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Increasing the cross-link density in a dual dissociative and associative polythiourethane covalent adaptable network improves both creep resistance and extrudability
Polymer ( IF 4.1 ) Pub Date : 2024-06-01 , DOI: 10.1016/j.polymer.2024.127232
Sergio Serna , Nathan S. Purwanto , Logan M. Fenimore , John M. Torkelson
Polymer ( IF 4.1 ) Pub Date : 2024-06-01 , DOI: 10.1016/j.polymer.2024.127232
Sergio Serna , Nathan S. Purwanto , Logan M. Fenimore , John M. Torkelson
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There have been significant, recent reports of the effects of cross-link density on the relaxation dynamics and processability of exclusively associative covalent adaptable networks (CANs), also called vitrimers. Similar characterization is lacking for the substantial number of CANs that exhibit dual associative and dissociative dynamic covalent chemistries. Polythiourethane (PTU), which is a thiol-based analogue of polyurethane, is one such polymer class that exhibits both dissociative and associative dynamic chemistries. Here, we tune the cross-link density of PTU CANs by systematic incorporation of long-chain and short-chain thiols. As would be commonly expected, relative to networks with lower cross-link density, PTU networks with higher cross-link density exhibit improved creep resistance at 60 °C and 100 °C. However, we also observe faster elevated-temperature stress relaxation with increasing cross-link density, which is attributable to the dual nature of the PTU dynamic chemistry, with the associative dynamic mechanism being increasingly favored and becoming increasingly more rapid with increasing cross-link density. Because of this shift, our PTU CAN with the highest cross-link density undergoes facile melt extrusion at 150 °C; in contrast, our PTU CAN of lowest cross-link density cannot be melt extruded. Overall, this work highlights the significance of cross-link density in networks exhibiting two or more dynamic chemistries and how that may lead to otherwise unexpected outcomes, e.g., better processability at higher cross-link density.
中文翻译:
增加双解离和缔合聚硫氨酯共价适应性网络中的交联密度可提高抗蠕变性和挤出性
最近有一些重要的报道表明,交联密度对排他性缔合共价适应性网络(CAN)(也称为玻璃体)的弛豫动力学和可加工性的影响。大量具有双重缔合和解离动态共价化学性质的 CAN 缺乏类似的表征。聚硫氨酯 (PTU) 是一种基于硫醇的聚氨酯类似物,是一种具有离解和缔合动态化学性质的聚合物类别。在这里,我们通过系统地掺入长链和短链硫醇来调整 PTU CAN 的交联密度。正如人们普遍预期的那样,相对于交联密度较低的网络,交联密度较高的 PTU 网络在 60°C 和 100°C 下表现出更高的抗蠕变性。然而,我们还观察到随着交联密度的增加,高温应力松弛更快,这归因于 PTU 动态化学的双重性质,随着交联密度的增加,缔合动态机制越来越受青睐并且变得越来越快。由于这种转变,我们具有最高交联密度的 PTU CAN 可在 150°C 下轻松进行熔融挤出;相比之下,我们的 PTU CAN 的交联密度最低,无法熔融挤出。总的来说,这项工作强调了交联密度在表现出两种或多种动态化学性质的网络中的重要性,以及这如何导致意想不到的结果,例如,在更高的交联密度下更好的可加工性。
更新日期:2024-06-01
中文翻译:
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增加双解离和缔合聚硫氨酯共价适应性网络中的交联密度可提高抗蠕变性和挤出性
最近有一些重要的报道表明,交联密度对排他性缔合共价适应性网络(CAN)(也称为玻璃体)的弛豫动力学和可加工性的影响。大量具有双重缔合和解离动态共价化学性质的 CAN 缺乏类似的表征。聚硫氨酯 (PTU) 是一种基于硫醇的聚氨酯类似物,是一种具有离解和缔合动态化学性质的聚合物类别。在这里,我们通过系统地掺入长链和短链硫醇来调整 PTU CAN 的交联密度。正如人们普遍预期的那样,相对于交联密度较低的网络,交联密度较高的 PTU 网络在 60°C 和 100°C 下表现出更高的抗蠕变性。然而,我们还观察到随着交联密度的增加,高温应力松弛更快,这归因于 PTU 动态化学的双重性质,随着交联密度的增加,缔合动态机制越来越受青睐并且变得越来越快。由于这种转变,我们具有最高交联密度的 PTU CAN 可在 150°C 下轻松进行熔融挤出;相比之下,我们的 PTU CAN 的交联密度最低,无法熔融挤出。总的来说,这项工作强调了交联密度在表现出两种或多种动态化学性质的网络中的重要性,以及这如何导致意想不到的结果,例如,在更高的交联密度下更好的可加工性。