Thermochromic Polydiacetylene Micro- and Nanocrystals:  An Unusual Size Effect in Electronic Spectra

Abstract

Micro- and nanoscale crystals of the thermochromic polydiacetylenes (PDAs) ETCD and PUDO exhibit electronic absorption maxima at wavelengths longer than those observed in bulk crystal specimens of the same materials. This observation is in contrast to the reported behavior of PDA−DCH where the absorption maximum shifts to shorter wavelengths as crystal size decreases. Infrared spectra and X-ray powder data indicate that the small crystals have the same composition and a structure similar to the bulk specimens. Differential scanning calorimetry (DSC) reveals a larger endothermic heat of the thermochromic phase transition in the small crystals vs bulk specimens. The crystal morphology and structure of microsized, nanosized, and bulk crystals of PDA−ETCD and PDA−PUDO were studied by transmission electron microscopy (TEM) and electron diffraction (ED). For both PDAs, no drastic changes in lattice parameters were observed as crystal size decreases from bulk to micro- and nanoscale.

Tuning of Thermochromic Properties of Polydiacetylene toward Universal Temperature Sensing Materials through Amido Hydrogen Bonding

“…Interestingly, with longer linkers like butylene and hexylene, PDA sols prepared from BA-2DA and HA-2DA showed a new absorption maximum at curiously longer wavelength of over 675 nm, along with the usual absorption bands around 620 and 575 nm. The three absorption peaks including the one at 675 nm observed here is quite different from the recently reported observation of long wavelength absorption caused by the crystal size effect . It is also important to note here that, with the same starting concentration of the monomeric lipids, the polymers obtained from BA-2DA and HA-2DA show the deepest blue color.…”

“…The three absorption peaks including the one at 675 nm observed here is quite different from the recently reported observation of long wavelength absorption caused by the crystal size effect. 11 It is also important to note here that, with the same starting concentration of the monomeric lipids, the polymers obtained from BA-2DA and HA-2DA show the deepest blue color. The low-energy absorption and the highly intense blue color suggest either unusually high backbone strain or long conjugation length associated with superior packing of the long aliphatic linkers between the amide groups.…”

Фотохромно-Термохромные Системы С Отрицательным Хромизмом

“…Превосходные термохромные свойства проявляют полидиацетилены ПДА 1 и ПДА 2 (рис. 18) [60][61][62][63].…”

Reversible Micro- and Nano- Phase Programming of Anthraquinone Thermochromism Using Blended Block Copolymers

“…However such highly tunable materials have been difficult to design. Fabrication of nano and microcrystals have been studied to determine the intermediate states between the molecules and bulk crystals owing to their characteristic properties 27 . Nanostructured materials have been studied extensively and microcrystals are used in practical applications such as in semiconductors 28 and pharmaceuticals 29 .…”

“…Fabrication of nano and microcrystals has been studied to determine the intermediate states between the molecules and bulk crystals owing to their characteristic properties. 27 Nanostructured materials have been studied extensively and microcrystals are used in practical applications such as in semiconductors 28 and pharmaceuticals. 29 However, relatively few studies have reported reversible transitions between micro and nano structured particles for thermochromism.…”