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Surface interaction parameter measurement of solvated polymers via model end-tethered chains
Richard J Sheridan1, Sara V Orski1, Ronald L Jones1
1Material Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD.
Macromolecules
|October 4, 2017
Summary
Researchers developed a direct method to measure polymer-surface interactions. They found that polymer affinity for the surface decreases as temperature increases, impacting polymer behavior in different solvents.
Area of Science:
- Polymer Science
- Surface Chemistry
- Thermodynamics
Background:
- Understanding polymer-surface interactions is crucial for materials science and nanotechnology.
- Existing methods often rely on indirect measurements or complex modeling.
- Direct measurement of interaction energy provides fundamental insights into polymer behavior at interfaces.
Purpose of the Study:
- To develop and validate a direct method for measuring the relative interaction energy between solvated polymers and solid interfaces.
- To investigate the temperature dependence of polymer-surface interactions.
- To estimate key thermodynamic parameters governing polymer-interface systems.
Main Methods:
- Covalently tethering linear polymer chains to a solid surface to ensure a constant molecular configuration.
- Direct measurement of interaction energy using a novel experimental approach.
- Utilizing spectroscopic techniques for precise measurements in deuterated solvents (cyclohexane-d12, toluene-d8).
Main Results:
- Successfully estimated the Flory-Huggins interaction parameter (χ) for polystyrene in cyclohexane-d12 across a temperature range of 10.7 °C to 52.0 °C.
- Observed a decrease in the χ parameter with increasing temperature, crossing the χ = 0.5 threshold (indicating a transition from poor to good solvent conditions) between 37 °C and 40 °C.
- Estimated the surface interaction parameter (χs), revealing a temperature-dependent decrease in polymer chain affinity for the surface.
- Demonstrated qualitative changes in χ and χs in a stronger solvent (toluene-d8) with increasing temperature, indicating enhanced solvency and reduced surface interaction.
Conclusions:
- The developed method allows for direct and accurate measurement of polymer-surface interaction energies.
- Temperature significantly influences polymer solvency and surface interactions, with increasing temperature generally favoring weaker surface binding.
- The findings provide valuable data for designing and optimizing polymer-based materials for specific interfacial applications.
