侧链超支化聚羧酸减水剂的合成与作用机理研究

Polycarboxylate superplasticizer (PCE) is the most widely used concrete admixture at present. Traditional PCE has a comb structure, and the anions such as carboxylic acid on the main chain act as anchor to absorb on the cement particles and produce electrostatic repulsion. At the same time, the steric resistance of side chain prevents cement particles from contacting each other, therefore PCE can reduce the usage of water in concete. According to the mechanism of PCE, We design a novel PCE with side chain hyperbranched structure, which is connected to the main chain by two or four side chains of polyoxyethylene ether. Compared with the comb PCEs, the steric resistance of PCEs is higher, however, the adsorption capacity and electrostatic repulsion are not weakened. Using ethanolamine as the core, polyamide-amine hyperbranched molecules will be prepared by Michael addition and ammonolysis. Then the hyperbranched polyoxyethylene ether macromonomer will be synthesized by Michael addition with methoxy polyethylene glycol acrylate to introduce long chain, the macromonomer will be further copolymerized with acrylic acid and other small monomers to synthesize side chain hyperbranched PCEs, and the intermediate and final products of the synthesis process will be characterized. The surface physicochemical, adsorbtion, cement paste and concrete performances of the side chain hyperbranched PCE will be studied and the mechanism will be discussed. The theoretical basis and basic data will be provided for the preparation of PCE with high water-reducing dispersion.

聚羧酸减水剂(PCE)是目前研究应用最广泛的混凝土外加剂。传统PCE具有梳型结构，主链上的羧酸根等阴离子作为锚固点吸附在水泥颗粒上产生静电斥力作用，侧链的空间位阻作用阻止水泥颗粒相互接触，起到减水分散效果。根据PCE的作用机理，申请人设计一种具有新型侧链超支化结构的PCE，其以两个或四个聚氧乙烯醚侧链为一个单元与主链相连，推测其相对于梳型PCE，空间位阻更高，而吸附能力和静电斥力未减弱，减水分散效果更好。本项目拟以乙醇胺为核，通过迈克尔加成和氨解反应制备聚酰胺-胺超支分子，再与甲氧基聚乙二醇丙烯酸酯发生迈克尔加成引入长链，合成超支化聚氧乙烯醚大单体；进一步将大单体与丙烯酸等小单体自由基共聚合成侧链超支化型PCE；对合成过程的中间和最终产物进行结构表征；结合侧链超支化PCE的表面物化、吸附、水泥净浆和混凝土性能，探讨其作用机理。可为制备具有高减水分散作用的PCE提供理论依据和基础数据。

聚羧酸减水剂（PCEs）是目前研究应用最广泛的混凝土外加剂。本项目设计了一种具有新型侧链超支化结构的聚羧酸减水剂（HB-PCEs），重点围绕以下三个方面开展研究：1）通过亲核取代、迈克尔加成、氨解和酰胺化等反应合成了二臂超支化聚氧乙烯醚大单体（TAHBPE）和四臂超支化聚氧乙烯醚大单体（FAHBPE）。2）通过水溶液自由基聚合反应以TAHBPE和FAHBPE为大单体合成了二臂侧链超支化聚羧酸（TAHB-PCEs）和四臂侧链超支化聚羧酸（FAHB-PCEs）两类HB-PCEs。HB-PCEs比传统梳型聚羧酸减水剂（TPCEs）具有更好的减水分散作用。随着侧链支化程度的提高，HB-PCEs的表面张力减小，润湿性提高，起泡性提高，表观黏度减小。3）从空间位阻作用、润湿作用和气泡隔离作用等方面阐明了HB-PCEs的作用机理：HB-PCEs相较于TPCEs具有更高的侧链密度，更高的吸附层厚度和更显著的空间位阻作用；HB-PCEs的亲水润湿性提高，相较TPCEs更容易在水泥颗粒表面形成水化膜；HB-PCEs的表面张力减小，起泡性提高，气泡的隔离“滚珠”效应增强，以上三方面共同促进了HB-PCEs减水分散作用的提高。. 本项目相关研究成果在Cement and Concrete Composites、Construction and Building Materials、Journal of Building Engineering、Journal of Dispersion Science and Technology、高分子材料科学与工程等期刊上发表，其中被SCI和EI收录7篇。本项目授权国家发明专利2项，参加国内外学术会议2人次，培养博士研究生1名，硕士研究生4名。