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Structural Characterization of Segmented Polyurethanes by Small Angle Neutron Scattering

机译：小角度中子散射对嵌段聚氨酯的结构表征

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The beneficial mechanical properties of segmented polyurethanes derive from microphase separation of immiscible hard and soft segment-rich domains at room temperature. We are interested in the structure of the domains, how these are affected by hydrolytic aging, and how the structure is modified by low molecular weight plasticizers. To assessed the distribution of the plasticizer in polyurethane, we did small-angle neutron scattering measurements on mixtures of 23% hard segment poly(esterurethane) with different amounts of either non-deuterated or deuterated plasticizer. We analyzed the results using a simple model in which the contrast, Δ_ρ = ρ_H - ρ, between the hard and soft segment-rich domains is varied by the amount of deuterated or hydrogenated plasticizer, using the fact that I(Q) ～ ΔΔ~2. The result demonstrated that the plasticizer is largely associated with the soft segment rich domains. The structure of PESU with the chain extender of the hard segment was assessed after aging under hydrolytic conditions. The results show that the microphase structure coarsens and segregates and that the hard and soft segments segregated as a result of the loss of constraints from hydrolytic soft segment chain scission. The results on plasticizer distribution and the effects of hydrolytic aging give insight on the loss of mechanical properties that occur in each case.
机译：嵌段聚氨酯的有益机械性能源自室温下不混溶的富含硬链段和软链段的微区的微相分离。我们对这些域的结构，水解老化如何影响这些域以及低分子量增塑剂如何修饰该结构感兴趣。为了评估增塑剂在聚氨酯中的分布，我们对23％硬链段的聚（酯氨酯）与不同量的非氘代或氘代增塑剂的混合物进行了小角度中子散射测量。我们使用一个简单的模型分析了结果，其中，富含软链段和硬链段的区域之间的对比度Δ_ρ=ρ_H-ρ随氘化或氢化增塑剂含量的变化而变化，这取决于I（Q）〜ΔΔ〜 2。结果表明，增塑剂主要与富含软链段的区域有关。在水解条件下老化后，评估具有硬链段扩链剂的PESU的结构。结果表明，由于水解性软链段断裂导致的约束丧失，微相结构变粗大和偏析，硬链段和软链段发生偏析。有关增塑剂分布和水解老化影响的结果可洞悉每种情况下发生的机械性能损失。

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