【作者】 贾鑫；

【导师】 李彦锋； 朱晓夏；

【作者基本信息】 兰州大学 ， 高分子化学与物理， 2009， 博士

【摘要】 聚乙烯醇是一种化学性质稳定,有良好的耐酸、耐碱、耐干热性能,溶于水但几乎不溶于有机溶剂的用途相当广泛的水溶性高分子聚合物,性能介于塑料和橡胶之间,它的用途可分为纤维和非纤维两大用途。近年来,由于PVA的产量急剧扩大,加上煤,电,石油等资源的日趋紧张,主要原料价格持续高涨,产品利润率逐渐降低。因此,只有加强PVA产品的应用开发,拓宽应用领域,研发科技含量高,附加价值高的下游产品,延长产品链,聚乙烯醇生产企业才能提高核心竞争能力,实现行业的可持续发展。本文简述了聚乙烯醇的基本特性及在传统领域中的应用;并综述了近年来在新领域中的拓宽及功能化,在此基础上提出了两种有效的功能化途径:一是通过和无机物复合形成新的高性能纳米复合材料;另外是通过利用聚乙烯醇本身的特性,进行功能化后运用于固相有机合成。在此思路的指导下,制备了四种新型的功能化聚乙烯醇材料,并研究了其性质,主要结论如下:一、通过和硅烷偶联剂乙烯基三乙氧基的偶联反应,成功地对纳米二氧化硅进行了表面乙烯基化,并研究了此反应的可控性,通过不同的反应条件,可以使乙烯基含量达到1.956到8.922 mmol/g之间;通过醋酸乙烯酯和乙烯基化后的纳米二氧化硅共聚,并直接进行醇解反应,FT-IR及聚合物中硅元素分析证明成功的制备了聚乙烯醇/二氧化硅纳米复合材料;特性粘度及醇解度的研究表明,少量二氧化硅的引入影响了聚乙烯醇的一些特征性能;热性能和机械性能的研究表明,通过共价键和聚合物连接,少量的纳米二氧化硅就能很大程度的提高了聚合物的热性能和机械性能。复合物的起始热分解温度从250.1℃上升至261.1℃;玻璃化转变温度从71.0℃上升到91.2℃:而在800℃时的残留率从3.53%增加到16.72%。同时,杨氏模量从36.3MPa上升至52MPa,拉伸强度从16.4MPa上升至30.2MPa。二、用DMSO插层的高岭土作为中间体,成功地通过客体置换法使得醋酸乙烯酯单体进入高岭土层间,经DMSO插层后,高岭土的层间距由原来的0.72 nm增大为1.13 nm,经过醋酸乙烯酯插层后,其层间距进一步增大为1.44 nm。DMSO和醋酸乙烯酯的插层率分别为72%和78.6%;通过经典的自由基溶液聚合,合成了聚醋酸乙烯酯/高岭土插层聚合物,该聚合物通过直接醇解后到了聚乙烯醇/高岭土插层聚合物:FT-IR和XRD表征证明了这个结果,所得聚乙烯醇/高岭土插层聚合物的热性能较纯的聚合物有了很大的提高,复合物的起始热分解温度从240.1℃上升至262.5℃;玻璃化转变温度从61.2℃上升到81.5℃;而在800℃时的残留率从3.68%增加到22.72%。三、成功的应用悬浮交联的方法从线性的聚乙烯醇出发制备了交联的PVA小球,然后用阴离子聚合的方法,以环氧乙烷为单体,使得PVA表面接枝上了PEG链段,制备了新型的PVA-g-PEG树脂,并用FT-IR,NMR表征了其结构;用SEM,光学显微镜研究了PVA小球和PVA-g-PEG树脂的形貌特征,用DSC和TGA研究了其热性能;在不同溶剂中的溶胀性能的研究表明,PVA-g-PEG树脂在溶胀性方面具有广泛的溶剂适用性,其在各种不同性质的溶剂中的溶胀指数都优于现在普遍使用的固相载体;更为重要的是,这种载体本身具有的官能团的含量很高,是现在使用树脂的几倍乃至十几倍,所以该树脂具有很好的应用前景,为了给以后的工业化生产给予一定得理论指导,通过实验室的对悬浮交联过程和阴离子聚合过程的放大,初步摸索了放大实验的影响因素。四、通过上升聚合法制备尺寸均一的聚醋酸乙烯酯小球,其直径为1.8 mm;然后通过传统的醇解反应,我们把所得的聚醋酸乙烯酯小球成功地转化为聚乙烯醇小球,其醇解度达到85%,聚乙烯醇小球上的羟基含量为18 mmol/g;通过元素分析,CP/MAS ¹³C NMR和FT-IR表征,我们确定了所得聚醋酸乙烯酯及聚乙烯醇小球的结构,并且得出实验结果和理论值是相符合的。更多还原

