聚羧酸共聚物侧链结构对水泥水化及硬化过程的影响

以聚乙二醇系列、丙烯酸、顺酐、丙烯酸羟乙酯为原料合成聚羧酸减水剂,讨论聚羧酸共聚物侧链长度对水泥分散性能和水化过程的影响,并测试掺加减水剂的混凝土性能.实验结果表明:通过调整聚羧酸共聚物中侧链链长的比例使其具有最佳的分散性.实验合成的聚羧酸共聚物聚乙二醇侧链为nPEG600∶nPEG400=1∶1时,分散效果最好,水泥浆体的流动度及分散力最佳,分别为289 mm和10.36.聚羧酸减水剂具有缓凝特性,能够显著延缓水泥水化及硬化过程,使水泥石的后期水化更充分、水化产物结构更紧密更有力量,各龄期混凝土抗压强度都有较大提高.在水泥中添加0.3%聚羧酸减水剂(PEG600∶400),32.5#水泥3 d,7 d和28 d的抗压强度分别提高了50.4%,40.8%,35.1%,42.5#水泥3 d,7 d,28 d的抗压强度分别提高了16.7%,31.0%和22.3%.     

甲氧基聚乙二醇-b-聚L-半胱氨酸两亲性嵌段共聚物的合成与表征

首先以聚乙二醇单甲醚(mPEG-OH)为单体,采用经典的盖布瑞尔伯胺合成法合成了端氨基聚乙二醇单甲醚(mPEG-NH_2);然后以mPEG-NH_2为引发剂,S-苄基L-半胱氨酸N-羧酸内酸酐(BCys-NCA)为原料,通过N-羧酸内酸酐(NCA)开环聚合反应和液氨/钠处理脱除侧链上的保护基团,合成了两亲性嵌段共聚物甲氧基聚乙二醇-b-聚L-半胱氨酸(mPEG-b-PCys)。采用傅里叶变换红外光谱、核磁共振氢谱对聚合物的结构和组成进行了表征。结果表明:成功制备了侧链具有还原性巯基的两亲性嵌段共聚物mPEG-b-PCys,并且其聚合度可控性良好。     

聚甲基丙烯酸胆甾醇酯共聚物的合成、结构与性能研究 Ⅳ.PMACE的相态转变及光学性质

Finkelmann和等人对侧链胆甾型高分子液晶的研究表明,将具有液晶功能的低分子基团,经过一个软段连接到柔性高分子主链上的梳型高分子在一定的温度下可以形成液晶态,调节侧链高分子液晶的分子结构、软段长度,可以改变其相态转变温度及微区形态。前已报导具有不同侧链结构的聚甲基丙烯酸胆甾醇酯共聚物的合成、相态转变及光学性质,本文通过对聚甲基丙烯酸胆甾醇乙烯酯共聚物(PMACE)的液晶态及结晶态的微细结构及相态转变与胆甾侧链含量关系的研究,给出了液晶态的形成条件及结构特征。     

不同结构聚羧酸减水剂对超高性能混凝土性能的影响

将相对分子质量不同的常规聚醚甲基烯丙基聚氧乙烯基醚(HPEG)、异戊烯基聚氧乙烯基醚(TPEG)、乙二醇单乙烯基聚氧乙烯基醚(EPEG)和4-羟丁基聚氧乙烯基醚(VPEG)分别与丙烯酸进行自由基共聚反应制得系列聚羧酸减水剂,研究了具有不同聚醚侧链类型和长度、不同酸醚比以及不同相对分子质量的聚羧酸减水剂对UHPC工作性和强度的影响。结果表明:聚醚侧链长度为2400的系列聚羧酸减水剂对UHPC拌合物坍落扩展度和排空时间的影响程度从高到低依次为酸醚比、相对分子质量和聚醚侧链类型;聚醚侧链类型对UHPC拌合物坍落扩展度和排空时间的影响程度从高到低依次为EPEG、HPEG、TPEG和VPEG;对于侧链长度分别为2400、2700、3000、3500和4000的HPEG聚醚侧链的系列聚羧酸减水剂,酸醚比宜分别为4.0:1、4.0:1、4.5:1、4.5:1和5.0:1,且相对分子质量宜分别为32000±2000、32000±2000、38000±2000、38000±2000和44000±2000;聚羧酸减水剂分子中聚醚侧链类型和长度、酸醚比及相对分子质量的变化对UHPC28d抗压、抗折强度的总体...     

