液体聚异戊二烯的合成与应用研究进展

固态橡胶具有较高的分子量、强度及伸长率,在工业和日常生活中均得到广泛应用.然而,固态橡胶黏度较高,在应用中往往必须引入添加剂.而液体聚异戊二烯是一种液态橡胶,可以作为固态橡胶的软化剂;得益于其特殊的形态和性能,液体聚异戊二烯可望在多方面得到应用.对液体聚异戊二烯的合成与应用进行了评述.     

Addition-curable type liquid silicone rubbers based on phenyl-containing organopolysiloxanes with terminal vinyl groups

Russian Chemical Bulletin - A series of organosilicon rubbers of the addition-curable type containing dimethyland methylphenylsiloxy, or diphenylsiloxy units with terminal vinyl groups were...     

Depolymerization and ionic conductivity of enzymatically deproteinized natural rubber having epoxy group

Preparation of liquid epoxidized natural rubber (ENR) was made by oxidative depolymerization of ENR in latex stage without loss of epoxy group. Epoxidation of fresh natural rubber latex, which was purified by deproteinization with proteolytic enzyme and surfactant, was carried out with freshly prepared peracetic acid. The glass transition temperature (T_g) and gel content of the rubbers increased after the epoxidation, both of which were dependent upon an amount of peracetic acid. The gel content was significantly reduced by oxidative depolymerization of the rubber with (NH₄)₂S₂O₈ in the presence of propanal. The resulting liquid epoxidized rubber (M_n≈10⁴) was found to have well-defined terminal groups, i.e. aldehyde groups and α-β unsaturated carbonyl groups. The novel rubber was applied to transport Li⁺ as an ionic conducting medium, that is, solid polymer electrolyte.     

Reactivities of silane coupling agents in the silica/rubber composites: Theoretical insights into the relationships between energy barriers and electronic characteristics

Si69 and Si75, typical commodities of silane coupling agents, are often employed in tire recipes to work as the bridges connecting silica and polymers, with which rolling resistance and wet traction are enhanced without loss in abrasion resistance. In this article, the reactivities of Si69 and Si75 with silica and various rubbers were theoretically investigated by using density functional theory (DFT). When the agents were coupled with silica, not only the acid+water condition but also the pure acid condition was confirmed to readily trigger the condensation reactions. The corresponding Gibbs free energy barriers were related to the charge distributions of reaction regions. As the agents suffered from the homolysis of central S S bonds, the generated single-S-tailer radicals (R S·) showed significantly higher reactivities of both the radical addition and the α-H transfer reactions with rubbers, due to the stronger radical philicities of the terminal sulfur radicals with larger condensed local softnesses [s⁰(S)]. When the agents underwent the heterolysis of central S S bonds, the terminal sulfur anions with smaller s⁻(S) indices, however, facilitated the nucleophilic addition reactions with rubbers. Several derivative indices based on the condensed local softnesses were also proposed here to shed light on the reactivities from the viewpoint of the relationship between energy barriers and electronic characteristics. The above findings pave the way for the design of new kinds of silane coupling agents using computer-aided techniques, and meanwhile, provide references for the practical application of Si69 and Si75 to the silica/rubbers systems.     

Diene Rubber Modification Using Thiol-Type Derivatives

Thiol-containing antioxidants such as 4-(mercaptoacetamido)-diphenylamine (MADA) undergo ready addition of-SH groups to the double bonds in diene rubbers in the presence of initiators. The reaction is a radical chain process leading to rubbers with improved thermooxidative resistance. The modification reaction has been carried out on high cis-polyisoprene and polybutadiene, and conditions under which the physicochemical properties (e.g., inherent viscosity, gel content, and microstructure) are less affected have been found. An oxygen absorption test and DSC were used as rapid methods for evaluation of thermooxidative stability of modified rubbers. The superiority of rubbers with MADA chemically attached (ranging from 1 to 4 phr) was shown by a circulating air oven test and by an extraction process which simulates the aggressive environments experienced by many rubbers under practical conditions. The results obtained show that a small degree of modification (1 phr MADA) is large enough to provide good thermooxidative stability without alteration of the molecular characteristics of the parent rubbers. At higher degrees, cistrans isomerization can occur.     

Cross-linking of liquid low-molecular-weight siloxane rubbers with orthotitanic acid esters

The kinetics of cross-linking of SKTN liquid low-molecular-weight siloxane rubbers with orthotitanic acid esters (tetraethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium) was studied. The effective rate constants of the cross-linking at 130, 140, 150, and 160°C and the activation energies of the reaction were calculated. The effect of a catalyst, tin phthalocyanine, on the cross-linking of SKTN liquid rubbers with orthotitanic acid esters was examined.     

Cross-linking of borosiloxane oligomers and properties of materials with vulcanized borosiloxane coating

Cross-linking of liquid borosiloxane oligomers was studied. The reaction is described by a first-order rate equation for irreversible reactions. The effective cross-linking rate constants and activation energies of the reaction were calculated. The properties of materials with the vulcanized borosiloxane coating were studied. The physicomechanical properties of materials with borosiloxane coating are higher than those of materials with coatings based on vulcanized liquid siloxane rubbers.     

