Unusual Stress Upturn in Elastomers Prepared Using Macro Cross-Linkers with Multiple Vinyl Side Groups

Area of Science:

• Polymer Chemistry
• Materials Science
• Elastomer Engineering

Background:

• Traditional elastomers utilize divinyl cross-linkers, leading to predictable mechanical responses.
• Understanding and controlling elastomer properties at large deformations is crucial for advanced applications.

Purpose of the Study:

• To analyze the unique tensile properties of acrylate elastomers prepared with macro cross-linker polymers.
• To investigate the influence of macro cross-linker structure on elastomer mechanical behavior.
• To demonstrate a new method for tuning elastomer properties, especially at large deformation.

Main Methods:

• Synthesis of poly(ethyl acrylate) copolymers with hydroxy functional groups.
• Reaction of hydroxy groups with 2-isocyanatoethyl acrylate to form macro cross-linkers.
• UV polymerization of ethyl acrylate using the synthesized macro cross-linkers.
• Analysis of tensile properties using theoretical models.

Main Results:

• Elastomers exhibit small elongation properties similar to conventional elastomers.
• A significant difference in stress upturn at large elongations was observed compared to divinyl cross-linked elastomers.
• Stress upturn is tunable by altering the vinyl side group fraction in macro cross-linkers.
• Artificial inhomogeneity in cross-link density was identified, limiting chain stretchability.

Conclusions:

• Macro cross-linkers provide a new route to engineer elastomer mechanical properties.
• The method allows for precise control over stress-strain behavior at large deformations.
• This approach offers a pathway to develop advanced elastomers with tailored performance characteristics.