Modulating the coefficient of thermal expansion (CTE) and realizing low or negative thermal expansion (NTE) for epoxy polymers are challenging issues. In this study, we developed an effective strategy to prepare epoxy polymers with an NTE performance. A novel motif DBCOD-NH₂ based on the dibenzocyclooctadiene (DBCOD) was designed, synthesized, and utilized as a curing agent for several commercial epoxy resins. DBCOD-NH₂ suppressed the thermal expansion of the epoxy polymer due to the conformational transition of DBCOD from boat to chair, resulting in low or negative CTE. The AFG90-based polymer showed the most significant thermal contraction behavior (−43.6 ppm/K, 40–80 °C) in the glassy state due to the high DBCOD content, chain rigidity, and cross-link density, which resulted from the high epoxy values, rigidity, and functionality of AFG90 resins. The structure–property interactions were examined and applied to modulate the NTE of epoxy polymers. Our findings are useful for the regulation of thermal expansion and the preparation of materials with desired CTE values.

中文翻译：

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环氧树脂聚合物负热膨胀的设计和调制


调节环氧树脂聚合物的热膨胀系数 （CTE） 和实现低热膨胀或负热膨胀 （NTE） 是具有挑战性的问题。在这项研究中，我们开发了一种有效的策略来制备具有 NTE 性能的环氧树脂聚合物。设计、合成了基于二苯并环辛二烯 （DBCOD） 的新型基序 DBCOD-NH₂，并将其用作几种商业环氧树脂的固化剂。由于 DBCOD 从船到椅子的构象转变，DBCOD-NH₂ 抑制了环氧树脂聚合物的热膨胀，导致低 CTE 或负 CTE。由于 AFG90 树脂的高环氧值、刚度和功能性导致高 DBCOD 含量、链刚度和交联密度，基于 AFG90 的聚合物在玻璃态下表现出最显着的热收缩行为（-43.6 ppm/K，40-80 °C）。检查结构-性能相互作用并应用于调节环氧聚合物的 NTE。我们的研究结果可用于调节热膨胀和制备具有所需 CTE 值的材料。