含聚二甲基硅氧烷侧链的丙烯酸酯共聚物的研究

采用含活性基团的聚二甲基硅氧烷与丙烯酸酯进行自由基共聚合，合成了自聚二甲基硅氧烷侧链的丙烯酸酯共聚物。采用ＩＲ，＾１Ｈ－ＮＭＲ，ＧＰＣ等分析方法对共聚物结构和组成进行了表征。通过接触角和Ｘ－射线光电子能谱对共聚物的表面性能和表面组成进行了研究，并通过粘接性能和破坏面形貌对共聚物与金属铝材和加成型硅橡胶的粘接性进行了探讨。     

含羧基的含氟嵌段共聚物的合成及表面性能研究

利用原子转移自由基聚合反应以及随后的大分子链中叔丁酯基团的水解反应,合成了一系列具有不同含氟量和羧基含量的二嵌段共聚物,并分别通过GPC, ¹H NMR和FT-IR对共聚物的组成和结构进行了表征.进一步考察了这些含羧基或羧酸钠基团的含氟嵌段共聚物在吡咯烷酮或水中的溶解性能、临界胶束浓度、表面活性、达到饱和吸附时每个分子在表面所占据的面积,以及成膜后的临界表面张力等性能.实验结果表明,此含氟嵌段共聚物能显著降低吡咯烷酮和水的表面张力,成膜后表现出与聚四氟乙烯极为接近的低表面能特性.     

聚膦腈-g-聚己内酯共聚物的合成与表征

通过三甲基碘硅烷与聚二(2-甲氧基乙氧基)膦腈侧链上的醚键反应后水解得到侧链含部分羟基的聚膦腈,然后利用聚膦腈的侧链羟基在异辛酸亚锡催化作用下,引发己内酯单体开环聚合制备了聚膦腈-g-聚己内酯共聚物.该共聚物中聚己内酯链段的接枝率和侧链长度可通过改变三甲基碘硅烷和己内酯单体的投料来控制.     

蠕虫状链模型下梳状共聚物分子的均方回转半径的理论分析及其在聚羧酸系减水剂分子中的应用

利用蠕虫状链模型对梳状共聚物分子的均方回转半径进行了理论分析,建立了回转半径与主链轮廓长度、主链持久长度、侧链轮廓长度、侧链持久长度、侧链数目以及侧链沿主链的分布情况(均匀分布和梯度分布)之间的定量数学关系.在此基础上,以被称为"第一代聚羧酸系高性能减水剂"(以下简称为MPEG-type PCE)的甲基丙烯酸(MAA)/烯酸甲酯(MAA-MPEG)梳状共聚物分子为研究对象,结合实验数据,对其聚电解质主链的持久长度进行了分析,并考察了主侧链长度、刚柔性、侧链分布、接枝密度等分子结构参数对PCE回转半径的影响,最后对模型的局限性作简要说明.梳状共聚物分子的蠕虫状链模型物理图像简洁,参数意义明确,应用于PCE分子体系时较之前所报道的柔性链模型要更为合理,能够为分析PCE的分子结构与溶液构象和吸附构象之间的关系提供更科学的视角.     

丙烯酰胺-二氰二胺大单体及其与苯乙烯共聚物的研究(Ⅰ)——大单体及其共聚物的合成和表征

通过丙烯酰胺、二氰二胺、甲醛及氯化铵的缩合反应,合成了分子链端含C=C双键的大单体,缩合过程用高压液相色谱考察,以AIBN为引发剂,二甲基亚砜为溶剂,使大单体与苯乙烯共聚,得到主链具有疏水性、侧链具有亲水性的共聚物,用GPC、IR光谱及溶解性对共聚物进行鉴定,苯乙烯含量较低时,共聚物溶于水,共聚物在MeOH/H₂O混合溶剂中的粘性行为表明它是带有疏水基团的聚电解质。     

三苯胺-芴类共聚物的合成及发光性能

在主链上嵌入三苯胺基团来改善聚芴的空穴传输能力、平衡载流子的注入是目前改善聚芴材料发光效率的一种好方法。本文用Suzuki缩聚法合成了芴-三苯胺类共聚物。实验结果表明．在聚芴主链上引入少量的TPA(10％～20％)时．不仅提高了EL效率．而且可以改善光谱的色纯度。TPA含量为20％时,共聚物的EL效率为1．28％。     

Effect of Functionalized Copolymer on Titanium Dioxide Pigment Dispersion

The influence of adsorption of polymers containing different functional groups on the dispersion behavior of pigment particles has been investigated in water. The polymers chosen are styrene‐maleic anhydride copolymer modified with three different amines, tris (hydroxymethyl) amine, semicarbazide, and thiosemicarbazide of different hydrophilicity, to yield the corresponding grafted amic acids. The modified graft copolymers were characterized by Fourier transform infrared spectroscopy and ¹H‐nuclear magnetic resonance spectroscopy. Application of these amic acids as a dispersing agent to disperse titanium dioxide in water was studied. The Daniel flow method was used to assess the dispersing ability of these amic acids, and it was found that all the synthesized dispersants showed dispersion action on the pigment particles.     

