Influence of molecular weight on selective oligomer-assisted dispersion of single-walled carbon nanotubes and subsequent polymer exchange

A series of oligofluorenes was synthesized and used as a SWNT selecting template to study the chain length effect on SWNTs dispersions in toluene. The octamer exhibits the same selectivity as the corresponding polymer. Nevertheless, SWNT/oligomer complexes are unstable, which allows fast exchange of the oligomer with a coating polymer.     

CRYSTALLIZATION BEHAVIOR OF PURE AND ADDITIVE-CONTAINING POLY (ETHYLENE TEREPHTHALATE)

The isothermal crystallization of poly (ethylene terephthalate ) (PET),which is free of catalyst, stabilizer, oligomer and diethylene glycol (DEG), was studied by DSC. The crystallization behaviour of pure PET is different from commercial PET and a reasonable explanation is presented. The influences of catalyst, stabilizer, oligomer and DEG on the crystallization of pure PET were examined. It is shown that catalyst (Manganese acetate)and stabilizer (Triphenyl phosphite) result in an increase of the crystallization rate of PET; on the contrary, DEG and oligomer (cyclotetramer) result in a reduction of the crystallization rate. When catalyst and stabilizer coexist together, both of them promote the crystallization at lower temperature ,only a smaller effect was found at higher temperature, it is evident that metal phosphite is formed between the catalyst and stabilizer at higher temperature.     

“水包水”型阳离子聚丙烯酰胺乳液的合成

The emulsion of cationic polyacrylamide was prepared by a soap-free polymerization,using water as media,the oligomer that prepared by myself as emulsifier and stabilizer,(NH_4)_2S_2O_8 as initiator.The effect of the amount of isopropanol,oligomer and the ratio of DMC/AM on the molecular weight of cationic polyacrylamide were all studied.The best amount of isopropanol,oligomer are 25%,20% of the total monomer and the ratio of DMC/AM is 3/7.     

Effects of chemical structure on low-temperature modulus for UV-curable polybutadiene acrylates as an optical fiber coating material

The relationship between chemical structure and low-temperature modulus of ultraviolet(UV)-radiation-cured optical-fiber coating materials has been investigated. The coating materials are low-viscosity liquid compounds consisting of a 1,4-polybutadiene diacrylate oli-gomer, a monomer, and a photoinitiator. Dynamic mechanical test results show that low-temperature modulus and glass transition temperature (T_g) are affected by the monomer structure and monomer concentration in the coating material in cases where the same oligomer is used. With increasing alkyl group chain length of the alkylacrylate monomer, the T_g value is shifted to lower temperatures. Low-temperature modulus increases with increasing monomer concentration in the coating material. Low-temperature excess optical losses of coated fibers have been found to be closely related to low-temperature modulus of the coating.     

Organic light‐emitting devices having chemically‐doped arylamine oligomer as a hole injection layer

A soluble and thermally stable arylamine oligomer containing difluorenyl groups was prepared and applied to organic light‐emitting devices (OLEDs) as a hole injection layer. The oligomer layer was doped with a Lewis acid and formed by spin coating from the dichloroethane solution. The OLED with a structure of indium tin oxide (ITO)/Lewis‐acid‐doped arylamine oligomer/N,N′‐dinaphthyl‐N,N′‐diphenyl bendizine (α‐NPD)/tris(8‐quinolinolato)aluminum(III) (Alq₃)/LiF/Al showed lower drive voltages and higher power efficiencies, compared with the devices without the hole injection oligomer layer. Copyright © 2005 John Wiley & Sons, Ltd.     

Quantitative studies of interaction between complementary polymers and oligomers in solutions

A theoretical model for interpolymer reaction of the type: matrix + oligomer ? polycomplex has been considered. Matrix and oligomer are complementary macromolecules with the matrix chain length substantially greater than that of the oligomer chain. Theoretical relations connecting the conversion degree in the interpolymer reaction with temperature, oligomer length and oligomer concentration are developed. The limits for application of the considered theoretical model are indicated. High selectivity of the interpolymer reaction with respect to the oligomer chain length is predicted theoretically. The validity of the theoretical relations is demonstrated by the reactions between polycarboxylic acids and polyethylene glycol in aqueous and water-methanol media. The selectivity of the interpolymer reactions with respect to chain length is experimentally proved for the example of fractionated relatively low molecular poly-N-vinyl pyrrolidone complexing with polyacrylic acid.     

