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Surface-tethered chains entangled in a polymer melt: effects on adhesion dynamics.
S W Sides1, G S Grest, M J Stevens
1Sandia National Laboratories, Albuquerque, New Mexico 87185-1411, USA.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|December 12, 2001
Summary
Polymer-substrate adhesion depends on how tethered chains break or pull out. Longer chains lead to breakage, while lower temperatures shift this behavior towards chain pullout near entanglement length.
Area of Science:
- Polymer Science
- Materials Science
- Surface Chemistry
Background:
- Understanding polymer-substrate adhesion is crucial for material design.
- Chemically attached chains significantly influence interfacial properties.
- Adhesive failure mechanisms dictate material performance and durability.
Purpose of the Study:
- Investigate polymer melt adhesion to substrates with tethered chains.
- Analyze the impact of temperature, tethered chain density, length, and pull velocity on failure mechanisms.
- Determine the transition from chain pullout to chain scission.
Main Methods:
- Utilized extensive molecular dynamics simulations.
- Systematically varied parameters: temperature, tethered chain density (Sigma), tethered chain length (N(t)), and tensile pull velocity (v).
- Observed and analyzed adhesive failure modes: pullout and scission of tethered chains.
Main Results:
- A crossover from pure chain pullout to chain scission was observed with increasing tethered chain length (N(t)).
- The critical N(t) for this crossover decreased as temperature was lowered.
- Lower temperatures shifted the failure mechanism towards chain pullout.
Conclusions:
- Tethered chain length and temperature are key factors governing polymer-substrate adhesive failure.
- The entanglement length (N(e)) provides a relevant scale for failure transitions.
- Simulation results offer insights into designing robust polymer-substrate interfaces.