The Effect of the Chain Length on MMA Free Radicl Polymerization

It has been known that the propagation rate coefficient (kp) will change with monomer conversion, Friss, Hamielec et al.1-5 have proposed many formulas about kp to fit this change. In order to obtain the relation between Arrhenius parameters and monomer conversion, a group of kp values at the same monomer conversion must be measured. We adopted a new method through analysis of kp values measured by usual experimental techniques for this purpose. Firstly, we chose a value of monomer convers…     

Impact of Substitution Pattern and Chain Length on the Thermotropic Properties of Alkoxy-Substituted Triphenyl-Tristriazolotriazines

Tristriazolotriazines (TTTs) with a threefold alkoxyphenyl substitution were prepared and studied by DSC, polarized optical microscopy (POM) and X-ray scattering. Six pentyloxy chains are sufficient to induce liquid-crystalline behavior in these star-shaped compounds. Thermotropic properties of TTTs with varying substitution patterns and a periphery of linear chains of different lengths, branching in the chain and swallow-tails, are compared. Generally, these disks display broad and stable thermotropic mesophases, with the tangential TTT being superior to the radial isomer. The structure–property relationships of the number of alkyl chains, their position, length and structure were studied.     

Synthesis,Characterization and Investigation of Side Chain Length and/or Substituents Effect on the Liquid Crystal Properties of New Mesogens

New substituted and unsubstituted phenol based mesogene series having an azo central linkage was synthesized by fixing phenol as rigid core unit with aromatic amine. The terminal –OH group was esterified successively by long alkyl chain acid chloride of variable length (n=2, 6, 11, 15, 17). All 25 synthesized compounds exhibit mesomorphism. The effect of side chain length and substituents on the stability of liquid crystals was studied. The study reveals that nitro substituent destabilizes nematic and smectic phases more than floro substituent. Furthermore, the transition temperature decreases as the length of side chain increases.     

二苯多烯分子的光物理性质与共轭长度的关系

应用无辐射跃迁理论, 结合密度泛函理论, 研究了共轭多烯体系光物理性质随共轭长度变化的规律. 结果表明, 辐射跃迁速率与共轭长度几乎无关, 但无辐射跃迁速率随链长而增加. 这是因为当共轭链增长时, 振子强度增加, 跃迁能减小, 从而对辐射跃迁速率相抵消, 而在无辐射跃迁过程中, 能隙规则起到主导作用.     

Studies on the Surface Free Energy of Carbon-Carbon Composites: Effect of Filler Addition on the ILSS of Composites

The effect of an inorganic oxidation inhibitor, such as MoSi(2), on the surface energetics of carbon-carbon composites has been studied. According to contact angle measurements based on a linear fit method obtained from multiple testing liquids, such as water, diiodomethane, ethylene glycol, and glycerol, it is observed that increasing the MoSi(2) filler content of the composites leads to an increase of the surface free energy, mainly due to the increase of the London dispersive component of surface free energy, even if its specific or polar component is decreased. As an experimental result, the London dispersive component is strongly dependent on the results of the interlaminar shear strength of the composites. In this work, it has been possible to show that the results obtained from the linear fit method correlate with those determined from a two-liquid geometric mean when water and diiodomethane testing liquids are considered as a two-liquid pair. Copyright 2000 Academic Press.     

侧链结构对侧链型磺化聚砜质子交换膜性能的影响

以双酚A型聚砜(PS)为基础,与自制的1,4-二氯甲氧基丁烷反应制备氯甲基化聚砜(CPS),接着与2-萘酚-6,8-二磺酸钾(NSK)进行亲核取代反应制备萘磺酸型侧链磺化聚砜(PS-NS)。采用溶液浇注法制备相应的质子交换膜(PEMs),结合前期研究的脂肪磺酸型侧链磺化聚砜(PS-ES)和苯磺酸型侧链磺化聚砜(PS-BS) PEMs,考察侧链结构对PEMs的吸水率、吸水溶胀率和尺寸稳定性的影响关系。结果表明,与主链型芳香聚合物PEMs相比,3种侧链型磺化聚砜PEMs由于亲水基团远离疏水主链,能够形成类似于Nafion膜的相分离结构,在高吸水率下保持更好的尺寸稳定性;在相同的离子交换膜容量(IEC)下,PS-ES、PS-BS和PS-NS膜随着侧链刚性苯环数目的增加,侧链的运动能力减弱,导致PEMs的尺寸稳定性增加,相应的质子传导率减小; PS-ES膜在25℃和85℃的质子传导率分别达到0. 072和0. 141 S/cm,PS-NS在25℃和85℃的尺寸溶胀性仅为21. 8%和51. 5%,性能与商业化的Nafion115膜十分接近。     

