Impact of Dynamic Bond Concentration on the Viscoelastic and Mechanical Properties of Dynamic Poly(alkylurea‐co‐urethane) Networks,Macromolecular Chemistry and Physics

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Impact of Dynamic Bond Concentration on the Viscoelastic and Mechanical Properties of Dynamic Poly(alkylurea‐co‐urethane) Networks
Macromolecular Chemistry and Physics ( IF 2.5 ) Pub Date : 2019-11-12 , DOI: 10.1002/macp.201900440
Lifeng Chen ₁ , Longhe Zhang ₂ , Philip J. Griffin ₁ , Stuart J. Rowan _{1,

3}

Affiliation

Polymer networks containing dynamic covalent bonds do not exhibit traditional thermoset material properties. Such dynamic covalent networks have the ability to undergo stress relaxation processes associated with dynamic covalent bond exchange, imparting these materials with adaptive/responsive properties. Reported herein is an investigation on the effect that changing the amount of dynamic hindered alkylurea bonds has on the viscoelastic behavior of a series of poly(alkylurea‐co‐urethane) networks prepared by reacting a trifunctional isocyanate crosslinker with varying ratios of an N‐isopropyl amine endcapped poly(propylene glycol) and a poly(propylene glycol). Films that contain >50% dynamic alkylurea bonds (wrt. alkylurea + urethane bonds) exhibit facile reprocessability, while those films with <50% dynamic alkylurea bonds exhibit poor reprocessability under these same conditions. Analysis of the temperature‐dependent shear rheometry and uniaxial stress relaxation measurements demonstrates that the primary stress relaxation mode in these materials is linked to the dynamic bond exchange process. Interestingly, these films exhibit an increasingly rich viscoelastic spectrum with increasing fraction of non‐dynamic urethane bonds. In addition to the primary relaxation process an order‐of‐magnitude slower relaxation emerges, which is identified as being related to the relaxation of larger, permanently crosslinked polymeric clusters in an otherwise dynamic matrix.

中文翻译：

动态键浓度对动态聚（烷基脲-氨基甲酸酯）网络的粘弹性和力学性能的影响

包含动态共价键的聚合物网络不显示传统的热固性材料性能。这种动态共价网络具有经历与动态共价键交换相关的应力松弛过程的能力，从而赋予这些材料以适应性/响应性。本文报道的是对变化的动态量受阻烷基脲键对一系列聚的粘弹性行为的影响的调查（alkylurea-共-urethane）网络制备的三官能异氰酸酯交联剂与的不同比率进行反应Ñ异丙胺封端的聚丙二醇和聚丙二醇。包含> 50％动态烷基脲键（烷基脲+氨基甲酸酯键）的薄膜表现出容易的再加工性，而具有<50％动态烷基脲键的薄膜在相同条件下表现出较差的再加工性。对温度相关的剪切流变学和单轴应力松弛测量结果的分析表明，这些材料中的主要应力松弛模式与动态键交换过程有关。有趣的是，这些薄膜显示出越来越丰富的粘弹性谱，其中非动态氨基甲酸酯键的比例不断增加。除了主要的弛豫过程外，还会出现数量级较慢的弛豫，这被认为与较大的弛豫有关，

更新日期：2019-11-12

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