On modifying properties of polymeric melts by nanoscopic particles

We study geometric and energetic factors that partake in modifying properties of polymeric melts via inserting well‐dispersed nanoscopic particles (NP). Model systems are cis‐1,4‐polybutadiene melts including a single atomic clusters of size varied in the range 10–150 atoms (3–7 Å in radius; 0.1–1.5% v/v). We modify the interactions between the chains and the particle by tuning attractive van der Waals interactions. Using molecular dynamics, we study equilibrium fluctuations and dynamical properties at the interface. The NPs move in the polymer matrix in two different regimes corresponding to trapped and free diffusion, depending on the NP size. Furthermore, degree of crowding around the NP by the polymer chains is quantified. Effect of NP size and interaction strength both on volume and volumetric fluctuations is manifested in mechanical properties, quantified here by bulk modulus, K. Tuning NP size and nonbonded interactions results in ～15% enhancement in K by addition of a maximum of 1.5% v/v NP. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Preparation of a Conducting Flexible Material from Silane Coupling Agent and Hydroxyl Terminated Polybutadiene Rubber by Hydrolysis and Condensation

Abstract

Synthesis and characterization of a flexible polymer produced from silane coupling agent (SCA) and hydroxyl terminated polybutadiene (HTPB) were performed. Mechanical properties of chemically and electrochemically prepared conducting composites synthesized from this polymer were investigated. Conductivities of the composites were also measured. Polypyrrole enhanced the mechanical properties of the chemically prepared conducting composite. Doping with iodine greatly changed the conductivity of the composite. However, the change in mechanical properties and the conductivities of the electrochemically prepared composite were not as significant when compared with the electrochemically prepared polypyrrole. Among the composites, a chemically prepared composite was highly flexible like rubber. However, the electrochemically produced composite possesses two orders of magnitude higher conductivity. Also, this composite revealed higher tensile strength and elasticity with respect to pristine polypyrrole.     

Synthesis and Characterization of Amphiphilic Block Copolymer by Block Copolymerization of Butadiene and Acrylamide using Macroazoinitiator

Abstract

Macroazoinitiator (MAI) was prepared from hydroxyl‐terminated polybutadiene (HTPB) and 4,4′‐azobis‐4‐cyanopentanoic acid by direct polycondensation in the presence of 1‐methyl‐2‐chloropyridinium iodide at room temperature. This MAI used for block copolymerization of AAm at 60°C gave the best results in chloroform but the formation of a crosslinked product could not be ruled out in dioxane. It was inferred that for production of a linear block copolymer, homogeneous reaction mixture was required.

The resulting products were characterized by spectral studies IR and NMR, viscosity measurements. Distinct phase segregation of hydrophobic and hydrophilic blocks was evident through DSC analysis.     

Synthesis of Low Molecular Distribution Dihydric Polybutadiene in the Presence of Triflic Acid

A method is described for the preparation of functional polybutadiene (PB) with hydroxyl groups along the polymer chain. This material can be used directly or as the starting substrate for further polymerization in both academic and industrial processes. We have developed a convenient method to obtain a polymer with a narrow molecular weight distribution and with a known content of hydroxyl groups along the backbone. By controlling the hydroxylation reaction conditions, the appropriate molar ratios of THF, water and acid with the epoxide are 30, 15 and 1.5, respectively. By minimizing the crosslinking reaction, the desired PB was prepared and subsequently characterized.     

Microstructure and morphology of self‐assembling multiblock poly(ethylene‐1‐butene)‐n copolymers in solution studied by wide‐Q small‐angle neutron scattering and microscopy

Multiblock ethylene‐1‐butene copolymers (PEB‐n) with graded ethylene content (where n is the number of ethyl branches per 100 backbone carbons) represent efficient cold filter plugging point (CFPP) depressants for crude oils and middle distillates. The aggregation behavior and the interaction with wax molecules of a tetrablock PEB‐2.6/PEB‐6.0/PEB‐10.9/PEB‐13.2 and triblock PEB‐6.5/PEB‐8.9/PEB‐10.1 copolymers in decane solutions were investigated over a wide temperature range by combining different small‐angle neutron scattering techniques and optical microscopy. The experimental results revealed in the decrease of temperature formation and evolution of multisized structural levels showing a hierarchical organization on the length scale from 1 nm up to 10 μm. One‐dimensional polymer aggregates arising as initial structures associate and branch that lead to the occurrence of complex macroaggregates with diffusive interfaces and sizes of several microns. The one‐dimensional copolymer structure shows longitudinal density modulation and micellar‐like substructures in neat polymer solutions. When wax is added, this structure becomes more homogeneous in decrease of temperature as a consequence of the cocrystallization of wax and copolymer. The wax crystallization in board‐like objects of much smaller size than required by the CFPP criterion of oil and refinery industry (filter mesh size of 45 μm) is templated and controlled by the assembling features of the crystalline–amorphous PEB‐n multiblock copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Inertial contributions to the pressure in the truncated-cone-and-plate apparatus with application to dilute polymer solutions

