Study of L-pyroglutamic acid and elucidation of thermosalient effect

Termoodskočni materijali su materijali koji bi jednog dana mogli omogućiti pretvaranje termalne energije u mehanički rad na nanoskali. Grijanjem ili hlađenjem ove materijale dovodimo do naglih i oštrih polimorfnih faznih prijelaza s očuvanjem integriteta jediničnih kristala. U tom se procesu mijenja oblik kristala i veličina jedinične ćelije. Ta promjena je toliko intenzivna da kristali skaču na visine i do tisuću puta veće od njih samih. Trajanje ovog efekta je nekoliko mikrosekundi. Termoodskočni materijali imaju veliki diskontinuitet u promjeni volumena jedinične ćelije tijekom faznog prijelaza. Uočeno je da je piroglutaminska kiselina (eng. - pyroglutamic acid) ili skraćeno PGA termoodskočni materijal. Za potrebe ovog rada proučavana je L-PGA, kiralna forma PGA. Ispitivani su visokotemperaturni fazni prijelazi α → β i β → α. Naša mjerenja su potvrdila rezultate prijašnjih istraživanja. Tijekom faznih prijelaza kristali PGA skaču u zrak, uz očitu promjenu vanjskih dimenzija.Thermosalient materials are materials which in future could enable us to transform thermal energy to mechanical work at nanoscale. We bring these materials to sudden polymorphous ”monocrystal to monocrystal” phase transitions by heating or cooling them. Shape of the crystal and size of the unit cell are changed in that process. That change is so intense that crystals jump to the heights thousand times higher then themselves. This effect usually happens in a matter of miliseconds. Thermosalient materials have a great discontinuity in the unit cell change in volume during the phase transition. It was noticed that pyroglutamic acid or PGA is a thermosalient material. In this study L-PGA, chiral form PGA was investigated. We have examined high temperatures phase transitions α → β i β → α. Our measurements confirmed the results of previous studies. During phase transitions the crystals of PGA jump in the air with obvious change in overall size