反气相色谱法表征漆酚钛螯合高聚物的表面性质

漆酚钛螯合高聚物(UTP)具有优异的耐强酸、耐强碱、耐盐类溶液、耐多种有机溶剂和耐热性能。为进一步扩大其应用领域提供理论和实验依据,采用反气相色谱法(IGC)测定了UTP在70、80、90、100和110 ℃下的表面色散自由能和表面Lewis酸碱常数。以正戊烷(C5)作为标定色谱死时间的探针分子,正己烷、正庚烷、正辛烷和正壬烷作为非极性探针分子,计算了不同温度下UTP的色散表面自由能;以四氢呋喃、丙酮和三氯甲烷作为极性探针分子,计算得到了UTP表面的酸碱作用吸附自由能和吸附焓。实验结果表明: 在70、80、90、100和110 ℃时UTP的色散表面自由能分别为37.68、33.53、35.92、24.01和31.32 mJ/m2; UTP为弱的Lewis碱,Lewis酸常数Ka为0.1853,碱常数Kb为0.9662。这一结果对研究漆酚金属螯合高聚物的表面性质与应用具有指导作用。     

反相气相色谱表征可溶性聚酰亚胺的表面性质

采用反相气相色谱技术,将正己烷、正庚烷、正辛烷、正壬烷作为非极性分子探针,乙醚、丙酮、三氯甲烷作为极性分子探针在50℃、60℃、70℃和80℃条件下测定了可溶性聚酰亚胺HQDPA-DMMDA的表面色散自由能与表面Lewis酸碱性质.HQDPA-DMMDA在50℃、60℃、70℃和80℃的表面色散自由能分别为34.37、31.80、29.50和27.64 mJ/m2,自由能随温度的升高而线性降低.实验发现,HQDPA-DMMDA为弱的Lewis两性聚合物材料,其Lewis酸常数Ka为0.4115,碱常数Kb为0.5812.     

反气相色谱法研究煤直接液化残渣经分级提取前后的表面性质变化

采用反气相色谱法（IGC）分别对煤直接液化残渣（DCLR）脱灰处理后不溶物、正己烷不溶物、甲苯不溶物、四氢呋喃不溶物的表面性质进行表征。基于非极性探针净保留体积V_n分别采用Dorris-Gray方法和Schultz方法得到表面色散自由能,基于极性探针V_n得到吸附焓△H^sp,并通过△H^sp作图计算得到酸常数K_a和碱常数K_b。结果表明,经溶剂分级提取后表面色散自由能、K_a和K_b均发生明显变化。而DCLR呈现两性偏碱性这一特征并未随分级提取发生改变。IGC作为一种动力学吸附技术,可快速准确表征DCLR在经分级提取过程中表面性质的变化,相同温度下应用Dorris-Gray方法得到DCLR表面色散自由能略高于Schultz方法。     

反相气相色谱法表征1-烯丙基-3-甲基氯代咪唑离子液体的表面性质

采用反相气相色谱(IGC)技术研究了不同温度下1-烯丙基-3-甲基氯代咪唑(［AMIM］Cl)的表面性质。以正己烷、正庚烷、正辛烷和正壬烷作为非极性探针分子测定［AMIM］Cl在343.15、353.15、363.15和373.15 K温度下的表面色散自由能;以二氯甲烷、三氯甲烷、丙酮、乙酸乙酯、四氢呋喃作为极性探针分子测定离子液体Lewis酸碱性质,并测定了吸附自由能和吸附自由焓变等热动力学参数。实验结果表明,［AMIM］Cl的酸解离平衡常数Ka为0.34,碱解离平衡常数Kb为1.68,其表面呈Lewis两性偏碱性特点。在343.15、353.15、363.15和373.15 K温度下,［AMIM］Cl的表面色散自由能分别为52.26、50.82、46.08和42.05 mJ/m2。这一结果对研究离子液体的表面性质及应用有指导作用。     

反气相色谱法表征聚合物表面性质的方法比较

以聚甲基丙烯酸甲酯-丙烯酸丁酯-苯乙烯基七环戊基多面齐聚倍半硅氧烷三元共聚物为模型聚合物,全面介绍了反气相色谱技术表征聚合物表面性质的方法,探讨了不同的计算方法对测定结果的影响。结果表明:Schultz方法和Dorris/Gray方法均可用于计算聚合物的表面能的色散分量γsD,但两者测得的γsD值存在一定的差异,且随温度的升高,差异逐渐增大,Dorris/Gray方法更适合于计算聚合物的γsD;而Sawyer、Schultz和Papirer 3种方法都能表征聚合物表面与极性探针的特殊相互作用以及聚合物表面的酸碱特征,其中以溶剂探针的沸点作参照点的Sawyer计算方法更具有简单、快捷的优点,更具有实用性。     

反气相色谱法测定锌镁铝类水滑石的表面性能

采用水热合成法制备了锌镁铝类水滑石(ZnMgAl-HTLC),利用X射线衍射仪(XRD)对ZnMgAl-HTLC的晶体结构进行了表征,并以一系列非极性和极性分子为探针分子,采用反气相色谱法(IGC)研究了ZnMgAl-HTLC的表面性能.结果表明:XRD特征衍射峰窄、尖、高,水热合成法能够制得纯度较高的ZnMgAl-HTLC; ZnMgAl-HTLC表面吸附自由能小于零,表面色散自由能最大为6.02 mJ/m²,酸碱作用自由能最大为5.33 kJ/mol,吸附焓为43.6 kJ/mol,吸附熵为0.15 kJ/mol.本文的反气相色谱方法对研究锌镁铝类水滑石的表面性能具有重要的指导意义.     

