Formation of color centers and paramagnetic species by alkaline hydrolysis of polydiphenylenesulfophthalide

Blue color centers (CC) (an intense absorption band (AB) at 566 nm and a weaker AB at 350 nm) and paramagnetic species (PMS) that give an ESR singlet withg=2.0028 and δH=10 Oe are formed by the treatment of a DMSO solution of polydiphenylenesulfophthalide with an excess of LiOH. The formation of blue CC is accompanied by a decrease in the intensity of the absorption band of the phenyl groups of the polymer at 270 nm. The blue CC were attributed to quinoid structures like the Chichibabin hydrocarbon. The long-wave absorption at 650–800 nm was assigned to the regions of quinoid-benzoid conjugation. The color centers and PMS were also observed when the polymer was hydrolyzed in cyclohexanone; however, in this case, the reaction was accompanied by polymer aggregation. The electronic spectrum of the Chichibabin hydrocarbon was calculated by the PM3 method. The identity of CC formed by alkaline hydrolysis and appearing in the polymer—aniline—cyclohexanone system was shown. The absence of “quinoid” CC for polyterphenyl sulfophthalide was explained by the energetically unfavorable singlet state for structures similar to the Müller hydrocarbon. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya No. 2, pp. 295–300, February, 2000.     

Factorization and recursion relations of the matching and characteristic polynomials of periodic polymer networks

Recent developments in the analysis of mathematical structure of the matching and characteristic polynomials of linear and cyclic periodic polymer networks are surveyed, especially on the newly found efficient algorithms and techniques for deriving their recursion relations and factorization expressions. Advantages and disadvantages of these two polynomials for manipulating large networks are compared and discussed with examples. Contrary to the case of singly connected polymer networks, only a few useful mathematical properties are shown to be found for doubly connected polymer networks. Linear and cyclic fence graphs are proposed to be defined instead of the conventional definitions of the so-called Hückel and Möbius ladder graphs, so that simpler and more useful mathematical relations hold for their matching polynomials.     

Raman study of the polybenzimidazole-phosphoric acid interactions in membranes for fuel cells

Poly(2,5-benzimidazole) (AB-PBI) membranes are investigated by studying the FT-Raman signals due to the benzimidazole ring vibration together with the C-C and C-H out-of- and in-plane ring deformations. By immersion in aqueous ortho-phosphoric acid for different time periods, membranes with various doping degrees, i.e. different molar fractions of acid, are prepared. The chemical-physical interactions between polymer and acid are studied through band shifting and intensity change of diagnostic peaks in the 500-2000 cm(-1) spectral range. The formation of hydrogen bonding networks surrounding the polymer seems to be the main reason for the observed interactions. Only if the AB-PBI polymer is highly doped, the Raman spectra show an additional signal, which can be attributed to the presence of free phosphoric acid molecules in the polymer network. For low and intermediate doping degrees no evidence for free phosphoric acid molecules can be seen in the spectra. The extent of the polymer-phosphoric acid interactions in the doped membrane material is reinvestigated after a period of one month and the stability discussed. Our results provide insight into the role of phosphoric acid as a medium in the conductivity mechanism in polybenzimidazole.     

Polymer drag-reducing agents for transportation of hydrocarbon liquids: Mechanism of action,estimation of efficiency,and features of production

The mechanisms of action of polymer additives that affect drag during the turbulent flow of hydrocarbon liquids is studied. A laboratory method for estimating the ability of these additives to reduce the drag is developed. It is established that the data of laboratory experiments can be used for predicting the efficiency of polymer drag-reducing agents in the transportation of hydrocarbon liquids in industrial applications. The advantages and disadvantages of different methods for producing polymer drag-reducing agents are discussed.     

Hydrocarbon separations by glassy polymer membranes

Polymers are unarguably the most broadly used membrane materials for molecular separations and beyond. Motivated by the commercial success of membrane-based desalination and permanent gas separations, glassy polymer membranes are increasingly being studied for hydrocarbon separations. They represent a class of challenging yet economically impactful bulk separations extensively practiced in the refining and petrochemical industry. This review discusses recent developments in membrane-based hydrocarbon separations using glassy polymer membranes relying on the sorption-diffusion mechanism. Hydrocarbon separations by both diffusion-selective and sorption-selective glassy polymer membranes are considered. Opinions on the likelihoods of large-scale implementation are provided for selected hydrocarbon pairs. Finally, a discussion of the challenges and outlook of glassy polymer membrane-based hydrocarbon separations is presented.     

