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Effects of nanoscopic-confinement on polymer dynamics.
Kiriaki Chrissopoulou1, Spiros H Anastasiadis
1Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, P. O. Box 1527, 711 10 Heraklion Crete, Greece. spiros@iesl.forth.gr.
Soft Matter
|April 15, 2015
Summary
Polymer dynamics change significantly under nanoconfinement in layered silicates. While local motions of linear polymers are unaffected, segmental relaxation speeds up and occurs below the glass transition temperature due to reduced cooperativity.
Area of Science:
- Polymer Science
- Materials Science
- Nanotechnology
Background:
- Polymer behavior near interfaces differs from bulk properties.
- Intercalated nanocomposites with thin polymer films offer unique insights into nanoconfinement effects.
- Layered silicates provide a model system for studying polymers under severe confinement.
Purpose of the Study:
- To review research on polymer dynamics under severe confinement in intercalated nanocomposites.
- To investigate the influence of nanoconfinement on both polar and non-polar polymers, as well as hyperbranched polymers.
- To compare polymer dynamics in confined systems with their bulk counterparts.
Main Methods:
- Utilizing quasielastic neutron scattering (QENS) and dielectric relaxation spectroscopy (DRS).
- Preparing intercalated nanocomposites with varying polymer types (polar, non-polar, hyperbranched) and silicate surface properties (hydrophilic, organophilic).
- Analyzing local sub-Tg processes and segmental alpha-relaxation dynamics.
Main Results:
- Distinct differences in local and segmental dynamics were observed between bulk and confined polymers.
- Confinement did not alter very local motion in linear chains but facilitated it in hyperbranched polymers.
- Segmental relaxation in confined systems was faster than in bulk, showed Arrhenius behavior, and occurred below the bulk glass transition temperature (Tg).
Conclusions:
- Severe nanoconfinement significantly alters polymer dynamics, particularly segmental relaxation.
- Reduced cooperativity in confined systems leads to faster segmental relaxation and a depression of the glass transition.
- The architecture of polymers (linear vs. hyperbranched) influences their response to confinement, especially concerning local motions and hydrogen bonding.
