DSC studies on thermally induced structural transformation of hydrogen-bonded amphoteric molecular assemblage

D. Ishii, T. Yamada, M. Nakagawa, T. Iyoda, H. Yoshida

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Thermally induced structural transformation of fibrous hydrogen-bonded molecular assemblage formed from an amphoteric pyridinecarboxylic acid of 6-[2-propyl- 4-(4-pyridylazo)phenoxy]hexanoic acid (C5PR) was studied using differential scanning calorimetry (DSC), differential thermal analysis (DTA), and thermogravimetry (TG). The organized fibrous morphology formed in an aqueous solution was stable at temperatures below 150°C. The ordered crystalline solid phase (K1) of the original fibrous material altered to a disordered crystalline solid phase (K2) at 150°C and subsequently to an isotropic phase (I) at 172°C. In the isotropic state, the C5PR molecule was slowly decomposed by decarboxylation. Once the molecular assemblage was subjected to the mesophase by heating, another ordered crystalline solid phase (K3) appeared reversibly at 17°C. The heat budget analyses by DSC indicated that a conformational entropy change such as the side-chain propyl group and the main-chain pentamethylene unit in the hydrogen-bonded molecular assemblage took place between the two ordered crystalline solid phases K1 and K3.

Original languageEnglish
Pages (from-to)569-573
Number of pages5
JournalJournal of Thermal Analysis and Calorimetry
Volume81
Issue number3
DOIs
Publication statusPublished - 2005 Aug
Externally publishedYes

Keywords

  • Amphoteric compound
  • DSC
  • DTA
  • Decarboxylation
  • Fibrous material
  • Hydrogen bond
  • Liquid crystal
  • Structural transition
  • Supramolecular polymer
  • TG

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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