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首页> 外文期刊>Journal of Applied Polymer Science >Ultra-low degree of polymerization polyvinyl alcohol products prepared by oxidative chain scission: Method and mechanism
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Ultra-low degree of polymerization polyvinyl alcohol products prepared by oxidative chain scission: Method and mechanism

机译：通过氧化链群制制备的超低聚合聚乙烯醇产物：方法和机理

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摘要

In this paper, the high value-added (ultra-low degree of polymerization [ULDP]) polyvinyl alcohol (PVA) product was successfully prepared by oxidative chain scission method with sodium hypochlorite as an oxidant. When the molar ratio of PVA to NaClO is not less than 1:1.8, the reaction is stirred for several hours (>= 2 h) at a temperature not exceeding 50 degrees C. After precipitation and washing in methanol, PVA with polymerization degree of 38-150 can be obtained after drying. The infrared spectrum (IR) and nuclear magnetic hydrogen spectrum (H-1-NMR) test proved that the product obtained by this method is indeed PVA. The results of H-1-NMR also showed that the chain broken has no selectivity and the stereoregularity of hydroxyl group did not change significantly. Through radical quenching experiment and electron paramagnetic resonance (EPR) analysis, it is proved that OCl- is the main active oxide, center dot Cl makes the oxidative chain scission process can be realized quickly, and center dot OH is an indispensable factor for obtaining ULDP PVA. Under the combined action of these three, high value-added PVA with ULDP was successfully prepared. Additionally, the sodium hypochlorite oxidized the center dot OH captured by 5,5-dimethyl-1-pyrroline-n-oxide (DMPO-OH) to 2-hydroxy-5,s-dimethyl-1-pyrroline-N-oxide (HDMPO-OH) in an alkaline environment.
机译：本文以次氯酸钠为氧化剂，采用氧化断链法成功制备了高附加值（超低聚合度[ULDP]）聚乙烯醇（PVA）产品。当PVA与NaClO的摩尔比不小于1:1.8时，在不超过50℃的温度下搅拌反应数小时（>=2小时）。在甲醇中沉淀和洗涤后，干燥后可获得聚合度为38-150的PVA。红外光谱（IR）和核磁氢谱（H-1-NMR）测试证明，该方法得到的产物确实是聚乙烯醇。核磁共振氢谱（H-1-NMR）结果也表明，链断裂没有选择性，羟基的立体规整性没有明显变化。通过自由基猝灭实验和电子顺磁共振（EPR）分析，证明OCl-是主要的活性氧化物，中心点Cl使氧化断链过程得以快速实现，中心点OH是获得ULDP-PVA不可缺少的因素。在这三者的共同作用下，成功制备了高附加值聚乙烯醇和ULDP。此外，次氯酸钠在碱性环境中将5,5-二甲基-1-吡咯啉-n-氧化物（DMPO-OH）捕获的中心点OH氧化为2-羟基-5，s-二甲基-1-吡咯啉-n-氧化物（HDMPO-OH）。

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