The Relationship between Pendant Phosphate Groups and Mechanical Properties of Polyisoprene Rubber
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ARTICLE
POLYMER SCIENCE
https://doi.org/10.1007/s10118-021-2497-z Chinese J. Polym. Sci.
The Relationship between Pendant Phosphate Groups and Mechanical Properties of Polyisoprene Rubber Shi-Qi Li, Mao-Zhu Tang, Cheng Huang, Rong Zhang, Guang-Su Huang*, and Yun-Xiang Xu* College of Polymer Science & Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, China.
Electronic Supplementary Information Abstract It is still a great challenge to mimic the structure and function of natural rubber by introducing polar components into synthetic polyisoprene. In order to explore the function of phosphate groups on the mechanical properties of polyisoprene rubber, a terminally functionalized compound (PIP-P) containing phosphate groups was synthesized and further vulcanized to prepare the model compound V-PIP-P. Through analyzing the test results, it was found that these phosphate groups formed polar aggregates in non-polar polyisoprene rubber matrix, serving as an additional dynamic cross-linking sites, which increases the cross-linking density and improves mechanical properties. The influence of the phosphate groups on the strain-induced crystallization (SIC) was further investigated via synchrotron wide-angle X-ray diffraction (WAXD) experiment. These phosphate group aggregates not only reduced the onset strain of SIC, but also slowed down the molecular chain mobility, which hinder the crystal lateral growth. The above results help us to gain a deeper understanding for the function of phosphate groups in the formation of “naturally occurring network” and guide the molecular design of next generation polyisoprene rubber. Keywords Phosphate groups; Strain-induced crystallization; Naturally occurring network; Natural rubber Citation: Li, S. Q.; Tang, M. Z.; Huang, C.; Zhang, R.; Huang, G. S.; Xu, Y. X. The relationship between pendant phosphate groups and mechanical properties of polyisoprene rubber. Chinese J. Polym. Sci. https://doi.org/10.1007/s10118-021-2497-z
INTRODUCTION Natural rubber (NR) is widely applied in daily life and industry due to its outstanding comprehensive properties.[1] However, due to the constraints of geographical location and climatic conditions, the supply-demand relationship of NR in some regions is seriously unbalanced. Under this circumstance, synthetic cis-1,4 polyisoprene rubber (PIP) is considered to be the most promising alternative to NR because of its similar molecular chain structure. Previous scholars have done a lot of work to mimic the structure and function of NR by PIP. Unfortunately, the comprehensive properties of PIP were still inferior to NR. As widely recognized, it is attributed to the nonrubber components of NR.[2] Previous studies have revealed that the αterminal and ω-terminal of NR are connected to phospholipids and proteins, respectively, forming a “naturally occurring network”. This natural network has a strong enhancement effect on the strain-induced crystallization (SIC) behavior and greatly improves the m
