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Electronic relaxation dynamics of PCDA-PDA studied by transient absorption spectroscopy
Joonyoung F Joung1, Junwoo Baek1, Youngseo Kim1
1Department of Chemistry, Korea University, Seoul 136-701, Korea. spark8@korea.ac.kr.
Physical Chemistry Chemical Physics : PCCP
|August 6, 2016
Summary
Photo-curable polymers, polydiacetylenes (PDAs), show reversible color changes with temperature up to 60°C. Above this, heating causes irreversible structural changes due to H-bond breaking, altering their optical properties.
Area of Science:
- Materials Science
- Polymer Chemistry
- Spectroscopy
Background:
- Polydiacetylenes (PDAs), such as those derived from 10,12-pentacosadiynoic acid (PCDA-PDA), are known for their photo-curable properties.
- PCDA-PDA exhibits thermochromism, changing color from blue to red with increasing temperature.
Purpose of the Study:
- To investigate the temperature-dependent optical properties of PCDA-PDA.
- To elucidate the mechanisms behind its reversible and irreversible thermochromic transitions.
- To correlate structural changes with observed optical property variations.
Main Methods:
- UV-visible absorption spectroscopy
- FTIR and Raman spectroscopy
- Transient absorption (TA) spectroscopy
- Quantum chemical calculations
Main Results:
- PCDA-PDA shows reversible thermochromism up to 60 °C, becoming irreversible above this temperature.
- Transient absorption spectroscopy revealed different electronic relaxation pathways for the blue (20 °C) and red (80 °C) forms.
- FTIR, Raman, and computational studies confirmed that hydrogen bonds break at higher temperatures, causing irreversible structural changes.
Conclusions:
- The study details the reversible and irreversible thermochromic behavior of PCDA-PDA.
- Electronic relaxation dynamics and structural changes, specifically H-bond disruption, are key to understanding PCDA-PDA's thermochromism.
- These findings offer insights into designing PDAs with tunable optical properties for various applications.
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