Effects of pressure and temperature on the kinetics of L-lactide polymerization in supercritical chlorodifluoromethane

Ji Won Pack, Soo Hyun Kim, Soo Young Park, Youn Woo Lee, Young Ha Kim

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The ring-opening polymerization of L-lactide initiated by 1-dodecanol/stannous 2-ethylhex-anoate (DoOH/Sn(Oct)2) was carried out in supercritical chlorodifluoromethane at pressures ranging from 180 to 360 bar and at temperatures ranging from 100 to 130°C. Increasing the pressure resulted in an accelerated polymerization rate. The activation volume for [DoOH]0/[Sn]0 = 0 was determined to be -50 cm 3/mol. The partial bond formation in the transition state contributed to the negative value of the activation volume and the pressure-induced acceleration in the rate of L-lactide polymerization, i.e., by producing a four-center transition state and a lower partial molar volume. A further stabilization of the transition state in terms of the activation volume of-61 cm3/mol by the use of DoOH ([DoOH]0/[Sn]0 = 1.0) can be explained by sterically crowded transition state. A computational study using semiempirical methods showed the transition state is subject to weak electrostriction effects. The observed activation energy (88.7 kJ/mol), which is higher than that in bulk, reflects a partial blocking of the active coordinate site by chlorodifluoromethane.

Original languageEnglish
Pages (from-to)3564-3568
Number of pages5
JournalMacromolecules
Volume37
Issue number10
DOIs
Publication statusPublished - 2004 May 18

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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