Characterizing polymorphism and crystal transformation of polylactide by terahertz time-domain spectroscopy. (February 2017)

• Record Type: Journal Article
• Authors: Li, Han; Ye, Hai-Mu; Yang, Yuping
• Is Part Of: Polymer testing. Volume 57(2017)
• Page Start: 52
• Page End: 57
• Publication Date: 2017-02
• Subjects: Terahertz time-domain spectroscopy -- Polylactide -- Crystal transformation -- Stereocomplex; Polymers -- Testing -- Periodicals; Polymères -- Tests -- Périodiques; 620.1920287
• DOI: 10.1016/j.polymertesting.2016.11.017
• Languages: English
• ISSNs: 0142-9418

Abstract

Abstract: Terahertz time-domain spectroscopy (THz-TDS), which has been proved to show promising application in complex polymer systems, was employed to investigate the polymorphism phenomenon and crystal transformation of polylactide (PLA) in this study. The THz-TDS shows sensitive response on the crystal structure. The α' -form, α -form and stereocomplex crystals exhibit absorption peaks of lattice vibration at 1.82, 2.01 and 2.09 THz, respectively. THz-TDS has no direct chirality identification on the difference between poly (d -lactide) (PDLA) and poly(l -lactide) (PLLA). However, the PLA stereocomplex shows an extra and distinctive absorption peak at 1.43 THz compared with homo-PLA, and the peak was proved to be stemmed from the collective vibration of L-lactic unit and D-lactic unit pairs connecting by hydrogen bonds. This is the first time that THz-TDS has been proved to be of great potential in identification of polymer stereocomplex crystal. Also, the α' → α crystal transformation of PLA were intuitively investigated at 120 °C using THz-TDS, while the transformation rate was quite slow.