Molecular Weight Distribution of Lactic Acid Oligomer from the Polycondensation Without Catalyst and Its Application for the Starch Modification

Evi Triwulandari, Muhammad Ghozali, Witta Kartika Restu, Melati Septiyanti, Yulianti Sampora, Dewi Sondari, Yenni Apriliani Devi, Rista Siti Mawarni, Yenny Meliana, Mochamad Chalid

Research output: Contribution to journalArticlepeer-review

Abstract

The lactic acid oligomer was synthesized by varying the reaction time and processing it without a catalyst. Gel permeation chromatography (GPC) analysis was carried out to study the molecular weight distribution of lactic acid oligomers at different reaction times (4, 6, 8 and 24 h). The chromatogram of the lactic acid oligomer from 4 to 6 h showed three peaks, while 8 and 24 h showed two. In reaction times of 4 and 6 h, there were peaks from lactide (a cyclic dimer of lactic acid). When the reaction continued for 8 and 24 h, the lactide disappeared. The cyclic structure was cleaved, producing linear dimer lactic acid with an average molecular weight of 179 Da and 171 Da, respectively. The weight average molecular weight of the lactic acid oligomer increases with the reaction time. The highest weight average molecular weight was shown by the reaction time of 24 h, i.e., 680 Da. The 1HNMR and FTIR analyses were conducted to identify the structure of the lactic acid oligomer product. Furthermore, the lactic acid oligomer from the reaction time of 24 h was applied to modify starch. The modified starch was characterized by 1HNMR, FTIR, solubility, and TGA analyses.

Original languageEnglish
JournalJournal of Polymers and the Environment
DOIs
Publication statusAccepted/In press - 2023

Keywords

  • Distribution
  • Lactic acid
  • Modification
  • Molecular weight
  • Oligomer
  • Starch

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