Thermal Expansion Behavior of the Ordered Domain in Polyimide Films Investigated by Variable Temperature WAXD Measurements
Thermal Expansion Behavior of the Ordered Domain in Polyimide Films Investigated by Variable Temperature WAXD Measurements
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DOI：
10.2494/photopolymer.26.327
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发表时间：
2013-01-01
影响因子：
0.8
通讯作者：
Ando, Shinji
中科院分区：
文献类型：
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作者：
Sekiguchi, Kenji;Takizawa, Kazuhiro;Ando, Shinji
为了研究自支撑 PI 薄膜在平行于薄膜平面方向上的热膨胀行为，测定了芳香族和半脂肪族聚酰亚胺 (PI) 薄膜有序域中沿主链方向的热膨胀系数 (CTE) (α(c))。使用同步加速器辐射设备在 60-360 摄氏度的温度范围内进行变温广角 X 射线衍射 (VT-WAXD) 测量。所有 PI 薄膜都显示出特征性的 WAXD 轮廓，即类液晶有序域与宽而强烈的非晶晕重叠，并且清晰地解析了与沿主链 (c 轴) 的重复单元和链间有序 (Ch-pack) 相对应的衍射峰。具有刚性棒结构的PI沿c轴的α(c)为负值，而主链中含有弯曲键如醚(-O-)或亚甲基(-CH2-)的PI则沿c轴的α(c)值较大且为正值。 α(c) 值与通过热机械分析 (TMA) 估算的 PI 薄膜的面内 CTE 非常吻合。这表明，观察到的刚性棒 PI 薄膜的负面内 CTE 源自有序域中的负 alpha(c)，而有序域源自在薄膜平面中具有明显取向的延伸主链。
Coefficients of thermal expansion (CTEs) along the main chain direction in the ordered domain of aromatic and semi-aliphatic polyimide (PI) films (alpha(c)) were determined in order to investigate the thermal expansion behaviors of self-standing PI films in the direction parallel to the film plane. Variable temperature wide-angle X-ray diffraction (VT-WAXD) measurements were performed using a synchrotron radiation facility in the temperature range of 60-360 degrees C. All the PI films showed characteristic WAXD profiles to liquid-crystalline-like ordered domain overlapped with broad and intense amorphous halos, and diffraction peaks corresponding to the repeating unit along the main chain (c-axis) and the inter-chain ordering (Ch-pack) were clearly resolved. The alpha(c)s along the c-axis of PIs having rigid-rod structure are negative, whereas those for PIs containing bent linkages, such as ether (-O-) or methylene (-CH2-), in the main chains are large and positive. The alpha(c) values coincide well with the in-plane CTEs of the PI films estimated by thermal mechanical analysis (TMA). This indicates that the negative in-plane CTEs observed for the rigid-rod PI films originates from the negative alpha(c) in the ordered domain, which originates from the extended main chains with appreciable orientation in the film plane.