Promising European trends in the use of epoxy-based compounds

A review of the foreign literature on promising trends in the study of adhesives is presented. The following technologies have been noted as the main trends of development: use of adhesive hybrid systems, use of liquid rubber with terminal carboxyl and amine groups (core shell structure), combination of nanotechnology and rubber introduction, structural gluing and curing with induction-current heating.     

含氟液晶研究进展

本文简述了含氟液晶的研究进展。根据小分子含氟液晶中氟原子或含氟基团的位置不同,将其分为3类：末端是氟原子或含氟基团的液晶、苯环上氢原子被氟原子取代的液晶、中心桥键上的氢原子被氟原子取代的液晶。根据小分子含氟液晶特点,归纳了氟原子或含氟基团对液晶分子物理性质的影响。同时对高分子含氟液晶的研究进展也做了介绍。     

可溶性聚酰亚胺液晶取向膜的制备与性能

液晶取向膜是液晶显示器中的关键材料,为了制得性能优良的液晶取向膜,我们通过铃木偶联反应制备了3种含有不同末端基团的3,5-二氨基联苯,将制得的3种二胺单体分别与环丁烷四甲酸二酐聚合得到3种新型的聚酰亚胺。 利用核磁氢谱对单体和聚合物的结构进行了表征,测试了聚合物的溶解性、热稳定性以及用作液晶取向膜的性能。 结果表明,所得的聚酰亚胺具有良好的溶解性和热稳定性,经过机械摩擦后,末端带有甲氧基的聚酰亚胺能使液晶分子平行于摩擦方向取向,末端带有苯氧羰基和联苯氧羰基的聚酰亚胺能使液晶分子垂直于摩擦方向取向。 此类可溶性的聚酰亚胺液晶取向膜将简化制备工艺并在柔性显示器件中具有较大的应用价值。     

The synthesis and liquid crystal behaviour of monosubstituted ferrocenomesogens

The synthesis and characterization of several new series of monosubstituted ferrocenyl-containing liquid crystals has been achieved. The results indicate that a terminal ferrocenyl group can promote stabilization of a nematic liquid crystal state. At least three phenyl rings are required in the molecular core in order to provide nematic properties and addition of a fourth ring substantially enhances it. Bulky lateral substituents or the introduction of linker groups that introduce kinks inhibit liquid crystal phase formation. Short highly polarising terminal groups or terminal groups that support hydrogen bonding support liquid crystal behaviour.     

Kerr effect in solutions of carbosilane dendrimers with terminal mesogenic groups

First results of investigations of electro-optical properties of liquid crystalline (LC) dendrimers in solution are presented. Measurements of electric birefringence (Kerr effect) and dielectric polarization of first generation carbosilane dendrimers with different ester linked terminal mesogenic groups (cholesteryl, cyanobiphenylyl and 4-methoxyphenyl benzoate) have been carried out using dilute solutions in CCl4. The results show that the dielectric polarization is proportional to the second power of the electric field in accordance with Kerr law. The Kerr constants calculated are close to those of the low molar mass analogues of the corresponding mesogenic groups. Thus the electric birefringence of the LC dendrimer solutions is mainly determined by the electro-optical properties of their terminal mesogenic groups oriented in the electric field independently of the main chain.     

Modification of epoxy resins with liquid polysulfide and carboxylated butadiene rubbers

In this work, we present the results of studying the effect of liquid carboxylated butadiene and polysulfide rubbers on the physicomechanical and adhesive properties of epoxy adhesive compositions with curing agents of different chemical nature—diethylene triamine and polyoxypropylene triamine. It is found that carboxylated butadiene rubbers are more effective modifiers than polysulfide rubbers because they yield a higher complex of properties. It is also shown that the change in the chemical nature of a curing agent has no significant effect on the properties of epoxy-rubber adhesive compositions, which allows one to control their key technological parameters without fear of losing strength characteristics.     

Preparation of the pigment mixtures (“masterbatches”) using rubbers Li-PBR synthesized by the solution polymerization

A method of liquid phase filling by hydrophobized aerosil (white carbon) of the solution styrenebutadiene rubbers SSBR of different structures for use in the tread rubbers in the production of “green” tires. Surface modification of the silicic filler was carried out in a hydrocarbon solvent environment by various silicon and nitrogen-containing agents.     

Experimental branching results for diene polymers by use of gel-permeation chromatography

Branching analyses in styrene–butadiene rubbers and polybutadiene rubbers have revealed large differences in branching between rubbers polymerized in different ways. The functionalities of several star-branched solution-polymerized styrene–butadiene rubbers were calculated and compared to their expected structures. Emulsion-polymerized polybutadiene rubber and a series of solution-polymerized polybutadienes made with different catalysts had different degrees of random branching, and evidence is presented indicating that the different available catalyst systems provide some latitude in making rubbers of different branching contents. Random branching analyses on a series of emulsion-polymerized styrene–butadiene rubbers revealed the dependency of branching on molecular weight and molecular weight distribution. The influence of polymerization temperature on the branching of emulsion-polymerized styrene–butadiene rubber was also studied.     