The Effect of Side Chain Association on Thermal and Viscoelastic Properties: Cellulose acetate based polycaprolactones

Cellulose acetate-based polycaprolactones (CAPCL's) were synthesized by the polymerization of -caprolactone which was initiated by non-substituted OH group in cellulose acetate. The CL/OH (mol mol^–1) ratios of the CAPCL's were changed from 2 to 20. Thermal and viscoelastic properties of the CAPCL sheets were studied by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Glass transition, cold crystallization and melting were determined by DSC. Dynamic modules (E'), dynamic loss modules (E') and tan were measured in a temperature range from –150 to 50°C by DMA. Apparent activation energy of a dispersion was calculated from the frequency dependency of E' peak temperature. It was found that the main chain motion of both CA and PCL is observed in a CL/OH ratio from 0 to 10 mol mol^–1. However, when CL/OH ratio exceeds 10 mol mol^–1, the crystalline region which is rearranged by the PCL chain association is observed and only the main chain motion of PCL can be detected.This revised version was published online in November 2005 with corrections to the Cover Date.     

Cellulose Acetate-g-Polycaprolactone Copolymerization Using Diisocyanate Intermediates and the Effect of Polymer Chain Length on Surface,Thermal, and Antibacterial Properties

The need for biodegradable and biocompatible polymers is growing quickly, particularly in the biomedical and environmental industries. Cellulose acetate, a natural polysaccharide, can be taken from plants and modified with polycaprolactone to improve its characteristics for a number of uses, including biomedical applications and food packaging. Cellulose acetate-g-polycaprolactone was prepared by a three-step reaction: First, polymerization of ε-caprolactone via ring-opening polymerization (ROP) reaction using 2-hydroxyethyl methacrylate (HEMA) and functionalization of polycaprolactone(PCL) by introducing NCO on the hydroxyl end of the HEMA-PCL using hexamethyl lenediisocyanate(HDI) were carried out. Then, the NCO–HEMA-PCL was grafted onto cellulose acetate (using the “grafting to” method). The polycaprolactone grafted cellulose acetate was confirmed by FTIR, the thermal characteristics of the copolymers were investigated by DSC and TGA, and the hydrophobicity was analyzed via water CA measurement. Introducing NCO-PCL to cellulose acetate increased the thermal stability. The contact angle of the unreacted PCL was higher than that of cellulose acetate-g-PCL, and it increased when the chain length increased. The CA-g-PCL50, CA-g-PCL100, and CA-g-PCL200 showed very high inhibition zones for all three bacteria tested (E. coli, S. aureus, and P. aeruginosa).     

Effect of Side Chain Substituent Volume on Thermoelectric Properties of IDT-Based Conjugated Polymers

A p-type thermoelectric conjugated polymer based on indacenodithiophene and benzothiadiazole is designed and synthesized by replacing normal aliphatic side chains (P1) with conjugated aromatic benzene substituents (P2). The introduced bulky substituent on P2 is detrimental to form the intensified packing of polymers, therefore, it hinders the efficient transporting of the charge carriers, eventually resulting in a lower conductivity compared to that of the polymers bearing aliphatic side chains (P1). These results reveal that the modification of side chains on conjugated polymers is crucial to rationally designed thermoelectric polymers with high performance.     

Effect of Alkyl Chain Length on the Interfacial Dilational Properties of Hydroxy-Substituted Alkyl Benzenesulfonates

Dilational rheological behaviors of adsorption layers of three surfactants, sodium 2-hydroxy-3,5-dioctyl benzene sulfonate (C₈C₈), sodium 2-hydroxy-3-octyl-5-decyl benzene sulfonate (C₈C₁₀), and sodium 2-hydroxy-3-octyl-5-dodecylbenzenesulfonate (C₈C₁₂) formed at air–water and decane–water interfaces, have been investigated as a function of concentration and frequency (0.002–0.1 Hz) by the oscillating bubble/drop method. The experimental results show that the dilational moduli of hydroxy-substituted alkyl benzenesulfonates are obviously higher than those of the common surfactants, because the interfacial interactions between alkyl chains are improved drastically by the unique arrangement of C₈C₈ molecules at the interface. However, the moduli at the decane–water interface are much lower than those at the surfaces because decane molecules will insert into the surfactant molecules adsorbed at the interface and destroy the interactions between alkyl chains. With an increase in the number of carbon atom of 5-alkyl, the surface dilational modulus decreases because the orientation of the surfactant molecules at the surface varies from parallel to tilt. On the other hand, the diffusion-exchange process dominates the interfacial behavior and the interfacial modulus improves with the increase in the length of the alkyl chain.     

