Chowdhury M, Monnier X, Cangialosi D, Priestley RD. Decoupling of Glassy Dynamics from Viscosity in Thin Supported Poly(
n-butyl methacrylate) Films.
ACS POLYMERS AU 2022;
2:333-340. [PMID:
36267547 PMCID:
PMC9576260 DOI:
10.1021/acspolymersau.2c00010]
[Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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We utilized fast
scanning calorimetry to characterize the glass
transition temperature (Tg) and intrinsic
molecular mobility of low-molecular-weight poly(n-butyl methacrylate) thin films of varying thicknesses. We found
that the Tg and intrinsic molecular mobility
were coupled, showing no film thickness-dependent variation. We further
employed a unique noncontact capillary nanoshearing technique to directly
probe layer-resolved gradients in the rheological response of these
films. We found that layer-resolved shear mobility was enhanced with
a reduction in film thickness, whereas the effective viscosity decreased.
Our results highlight the importance of polymer–substrate attractive
interactions and free surface-promoted enhanced mobility, establishing
a competitive nanoconfinement effect in poly(n-butyl
methacrylate) thin films. Moreover, the findings indicate a decoupling
in the thickness-dependent variation of Tg and intrinsic molecular mobility with the mechanical responses (shear
mobility and effective viscosity).
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