Factors influencing additive interactions with calcium hydrogenphosphate dihydrate crystals

The effect of aspartic acid, glutamic acid, hexaammonium tetrapolyphosphate , calcium phytate, and polyaspartic acid on calcium hydrogenphosphate dihyd rate (CaHPO4. 2H(2)O, DCPD) crystal growth morphology was studied. The mech anism of additive-DCPD crystal interaction depends on the size and structur e of the additive molecule and the structural fit between the organic molec ule and the ionic structure of particular crystal face. Small molecules wit h low charge (aspartic and glutamic acid) do not have a significant effect, whereas small molecules with several functional groups (citrate and hexaam monium tetrapolyphosphate) adsorb on lateral faces primarily by electrostat ic interactions. Molecules with hindered structures (phytate) and macromole cules (polyaspartic acid) specifically adsorb on the dominant (010) face, f or which a certain degree of structural fit is necessary.