聚乙烯醇-g-异氰酸酯-脂肪醇梳状接枝共聚物的合成、 结构及热性能

通过甲苯-2,4-二异氰酸酯(TDI)的连接作用, 利用接枝共聚法将具有储热功能的长链脂肪醇[如十八醇(C₁₈OH)、 十六醇(C₁₆OH)和十四醇(C₁₄OH)]接枝到聚乙烯醇(PVA)主链上, 制备出储热能力不同的聚乙烯醇-g-TDI-脂肪醇[PVA-g-TDI-C(n)]梳状接枝共聚物. 通过傅里叶变换红外光谱(FTIR)、 差示扫描量热分析(DSC)、 热重分析(TGA)和X射线衍射(XRD)等方法研究了PVA-g-TDI-C(n)共聚物的热行为和结晶结构. 结果表明, PVA-g-TDI-C(n)共聚物具有良好的储热能力, 储热能力随侧链碳原子数目和侧链接枝度的增加而增大, 但明显低于长链脂肪醇的储热能力. PVA-g-TDI-C(n)共聚物具有良好的热稳定性, 失重温度在324~330 ℃之间. 从侧链受限运动角度探讨了影响PVA-g-TDI-C(n)共聚物热性能和有序堆砌结构的原因.

Synthesis, Structure and Thermal Properties of Poly ( vinyl alcohol)-g-isocyanate-fatty Alcohol Comb Copolymers

Using the bridging role of tolylene diisocyanate(TDI), poly(vinyl alcohol)-g-tolylene diisocyanate-fatty alcohol copolymers were synthesized with the fatty alcohols as the thermal storage units along the PVA backbone via the "grafting to" method. The thermal storage behavior, thermal stability and crystalline structure of PVA-g-TDI-C(n) copolymers were detailed investigated by Fourier transform infrared spectroscopy(FTIR), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), X-ray diffraction(XRD). The results show that PVA-g-TDI-C(n) copolymers exhibit the better thermal storage ability, and the value of enthalpy increases with the side-chain length and the grafting ratio. Compared with the pure fatty alcohols, the grafted ones show the decreased thermal storage efficiency due to the confined mobility of longer methylene groups. Besides the confined mobility of methylene groups, the effect of PVA backbones and the bridging units of TDI also contribute to the decrement of thermal storage ability of PVA-g-TDI-C(n) copolymers. Additionally, PVA-g-TDI-C(n) copolymers exhibit the higher thermal stability than that of pure n-fatty alcohol, and the thermal degradation temperature is located at 324-330 ℃, proving that it can be used as the solid-solid phase change materials in the aspects of buildings, fiber and textiles, thermal fluids, etc. So, the packing manner and thermal behavior of PVA-g-TDI-C(n) copolymers were further discussed and analyzed from the viewpoints of microstructural mobility.