【摘要】：聚合物后反應(yīng)改性在提高材料性能的同時(shí),可以賦予材料嶄新的性能,拓寬其應(yīng)用領(lǐng)域。聚乙烯醇(PVA)作為為數(shù)不多的可人工合成的水溶性高分子材料,因其優(yōu)異的力學(xué)性能、氣體阻隔性、生物相容性和分子鏈上羥基的高反應(yīng)活性,被廣泛地用作高聚物改性的目標(biāo)。本文利用PVA分子鏈上羥基的高反應(yīng)活性,通過(guò)后反應(yīng)修飾的改性方法,將具有光響應(yīng)性的偶氮苯小分子和親水性3-羥基-L-酪氨酸通過(guò)酯化反應(yīng)接枝到PVA分子鏈上,制備得到了具有光響應(yīng)性和低溫水溶性的改性聚乙烯醇,并對(duì)產(chǎn)物進(jìn)行了相關(guān)表征。主要研究?jī)?nèi)容和取得的結(jié)論如下:1.通過(guò)重氮化反應(yīng)、親電加成、取代成醚和酰氯化反應(yīng),制備得到了具有五個(gè)柔性亞甲基且順?lè)串悩?gòu)體均可相對(duì)穩(wěn)定存在的偶氮苯長(zhǎng)鏈小分子,通過(guò)酯化反應(yīng)將光響應(yīng)性偶氮苯小分子接枝到PVA分子鏈上,得到了光響應(yīng)性功能化聚乙烯醇。采用傅里葉紅外變換光譜(FTIR)和核磁氫譜(1H NMR)表征了偶氮苯小分子和功能化聚乙烯醇的結(jié)構(gòu),并對(duì)功能化聚乙烯醇高分子進(jìn)行了差示掃描量熱分析(DSC)、熱重分析(TG)和紫外-可見(jiàn)吸收光譜表征(UVVis)。UV-Vis驗(yàn)證了功能化聚乙烯醇的光響應(yīng)性。DSC和TG結(jié)果顯示,偶氮苯小分子的引入,破壞了聚乙烯醇分子內(nèi)和分子間的氫鍵作用,促進(jìn)了分子鏈的運(yùn)動(dòng),弱化了結(jié)晶結(jié)構(gòu),同時(shí)與聚乙烯醇分子鏈上的羥基之間形成了更強(qiáng)的氫鍵作用。因此在降低聚乙烯醇熔點(diǎn)的同時(shí),提高了材料的熱穩(wěn)定性。2.針對(duì)PVA1799僅能在95℃熱水中溶解的特點(diǎn),采用親水性3-羥基-L-酪氨酸(L-dopa),通過(guò)一步酯化反應(yīng)將其接枝到聚乙烯醇分子鏈上,得到低溫下(10℃)即具有水溶性的功能化聚乙烯醇。通過(guò)FTIR和1H NMR表征了產(chǎn)物的結(jié)構(gòu),通過(guò)水溶性實(shí)驗(yàn)驗(yàn)證了功能化聚乙烯醇的低溫水溶性,并通過(guò)DSC和TG表征了產(chǎn)物的熱性能。DSC和TG結(jié)果顯示:L-dopa的引入,使聚合物分子鏈由結(jié)晶態(tài)向無(wú)定形態(tài)轉(zhuǎn)變,熔點(diǎn)降低了約80℃。同時(shí),L-dopa上的羥基、羧基氨基等基團(tuán)與PVA上的羥基形成了更強(qiáng)的氫鍵作用,使DTG曲線上功能化聚乙烯醇的羥基脫除峰后移,但因鄰苯二酚極易熱降解的特性,在低于羥基脫除溫度下即發(fā)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，

本文編號(hào)：2400434