The Effect of the Side Chain on Gelation Properties of Bile Acid Alkyl Amides

Six bile acid alkyl amide derivatives were studied with respect to their gelation properties. The derivatives were composed of three different bile acids with hexyl or cyclohexyl side chains. The gelation behaviour of all six compounds were studied for 36 solvents with varying polarities. Gelation was observed mainly in aromatic solvents, which is characteristic for bile-acid-based low molecular weight gelators. Out of 108 bile acid-solvent combinations, a total of 44 gel systems were formed, 28 of which from lithocholic acid derivatives, only two from deoxycholic acid derivatives, and 14 from cholic acid derivatives. The majority of the gel systems were formed from bile acids with hexyl side chains, contrary to the cyclohexyl group, which seems to be a poor gelation moiety. These results indicate that the spatial demand of the side chain is the key feature for the gelation properties of the bile acid amides.     

侧链结构对磺化聚芳醚性能及微观形貌的影响

比较了3种主链结构相同而侧链结构不同的磺化聚芳醚(SPAE)材料的性能. 分析了侧链结构对聚合物的吸水、 溶胀及质子传导行为的影响. 结果表明, 在相同的离子交换容量(IEC)条件下, 具有柔顺脂肪族侧链的聚芳醚材料具有较高的质子传导率. 其原因是由于柔顺的脂肪族侧链比刚性的芳香族侧链更易运动, 有利于侧链末端磺酸基团的聚集, 进而形成离子簇. 3种聚合物微观形貌的分析结果表明, 含柔顺侧链结构的聚合物薄膜具有更大的质子传输通道, 其结果与聚合物的宏观吸水和传导现象相吻合.     

Effect of Surfactant Chain Length on the Rheological Properties of Cationic Surfactants and a Hydrophobic Counterion

The rheological behavior of alkyimethylammonium 2-hydroxy-1-carboxy-naphthoate, C_xTA-2.1-HCN (x = 16, 14, 12, 10, and 8) is presented. With increasing 2.1 HNC/C_xTAOH (x = 16, 14, 12) ratio, the viscoelasticity of the solutions changes due to a transition in the micellar shape from small micelles to rodlike micelles and finally to multilamellar vesicles (MLV). On the other hand, a transition from small micelles to multilamellar vesicles (MLV) was observed for solution with C_xTA-2.1-HCN (x = 10 and 8). The MLV phases behave like a weak gel and have a yield stress value. Rheological measurements were performed for these viscoelastic systems in order to find out the dependency of the viscoelastic behavior on the surfactant chain length and hydrophobic counterion concentration. Some theoretical models as reptation mechanism was also applied in order to get some structural details and to illustrate the rheological behavior of these viscoelastic systems. Some models that correlate MLV-modulus on the surfactant morphology are also presented and discussed.     

Au(111)/咪唑基离子液体界面结构研究：阳离子侧链长度的影响

本文结合电化学方法与原子力显微镜力曲线技术,研究了两种烷基侧链长度不同的离子液体BMITFSA和OMITFSA在Au(111)电极表面附近的层状结构的数目和耐受力对电位的依赖性,探究了烷基侧链长度变化对界面层状结构的影响. 研究表明,不同烷基侧链长度的离子液体体系力-电位曲线形状基本相似. 在零电荷电位（the potential of zero charge,PZC）附近时,力值最小,因为此时电极表面荷电量较小,层状结构不稳定;电位偏离PZC的过程中,第一层层状结构力值呈现先增大后减小的趋势. 受到烷基侧链所处的不同位置影响,在PZC电位以负,短侧链离子液体的层状结构稳定性较好,而PZC电位以正,长侧链离子液体的稳定性较好.     

