Photoinduced plasticizing effect of the addition of azobenzene on the glass transition temperature and mechanical properties of polycarbonate
Photoinduced plasticizing effect of the addition of azobenzene on the glass transition temperature and mechanical properties of polycarbonate
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DOI：
10.1038/s41428-021-00598-5
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发表时间：
2022-01
期刊：
影响因子：
2.8
通讯作者：
Mai Maeda;S. Nobukawa;K. Inomata
中科院分区：
文献类型：
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作者：
Mai Maeda;S. Nobukawa;K. Inomata
研究了偶氮苯(AB)的光致异构化对聚碳酸酯(PC)的玻璃化转变温度(Tg)和杨氏模数的影响。紫外光照射下的介电松弛测量表明，较强的紫外光降低了PC共混物的Tg。尽管较强的紫外光促进了→的跨热异构化，但PC共混物的较高温度(接近120-130 °C)加速了→的跨热异构化。我们根据不同紫外光强度和温度下的傅里叶变换红外光谱结果，评估了反映异构化速率的特征时间，以比较两种异构化。结果，在Tg附近特征时间变得相似，表明紫外光照射下发生了重复的异构化反应。由于重复异构化速度加快，PC的自由体积增大，Tg降低。此外，我们还发现光致异构化降低了PC的杨氏模数。由紫外光照射下的拉伸试验测得的杨氏模数，随着光强的增加而减小。杨氏模数表现出与重复异构化的特征时间之和的单一依赖关系，与光的强度无关。这一结果表明，通过异构化增加自由体积会降低玻璃态下的杨氏模数。
We investigated the effects of the photoisomerization of doped azobenzene (AB) on the glass transition temperature (Tg) and Young’s modulus of polycarbonate (PC). Dielectric relaxation measurements with ultraviolet (UV) light irradiation revealed that stronger UV light decreased theTgof the PC blends. Although stronger UV light generatestrans→cisisomerization, higher temperatures (near theTgof 120–130 °C) of the PC blend acceleratecis→transthermal isomerization. We evaluated the characteristic times reflecting the isomerization rates to compare the two isomerizations based on the Fourier transform infrared spectroscopy results obtained at different UV light intensities and temperatures. As a result, the characteristic times became similar near theTg, indicating that repeating isomerization occurred as a result of UV light irradiation. Because of the faster repeating isomerization, the free volume of PC increased, resulting in a decrease in theTg. In addition, we discovered that photoisomerization decreases the Young’s modulus of PC. The Young’s modulus, as determined by the tensile test under UV light irradiation, decreased as the light intensity increased. Young’s modulus demonstrated a single dependence on the sum of the characteristic times for repeating isomerization regardless of the intensity of light. This result suggested that increasing the free volume via isomerization reduced Young’s modulus in the glassy state.