Structural basis for the discrepancy of spectral behavior in C-H stretching band between steroids and long chain hydrocarbon compounds

The discrepancies of the spectral behavior for the C-H stretching band between some long chain hydrocarbon compounds and steroids were investigated. At low temperature, the C-H stretching bands exhibit complex fine structure in steroids but remain simple in long chain hydrocarbon compounds. MM3 molecular mechanics calculation indicates that, for long chain hydrocarbon compounds, the C-H groups vibrate with large scale coupling. There exist a few bands where the C-H groups vibrate in synchronous and inphase mode. Thus the variations of dipole moment for these bands are enhanced and the intensities are obviously stronger than others and cover other band in the spectra. This is just the reason why the C-H stretching bands are simple even at low temperature environment. Nevertheless, for the steroids, the C-H stretching bands vibrate with local coupling mode. The synchronous enhancement effect does not occur, the differences of intensities for various modes are not as large as those in long chain hydrocarbo     

Theory of nematic networks with finite extensibility

A statistical molecular model of polymer networks, which takes into account inter-molecular orientational interaction and constancy of the chain contour length, is proposed. A simple formula for the network free energy valid for any deformations is obtained. A system of equations which describes orientational-elastic interactions in polymer networks is derived. The influence of deformation and degree of cross linking on the conditions of network phase transition into the orientationally ordered state of the nematic type is studied. The deformation curves considerably deviate from those predicted by the classical elasticity theory. A comparison of the proposed theory with experimental data for natural rubbers is carried out.     

Broadband reflection in polymer stabilized cholesteric liquid crystal cells with chiral monomers derived from cholesterol

In this study, a series of achiral monomers and chiral monomers of different flexible spacer chains based on cholesteryl moiety were synthesized. Polymer stabilized cholesteric liquid crystal (PSCLC) cells were then created by incorporation of the polymer networks. The influence of the nature of the monomers and the spacer length of chiral monomers on the reflectance properties of PSCLC was investigated as well as the polymerization condition. The results strongly suggest that the chirality of the polymer networks plays an integral role in the observed reflection spectra, and the chiral polymer networks with chiral centers separated well from the polymer backbone induce a greater change in the bulk helix pitch, and produce the broader reflection band in these LC composites. In addition, the temperature dependence of the pitch of the composites before and after polymerization was investigated. To broaden the reflection band further, the experimental processes of thermally induced pitch variation simultaneously with a UV crosslinking reaction of the composites were presented. The morphology of the polymer network in the composites was studied by scanning electron microscopy (SEM). Copyright © 2008 John Wiley & Sons, Ltd.     

Sequenced click chemistry and photopolymerization: a new approach toward semi‐interpenetrating polymer networks

Multi‐step curing systems involving photopolymerization are of great interest because they provide easy tunable properties and processes for polymer synthesis. Herein, new perspectives are proposed to form semi‐interpenetrated polymer networks through a versatile process involving two orthogonal chemistries. The sequence of reaction has been designed as follows: (i) a stoichiometric aza‐Michael addition between acrylates and amines in a methacrylate medium and (ii) ultraviolet curing of methacrylates. According to the structure of amine, this method affords the production of either mixed networks or semi‐interpenetrated polymer networks. Finally, it is shown that divinylsulfone can be used instead of acrylate, granting many opportunities to develop multifunctional materials with diverse and varied properties. Copyright © 2016 John Wiley & Sons, Ltd.     

Birefringence of semicrystalline polymeric networks

A simple theoretical development is proposed to explain the variation of birefringence with degree of crystallization for crosslinked, stretched polymer networks. The model adopted for the calculations is one proposed by Flory in order to calculate the thermodynamic properties of such systems and hence is restricted to the special case of network orientation prior to the onset of crystallization. Our findings are briefly discussed and possible applications of the results are considered.     

NMR analysis of distribution of chain lengths between crosslinks of polymer networks

A novel technique for the analysis of the distribution of chain lengths between crosslink junctions of polymer networks is proposed. The technique is based on the relation between the high-temperature nuclear magnetic resonance free-induction decay and the network structure. The distribution functions are determined for a number of networks. In particular, the evolution of structure of a thermally degrading network is studied. © 1994 John Wiley & Sons, Inc.     

超临界CO2在聚合物中的溶解计算研究进展

本文以超临界CO2在聚合物中的溶解计算模型为例,综述了状态方程、经验方程和人工神经网络计算方法的实现原理、研究现状和优缺点;依据人工神经网络预测方法存在的问题,重点阐述基于混合智能方法的神经网络溶解计算模型;并对溶解计算研究进行了总结和展望。     

Deformation behavior of polymer networks containing or interacting with a solvent

General formalism to describe both equilibrium and nonequilibrium states of polymer networks containing a solvent or interacting with the solvent medium is proposed. Two classes of problems have been formulated. It is necessary to determine the stress-strain state of an inhomogeneously swollen material in one case and that of a statically loaded material occurring in thermodynamic equilibrium with the solvent in the other case. The state of the swollen material is characterized in terms of the global mechanical stress tensor and the solvent chemical potential. In the case of incompressible material and liquid, an osmotic stress tensor is introduced. A method for deriving physical expressions for the mechanical stress tensor, the chemical potential, and the osmotic stress tensor is proposed on the basis of the known free energy relations that follow from different theories of rubber elasticity. The efficacy of the general formalism is demonstrated using particular examples in which the deformation behavior and the equilibrium swelling of mechanically loaded polymer networks are considered.     

