No abstract

Mesoscale particles ranging from 2.3 μm down to 180 nm of dimethylammonium magnesium formate, DMMgF, are generated, and characteristics of the known solid–solid phase transition, in which dimethylammonium ions residing in cavities of the metal formate framework undergo an order–disorder transition, are investigated. Detected by powder X-ray diffraction, the mesoscale particles undergo the same solid–solid phase change characterized for bulk samples, but calorimetry measurements reveal that the phase transition temperature decreases in the reduced-size particles from 263 K for the bulk materials to 251 K for the 180 nm particles, while the thermal hysteresis associated with the transition increases as the particles become smaller. Despite the solid–solid phase change, the mesoscale particles are too small to detect the pyroelectric current observed for the bulk. Taken together, the changes with particle size point to the elastic framework distortion as the determinant of the phase transition temperature in DMMgF. Synthetic challenges associated with the isolation of reduced size particles, specifically the role of the kinetic product magnesium formate dihydrate, are described.