TY - JOUR
T1 - Thickness dependence of structural relaxation in spin-cast polynorbornene films with high glass transition temperatures (>613 K)
AU - Lewis, Elizabeth A.
AU - Vogt, Bryan D.
N1 - Funding Information:
This work was financially supported by the National Science Foundation under grant no. CMMI-1462284. The authors thank Promerus LLC (Brecksville, OH) for providing the polymers used in this study. They thank Mark Ediger, Connie Roth, and Sindee Simon for fruitful discussions and suggestions about the data presented herein.
Publisher Copyright:
© 2017 Wiley Periodicals, Inc.
PY - 2018/1/1
Y1 - 2018/1/1
N2 - The isothermal structural relaxation (densification) of a family of glassy polynorbornene films with high glass transition temperatures (Tg > 613 K) is assessed via spectroscopic ellipsometry. Three polymers were examined: poly(butylnorbornene) (BuNB), poly(hydroxyhexafluoroisopropyl norbornene) (HFANB), and their random copolymer, BuNB-r-HFANB. The effective aging rate, β(T), of thick (∼1.2 μm) spun cast films of BuNB-r-HFANB is approximately 10−3 over a wide temperature window (0.49 < T/Tg < 0.68). At higher temperatures, these polymers undergo reactions that more dramatically decrease the film thickness, which prohibits erasing the process history by annealing above Tg. The aging rate for thick BuNB-r-HFANB films is independent of the casting solvent, which infers that rapid aging is not associated with residual solvent. β (at 373 K) decreases for films thinner than ∼500 nm. However, the isothermal structural relaxation of thin films of BuNB-r-HFANB exhibits nonmonotonic temporal evolution in thickness for films thinner than 115 nm film. The thickness after 18 h of aging at 373 K can be greater than the initial thickness. The rapid aging of these polynorbornene films is attributed to the unusual rapid local dynamics of this class of polymers and demonstrates the potential for unexpected structural relaxations in membranes and thin films of high-Tg polymers that could impact their performance.
AB - The isothermal structural relaxation (densification) of a family of glassy polynorbornene films with high glass transition temperatures (Tg > 613 K) is assessed via spectroscopic ellipsometry. Three polymers were examined: poly(butylnorbornene) (BuNB), poly(hydroxyhexafluoroisopropyl norbornene) (HFANB), and their random copolymer, BuNB-r-HFANB. The effective aging rate, β(T), of thick (∼1.2 μm) spun cast films of BuNB-r-HFANB is approximately 10−3 over a wide temperature window (0.49 < T/Tg < 0.68). At higher temperatures, these polymers undergo reactions that more dramatically decrease the film thickness, which prohibits erasing the process history by annealing above Tg. The aging rate for thick BuNB-r-HFANB films is independent of the casting solvent, which infers that rapid aging is not associated with residual solvent. β (at 373 K) decreases for films thinner than ∼500 nm. However, the isothermal structural relaxation of thin films of BuNB-r-HFANB exhibits nonmonotonic temporal evolution in thickness for films thinner than 115 nm film. The thickness after 18 h of aging at 373 K can be greater than the initial thickness. The rapid aging of these polynorbornene films is attributed to the unusual rapid local dynamics of this class of polymers and demonstrates the potential for unexpected structural relaxations in membranes and thin films of high-Tg polymers that could impact their performance.
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U2 - 10.1002/polb.24434
DO - 10.1002/polb.24434
M3 - Article
AN - SCOPUS:85028813508
SN - 0887-6266
VL - 56
SP - 53
EP - 61
JO - Journal of Polymer Science, Part B: Polymer Physics
JF - Journal of Polymer Science, Part B: Polymer Physics
IS - 1
ER -