POSS基聚羧酸减水剂的合成与表征

以八氯丙基笼型倍半硅氧烷为引发剂,对苯乙烯基磺酸钠、丙烯酸钠、甲基丙烯酸甲酯为单体,采用原子转移自由基聚合方法,制备八氯丙基POSS、对苯乙烯磺酸钠、丙烯酸钠和甲基丙烯酸甲酯三嵌段共聚物(T8-PSStNa-b-PAANa-b-PMMA),并通过酯交换方法在聚合物分子上接枝聚乙二醇单甲醚(MPEG)以得到聚羧酸类减水剂。利用FT-IR、1H-NMR测试手段对聚合物的结构进行表征,结果表明:我们成功地合成出POSS基三嵌段结构聚羧酸类高效减水剂,并且当聚合时间为24 h时,产物的净浆流动度性能较好。     

国内聚羧酸系高性能减水剂的合成及研究状况

简述了聚羧酸类减水剂合成方法、分子结构与性能的关系,讨论了大单体聚乙二醇丙烯酸酯等的制备工艺技术。     

不同结构聚羧酸减水剂在吸附质浆体表面的吸附-分散效应

为考察不同侧链密度的减水剂分子在水泥-钠基膨润土浆体中的吸附-分散效应,以丙烯酸和2-甲基丙-2-烯基聚乙二醇醚自由基共聚法,通过调整链转移剂构建出适当主链长度且不同侧链密度的聚羧酸减水剂.采用GPC、Zeta电位、TOC、流动度测试技术表征,着重考察了相近主链长度、不同侧链密度的减水剂在水泥-钠基膨润土混合浆体中的吸附-分散特性.结果 表明:侧链密度设计越高,主链长度同步减小,减水剂分子初始吸附量越小;内掺钠基膨润土后在分散性能方面侧链密度高的占优势,且内掺量越大,侧链密度高的减水剂抗泥质吸附能力越强.     

聚羧酸类高效减水剂研究进展及应用

文章筒述了国内外聚羧酸类高效减水剂的主要类型和性能及研究进展,同时介绍了合成聚羧酸类高效减水剂的方法和作用机理,合成原料及应用。     

聚羧酸类高效减水剂的研究现状与发展方向

介绍了目前聚羧酸类高效减水剂的结构特征与合成方法、分子结构与性能的关系、作用机理研究 ,提出一些亟待深入研究的问题及聚羧酸类高效减水剂今后的研究方向。     

季铵盐型聚羧酸类减水剂的合成和在水泥中的应用研究

合成了一种新型的季铵盐型聚羧酸类减水剂,并对影响减水剂性能的各种因素进行了研究,确定了最佳原料配比。通过对该减水剂在混凝土中应用性能的研究,说明该产品是一种用量少,水泥净浆流动度佳,具有一定抗泥能力的聚羧酸类减水剂。     

聚羧酸类减水剂中间大分子单体的合成工艺

通过丙烯酸和甲氧基聚乙二醇的酯化,生成了一种具有反应活性的聚羧酸类减水剂中间大分子单体——甲氧基聚乙二醇丙烯酸酯。探讨了各种实验条件对酯化反应的影响,得出了合成甲氧基聚乙二醇丙烯酸酯的最佳工艺条件。     

一种用于PVC制品的碳酸钙超分散剂制备及性能研究

通过分子设计,在传统合成聚羧酸减水剂的基础上引入亲油单体,制备了一系列不同单体配比和侧链长度的新型碳酸钙聚合物分散剂,并详细研究了不同分子结构对碳酸钙在PVC制品中分散性能的影响.结果表明:高分子分散剂的引入提高了碳酸钙与PVC的亲和力,增加了碳酸钙在PVC制品中的填充量.当亲水、亲油小分子单体和提供梳状结构的异丁烯醇聚氧乙烯醚(HPEG)大单体摩尔比为2∶1∶1,HPEG相对分子质量为2 400时,合成的聚羧酸超分散剂的分散效果最佳,该分散剂的适宜掺量为1％.     

SAS/MAA/MPEGMAA聚羧酸盐分散剂的制备与性能

以甲基丙烯酸（MAA）和 4 种不同侧链长度的甲氧基聚乙二醇（MPEG相对分子质量分别为350,500,750,1000）先聚合得到酯化大单体（MPEGMAA）,再以甲基丙烯酸,烯丙基磺酸钠（SAS）为单体,在引发剂过硫酸钾,阻聚剂对苯二酚作用下聚合得到 4 种具有不同侧链长度的聚羧酸盐分散剂。通过红外（FT-IR）、核磁共振氢谱（¹H NMR）和凝胶渗透色谱（GPC）对聚合物的结构、相对分子质量及其分布进行了表征和分析,并将其作用于彬长煤制浆,考察了浆体的表观黏度、流变性、zeta电位、吸附性以及最大成浆浓度和稳定性,测定其与煤的接触角,并通过X射线光电子能谱（XPS）分析,得出煤粒表面吸附分散剂后的吸附层厚度为 6.12 nm。结果表明,侧链长度为SAS/MAA/MPEGMAA750的聚羧酸盐分散剂具有良好的润湿和吸附效果,对彬长煤具有更好的降黏、分散和稳定作用。     