New measurements of the pressure distribution generated by two Newtonian liquids in the Truncated Cone-and-Plate Apparatus are presented, in order to evaluate the exact form of the inertial contribution for a range of Reynolds numbers (Re) fromRe = 140 toRe = 36,000;Re = R ² /, where and are the liquid density and viscosity respectively,R is the plate radius, and is the angular velocity of the cone. The Walters equation for lowRe, p ^w = 0.15 ² (r² – R²), is shown to be in excellent agreement with the measurements up toRe = 1000, provided an appropriate correction for the Newtonian hole pressure is made. Up toRe = 1000, the measured slope is within 1% of the theoretical value of 0.15 given by the Walters equation; as the Reynolds number increases above 1000, the data become increasingly nonlinear inr ². Other theoretical predictions made especially for largeRe begin to disagree with the data even belowRe = 1000. The application of the experimentally determined additive inertial contribution to measurements of pressure distribution in four dilute polymer solutions is found to reproduce adequately the expected form of the viscoelastic pressure distribution, even at highRe where the Walters equation is not valid. Measurements of a combination of normal-stress differencesN ₁ + 2N ₂ for polymer solutions involving specific polymer/solvent interaction sites show a difference of 45% with change of solvent, while no difference is observed in solutions of polymers without the interaction sites. The normal-stress ratio —N ₂/N ₁ for a 5% solution of cis-polybutadiene is 0.24 at a shear rate of 100 s^–1, and it appears to approach the zero shear limit of 2/7 given by the Doi-Edwards theory. The Higashitani-Pritchard-Baird-Lodge equation relating the elastic hole pressure to the normal-stress differenceN ₁ –N ₂ gives a qualitative agreement betweenN ₁ –N ₂ from the TCP Apparatus and the hole pressure from the Stressmeter; the percent difference is 0 at shear stress < 25 Pa, 35% at = 45 Pa, and 18% at the highest = 63 Pa.     

1,4‐Dilithio‐1,1,4,4‐tetraphenylbutane in diethyl ether: An effective initiator for the living anionic polymerization of dienes

The anionic polymerization of butadiene initiated with 1,4‐dilithio‐1,1,4,4‐tetraphenylbutane (LiTPB) in diethyl ether (DEE) gives polybutadiene (PBD) with high 1,2 content (>70%), narrow polydispersities (1.04 < M_w/M_n < 1.20), and predicted molecular weights. In THF, this polymerization does not work very well. After removal of DEE and addition of THF, the PBD dianion is end capped quantitatively by addition of 1,1‐diphenylethylene (DPE) to give the diphenylalkyl end capped PBD dianion. Subsequent addition of methyl methacrylate at low temperatures results in the formation of well‐defined PMMA‐b‐PBD‐b‐PMMA triblock copolymers. The results are accounted for by taking into account the effects of Li ion solvation on the BD initiation and end capping of the PBD anion by DPE. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2198–2206, 2009     

吡啶/喹啉单亚胺镍(Ⅱ)配合物的合成及液体聚丁二烯的制备

金属配合物中引入侧臂软电子给体膦或硫是提高配合物催化性能的有效途径。本文合成了一系列吡啶/喹啉单亚胺NNP三齿Ni(Ⅱ)配合物(2a~2d),采用傅里叶变换红外光谱、元素分析及单晶衍射对配合物进行了表征。配合物2a为方形锥体构型,配合物2d为三角双锥构型。该系列配合物在倍半乙基氯化铝(EASC)活化下,催化合成了数均相对分子质量为4200~7700、顺-1,4结构的摩尔分数在74.5%~79.9%的液体聚丁二烯。催化活性随着聚合温度的升高而提高。在90℃时,催化体系仍有很高的聚合活性,聚丁二烯的收率达到85.9%,表明其具有高的热稳定性。     

反相气相色谱法表征聚丁二烯橡胶的表面性质

采用反相气相色谱技术测定了聚丁二烯橡胶的表面性质。以正己烷、正庚烷、正辛烷、正壬烷作为非极性探针测定其表面色散自由能,以二氯甲烷、三氯甲烷、丙酮、乙酸乙酯、乙醚和四氢呋喃作为极性探针测定其路易斯酸碱常数。经计算得出聚丁二烯橡胶在303、313、323、333和343 K的表面色散自由能分别为47.07、46.46、45.85、45.60和45.09 mJ/m2。结果表明,聚丁二烯橡胶表面色散自由能随着温度的升高呈线性降低,路易斯酸常数Ka为0.34,碱常数Kb为1.77,总酸碱作用能力2.11,该聚合物为弱碱性Lewis两性聚合物材料。此外还计算出聚丁二烯橡胶的酸碱作用吸附自由能（~ΔGsa）和吸附焓（~ΔHsa）。     

钨酸钠/冰乙酸/过氧化氢作用下聚丁二烯橡胶环氧化及降解行为研究

本文研究了在钨酸钠/冰乙酸/过氧化氢催化体系作用下聚丁二烯橡胶环氧化及降解行为.采用红外(FT-IR)、核磁(1H-NMR)和气相凝胶渗透色谱(GPC)对降解产物进行了表征,结果表明60℃反应24h,聚丁二烯橡胶环氧度为21.27％,而其分子量没有明显降低.