A general strategy for highly efficient nanoparticle dispersing agents based on hybrid dendritic linear block copolymers

A modular approach to the synthesis of a library of hybrid dendritic‐linear copolymers was developed based on RAFT polymerization from monodisperse dendritic macroRAFT agents. By accurately controlling the molecular weight of the linear block, generation number of the dendrimer and the nature of the dendritic chains ends, the performance of these hybrid block copolymers as dispersing agents was optimized for a range of nanoparticles. For titanium dioxide nanoparticles, dispersion in a poly(methyl methacrylate) matrix was maximized with a second generation dendrimer containing four carboxylic acid end groups, and the quality of dispersion was observed to be superior to commercial dispersing agents for TiO₂. This approach also allowed novel hybrid dendritic‐linear dispersing agents to be prepared for the dispersion of Au and CdSe nanoparticles based on disulphide and phosphine oxide end groups, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1237–1258, 2009     

Synthesis and Characterization of Novel Monoazo Naphthalimide Disperse Dyes Containing Carboxylic Acid Group with High Heat Fastness Properties

A group of novel monoazo disperse dyes containing carboxylic acid‐1,8‐naphthalimide group has been synthesized. All intermediates and dyes were purified by recrystalization and the column chromatography method. The purified products were characterized by ¹H NMR, ¹³C NMR, FTIR, DSC, UV‐VIS and Elemental Analysis. Spectrophotometric investigations of the synthesized dyes in different solvents were carried out in order to obtain their absorption maxima, molar extinction coefficients and solvatochromic effects. The absorption maxima of the synthesized dyes in acetone varied (513‐549 nm) and the molar extinction coefficient was (17405‐38939 l/mol cm). By changing the media from chloroform to DMF, the solvatochromism effect for all dyes increased. Dispersion of the synthesized dyes was prepared in water containing dispersing agent and applied to polyester fabrics. The dyed fabrics showed that all of the synthesized dyes were suitable for coloring polyester fibers, producing deep red to bluish red with very good fastness properties.     

Comparison of the Electrochemical Reactivity of Electrodes Modified with Carbon Nanotubes from Different Sources

The electrochemical activity of five different commercial carbon nanotubes (CNT), prepared by the ARC discharge and chemical vapor deposition (CVD) methods, has been assessed and compared. The various multi‐walled CNT were immobilized onto a glassy carbon electrode using three different dispersing agents (Nafion, concentrated nitric acid and dimethylformamide (DMF)) and their voltammetric response to ferricyanide, NADH and hydrogen peroxide examined. SEM was used to characterize the surface morphology. The corresponding cyclic voltammetry and amperometric data showed that the electrocatalytic activity, the background current and the electroanalytical performance are strongly depended on the preparation of the CNT and on the dispersing agent used. The most favorable amperometric detection of NADH and hydrogen peroxide is observed at the NanoLab CVD‐produced CNT in connection to a DMF‐surface dispersion. ARC‐produced CNT display a smaller capacitance, particularly in connection to the DMF dispersion. Such differences in the electrochemical reactivity are attributed to the different surface chemistries (primarily defect densities) of the corresponding CNT layers, associated with the different production and dispersion protocols.     

低剪切速率下聚乙二醇／KCl／蒙脱土分散体系的剪切稠化现象

用Hakke RS75流变仪研究了聚乙二醇（PEG）／KCl/蒙脱土分散体系的流变性 。结果发现，当KCl和聚乙二醇浓度在一定范围内时，体系随剪切速率增加，表现 出剪切稀释－剪切稠化－剪切稀释的复杂结构变化，并且剪切稠化发生在低剪切速 率区。KCl浓度继续增加，剪切稠化逐渐减弱。TME表明，蒙脱土分散体系中加入 KCl使得蒙脱土颗粒聚集，而聚乙二醇导致经微絮凝；二者同时加入，体系形成细 枝条状的空间稳定结构。     

A biomimetic "polysoap" for single-walled carbon nanotube dispersion

As-synthesized single-walled carbon nanotubes (SWNTs) are bundled mixtures of different species. The current challenge in the field of carbon nanotube research lies in the processing and separation of SWNTs, which first require efficient dispersion of individual SWNTs in solvents. We report DNA-mimicking polysoap surfactants that disperse SWNTs in aqueous solutions more effectively than DNA. The polysoaps are synthesized by functionalizing the side chain of poly(styrene-alt-maleic acid) with aminopyrene. The synthetic nature of the polysoap opens a new approach to further optimization of not only SWNT dispersion efficiency but also multi-functional SWNT dispersing surfactant.     

