An Order–Disorder Transition in the Conjugated Polymer MEH-PPV
作者： Anna Köhler , Sebastian T. Hoffmann , Heinz Bässler
DOI: 10.1021/JA302408A
关键词: Chemical physics 、 Spectral line 、 Chemistry 、 Entropy (order and disorder) 、 Exciton 、 Stereochemistry 、 Phase transition 、 Fluorescence 、 Polymer 、 Ground state 、 Conjugated system
摘要: The poly(p-phenylene vinylene) derivative MEH-PPV is known to exist as two morphologically distinct species, referred red phase and blue phase. We show here that the transition from a critical phenomenon can be quantitatively described second order with temperature Tc of 204 K. criticality associated trade-off between gain in electronic stabilization energy when π-system planarized chain delocalize concomitant loss entropy. studied this by measuring absorption fluorescence methyltetrahydrofuran (MeTHF) different concentrations function temperature. spectra were analyzed based upon Kuhn exciton model extract effective conjugation lengths. At room temperature, chains have lengths about five repeat units ground state (the phase), consistent disordered defect cylinder conformation. Upon ...
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