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

Autor:	Xiaoyu Wang, Daniel J. Sandman, Samuel P. Gido, Shujun Chen
Rok vydání:	2008
Předmět:	Thermochromism Materials science Polymers and Plastics Stereochemistry Organic Chemistry Analytical chemistry Crystal structure Inorganic Chemistry Crystal Differential scanning calorimetry Nanocrystal Electron diffraction Transmission electron microscopy Materials Chemistry Polydiacetylenes
Zdroj:	Macromolecules. 41:773-778
ISSN:	1520-5835 0024-9297
DOI:	10.1021/ma070820x
Popis:	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.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::31413e44d3f033e06499d404950c5e6a https://doi.org/10.1021/ma070820x Zobrazit plný text záznamu