SAS/MAA/MPEGMAA聚羧酸盐分散剂的制备与性能

以甲基丙烯酸(MAA)和4种不同侧链长度的甲氧基聚乙二醇(MPEG相对分子质量分别为350,500,750,1000)先聚合得到酯化大单体(MPEGMAA),再以甲基丙烯酸,烯丙基磺酸钠(SAS)为单体,在引发剂过硫酸钾,阻聚剂对苯二酚作用下聚合得到4种具有不同侧链长度的聚羧酸盐分散剂。通过红外(FT-IR)、核磁共振氢谱(1H NMR)和凝胶渗透色谱(GPC)对聚合物的结构、相对分子质量及其分布进行了表征和分析,并将其作用于彬长煤制浆,考察了浆体的表观黏度、流变性、zeta电位、吸附性以及最大成浆浓度和稳定性,测定其与煤的接触角,并通过X射线光电子能谱(XPS)分析,得出煤粒表面吸附分散剂后的吸附层厚度为6.12 nm。结果表明,侧链长度为SAS/MAA/MPEGMAA750的聚羧酸盐分散剂具有良好的润湿和吸附效果,对彬长煤具有更好的降黏、分散和稳定作用。     

聚醚侧链聚羧酸类减水剂的结构及应用性能

通过大分子反应,合成了一类主链带羧基、磺酸基,支链带聚氧乙烯基醚的聚羧酸系高效减水剂。利用IR和1H NMR表征了其结构,并通过对减水剂溶液表面张力、水泥颗粒表面吸附量以及溶液的电导率的测定,发现研制的减水剂能降低水的表面张力,并被吸附在水泥颗粒表面从而降低了水泥颗粒的表面能,使得水泥净浆有较好的分散作用,实验表明本研究制备的聚羧酸系减水剂对水泥颗粒有较好的分散作用。     

Effects of polyethlene oxide chains on the performance of polycarboxylate-type water-reducers

A series of polycarboxylic acid-based copolymers with block and graft groups of polyethlene oxide (PEO) chains was synthesized; effects of the different PEO chains on the fluidity, Zeta potential and adsorption in cement paste and performances of the copolymer in concrete were discussed. It was proved that properties of the copolymer were affected by the length and density of PEO graft and block chains, and that copolymers with some block PEO chains at a certain length and moral percent had good performances in the water-reducing capability and fluid-retaining ability. Experimental results indicated that this kind of copolymers could be used as a high-range water-reducer because of the effects of electrostatic repulsive force and steric hindrance; one of its applications was to produce high-flowing concrete by incorporating with mineral admixtures, such as fly ash, etc.     

木钠接枝磺化三聚氰胺树脂高效减水剂的合成及性能

针对传统的磺化三聚氰胺树脂减水剂(SMF)塌落度损失大、泌水性大的缺陷,以过硫酸铵引发自由基接枝合成了木钠接枝磺化三聚氰胺甲醛树脂高效减水剂(SLMF),获得了优化的合成工艺。红外谱图和SLMF的性能表明木钠成功接枝于SMF结构中。合成的SLMF具有良好的分散性和保水性能。在水灰比为0.29(质量比)时,掺0.6%(质量分数)的SLMF高效减水剂的水泥净浆流动度为253 mm,掺SLMF的水泥净浆在90 min内的流动度损失从100%降低为61.8%,而140 min内静态泌水率从4.84%降低到1.61%。结果表明,SLMF高效减水剂能有效克服传统三聚氰胺高效减水剂的缺陷,具有良好的应用前景。     

基于核磁-能谱实验的中变质烟煤煤尘低润湿性分析

为从微观角度分析中变质烟煤的低润湿特性,以巨野煤田赵楼气肥煤为例,选用核磁共振（NMR）与X射线光电子能谱（XPS）手段对其微观分子结构进行实验,并分析了分子结构参数对其润湿性的影响规律。结果表明,赵楼气肥煤煤尘的芳香度为0.77,芳香结构含量较高,且主要以质子化芳环为主;脂肪链结构中以链状烷烃和环烷烃侧链为主,且存在一定的甲基侧链;煤尘表面含氧官能团主要为醚基（C-O-C）,其次为羰基（C=O）与羟基（C-OH）,含量最少的是羧基（COOH）,上述4种含氧官能团含量之比约为4∶2∶2∶1.5。赵楼气肥煤煤尘不仅芳香度较高,芳香簇尺寸较大,缩合度偏高,而且烷基侧链少而短,导致煤尘分子结构单元表现出较强的疏水性;而对表面亲水性贡献较大的羧基（COOH）和羟基（C-OH）含量却只占表面含氧官能团总量的13.53%、21.45%。因此,受微观分子结构的影响,赵楼气肥煤煤尘总体表现出疏水性的特点,润湿性较差。     

