Enhanced Interfacial Bonding of Graft Copolymers

Area of Science:

• Polymer Science
• Materials Science
• Computational Chemistry

Background:

• Thermoplastic welding is crucial for advanced manufacturing.
• Controlling weld strength through polymer architecture is an ongoing challenge.
• Understanding molecular mechanisms of polymer welding is essential for material design.

Purpose of the Study:

• To investigate how chemical modifications and macromolecular topology influence thermoplastic welding strength.
• To elucidate the molecular dynamics governing polymer diffusion and interdigitation at interfaces.
• To correlate simulation findings with experimental observations of polymer weld behavior.

Main Methods:

• Coarse-grained molecular dynamics (MD) simulations of linear and graft polymers.
• Analysis of polymer diffusion dynamics and interdigitation across interfaces.
• Experimental validation using lap-shear tests on linear and grafted polyethylene elastomers.

Main Results:

• Grafting density inversely affects the power law exponent of diffusion-controlled interdigitation (0.34 to 0.11).
• Bottlebrush polymers exhibit faster welding to maximum strength but lower saturated strength than linear polymers.
• Grafted side chains promote welding via entropic van der Waals contacts, in addition to entanglement dilution.
• Molecular topology dictates rupture behavior: brittle for linear/comb-like, elastomeric for bottlebrush polymers.
• Polymer deformation rate relative to strain rate is topology-dependent, impacting mechanical response.

Conclusions:

• Macromolecular topology is a key factor in tuning thermoplastic weld strength and mechanical properties.
• Bottlebrush polymer architecture offers a route to enhanced welding efficiency and controlled deformation behavior.
• Findings provide insights into topological polymer welding mechanisms and interface anisotropy mitigation for additive manufacturing.