【Abstract】 Poly（vinyl alcohol）（PVA） is a kind of water-soluble polymer,which possess excellent chemical stability,acid resistance,base resistance,dry heat resistance, soluble in water and insoluble in most organic solvents and widely used in many fields.It’s properties is between plastic and rubber and usually used as fiber and non-fibrous matters.Recently,because of increasing amount and decreasing profit of PVA,it is very urgent to discover novel functional PVA matters to make PVA sustainable development.This paper summarizes basic properties and conventional applications in every fields and give an introduction of novel functionalized PVA in recent years.Based on this,we propose that two methods to functionalize PVA are possible.The first way is to combine PVA and inorganic materials to form new PVA nano-composites to improve properties.The other is to use PVA as solid-phase synthesis support because PVA is very stability.Guided by this,four novel functional PVA matters were prepared in this paper and their properties was studied.The main conclusion is following:1.Firstly,silica nanoparticles were modified by vinyltriethoxysilane（VTEOS） and the amount of vinyl group was controllable by changing reaction conditions.The amount of vinyl group was up to 8.922 mmol/g.Secondly,these modified silica nanoparticles were copolymerized with vinyl acetate to form PVAc/silica nano-composites.Finally,PVA/silica nano-composites could be obtained by alcoholysis of PVAc/silica nano-composites.FT-IR and silica analysis were used to characterize PVAc/silica nano-composites.The properties of PVAc/silica nano-composites such as intrinsic viscosity and alcoholysis degree were changed even the amount of silica nanoparticles introduced into polymer was very small.At the same time,the thermal and mechanical properties of PVAc/silica nano-composites were improve greatly because of introduction of silica nanoparticles.For example,the onset of the thermal degradation temperature was shifted from 250.1℃to 261.1℃ and the glass transition temperature was improved from 71.0℃to 91.2℃.The Young’s modulus increased from 36.3MPa to 52MPa and the tensile strength changed from 16.4MPa to 30.2MPa.2.Vinyl acetate was intercalated into kaolinite by a displacement method using dimethyl sulfoxide/kaolinite（Kao-DMSO） as the intermediate.The d（001） spacing of Kao-DMSO increased to 1.13 nm and Kao-VAc demonstrated the d（001） spacing was further enlarged to 1.44 nm.he intercalation rates（IR） of Kao-VAc was increased from 72%of Kao-DMSO to 78%.After,PVAc/kaolinite nano-composites was prepared via in situ free radical polymerization and PVA/kaolinite nano-compositeds was successfully obtianed by alcoholysis of PVAc/kaolinite nano-composites.The materials were characterized by FT-IR and XRD.The onset of the thermal degradation temperature was shifted from 240.1℃to 262.5℃and the glass transition temperature was improved from 61.2℃to 81.5℃.3.Firstly,highly crosslinked PVA beads were prepared by suspension crosslinking of linear PVA and epichlorohydrin.Then,ethylene oxide was grafted onto the PVA beads by anionic polymerization to form PVA-g-PEG resins.These resins were characterized by NMR,FT-IR,SEM,microscopy,DSC and TGA.All results indicated that this novel resin possess good solubility both in polar and no-polar solvents.At the same time,the functional group is up to 10 fold comparing to Tentagel and Argogel, which were popularly used in many fields.Last,scaling-up was carried out in the lab because this novel resin is so promising.4.The uniform PVAc beads with diameter between 1.8 mm and 2.0 mm were prepared via ascension polymerization and corresponding uniform PVA beads were obtained by methanolysis.The alcoholysis degree is up to 85%and the amount of hydroxyl group is 18 mmol/g.These beads were characterized by elements analysis, CP/MAS ¹³C NMR and FT-IR.更多还原