Mechanical Properties and Swelling Behaviors of Ultrathin Chemically Cross-Linked Polybutadiene Films

With the advancement of nanoscience and nanotechnology,understandingthe unique mechanical properties of ultrathin polymer films is becomingincreasingly important. We report the mechanical properties and swellingbehaviors of ultrathin chemically cross-linked polybutadiene films.Upon reducing the film thickness, the Young's modulus increased,and an unusual stress-relaxation behavior was observed. After stressrelaxation, the fully relaxed modulus was significantly higher thanthat expected from the amount of added cross-linker and the entanglementdegree. The out-of-plane swelling of the ultrathin films preparedon a substrate was comparable to that in the bulk, whereas the in-planeswelling of films floating on water was significantly suppressed.Such suppression of the in-plane deformation may be attributed tothe effects of interface-induced orientations of the chains and thechain segments trapped at the interfaces acting as pseudo-cross-linkingpoints. This study contributes to an understanding of the physicalproperties of ultrathin cross-linked elastomer films.

Automated summary

Understanding the mechanical properties and swelling behaviors of ultrathin polymer films is crucial in the field of nanoscience and nanotechnology. This study investigates the mechanical properties and swelling behaviors of ultrathin chemically cross-linked polybutadiene films. It was found that reducing the film thickness increased the Young's modulus and resulted in an unusual stress-relaxation behavior. Moreover, the in-plane swelling of films floating on water was significantly suppressed due to the effects of interface-induced orientations and trapped chain segments acting as pseudo-cross-linking points.