Fourier Self-Deconvolution Analysis of Hydrogen Bonding States of Polyvinylpyrrolidone in an Amorphous Sugar Matrix Below and Above the Glass Transition Temperature

ABSTRACT

In an amorphous mixture of sugar and polyvinylpyrrolidone (PVP), PVP carbonyl groups form hydrogen bonds with sugar hydroxyl groups, thereby improving the physical stability of the amorphous matrix against a glass-to-rubber transition. Herein, Fourier self-deconvolved IR bands due to the C=O stretching vibration of PVP in sugar–PVP mixtures were analyzed. The C=O groups in sugar–PVP mixtures generally had four vibrational states, corresponding with free and hydrogen-bonded C=O in three different modes. Changes in these vibrational states induced by increasing the temperature were compared among various sugar–PVP mixtures. Formation and thermal disruption characteristics of different modes of sugar–PVP hydrogen bondings are discussed.

KEYWORDS:

• amorphous sugar
• carbonyl stretching vibration
• fourier self-deconvolution
• glass transition temperature
• polyvinylpyrrolidone

ACKNOWLEDGMENT

This work was supported by grant-in-aid for the Encouragement of Young Scientists (no. 18760594) from the Ministry of Education, Science, Sport and Culture of Japan and by the Okayama Foundation for Science and Technology.

Notes

^a The increase in Tg [R _Tg (−)] was normalized as follows^{[ 4 ]}:

where Tg^mix, Tg^sugar, and Tg^PVP are the Tg values for the sugar–PVP mixture, sugar alone, and PVP alone, respectively. Tg^PVP = 180°C.^{[ 4 ]}

^b Deviations of the peak position were within ±1 cm⁻¹.