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The special mechanical properties of natural rubber originate from the stretching of the network chains (i.e., cis‐1,4‐polyisoprene chains) in the rubber network. The chains with various lengths exhibit various relative extensions, leading to various normalized energy contributions to the mechanical properties of rubber. However, the stretching behaviors of cis‐1,4‐polyisoprene chains with different lengths are not studied clearly. Here, the stretching behavior, which is the basis for analyzing the normalized energy contribution, is obtained by the modified freely jointed chain model. Next, using a new statistical model, i.e., the two‐component quantum‐mechanics Gaussian (TCQMG) model, the relative extension–length relationship of network chains is determined. Combining the above results, the energy contributions of network chains with different lengths are analyzed. The results show that long and short chains show different stretching states. The following can be explained by these results: short chains play an important role in the mechanical properties of rubber. As the network chain density increases, the average length of the chains decreases, leading to the variation of the normalized extensions. It is found that the variation of the normalized extensions is responsible for both the effects of the network chain density and network chain length on the mechanical properties of rubber. [ABSTRACT FROM AUTHOR]

Bitumen, a vital component in asphalt mixtures for road construction, confronts persistent challenges stemming from traffic loads and temperature fluctuations, leading to issues such as permanent deformation, fatigue, and thermal cracking, ultimately jeopardizing road safety. A promising solution involves enhancing asphalt mixture performance through asphalt binder modifiers, including biopolymer materials. Among these, non-petroleum-based biodegradable polymers, such as natural rubber and natural oil, stand out as viable options in highway engineering. This comprehensive review commences by introducing various biopolymeric materials, delving into their types, sources, and processing methods. Their interaction mechanism with bitumen is also discussed. Subsequently, it summarizes the production of bio-advantaged polymer-modified bitumens and mixtures. The study meticulously analyzes the rheological and chemo-mechanical properties of biopolymer-modified bitumens and underscores their mixture performances. Finally, the economic and environmental sustainability of the biopolymer-based bitumens was also evaluated. Natural rubbers enhance rutting, fatigue, thermal cracking, aging resistance, and moisture resistance in bitumen or mixtures, but do increase viscosity, which reduces workability. Natural oils improve fatigue, thermal cracking, and aging resistance without impacting rutting or moisture susceptibility in bitumen or mixtures. Biopolymer-modified asphalt presents the potential to reduce annual maintenance expenses while promoting sustainable road construction. To satisfy road pavement applications, cup lump rubber and extraction oil can be utilized. To further advance this field, future research should focus on utilizing more advanced biopolymers through innovative optimization and interaction mechanisms with other modifiers (e.g., epoxidation and polymerization) to render asphalt mixtures both economical and environmentally friendly without compromising their performance. [ABSTRACT FROM AUTHOR]