Characterization of poly(ethylene glycol) esters using low energy collision-induced dissociation in electrospray ionization mass spectrometry

A method of characterizing polyglycol esters, an important class of industrial polymer, has been developed using electrospray ionization ion trap mass spectrometry (ESI ITMS). The fragmentation behavior of polyglycol esters is found to be different from that of polyglycols whose functional end groups are linked to the polymer chain via ether bonds (i.e., polyglycol ethers). The fragmentation pattern of an oligomer ion generated by low-energy collision-induced dissociation is strongly dependent on the type of cation used for ionization. It is shown that structural information on the polymer chain and end groups is best obtained by examining the fragment ion spectra of oligomers ionized by ammonium, alkali, and transition metal ions. The application of this method is demonstrated in the analysis of two surfactants based on fatty acid methyl ester ethoxylates.     

Temperature dependence of peptide carboxylic group IR spectra in the amide I′ region at neutral and acidic pH

Analysis of the temperature-dependent amide I′ bands of peptides and proteins can be complicated by their overlap with other IR bands, particularly those of carboxylic groups of amino acid side-chains and the C-terminus. Previously, we reported IR spectra of charged carboxylic side-chains in Asp and Glu amino acids, and C-terminal groups of several amino acids and dipeptides at neutral pH. To complement these results, here we investigate the IR absorptions of Asp and Glu side-chains in capped amino acids (AcAspNMe and AcGluNMe), at both neutral and acidic pH. Spectra of protonated (acidic pH) C-terminal group absorptions are also investigated, using three dipeptides (AlaGly GlyAla and GlyGly) as model compounds. Sets of temperature-dependent experimental IR spectra were analyzed using pseudo-Voigt lineshape profiles. We find that the temperature-dependent behavior of the IR bands of deprotonated (neutral pH) side-chains in AcAspNMe and AcGluNMe dipeptides are generally similar to those reported previously for Asp and Glu. Protonated carboxylic group (acidic pH) IR bands behave uniformly with respect to temperature, showing very similar magnitude frequency shifts and intensity changes. Implications for analyses of amide I′ bands of peptides and proteins are discussed.     

Hydrophilic polymethacrylates containing cholic acid‐ethylene glycol derivatives as pendant groups

In an effort to improve the hydrophilicity of bile acid containing polymers, we have synthesized new methacrylate monomers by incorporating ethylene glycol and oligo(ethylene glycol) spacers of different lengths between cholic acid and methacrylate residues. The monomers were subsequently polymerized by free radical reaction in solution. The methyl ester protecting groups on the cholic acid residue were selectively hydrolyzed to restore the carboxylic acid group of cholic acid. Water absorption tests showed that the hydrophilicity of the polymers was improved with increasing length of oligo(ethylene glycol) spacers and upon restoration of the carboxylic acid group of the cholic acid residue.     

铅纳米微粒用作油性润滑的摩擦学性能研究

The solution dispersion method has been successfully used to prepare Pb nanoparticles in a paraffin oilpolyglycol mixed solution by directly dispersing melted Pb granules. In this solution system,paraffin oil was used as reacting media and polyglycol served as an antioxidant to protect Pb nanoparticles from oxidizing. The size and structure of the prepared Pb nanoparticles were characterized by means of the transmission electron microscopy （TEM）and powder X-ray diffraction（XRD）. Their tribological behavior was evaluated with a four-ball tester. The TEM and XRD investigations reveal that the prepared Pb nanoparticles,with the average particle diameter of 70 nm,appear to be of close spherical shape and possess the same crystal structure as the bulk Pb. The tribological results show that the Pb nanoparticles as an oil additive exhibit good friction-reduction and antiwear properties at different additive concentration and applied load. Meanwhile,they can also strikingly improve the load-carrying capacity of the base oil. The rubbed surface was also investigated by the scanning electron microscope（SEM）and energy dispersive spectroscopy（EDS）. However,there was not presence of Pb element on the worn surfaces,which indicated that no chemical reaction occurred between the Pb nanoparticles and the rubbing surfaces. In addition,the tribological mechanism of the formation of the sliding-bearing system was also proposed.