Kinetics of shrinking of polymer gels induced by ultracentrifugal fields

The kinetics of the shrinking of polymer gels induced by ultracentrifugal fields is investigated. A theory is proposed to describe the diffusion process of polymer networks under centrifugal fields. The initial shrinking rate is proportional to the ratio of the centrifugal force to the frictional force of networks. The shrinking attains the stationary state as a result of the balance between the centrifugal force and the swelling force of networks. The characteristic time for shrinking is of the order of a2/D where a and D are the stationary displacement and diffusion constant, respectively. We also present the experimental data for the shrinking of the poly(acrylamide) (PAAm) gels under ultracentrifugal fields. The shrinkage increases linearly with time in the initial stage whereas it reaches the steady state in the long time limit as expected by the theory. Each of longitudinal elastic modulus and friction coefficient of the PAAm gels is evaluated from the data on the basis of the theory.     

A New Approach to the Determination of Adhesion Properties of Polymer Networks

Summary: A new approach for the determination and comparison of adhesion properties of polymer networks was proposed. One permits to optimize the choice of polymers for composite materials with inorganic fibers (at the absence of binder diffusion to the fiber). For the first time the works of adhesion of polymer to liquids simulating polar or non-polar phases were used for prediction of adhesive properties of network (binder, coupling agent) and for the choice of network provided the best tensile strength of composite material. The correctness of proposed approach was experimentally proved by measuring of tensile strength micro plastics.     

Molecular simulation of the frictional behavior of polymer-on-polymer sliding

Molecular simulations of the sliding processes of polymer-on-polymer systems were performed to investigate the surface and subsurface deformations and how these affect tribological characteristics of nanometer-scale polymer films. It is shown that a very severe deformation is localized to a band of material about 2.5 nm thick at the interface of the polymer surfaces. Outside of this band, the polymer films experience a uniform shear strain that reaches a finite steady-state value of close to 100%. Only after the polymer films have achieved this steady-state shear strain do the contacting surfaces of the films show significant relative slippage over each other. Because severe deformation is limited to a localized band much thinner than the polymeric films, the thickness of the deformation band is envisaged to be independent of the film thickness and hence frictional forces are expected to be independent of the thickness of the polymer films. A strong dependency of friction on interfacial adhesion, surface roughness, and the shear modulus of the sliding system was observed. Although the simulations showed that frictional forces increase linearly with contact pressure, adhesive forces contribute significantly to the overall friction and must therefore be accounted for in nanometer-scale friction. It is also shown that the coefficient of friction is lower for lower-density polymers as well as for polymers with higher molecular weights.     

Fullerene grafted amine-containing polymers

We have covalently attached fullerenes to amine containing flexible hydrocarbon polymers such as amino-ethylene propylene terpolymer (EPDM-amine) to obtain novel fullerene functionalized polymers. These materials are soluble in solvents such as heptane or tetrahydrofuran (THF), in which the fullerene is essentially insoluble. The reaction of the fullerene and polymer was followed by infra-red spectroscopy and viscosity measurements. Thermogravimetric analysis (TGA) scans of EPDM-amine and Fullerene reacted EPDM-amine show that the fullerene grafted polymer is thermoxidatively more stable than the original polymer. Furthermore, the fullerene grafted polymer could be reacted further with primary-tertiary diamines to obtain novel polymers in which the fullerene acts as a bridging group for attaching polar functional groups to nonpolar hydrocarbon polymers.     

Viscoelastic dynamic properties of heterogeneous polymer networks with domain structure

A dynamic model of a heterogeneous polymer network system is proposed. A polymer network is presented as an ensemble of cross‐linked regions (domains) of different sizes, the domains have similarly regular internal structures. To a first approximation, these domains are treated independently of each other. Relaxation modulus, storage modulus, and loss modulus of the heterogeneous polymer network are calculated. For the purpose of averaging over all network domains the exponential number distribution of chain segments in domains is used. This type of distribution has been previously proposed by one of the authors in the frame of the aggregation model. It is shown that a structure heterogeneity introduced into a network model according to the above domain approach leads, at long times, to the stretched exponential type of time dependence of relaxation modulus instead of the power‐law dependence predicted by the theories dealing with regular networks. The network heterogeneity also leads to a more rapid decrease in the storage modulus in the region of low frequencies, as compared with regular polymer networks. It is shown that the loss modulus in the region of its maximum is very slightly sensitive to the “long‐range” network heterogeneity considered.     

Parameterization of Models for Vapor Solubility in Semicrystalline Polyethylene

This paper extends the previous article by the authors on the solubility of hydrocarbon vapors in semicrystalline polyethylenes produced in the gas phase process. That work demonstrates a computational model for solubility based on an activity coefficient modification of the Sako–Wu–Prausnitz equation of state. In that work, by fitting a key parameter, one related to the constraint of tie chains on polymer fluid behavior, to a single isopentane solubility isotherm, accurate predictions of hydrocarbon solubility in polymer granules over a range of temperature, pressure, and composition are reported. In the present work, additional experimental solubility data are reported, an error in the authors' previous article is corrected, and a useful parameterization method that improves the predictive capabilities of the model is demonstrated. By using the model to predict much of the authors' own experimental data, as well as that published by others in the field, it is demonstrated how the proposed parameterization method allows for accurate predictions using a limited amount of experimental measurements.