Attenuated Total Reflection-Far-Ultraviolet Spectroscopy and Quantum Chemical Calculations of the Electronic Structure of the Top Surface and Bulk of Polyethylenes with Different Crystallinities.
Appl Spectrosc
; 75(8): 971-979, 2021 Aug.
Article
em En
| MEDLINE
| ID: mdl-33876981
ABSTRACT
In this study, we explored the electronic structure of the surfaces of polyethylene samples having different crystallinities using attenuated total reflection (ATR) far-ultraviolet (FUV) spectroscopy and quantum chemical calculations. Specifically, the ATR-FUV spectra of five types of high-density polyethylene (HDPE), six types of linear low-density PE (LLDPE), and seven types of low-density PE (LDPE) were obtained. All the spectra contained an intense band near 156 nm and a broad band between 180 and 190 nm. Transmission spectra were obtained for the thin-film (30 µm) PE samples between 165 and 250 nm. In this region, the HDPE films show very low-intensity bands. In contrast, the transmission spectra of the LLDPE and LDPE samples yielded weak-to-medium and medium-intensity bands around 180-190 nm, respectively. In addition, to understand the differences in the absorption spectra among the PEs observed, we simulated the spectra of n-pentane as a PE crystal model using time-dependent density functional theory and found that the common intense band at 156 nm is due to the σ (C(2p)-H)âRydberg 3s, 3p transition. The absorption bands near 180-190 nm may correspond to aggregates of numerous molecular chains in the amorphous parts of the LLDPE and LDPE samples.
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2021
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Article