Quantitative analysis of hindered amine light stabilizers by CZE with UV detection and quadrupole TOF mass spectrometric detection

The current work describes the development of a CZE method with quadrupole QTOF‐MS detection and UV detection for the quantitation of Cyasorb 3529, a common hindered amine light stabilizer (HALS), in polymer materials. Analysis of real polymer samples revealed that the oligomer composition of Cyasorb 3529 changes during processing, a fact hampering the development of a straightforward method for quantitation based on calibration with a Cyasorb 3529 standard. To overcome this obstacle in‐depth investigations of the oligomer composition of this HALS using QTOF‐MS and QTOF‐MS/MS had to be performed whereby 22 new oligomer structures, in addition to the ten structures already described, were identified. Finally, a CZE method for quantitative analysis of this HALS was developed starting with a comprehensive characterization of a Cyasorb 3529 standard using CZE‐QTOF‐MS, subsequently allowing the correct assignment of most Cyasorb 3529 oligomers in an electropherogram with UV detection. Employing the latter detection technique and hexamethyl‐melamine as internal standard, peak areas obtained for the melamine could be correlated with those from the triazine ring, the UV‐absorbing unit present in the HALS. This approach finally allowed proper quantitation of the single oligomers of Cyasorb 3529, an imperative for the quantitative assessment of this HALS in real polymer samples.     

Study of structuring of surface-modified technical-grade carbon particles with metal oxides in oligo(divinyl-isoprene)

Effect of a nanosize coating of technical-grade carbon particles with metal oxides NiO, CuO, PbO, and Bi₂O₃ on processes in which continuous carbon structures are formed in an oligomer formulation was studied. The elastic and dissipative constituents of rheological properties of the 3D carbon structures being formed were determined. An optical method and computerized data processing yielded data on structuring of a filled oligomer system under various testing conditions.     

Synthesis and characterization of UV‐curable phosphorus containing hybrid materials prepared by sol–gel technique

In this study, a series of ultraviolet (UV)‐curable organic–inorganic hybrid coating materials containing phosphorus were prepared by sol–gel approach from acrylate end‐capped urethane resin, acrylated phenyl phosphine oxide oligomer (APPO), and inorganic precursors. TEOS and MAPTMS were used to obtain the silica network and Ti:acac complex was employed for the formation of the titania network in the hybrid coating systems. Coating performance of the hybrid coating materials applied on aluminum substrates was determined by the analysis techniques, such as hardness, gloss, impact strength, cross‐cut adhesion, taber abrasion resistance, which were accepted by international organization. Also, stress–strain test of the hybrids was carried out on the free films. These measurements showed that all the properties of the hybrids were enhanced effectively by gradual increase in sol–gel precursors and APPO oligomer content. The thermal behavior of the hybrid coatings was investigated by thermogravimetric analysis (TGA) analysis. The flame retardancy of the hybrid materials was examined by the limiting oxygen index (LOI); the LOI values of pure organic coating (BF) increased from 31 to 44 for the hybrid materials containing phosphorus (BF‐P:40/Si:10). The data from thermal analysis and LOI showed that the hybrid coating materials containing phosphorus have higher thermal stability and flame resistance properties than the organic polymer. Besides that, it was found that the double bond conversion values for the hybrid mixtures were adequate in order to form an organic matrix. The polycondensation reactions of TEOS and MAPTMS compounds were also investigated by ²⁹Si‐NMR spectroscopy. SEM studies of the hybrid coatings showed that silica/titania particles were homogenously dispersed through the organic matrix. In addition, it was determined that the hybrid material containing phosphorus and silica showed fibrillar structure. Copyright © 2009 John Wiley & Sons, Ltd.     

不同低聚乙二醇链长的聚对亚苯基亚乙烯基类交替型发光共聚物

合成了3种分子主链由1,4二苯乙烯基苯(DSB,聚对亚苯基亚乙烯基PPV三单元的低聚物)与不同长度的离子传导型隔离链段低聚乙二醇(OEO,或聚氧乙烯)组成的交替型蓝色发光共聚物DSB二缩三乙二醇(TEO)、DSB五缩六乙二醇(SEO)和DSBPEG1500.研究了3种聚合物在其氯仿溶液中的电荷传输机理.通过多种手段考察了不同长度的OEO链段对聚合物的结晶能力、相结构以及其对锂盐溶解能力的影响,并讨论了此类材料的合理结构设计原则.以DSBTEO为发光层材料,装配了电致发光器件.     