Preparation and properties of lateral monofluoro-substituted benzoxazole-based mesogenic compounds

A series of 2-(3?-fluoro-4?-alkoxy-1,1?-biphenyl-4-yl)-benzoxazole liquid crystals (coded as nPF(3)PBx) were prepared, where a lateral fluorine substituent, as well as methyl, chlorine and nitro terminal groups, was introduced into the molecules to investigate the effects of different polar substituents on the liquid crystal properties. The mesomorphic and photophysical properties were investigated. The results show that compounds nPF(3)PBx have enantiotropic mesophases; meanwhile, they exhibit UV–vis absorption bands with maxima at 323–326 nm and photoluminescence emission peaks at 389–395 nm, respectively. It is noted that nPF(3)PBx with terminal polar groups or electron-withdrawing groups (NO₂, Cl) display higher clearing temperatures and wider mesophase range than those of the corresponding homologues with terminal non-polar groups or electron-donating groups (CH₃, H). Meanwhile, compared with two lateral fluorine-substituted analogues containing 3,5-difluorophenyl unit, lateral monofluoro-substituted nPF(3)PBx display enhanced mesophase range both in heating and cooling except for terminal methyl-substituted compounds, as well as show obvious red-shifted UV–vis absorption bands and photoluminescence emission, which are attributed to the enhanced dipole–dipole interaction caused by increased dipole moment.     

遥爪型液体聚合物及其多相共聚物的合成与表征——Ⅰ.端羧基乙烯基四氢呋喃-环氧丙烷液体共聚醚的合成

本文探索了端羟基液体聚合物,四氢呋喃-环氧丙烷共聚醚,与顺丁烯二酸酐的酯化反应,得到了端羧基乙烯基液体聚合物。 通过控制反应温度,配料比以及选择适宜的催化剂,使端基转化率达到了100%。 用化学分析、核磁共振以及红外光谱分别对端基转化程度和聚合物结构进行了测定。     

Synthesis and properties of thermoplastic and dissolvable polysiloxanes containing polyhedral oligomeric silsesquioxane

There are many benefits associated with thermoplastic silicones, but very few examples exist: silicone resins or rubbers are normally thermosets. In this article, a facile and efficient approach was reported to prepare thermoplastic silicone by introducing a bulky side siloxane group. Monofunctional polyhedral oligomeric silsesquioxane (POSS), as the bulky siloxane group, was grafted onto the linear polysiloxane backbone via thiol–ene click reaction, endowing the liquid polysiloxane with thermoplastic nature. The POSS-grafted polysiloxane could be remolded by a hot-melting or solution casting process. It was worth noting that the novel thermoplastic silicone was composed of both linear siloxane main chains and siloxane side groups, which was distinctly different from previous researches on thermoplastic silicones consisted of siloxane main chains and organic side groups. Thermal analysis, rheological characterization and molecular dynamics simulation results revealed the thermoplastic properties of POSS-grafted polysiloxane depended on the bulky POSS's hindrance to the movement of the polymer backbone rather than the interaction between the organic side groups.     

Gasoline- and oil-proof rubbers based on cyclic α-oxides for heavy-duty rubber technical goods

The physicomechanical properties of oil- and gasoline-proof rubbers based on cyclic α-oxides (epichlorohydrin, propylene oxide) and hydrocarbon rubbers (butadiene-nitrile, chloroprene) are described. It is shown that epichlorohydrin rubbers (EKhGKs) have some advantages over butadiene-nitrile and chloroprene rubbers, particularly for operation in extreme conditions in oil drilling and gas equipment for environments with a high content of hydrogen sulfide. Examples of the application of low-molecular EKhGKs as adhesives and sealants are given.     

Chemiluminescence spectral analysis of styrene-butadiene and acrylonitrile-butadiene rubbers using a multichannel Fourier-transform chemiluminescence spectrometer

The chemiluminescence spectra of styrene-butadiene and acrylonitrile-butadiene rubbers isothermally heated in the range between room temperature and 200 °C were measured with a multichannel Fourier-transform chemiluminescence spectrometer. The observed spectra were analyzed by a least-squares fit using a Gaussian function to determine the peak intensity and the peak wavelength of emission bands. It was found that the peak wavelength of acrylonitrile-butadiene rubbers was slightly longer than that of styrene-butadiene rubbers due to the influence of the nitrile groups. The peak intensity of chemiluminescence from styrene-butadiene rubbers decreased with the styrene content, while that from hydrogenated acrylonitrile-butadiene rubbers increased with the iodine value. From these experimental results, it is concluded that the content of double bonds in the butadiene units in rubbers is measurable by chemiluminescence spectral analysis.