Phthalonitrile polymer and phthalonitrile-polyhedral oligomeric silsesquioxane (POSS) copolymer were sintered at 500 °C, 600 °C, or 800 °C. The samples before and after sintering were evaluated by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) coupled to FT-IR (TG-FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results suggest that phthalonitrile-polyhedral oligomeric silsesquioxane copolymers have better thermal stability than phthalonitrile polymers. After sintering at 800 °C, the phthalonitrile polymers decomposed completely while the phthalonitrile-polyhedral oligomeric silsesquioxane copolymers retain their original structure. The presence of the rigid POSS structure in the copolymer may limit the thermal movement of polymer chains at higher temperatures, thereby increasing the intermolecular forces between polymer chains. Moreover, POSS generates spatial steric hindrance, further restraining movement of chains and hindering degradation of labile groups; the overall effect is to improve the thermal stability of the composite under higher temperatures.

在500°C，600°C或800°C下烧结邻苯二甲腈聚合物和邻苯二甲腈-多面体低聚倍半硅氧烷（POSS）共聚物。烧结前后的样品通过差示扫描量热法（DSC），热重分析（TGA）耦合到FT-IR（TG-FTIR），X射线衍射（XRD）和X射线光电子能谱（XPS）进行评估。结果表明，邻苯二甲腈-多面体低聚倍半硅氧烷共聚物具有比邻苯二甲腈聚合物更好的热稳定性。在800°C下烧结后，邻苯二甲腈聚合物完全分解，而邻苯二甲腈-多面体低聚倍半硅氧烷共聚物保持其原始结构。共聚物中刚性POSS结构的存在可能会限制较高温度下聚合物链的热运动，从而增加了聚合物链之间的分子间力。此外，POSS会产生空间位阻，进一步限制链的移动并阻碍不稳定基团的降解；总体效果是提高复合材料在较高温度下的热稳定性。