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Advances in Nanoscale Infrared Spectroscopy to Explore Multiphase Polymeric Systems
Published on: June 23, 2023
Hydrostatic pressure effect on the phase transitions of a closed-loop type block copolymer by using 2D FTIR
Hye Jeong Kim1, Seung Bin Kim, Jin Kon Kim
1National Creative Research Center for Block Copolymer Self-Assembly, Department of Chemical Engineering, Department of Chemistry, Pohang University of Science and Technology, Kyungbuk 790-784, Korea.
The Journal of Physical Chemistry. B
|November 4, 2008
Summary
Hydrostatic pressure shrinks the phase transition loop in polystyrene-block-poly(n-pentyl methacrylate) copolymer. Block chain mobility shifts with temperature and pressure, influencing disorder-to-order and order-to-disorder transitions.
Area of Science:
- Polymer science
- Materials science
- Physical chemistry
Background:
- Polystyrene-block-poly(n-pentyl methacrylate) copolymer (PS-b-PnPMA) exhibits complex phase behavior.
- Understanding pressure effects on copolymer phase transitions is crucial for materials design.
Purpose of the Study:
- To investigate the impact of hydrostatic pressure on the phase transitions of PS-b-PnPMA.
- To elucidate the relationship between pressure, temperature, and block chain dynamics.
Main Methods:
- Fourier-transform infrared (FTIR) spectroscopy was employed.
- Experiments utilized a specialized low-pressure ( <100 bar) high-resolution ( ~1 bar) pressure cell.
- Phase transitions were studied across a range of temperatures.
Main Results:
- Increasing hydrostatic pressure reduces the size of the closed loop encompassing both lower disorder-to-order (LDOT) and upper order-to-disorder (UODT) transitions.
- At lower temperatures, polystyrene (PS) chains move before poly(n-pentyl methacrylate) (PnPMA) chains due to restricted PnPMA mobility from alkyl side chain clustering.
- At higher temperatures, PnPMA chains exhibit greater mobility than PS chains due to larger specific volumes.
Conclusions:
- The LDOT is primarily influenced by favorable interactions between PS and PnPMA blocks, driven by alkyl side chain clustering.
- The UODT is mainly governed by combinatorial entropy.
- Hydrostatic pressure significantly alters the phase transition behavior and block chain dynamics in PS-b-PnPMA copolymers.
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