Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session A17: Dynamics of Glassy Polymers Under Nanoscale Confinement I
8:00 AM–11:00 AM,
Monday, March 14, 2022
Room: McCormick Place W-184BC
Sponsoring Units: DPOLY DSOFT DCP
Chair: Danielle Cangaliosi, University of the Basque Country
Abstract: A17.00012 : How Do End-Tethered Chains Alter the Local Glass Transition Temperature Next to Solid Substrates?
10:36 AM–10:48 AM
James H Merrill
James H Merrill
Connie B Roth
Grafted polymer chains are widely used for modifying interfacial interactions in polymer materials and nanocomposites, but the mechanisms by which the changes to material properties are conferred to the system are not well understood. Recently, our group demonstrated that end-tethered polystyrene (PS) chains with a molecular weight Mw = 100 kg/mol increased the local glass transition temperature Tg(z) of PS matrices by several decades and persisted out to distances of z = 100-125 nm away from the substrate interface [Huang, Roth, ACS Macro Lett. 2018, 7, 269]. Surprisingly, the largest local Tg(z=0) increase next to the substrate interface of +50 K above the bulk Tg of PS occurred for a very low grafting density of 0.011 chains/nm2, within the mushroom-to-brush transition regime. These results are puzzling because typically the glass transition in polymers is not associated with chain connectivity. We investigate this phenomenon further by studying the local glass transition temperature Tg(z=0) next to the substrate interface as a function of tethered chain length, end functional group, and grafting density to identify the underlying factors controlling this behavior. Good interpenetration between the grafted and matrix chains are central to creating an elevated Tg.
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