Comb Polymers with Triazole Linkages under Thermal and Mechanical Stress
Comb Polymers with Triazole Linkages under Thermal and Mechanical Stress
复制标题
热应力和机械应力下具有三唑键的梳状聚合物
DOI：
10.1021/acs.macromol.8b02174
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发表时间：
2019
期刊：
影响因子：
5.5
通讯作者：
Barner-Kowollik
中科院分区：
文献类型：
--
作者：
Abbasi;Fischer;Wilhelm;Goldmann;Barner-Kowollik
评估聚合物结构中分子键的稳定性对于确定挤出、成型和加工条件至关重要。支化聚合物的拓扑复杂性决定了它们的应变硬化，从而决定了它们的熔体强度性质，这是它们在应用中开发的关键参数。它们的分子结构由接枝密度和主链以及支链的链长限定。在这里，我们介绍了一组聚合物梳，以建立对流行的三唑键的稳定性的上述参数的理解，经常利用拴支的骨干，在热处理和剪切。我们利用可逆失活自由基聚合（RDRP）和铜催化的炔-叠氮环加成（CuAAC）的组合来构建梳形聚合物（主链数均分子量为39.9至55.6 kg mol-1，分支长度为3.3至18 kg mol-1），其统计位置的分支通过基于三唑的连接连接到主链上。随后在惰性气氛中在150 °C（或180 °C）下对这些聚合物梳进行热挑战，并在相同温度下进行剪切。通过尺寸排阻色谱法（SEC）以及SEC耦合高分辨率电喷雾电离质谱法（SEC-HR ESI MS）分析所得的分子裂解过程，以建立分支脱键发生时的机理图像。此外，通过这种方法，我们深入了解了梳状结构如何通过三唑单元在其他不变的化学键合条件下决定其稳定性，从而允许采用设计标准来产生热稳定和机械稳定的梳状结构。
Assessing the stability of molecular bonds in polymer architectures is of critical importance for determining conditions for extrusion, molding, and processing. The topological complexity of branched polymers defines their strain hardening and consequently their melt strength properties, critical parameters for their exploitation in applications. Their molecular architecture is defined by the grafting density and the chain length of the backbone as well as branches. Herein, we introduce a set of polymer combs to establish an understanding of the above parameters on the stability of the popular triazole linkage—often exploited in tethering the branches to the backbone—during thermal treatment and shearing. We exploit a combination of reversible deactivation radical polymerization (RDRP) and copper-catalyzed alkyne–azide cycloaddition (CuAAC) to construct comb polymers (ranging in backbone number-average molecular weight from 39.9 to 55.6 kg mol–1and a branch length from 3.3 to 18 kg mol–1) with statistically located branches tethered via triazole-based ligation to the backbone. These polymer combs were subsequently thermally challenged at 150 °C (or 180 °C) in an inert atmosphere as well as subjected to shearing at the same temperature. The resulting molecular cleavage processes were analyzed via size exclusion chromatography (SEC) as well as SEC coupled to high-resolution electrospray ionization mass spectrometry (SEC-HR ESI MS) to establish a mechanistic image of branch debonding when it occurs. In addition, by virtue of this approach, we establish an in-depth understanding of how the comb architecture dictates its stability under otherwise unchanged chemical bonding conditions via triazole units, allowing to adopt design criteria for generating thermally and mechanically stable comb structures.
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