Fourier transform infrared (FTIR) and two-dimensional IR (2D-IR) spectroscopies were applied to polydimethylsiloxane (PDMS) cross-linked elastomer films. The vibrational probe for the systems studied was a silicon hydride mode that was covalently bound to the polymer chains. The structure and dynamics reported by this mode were measured in response to a wide range of chemical and physical perturbations, including elevated curing temperature, increased curing agent concentration, mechanical compression, and cooling to near the glass transition temperature. The FTIR spectra were found to be relatively insensitive to all of these perturbations, and 2D-IR spectroscopy revealed that this was due to the overwhelming influence of heterogeneity on the spectral line shape. Surprisingly, the deconvoluted spectral line shapes showed that there were only slight differences in the heterogeneous and homogeneous dynamics even with the drastic macroscopic changes occurring in different systems. In the context of modeling polymer behavior, the results confirm that dynamics on the ultrafast time scale need not be included to properly model PDMS elasticity.
|Original language||English (US)|
|Journal||Journal of Chemical Physics|
|State||Published - May 7 2021|
Bibliographical noteFunding Information:
The authors gratefully acknowledge partial support from the National Science Foundation under Grant Nos. CHE-0847356 and CHE-1464416 (to A.M.M.). C.M.O. was supported by a National Science Foundation Graduate Student Research Fellowship (Grant No. 00039202). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
© 2021 Author(s).
PubMed: MeSH publication types
- Journal Article