Ferroelectric Compounds Containing Amino-Acid Groups

Several ferroelectric compounds are known to contain glycine, diglycine and triglycine groups, some of them ferroelectric at room temperature and above, some of them ferroelectric only below room temperature. Glycine is of course the simplest aminoacid with the standard aminoacid structure NH2-CH(R)-CO.OH with R H, a simple hydrogen atom. Another amino-acid, -alanine, has been used as dopant in tryglycine sulfate to improve its properties as pyroelectric detector and energy converter. For the time being, no other aminoacids are known as components of ferroelectric systems, but the possibility that such amino-acid containing compounds is realized cannot be completely discarded. A systematic investigation is presented of the known glycine containing ferroelectrics and it is found that the elementary dipole moment for tryglycine compounds is about 3 debye (1 debye = 10- 18 esu. cm) for tryglycine compunds, 1 debye for diglycine compounds and 0.5 debye for glycine compounds with comparable elementary dipole densities for all tri-glycine, di-glycine and single glycine compounds examined.