Novel UV-protective formulations for cotton, PET fabrics and their blend utilizing irradiation technique

A novel coating formulation to impart ultraviolet (UV) protection property to cotton, Polyethylene trephethalate (PET) and cotton/PET fabrics was prepared and gamma rays as an ionizing radiation was utilized for surface curing. Natural occurring aluminum potassium sulfate (Alum) was used individually and in binary coat with Zinc Oxide (ZnO), to induce the UV-blocking properties. It was found that using Alum (0.3 g/ml) caused a prompt increase in ultraviolet protection factor (UPF) over the uncoated fabrics. Moreover, the incorporated ZnO in the binary coat increased the UPF for two to threefold than the stand-alone Alum coating, specially in case of PET coated fabric. Water absorbance and moisture regain of ZnO and Alum/ZnO coated fabrics showed a decrease over the blank samples, due to the usage of oligomer/monomer combination. On contrary, Alum showed a hydrophilic effect with the increase in its content in the formulation. Surface Electron Microscope showed the homogenous coating of fibers. X-ray diffraction (XRD), energy dispersive X-ray (EDX) and water vapor permeability were also tested for coated samples.     

超临界二氧化碳中无水相涂料的合成与表征

为了减小传统纸张涂布中涂料水分对涂布能耗、涂布质量以及对涂布原纸质量的影响,研究了以超临界二氧化碳为反应介质,制备聚甲基丙烯酸甲酯(PMMA)和碳酸钙颜料混合的粉末涂料粒子.通过FTIR、GPC-十八角度激光光散射联用技术对PMMA组成结构进行了表征,考察了反应体系中引发剂浓度、单体浓度、稳定剂浓度、反应温度和反应时间对聚合反应的转化率和聚合产物的分子量的影响.实验表明,当反应条件为反应压力10MPa,反应温度75℃,反应时间8h,单体浓度0.10g/mL,引发剂浓度0.10×10-2g/mL,稳定剂浓度0.06×10-2g/mL时,其聚合反应的转化率较高,同时PMMA的分子量适中,分子量分布窄.SEM观察到混合涂料粒子颗粒均匀,表明颜料在粉末涂料体系中分散性良好.     

Self-assembly of folded m-phenylene ethynylene oligomers into helical columns

Circular dichroism spectroscopy has been used to study the self-assembly of two series of m-phenylene ethynylene oligomers in highly polar solvents. The helical conformation of shorter oligomer lengths was found to be stabilized in aqueous acetonitrile solutions, while longer oligomers began to interact intermolecularly. The intermolecular aggregation of the oligomers in aqueous solutions revealed a chain length dependent association that required the presence of a stable helical conformation. Evidence for intermolecular interactions is provided by Sergeants and Soldiers experiments in which the twist sense bias of a chiral oligomer is transferred to an achiral oligomer.     

Synthesis and Characterization of Poly(ethylene glycol) Dimethacrylate Hydrogels

Facile synthesis and detailed characterization of photo-polymerizable and biocompatible poly(ethylene glycol) dimethacrylates (PEGDM) and their hydrogels are described. Combined analyses of ¹H NMR and MALDI-TOF MS confirmed the formation of prepolymers of high purity and narrow mass distribution (PD < 1.02). A systematic investigation into the structure and mechanical properties of PEGDM hydrogels was performed to characterize the relationships between the network structure and gel properties. Small-angle neutron scattering was used to characterize the structural features of hydrogels with respect to their semidilute solution precursors. A well-defined structural length scale (correlation length) manifested as a maximum in the scattering intensity was observed for hydrogels derived from high molecular mass PEGDMs and/or high oligomer mass fractions. Hydrogels derived from lower molecular mass PEGDMs and/or low oligomer mass fractions exhibited multiple correlation lengths suggesting the formation of inhomogeneous gel structures. The shear moduli, determined from uniaxial compression measurement, showed that the gel structures correlate well with the gel mechanical properties.     

亚碘酰苯低聚物的结构与振动光谱18O-同位素效应的理论研究

应用LDA-PWC方法对亚碘酰苯低聚物HO-(PhIO)n-H (n＝1～10)(链末端以羟基结束)共10个模型分子进行了理论研究. 计算结果表明PhIO分子链大致呈“T”形, I—O链的两个I—O键键长非常接近, 同时发现I—O链产生扭转, 整个亚碘酰苯低聚物呈螺旋状结构. 应用B3LYP法得到HO-(PhIO)6-H更为精确的亚碘酰苯低聚物稳定构型, 平均I—O键长为0.2089 nm, 标准偏差为0.0007 nm. 理论计算表明在600～400 cm－1段, PhI18O的吸收峰向低波数方向移动, 与实验观测结果一致. 振动模式分析发现该段吸收峰均涉及氧原子, 18O同位素效应将降低各振动峰值的频率. 峰值移动最大的吸收峰为591/566 cm－1 (16O/18O), 与之对应的理论计算值为590.409/557.788 cm－1 (16O/18O), 属于对称伸缩振动ν(I—O—I). 吸收峰(443/436 cm－1)对应的理论计算值为460.627/439.158 cm－1 (16O/18O), 归属于不对称伸缩振动ν(I—O—I).     

