POS2-1209
Unexpected Two-step Crystallization Driven by Isolated In-chain Groups in Polyethylene
Topic
S2. High-End Characterization/Polymer Physics/Properties
When and Where
Sep 30, 2026
08:30 - 09:30
Room 301 (Grand Ballroom)
Session Chairs
Hae Jung SON
Boseok KANG
Presenter(s)
Nontarin Roopsung (Institute of Industrial Science, The University of Tokyo)
Co-Author(s)
Abstract
Polyethylene (PE) is a widely used commodity polymer. Its functions can be expanded while maintaining PE-like properties via in-chain functional groups. We previously synthesized PE with isolated carbonyl groups (PE-CO) for photodegradability,1 and converted them into amide groups (PE-CONH) to enhance mechanical strength.2 However, the effects of these in-chain groups on crystallization remain unclear. In this work, we investigate the crystallization of PE-CO and PE-CONH to clarify their roles during crystallization.
PE-CO and PE-CONH contained 2.3% and 1.3% in-chain groups, with Mn of 5900 and 6700, respectively. Crystallization behavior during cooling at a constant rate was investigated by using differential scanning calorimetry (DSC), infrared (IR) spectroscopy, and wide-angle/small-angle X-ray scattering (SAXS/WAXS). DSC revealed two exothermic peaks for both samples. Such a two-step crystallization is rarely seen in random copolymers. The higher- and lower-temperature peaks were assigned to region 1 and 2, respectively. WAXS exhibited the lattice constant b of PE crystal increased on cooling in region 2 for both samples. IR spectroscopy of PE-CONH revealed two non-hydrogen-bonded NH bands assigned to amide groups in crystalline (free NH I) and amorphous (free NH II) phases. In region 2, free NH II increased while free NH I decreased. By combining the results of DSC, IR, WAXS, and SAXS, we propose the mechanism of two-step crystallization in PE-CONH. The amide group was excluded from the PE crystals in region 1, whereas the loosely-packed crystals with inclusion of the amide groups were newly formed in region 2. The carbonyl group in PE-CO was more easily included in the PE crystals than the amide group in PE-CONH. These findings offer guideline for controlling crystallization of PE-derived materials with in-chain functional groups.
References
1) S. Tang et al., Angew. Chem. Int. Ed., 2021, 60, 26506.
2) Y. Lu et al., Angew. Chem. Int. Ed., 2024, 63, e202410849.
PE-CO and PE-CONH contained 2.3% and 1.3% in-chain groups, with Mn of 5900 and 6700, respectively. Crystallization behavior during cooling at a constant rate was investigated by using differential scanning calorimetry (DSC), infrared (IR) spectroscopy, and wide-angle/small-angle X-ray scattering (SAXS/WAXS). DSC revealed two exothermic peaks for both samples. Such a two-step crystallization is rarely seen in random copolymers. The higher- and lower-temperature peaks were assigned to region 1 and 2, respectively. WAXS exhibited the lattice constant b of PE crystal increased on cooling in region 2 for both samples. IR spectroscopy of PE-CONH revealed two non-hydrogen-bonded NH bands assigned to amide groups in crystalline (free NH I) and amorphous (free NH II) phases. In region 2, free NH II increased while free NH I decreased. By combining the results of DSC, IR, WAXS, and SAXS, we propose the mechanism of two-step crystallization in PE-CONH. The amide group was excluded from the PE crystals in region 1, whereas the loosely-packed crystals with inclusion of the amide groups were newly formed in region 2. The carbonyl group in PE-CO was more easily included in the PE crystals than the amide group in PE-CONH. These findings offer guideline for controlling crystallization of PE-derived materials with in-chain functional groups.
References
1) S. Tang et al., Angew. Chem. Int. Ed., 2021, 60, 26506.
2) Y. Lu et al., Angew. Chem. Int. Ed., 2024, 63, e202410849.
