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Master thesis (Wenxuan Zhou).pdf (2.77 MB)

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Stoichiometry and Crystal Structure of Poly (Lactic Acid) (PLA) Stereocomplex (SC) in Cold-crystallization and Solution-grown Crystals as Studied by Solid-state NMR and 13C Isotope Labeling

Zhou, Wenxuan
http://rave.ohiolink.edu/etdc/view?acc_num=akron1522239647112751

Abstract Details

2018, Master of Science, University of Akron, Polymer Science.
Poly(L-Lactic Acid) (PLLA)/Poly(D-Lactic Acid) (PDLA) forms thermodynamically stable stereocomplex (SC). Stoichiometry and packing structure of PLLA/PDLA SC has been a debatable issue. In this study, both stoichiometry and packing structure of 13C labeled PLLA (l-PLLA) / non-labeled PDLA blends at mixing ratios of 7/3 - 3/7 were elucidated by using Solid-State (SS) NMR. The 13C carbonyl (CO) signals in natural abundance determined relative fractions of SC, a, and amorphous regions of l-PLLA/PDLA blends. The 33% methyl group (CH3) labeled PLLA was synthesized via ring-opening polymerization. Thereby, the intensity of 13C CH3 signal of l-PLLA is higher by 30 times than that of PDLA in natural abundance. Therefore, the CH3 signals could determine relative fractions of l-PLLA in the SC and amorphous regions. Comparisons of these two independent signals allow us to determine the stoichiometry of PLLA/PDLA = 1/1 in SC irrespective of mixing ratios. Moreover, this method could elucidate stoichiometry of PLLA/PDLA in the amorphous region. By comparisons of experimental and simulated Double Quantum (DQ) curves based on R3c (R3 ¯ c) or P3 model, it was concluded that all SC crystals adopt R3c (R3 ¯ c) packing structure.
Toshikazu Miyoshi (Advisor)
Mesfin Tsige (Committee Member)
Materials Science; Polymer Chemistry; Polymers

Recommended Citations

Citations

  • Zhou, W. (2018). Stoichiometry and Crystal Structure of Poly (Lactic Acid) (PLA) Stereocomplex (SC) in Cold-crystallization and Solution-grown Crystals as Studied by Solid-state NMR and 13C Isotope Labeling [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1522239647112751

    APA Style (7th edition)

  • Zhou, Wenxuan. Stoichiometry and Crystal Structure of Poly (Lactic Acid) (PLA) Stereocomplex (SC) in Cold-crystallization and Solution-grown Crystals as Studied by Solid-state NMR and 13C Isotope Labeling. 2018. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1522239647112751.

    MLA Style (8th edition)

  • Zhou, Wenxuan. "Stoichiometry and Crystal Structure of Poly (Lactic Acid) (PLA) Stereocomplex (SC) in Cold-crystallization and Solution-grown Crystals as Studied by Solid-state NMR and 13C Isotope Labeling." Master's thesis, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1522239647112751

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Akron and OhioLINK.