducting NMR experiments regarding tacticity for this study.
Funding Information:
This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. ( DGE-0824162 ). Any opinion, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.
Publisher Copyright:
© 2015 Elsevier Ltd. All rights reserved.
PY - 2016/1/15
Y1 - 2016/1/15
N2 - We used differential scanning calorimetry (DSC) to study the effect of confinement on the glass transition temperature (Tg) 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 (ttube) with bulk radius of gyration (Rg): (ttube2Rg+ 9 nm). The results indicate that ttube depends on overall conformation and size of the polymer coils and can be tuned at the nanoscale by polymer molecular weight. The Tg of AAO template-supported PMMA nanotubes increases with decreasing ttube, with Tg,tube Tg,bulk= 12 K in 18-nm-thick nanotubes; we attribute the Tg increase to hydrogen bonds between PMMA ester side groups and hydroxyl groups on the surface of the α-Al2O3 templates. Using ellipsometry, we characterized Tg-confinement effects for PMMA films supported on Si/SiOx, sputtered Al2O3 and sapphire (α-Al2O3). Films supported on substrates with higher concentrations of surface hydroxyl groups (α-Al2O3 sputtered-Al2O3 Si/SiOx) exhibit larger Tgconfinement effects. The DSC-determined Tg enhancements for nanotubes supported in α-Al2O3 templates fall between the ellipsometry-determined Tg enhancements determined for PMMA films on α- 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 Tg can be tuned by modulating the levels of interfacial, polymer-substrate interactions by using surfaces with different chemical or crystallographic properties.
AB - We used differential scanning calorimetry (DSC) to study the effect of confinement on the glass transition temperature (Tg) 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 (ttube) with bulk radius of gyration (Rg): (ttube2Rg+ 9 nm). The results indicate that ttube depends on overall conformation and size of the polymer coils and can be tuned at the nanoscale by polymer molecular weight. The Tg of AAO template-supported PMMA nanotubes increases with decreasing ttube, with Tg,tube Tg,bulk= 12 K in 18-nm-thick nanotubes; we attribute the Tg increase to hydrogen bonds between PMMA ester side groups and hydroxyl groups on the surface of the α-Al2O3 templates. Using ellipsometry, we characterized Tg-confinement effects for PMMA films supported on Si/SiOx, sputtered Al2O3 and sapphire (α-Al2O3). Films supported on substrates with higher concentrations of surface hydroxyl groups (α-Al2O3 sputtered-Al2O3 Si/SiOx) exhibit larger Tgconfinement effects. The DSC-determined Tg enhancements for nanotubes supported in α-Al2O3 templates fall between the ellipsometry-determined Tg enhancements determined for PMMA films on α- 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 Tg can be tuned by modulating the levels of interfacial, polymer-substrate interactions by using surfaces with different chemical or crystallographic properties.
KW - AAO template synthesis
KW - Polymer nanotubes
KW - T-confinement effect
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U2 - 10.1016/j.polymer.2015.11.054
DO - 10.1016/j.polymer.2015.11.054
M3 - Article
AN - SCOPUS:84949579942
VL - 82
SP - 327
EP - 336
JO - Polymer
JF - Polymer
SN - 0032-3861
ER -