疏水链长对聚氧乙烯失水山梨醇脂肪酸酯界面扩张流变性质的影响

利用悬挂滴方法研究了系列聚氧乙烯失水山梨醇脂肪酸酯(TweenX)在正癸烷-水界面的扩张流变性质. 实验结果表明, 疏水烷基链长较短的Tween20 分子在界面上吸附量较大, 分子排列更紧密, Tween40 和Tween60具有大致相同的“有效截面积”, 导致饱和吸附时界面张力(γ_cmc)比较接近. TweenX浓度大于临界胶束浓度(cmc)时, 由于Tween20 分子排列的更加紧密, 模量和弹性大于Tween40 和Tween60. 当TweenX的疏水烷基链长达到一定长度时, TweenX的界面膜性质受疏水链长的影响减弱, Tween40和Tween60的扩张参数相差不大.     

热解条件对LiFePO4/C表面自由能的影响

以葡萄糖为碳前驱体对水热合成的磷酸铁锂粉末进行碳包覆.测定磷酸铁锂粉末与三种探测液的接触角,并据此通过Young方程采用Wu方法计算了粉末的表面自由能.研究了表面自由能与电导率、放电比容量的关系及对工业化涂布性能的影响.结果表明,在电导率相同的前提下,粉末表面自由能中色散分量与极性分量的比值(γd/γp)对低倍率放电性能没有影响,但对高倍率放电性能影响较大.提高热解温度和延长热解时间可使γd/γp值增加,这有利于粉体与聚偏氟乙烯(PVdF)的粘合和高倍率放电容量的提高.     

Effect of Aliphatic Chain Length in the Ligand on Photophysical Properties and Thin Films Morphology of the Europium Complexes

Chelating ligands based on polydentate diamides of 2,2'-bipyridyl-6,6'-dicarboxylic acid with a high affinity for lanthanide ions have been synthesized. The effect of the size of lipophilic aliphatic substituents in the ligand on the photophysical characteristics of europium complexes in acetonitrile solutions and in the solid state, as well as on the morphology of thin films obtained by the spin-coating method, was studied. The external and internal luminescence quantum yields have been measured, the luminescence lifetimes at 300 and 77 K were determined, and the sensitization efficiency values for europium complexes were calculated. The phosphorescence of gadolinium(III) complexes was used to determine the energy difference between the triplet level of the ligand and the resonance level of europium.     

Polysiloxane-based Electrolytes: Influence of Salt Type and Polymer Chain Length on the Physical and Electrochemical Properties

An oligo/poly(methyl(2-(tris(2-H methoxyethoxy)silyl)ethyl)siloxane)), 390EO, and 2550EO, were synthesized. Dilute electrolyte solutions of 390EO and 2550EO were prepared using LiTFSI, LiFSI, and LiPF₆. The influence of the length of the siloxane polymer chain, salt type, and Si-tripodand centers at the side chain on ionic conductivity, t_Li⁺, and physical properties were examined. Both electrolyte systems showed high values of t_Li⁺ (0.35 for 2550EO/LiTFSI and 0.64 for 390EO/LiTFSI). Alternatively 390EO/LiPF₆ and 2550EO/LiPF₆ displayed high t_Li⁺ values of 0.61 and 0.44, respectively, while 390EO/LiFSI displayed the smallest t_Li+ (0.25). To clarify the role played by the Li⁺ environment in Li⁺ transport, the solvation states of electrolytes were examined. It was observed that anion solvation can be achieved using siloxane-based solvent in all systems. Walden plot analysis demonstrates that ionic diffusion was not controlled by either macroviscosity/microviscosity in the siloxane-based polymer electrolytes. Ions instead move along a relatively smooth ion-pathway without complete full segmental reorientation in 2550EO as a result of decoupling and high ion solvation behavior. Conversely, in 390EO, ions might move to available sites by a jumping after decoupling with low ion solvation behavior. Consequently, a high t _Li⁺ was achieved, and the oxidative stability of the salt was ensured.     

Effects of Spacer Chain Length and Additives on Solution Properties of Cationic Gemini Surfactant

The critical micelle concentration (CMC) has been determined for the gemini surfactant trimethylene-1,3-bis(dodecyldimethyl ammonium bromide)12-s-12,2Br^?1 by means of electricity conductivity measurements. For the same number of carbon atoms in the hydrophobic chain per hydrophilic head group, geminis have CMC values well below those of conventional single-chain cationic surfactants. The CMC of 12-3-12 reduces with the addition of n-alcohol except ethanol and with the increase of n-alcohol chain length as well as increase of concentration of n-butanol and sodium chloride. Steady-state fluorescence quenching technology has been employed to study the aggregation number of micelle, which increases with increase in the length of n-alcohol. The Kraft temperature measurements also indicate that the stability of solid surfactant hydrate decreases along with the improvement of concentration of n-butanol and sodium chloride.