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首页> 外文期刊>The Journal of Chemical Physics >How far can a rubber molecule stretch before breaking? Ab initio studyof tensile elasticity and failure in single-molecule polyisopreneand polybutadiene
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How far can a rubber molecule stretch before breaking? Ab initio studyof tensile elasticity and failure in single-molecule polyisopreneand polybutadiene

机译：橡胶分子断裂前能延伸多远？从头开始研究单分子聚异戊二烯n聚丁二烯的拉伸弹性和破坏

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摘要

We present ab initio calculations of the internal C–C bond dissociation curve for single moleculesof (cis-1,4) polyisoprene and polybutadiene. We define "bond rupture" as that point on the reactioncoordinate where the unrestricted Kohn–Sham, or diradical, solution falls below the restricted, orclosed-shell, solution. Using this definition, we find that rupture occurs at a tensile force of 6.8 nNfor polyisoprene and 7.2 nN for polybutadiene. Their respective rupture strains are 45% and 42%.Our calculations show that the energy density versus extension is not sensitive to the number ofisoprene units contained in the molecule, i.e., it is essentially independent of the chain length. Theserelatively large rupture strains have important implications for understanding the failure mechanismin rubber, and imply that purely enthalpic chain stretching must commence well before tensilefailure occurs.
机译：我们提出了从头算的内部C–C键解离曲线，用于（cis-1,4）聚异戊二烯和聚丁二烯单分子。我们将“键断裂”定义为反应坐标上无限制的Kohn-Sham（即双自由基）解低于限制或闭壳解的点。使用该定义，我们发现，在聚异戊二烯的拉伸力为6.8 nN且聚丁二烯的拉伸力为7.2 nN的情况下发生破裂。它们各自的断裂应变分别为45％和42％。我们的计算表明，能量密度对延伸对分子中所含异戊二烯单元的数目不敏感，即，它基本上与链长无关。这些相对较大的破裂应变对理解橡胶的破坏机理具有重要意义，并且意味着纯焓链拉伸必须在拉伸破坏发生之前就开始。

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