聚羧酸减水剂影响抗裂性能的机理研究

通过实验,以混凝土28d的拉压比大小为评价混凝土抗裂性能的优劣，分析了合成聚羧酸减水剂的羧基、氨基、磺酸基、羟基、酯基等各官能团比例，聚醚支链的长短，减水剂分子量大小等因素对混凝土抗裂性能的影响。初步探讨了聚羧酸减水剂提高混凝土抗劈裂性能机理。     

Grow to Fit Molecular Dynamics (G2FMD): an ab initio method for protein side-chain assignment and refinement

The rough energy landscapes and tight packing of protein interiors are two of the critical factors that have prevented the wide application of physics-based models in protein side-chain assignment and protein structure prediction in general. Complementing the rotamer-based methods, we propose an ab initio method that utilizes molecular mechanics simulations for protein side-chain assignment and refinement. By reducing the side-chain size, a smooth energy landscape was obtained owing to the increased distances between the side chains. The side chains then gradually grow back during molecular dynamics simulations while adjusting to their surrounding driven by the interaction energies. The method overcomes the barriers due to tight packing that limit conformational sampling of physics-based models. A key feature of this approach is that the resulting structures are free from steric collisions and allow the application of all-atom models in the subsequent refinement. Tests on a small set of proteins showed nearly 100% accuracy on both chi1 and chi2 of buried residues and 94% of them were within 20 degrees from the native conformation, 79% were within 10 degrees and 42% were within 5 degrees . However, the accuracy decreased when exposed side chains were involved. Further improvement and application of the method and the possible reasons that affect the accuracy on the exposed side chains are discussed.     

Gamma-radiation induced grafting of acrylonitrile onto guar gum: Influence of reaction conditions on the properties of the grafted and saponified products

In the gamma-radiation induced grafting of acrylonitrile onto guar gum, the influence of different concentration of the monomer acrylonitrile on the PAN add-on, the number average molecular weight of the PAN side chains, and the grafting frequency of the PAN side chains are reported. At 0.3 Mard dosage, the PAN add-on were 32.4, 48.5, and 66.2% and the number average molecular weight of the PAN side chains were 59,700, 132,200, and 238,900, respectively, at three different reaction conditions. The frequency of grafting also showed considerable variation at 0.2 Mrad dosage, for all three sets of samples. The viscosity of the aqueous dispersions of the saponified samples at different concentrations are also reported. The water absorbency of the saponified samples were evaluated and the values were around 250 g/g. The fall in viscosity of the aqueous dispersions on storage were also evaluated. The observed fall in viscosity was lower in the case of the product with higher PAN content. © 1993 John Wiley & Sons, Inc.     

Graft copolymer of gelatin/butyl acrylate and its use in the dye transferring blank film

Butyl acrylate was graft copolymerized onto gelatin using ceric ammonium nitrate as redox initiator. A series of grafted products with various gelatin-to-butyl acrylate ratios were prepared. The molecular weight of the grafted side chains and the number of grafting sites were measured. The possible grafting sites on gelatin macromolecules were pointed out through amino acid analysis. The electron micrograph and DSC analysis showed that the grafted chain (PBA) and backbone gelatin were in separated phases. The graft copolymer was used in the receiving layer of the dye transfer blank film, and the photographic, dye transfer printing, and some physicomechanical properties were studied with satisfactory results.     

Copolymerisate aus Ethylen und α-Olefinen

Some properties of ethylene-α-olefine-copolymers synthesized in the presence of Ziegler-catalysts were examined. It is shown that elongation and strength properties are not only dependent on molecular weight, molecular weight distribution and density but also on the length of the side chains. Copolymers with longer side chains show higher values of e.g. tensile impact strength than those with short side chains.     

Interaction of cyclodextrins with side chains of water soluble polymers: A simple model for biological molecular recognition and its utilization for stimuli-responsive systems

This article demonstrates that the interaction of cyclodextrins (CDs) with side chains of water soluble polymers is useful not only as simple models for biological molecular recognition but also as building blocks in nanotechnological applications. In the interaction of CDs with polymer side chains, the selectivity of CDs was enhanced by the steric effect of the polymer main chain and by interaction at multi-sites (i.e., collectivity). Utilizing the interaction of CDs with polymer side chains, stimuli-responsive systems were constructed from simple components.