水滑石焙烧产物-镁铝复合氧化物表面性质的反相气相色谱研究

用共沉淀法制备的镁铝水滑石(Mg/Al物质的量比为3),经一定温度焙烧后,得到“笼”状结构的复合氧化物,并采用反相气相色谱法(IGC)对复合氧化物和混合氧化物(氧化镁和氧化铝)的表面性质进行了研究。实验测得一系列探针分子在复合氧化物和混合氧化物上的保留时间,可计算出其吸附热力学函数(吸附自由能(ΔG^?),吸附焓(ΔH^?),吸附熵(ΔS^?)),表面能色散组分(γ_S^d)及复合氧化物的表面酸碱参数(K_A,K_D),并探讨了探针分子在复合氧化物上的吸附机理。结果表明,探针分子进入复合氧化物的“笼”状结构后,可以减小温度对探针分子吸附过程的影响。此外,计算出复合氧化物的表面酸碱参数K_A=3.21及K_D=21.02,定量地表明镁铝复合氧化物是一种两性偏碱的材料。     

反相气相色谱法研究1,3,5-三氨基-2,4,6-三硝基苯的表面特性

采用反相气相色谱技术(IGC)研究了4种不同粒度的1,3,5-三氨基-2,4,6-三硝基苯(TATB)的表面性质。4种不同粒度的TATB表面自由能的色散分量（γds）随着温度的升高而增加;粒度越大的粒子,其色散自由能上升越快;在较高温度下,粗颗粒TATB显示了更强的色散作用(γds=193.2 mJ/m2,353 K),粒度最小的亚微米TATB显示了最弱的色散作用(γds=64.0 mJ/m2,353 K)。由于制备方法不同和粒子大小的差异,4种TATB的表面酸碱性质显示了明显的差别,细颗粒TATB表面有较强的亲电子特性;而其他3种TATB在极性探针分子的作用下的吸附均表现为吸热吸附,表现出在分子内和分子间具有强烈的相互作用,其Ka和Kb值均为负。     

镁铝水滑石及其改性产物的表面性质的研究

采用共沉淀法制备了n_Mg/n_Al比为2∶1镁铝水滑石(Mg/Al-HTlc),经500 ℃焙烧后得到镁铝复合氧化物(C-HT),并用十二烷基苯磺酸钠(SDBS)对复合氧化物进行了改性(M-HT)。通过反相气相色谱法(IGC)对Mg/Al-HTlc、C-HT和M-HT的表面性质进行了研究,定量计算了表面吸附自由能、表面能色散组分以及表面自由能特征分量。结果表明,三者的表面自由能以及色散能的大小顺序为：C-HT＞Mg/Al-HTlc＞M-HT;温度对非极性分子与Mg/Al-HTlc间的色散能影响不大,而非极性分子与C-HT和M-HT间的色散能均随温度的升高而降低;极性分子与固定相的吸附作用包括色散能和吸附自由能特征分量两部分,表面改性会使Mg/Al-HTlc的自由能特征分量降低。     

两亲聚合物表面的反相气相色谱分析

采用反相气相色谱探针技术研究了苯乙烯－氧乙烯－苯乙烯三嵌段两亲聚合物的表面物理化学性质。包括表面吸附热力学函数,表面能的色散分量以及表面分子链与探针的分子间相互作用,。探讨了共聚物中亲油性链段聚苯乙烯（PS）和亲水性链段聚氧乙烯（PEO）的组成比例与其表面性质的关系。结果表明共聚物表面组成中随PEO含量的增加,其表面能增大,表面分子链与探针分子的相互作用增强,表面吸附能力也增强。     

Surface characterization of poly(methyl methacrylate-co-n-butyl acrylate-co-cyclopentylstyryl-polyhedral oligomeric silsesquioxane) by inverse gas chromatography

The surface properties of poly(methyl methacrylate-co-n-butyl acrylate-co-cyclopentylstyryl polyhedral oligomeric silsesquioxane) (poly(MMA-co-BA-co-styryl-POSS)) were studied by means of inverse gas chromatography (IGC) using 10 non-polar and polar solvents as the probes. Thermodynamic parameters of adsorption, e.g., specific retention volume, the dispersive component of the surface free energy, the specific interaction contribution to the free energy of adsorption and the acid/base constants were obtained to investigate the interactions between the surfaces of the copolymers and different solvents. It was found that incorporation of styryl-POSS into polymer resulted in increasing interactions between polymers and solvents, dispersive component of surface free energy of polymer and acidity of the surfaces of the polymers. The more the styryl-POSS were embedded, the stronger the interaction between the polymer surface and solvent, the dispersive component of the surface free energy and the acidity of the polymer surface were.     

