基于后反应法修饰的改性聚乙烯醇的制备及性能研究
发布时间：2019-01-04 14:54
【摘要】：聚合物后反应改性在提高材料性能的同时,可以赋予材料崭新的性能,拓宽其应用领域。聚乙烯醇(PVA)作为为数不多的可人工合成的水溶性高分子材料,因其优异的力学性能、气体阻隔性、生物相容性和分子链上羟基的高反应活性,被广泛地用作高聚物改性的目标。本文利用PVA分子链上羟基的高反应活性,通过后反应修饰的改性方法,将具有光响应性的偶氮苯小分子和亲水性3-羟基-L-酪氨酸通过酯化反应接枝到PVA分子链上,制备得到了具有光响应性和低温水溶性的改性聚乙烯醇,并对产物进行了相关表征。主要研究内容和取得的结论如下:1.通过重氮化反应、亲电加成、取代成醚和酰氯化反应,制备得到了具有五个柔性亚甲基且顺反异构体均可相对稳定存在的偶氮苯长链小分子,通过酯化反应将光响应性偶氮苯小分子接枝到PVA分子链上,得到了光响应性功能化聚乙烯醇。采用傅里叶红外变换光谱(FTIR)和核磁氢谱(1H NMR)表征了偶氮苯小分子和功能化聚乙烯醇的结构,并对功能化聚乙烯醇高分子进行了差示扫描量热分析(DSC)、热重分析(TG)和紫外-可见吸收光谱表征(UVVis)。UV-Vis验证了功能化聚乙烯醇的光响应性。DSC和TG结果显示,偶氮苯小分子的引入,破坏了聚乙烯醇分子内和分子间的氢键作用,促进了分子链的运动,弱化了结晶结构,同时与聚乙烯醇分子链上的羟基之间形成了更强的氢键作用。因此在降低聚乙烯醇熔点的同时,提高了材料的热稳定性。2.针对PVA1799仅能在95℃热水中溶解的特点,采用亲水性3-羟基-L-酪氨酸(L-dopa),通过一步酯化反应将其接枝到聚乙烯醇分子链上,得到低温下(10℃)即具有水溶性的功能化聚乙烯醇。通过FTIR和1H NMR表征了产物的结构,通过水溶性实验验证了功能化聚乙烯醇的低温水溶性,并通过DSC和TG表征了产物的热性能。DSC和TG结果显示:L-dopa的引入,使聚合物分子链由结晶态向无定形态转变,熔点降低了约80℃。同时,L-dopa上的羟基、羧基氨基等基团与PVA上的羟基形成了更强的氢键作用,使DTG曲线上功能化聚乙烯醇的羟基脱除峰后移,但因邻苯二酚极易热降解的特性,在低于羟基脱除温度下即发生了部分分解。
[Abstract]:The post-reaction modification of polymer can not only improve the properties of the materials, but also give new properties to the materials and broaden their application fields. Polyvinyl alcohol (PVA) is one of the few synthetic water-soluble polymer materials, because of its excellent mechanical properties, gas barrier, biocompatibility and high reactivity of hydroxyl groups in molecular chains. It is widely used as the target of polymer modification. In this paper, the photoresponsive small azobenzene and hydrophilic 3-hydroxy-L-tyrosine were grafted onto the PVA molecular chain by esterification reaction using the high reactivity of hydroxyl groups on the chain of PVA. Poly (vinyl alcohol) with photoresponse and low temperature water solubility was prepared, and the product was characterized. The main contents and conclusions are as follows: 1. Through diazotization, electrophilic addition, substitution of ethers and acyl chlorination, a series of long chain azobenzene long chain molecules with five flexible methylene and cis-trans isomers were prepared. Photoresponsive polyvinyl alcohol (PVA) was prepared by grafting photoresponsive azobenzene onto PVA chain by esterification. The structures of azobenzene and functionalized polyvinyl alcohol were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic hydrogen spectroscopy (1H NMR). The functional polyvinyl alcohol polymers were characterized by differential scanning calorimetry (DSC),). Thermogravimetric analysis (TG) and UV-Vis absorption spectra were used to characterize the photoresponse of functionalized polyvinyl alcohol by (UVVis). UV-Vis. The results of DSC and TG showed that the introduction of small azobenzene molecules, The internal and intermolecular hydrogen bonds of PVA were destroyed, the movement of molecular chains was promoted, the crystalline structure was weakened, and a stronger hydrogen bond was formed with the hydroxyl groups in the polyvinyl alcohol chains. Therefore, the melting point of polyvinyl alcohol was decreased, and the thermal stability of the material was improved. 2. 2. In view of the fact that PVA1799 can only be dissolved in hot water at 95 鈩，
本文编号：2400434
[Abstract]:The post-reaction modification of polymer can not only improve the properties of the materials, but also give new properties to the materials and broaden their application fields. Polyvinyl alcohol (PVA) is one of the few synthetic water-soluble polymer materials, because of its excellent mechanical properties, gas barrier, biocompatibility and high reactivity of hydroxyl groups in molecular chains. It is widely used as the target of polymer modification. In this paper, the photoresponsive small azobenzene and hydrophilic 3-hydroxy-L-tyrosine were grafted onto the PVA molecular chain by esterification reaction using the high reactivity of hydroxyl groups on the chain of PVA. Poly (vinyl alcohol) with photoresponse and low temperature water solubility was prepared, and the product was characterized. The main contents and conclusions are as follows: 1. Through diazotization, electrophilic addition, substitution of ethers and acyl chlorination, a series of long chain azobenzene long chain molecules with five flexible methylene and cis-trans isomers were prepared. Photoresponsive polyvinyl alcohol (PVA) was prepared by grafting photoresponsive azobenzene onto PVA chain by esterification. The structures of azobenzene and functionalized polyvinyl alcohol were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic hydrogen spectroscopy (1H NMR). The functional polyvinyl alcohol polymers were characterized by differential scanning calorimetry (DSC),). Thermogravimetric analysis (TG) and UV-Vis absorption spectra were used to characterize the photoresponse of functionalized polyvinyl alcohol by (UVVis). UV-Vis. The results of DSC and TG showed that the introduction of small azobenzene molecules, The internal and intermolecular hydrogen bonds of PVA were destroyed, the movement of molecular chains was promoted, the crystalline structure was weakened, and a stronger hydrogen bond was formed with the hydroxyl groups in the polyvinyl alcohol chains. Therefore, the melting point of polyvinyl alcohol was decreased, and the thermal stability of the material was improved. 2. 2. In view of the fact that PVA1799 can only be dissolved in hot water at 95 鈩，
本文编号：2400434
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