Ag/Au纳米粒子的没食子酸还原制备及其共振瑞利散射光谱测定人血清总蛋白

以没食子酸为还原剂和稳定剂,用种子生长法制备出粒径均匀、单分散性和稳定性好、近球形的Ag/Au 核壳纳米粒子.高分辨透射电镜(HRTEM)与 X-射线能量色散光谱仪(EDX)测试表明,在Ag/Au摩尔比为1:1.6时,Au已完全包裹在Ag纳米粒子表面时,平均粒径为25 nm.以此摩尔比制备的Ag/Au核壳纳米粒子为探针...     

Spatial correlations of a flexible-chain oligomer in an ionic liquid

The effect of the length of the cationic tail of an ionic liquid on the dependence of the scale of structural heterogeneities of a flexible-chain oligomer dissolved in the liquid on the oligomer concentration is studied in terms of the integral equation theory. The structure of the ionic-liquid-oligomer mixture is analyzed with the use of the calculated partial structure factors. The effect of the alkyl chain length of the cation on the dependence of the characteristic scale of ordering of the oligomer chains on their concentration in the solution is the most significant for an ionic liquid with medium-length and long cationic tails. It is shown that the behavior of this dependence is affected by the type of ordering of the ionic-liquid ions. For comparison, a similar dependence for an oligomer in a molecular solvent is calculated and analyzed.     

In situ formed silica nanofiber reinforced UV-curable phenylphosphine oxide containing coatings

A series of UV-curable nanocomposite coating materials were prepared by sol–gel technique from tetraethoxysilane (TEOS), methacryloxypropyltrimethoxysilane (MAPTMS) in the presence of urethane acrylate resin based on polyethylene glycol 400 (PEG400). The sol–gel precursor content in the hybrid coatings was varied from 0 to 30 wt.%. In addition, acrylated phenylphosphine oxide oligomer (APPO) is replaced with urethane acrylate resin in order to investigate its effect on the nanocomposite property. The physical and mechanical properties such as; gel content, hardness, adhesion, gloss, impact strength as well as tensile strength were examined. Results from these measurements showed that all the properties of the hybrid coatings improved effectively by gradual increase in sol–gel precursor and APPO resin content. The real time infrared technique was used to follow the degree of acrylic double bond conversion. The thermal stabilities of the UV-cured nanocomposites were investigated by thermogravimetric analysis. The results revealed that the addition of sol–gel precursor and APPO oligomer into the organic network leads to an improvement in the thermal and flame resistance properties of the hybrid materials. It was also determined that the APPO containing hybrid coating with 20 wt.% silica content gave higher char yield than the coating without APPO. It is a desirable achievement to improve simultaneously both the flame retardancy and mechanical properties of a protective coating. SEM studies indicated that inorganic particles were dispersed homogenously through the organic matrix. The hybrids were nanocomposite. It was also found that, incorporation of APPO resin might govern the silica organization and this leading to formation of nanofibrillar structure.     

Photophysics of monodisperse platinum-acetylide oligomers: delocalization in the singlet and triplet excited states

A series of monodisperse Pt-acetylide polymers that contain the [-CC-(p-C6H4)-CC-(t-Pt(PBu3)2)-]n repeat unit has been prepared for n = 1, 2, 3, 4, 5, and 7. The photophysical properties of the series provide information concerning the relationship between the oligomer length and delocalization in the singlet and triplet excited states of the pi-conjugated electron system. The results imply that the singlet excited state is delocalized over approximately 6 repeat units; however, the triplet state is considerably more localized. The triplet energy is almost invariant with oligomer length, but the phosphorescence spectra and triplet nonradiative decay rates indicate that the electron-vibrational coupling in the triplet state decreases with increasing oligomer length.     

Functional monomers and polymers. XCVII. Synthesis of oligomer models of polyethyleneimine derivatives containing pendant thymine bases

A series of oligomer models of polyethyleneimine derivatives having pendant thymine bases were prepared by the reaction of carboxyethyl derivatives of thymine with oligomer amines using an activated-ester method. It was found that the hypochromicity values obtained from UV spectra and pKa values obtained from spectrophotometric titrations depend on the chain length of the oligomers and the thymine content of the polymers.