A new method for measuring of molecular mobility in glassy materials has been developed using terahertz spectroscopy. The absorption level of amorphous drugs at terahertz frequencies below Tg correlates with the stability of the drug as an amorphous solid. The molecular mobility responsible for the glass crystallisation significantly decreases at around a universal value of 0.67 Tg. This explains why the commonly used rules of thumb for glasses to remain stable below 0.8 Tg or Tg – 20 K do not work reliably.
These results reveal a unique and completely novel opportunity to predict and test the stability of amorphous drugs by measuring the molecular mobility below the glass transition temperature of drugs and formulations at terahertz frequencies. It is not possible to measure this information using conventional dielectric spectroscopy due to the practical difficulties of measuring at low temperatures.
We are interested in meeting industrial contacts who would be willing to collaborate on developing this method further.
Visit http://thz.ceb.cam.ac.uk for more information of our group.