Jump to main content
Jump to site search
PLANNED MAINTENANCE Close the message box

Scheduled maintenance work on Wednesday 22nd May 2019 from 11:00 AM to 1:00 PM (GMT).

During this time our website performance may be temporarily affected. We apologise for any inconvenience this might cause and thank you for your patience.

Issue 18, 2007
Previous Article Next Article

2H-solid state NMR and DSC study of isobutyric acid in mesoporous silica materials

Author affiliations


Solid state deuterium NMR has been used to study the molecular motion of d6-isobutyric acid (d6-iBA) in the pure (unconfined) state and confined in the cylindrical pores of two periodic mesoporous silica materials (MCM-41, pore size 3.3 nm and SBA-15, pore size 8 nm), and in a controlled pore glass (CPG-10-75, pore size ca. 10 nm). The line shape analysis of the spectra at different temperatures revealed three rotational states of the iBA molecules: liquid (fast anisotropic reorientation of the molecule), solid I (rotation of the methyl group) and solid II (no rotational motion on the time scale of the experiment). Transition temperatures between these states were determined from the temperature dependence of the fraction of molecules in these states. Whereas the solid I–solid II transition temperature is not affected by confinement, a significant lowering of the liquid–solid I transition temperature in the pores relative to the bulk acid was found for the three matrix materials, exhibiting an unusual dependence on pore size and pore morphology. Complementary DSC measurements on the same systems show that the rotational melting (solid I–liquid) of d6-iBA in the pores occurs at a temperature 20–45 K below the thermodynamic melting point. This finding indicated that the decoupling of rotational and translational degrees of freedom in phase transitions in confined systems previously found for benzene is not restricted to molecules with non-specific interactions, but represents a more general phenomenon.

Graphical abstract: 2H-solid state NMR and DSC study of isobutyric acid in mesoporous silica materials

Back to tab navigation

Supplementary files

Publication details

The article was received on 05 Dec 2006, accepted on 28 Feb 2007 and first published on 15 Mar 2007

Article type: Paper
DOI: 10.1039/B617744A
Phys. Chem. Chem. Phys., 2007,9, 2249-2257

  •   Request permissions

    2H-solid state NMR and DSC study of isobutyric acid in mesoporous silica materials

    A. Vyalikh, Th. Emmler, I. Shenderovich, Y. Zeng, G. H. Findenegg and G. Buntkowsky, Phys. Chem. Chem. Phys., 2007, 9, 2249
    DOI: 10.1039/B617744A

Search articles by author