Investigation of acid–base and surface characteristics of a thermotropic semifluorinated salicylaldimine liquid crystal by inverse gas chromatography

The surface energy of a semifluorinated salicylaldimine liquid crystal has been characterised by inverse gas chromatography over the temperature range 303 to 323 K using n-alkanes, tetrahydrofurane, dichloromethane, chloroform, acetone and ethyl acetate molecular probes. The dispersive component of the surface free energy of the adsorbent surface studied was calculated according to the approaches of Fowkes and Dorris–Gray in the infinite dilution region. The specific free energy, enthalpy and entropy of adsorption of polar probes on the liquid crystal were determined. The values of the specific enthalpy of adsorption were correlated with both the donor and the acceptor numbers of the probes to quantify the acidic and the basic parameters of the liquid crystal surface. The surface of the semifluorinated salicylaldimine liquid crystal was found to show a basic nature, which determined the nature of its interaction with the polar probes.     

Characterisation of cement pastes by inverse gas chromatography

Two cement pastes, commonly used in concrete formulations, were characterised by IGC at 35-80 degrees C before and after coating with an epoxy resin and a hardener. The cements are mixtures of hydrates in various proportions, such as calcium silicate hydrate (CaO-SiO2-H2O) and calcium hydroxide Ca(OH)2. Apolar and polar probes were used to determine the dispersive and acid-base characteristics of the cement pastes. These materials have high surface energy as judged from the dispersive contribution to the surface free energy (gamma(s)d) values lying in the 50-70 mJ/m2 range at 60-80 degrees C. Examination of the specific interactions permitted to show that the cement pastes are strongly amphoteric species with a substantial predominant Lewis basicity that is in line with the basic pH of their aqueous suspensions. Following coating with an epoxy resin (DGEBA) and a hardener (triethylene tetramine), the surface energy of the cements decreases substantially with the mass loading of the organic material. The surface thermodynamic properties were also correlated with the surface chemical composition as determined by X-ray photoelectron spectroscopy.     

Influence of drawing and heat treatment on surface free energies of polyethylene terephthalate fibers

The surface free energies of polyethylene terepthalate fibers with different draw ratios were experimentally determined by contact angle measurements inn-alkane/water systems. The dispersive component of the surface free energy increased with increasing draw ratio, whereas the nondispersive one remained almost constant. After heat treatment, the dispersive surface free energy increased, but was reduced above 140°C. The nondispersive component increased by heat treatment at 190°C. The increases in the density and birefringence of the fibres due to the drawing and heat treatment suggested that the increase in the dispersive surface free energy was caused by the increase in the atomic density at the fiber surface due to drawing and heat treatment. ESCA results indicated that the increment in the nondispersive surface free energy due to heat treatment was caused by the addition of functional groups to the fiber surface due to heat treatment.     

Comparison of Dorris-Gray and Schultz methods for the calculation of surface dispersive free energy by inverse gas chromatography

Inverse gas chromatography (IGC) is an important technique for the characterization of surface properties of solid materials. A standard method of surface characterization is that the surface dispersive free energy of the solid stationary phase is firstly determined by using a series of linear alkane liquids as molecular probes, and then the acid-base parameters are calculated from the dispersive parameters. However, for the calculation of surface dispersive free energy, generally, two different methods are used, which are Dorris-Gray method and Schultz method. In this paper, the results calculated from Dorris-Gray method and Schultz method are compared through calculating their ratio with their basic equations and parameters. It can be concluded that the dispersive parameters calculated with Dorris-Gray method will always be larger than the data calculated with Schultz method. When the measuring temperature increases, the ratio increases large. Compared with the parameters in solvents handbook, it seems that the traditional surface free energy parameters of n-alkanes listed in the papers using Schultz method are not enough accurate, which can be proved with a published IGC experimental result.     

Wettability and surface free energy of electrolytically oxidized graphite fibers

Wettability of electrolytically oxidized graphite fibers has been investigated by contact angle measurements employing the Wilhelmy method. The atomic ratio of oxygen to carbon, O/C, in the surface layer of the graphite fiber increased with increasing electric specific charge. Contact angle hysteresis was not observed for the untreated graphite fiber (O/C=0.01). The contact angles decreased with increasing O/C, especially for the receding angle, and approached constant for O/C>0.2. The nondispersive and dispersive surface free energies of the oxidized graphite fibers were calculated from the experimentally determined contact angles. The nondispersive surface free energy increased by the oxidation, whereas the dispersive one decreased. From the results of surface analysis, it was found that the changes in the nondispersive and dispersive surface free energies were caused by the increase in O/C ratio and the decrease in surface crystallinity, respectively.