Electrophoretic deposition of chiral polymers and composites

Electrophoretic deposition (EPD) method has been developed for the deposition of thin films of chiral polymers. EPD of poly-L-lysine (PLL) and poly-L-ornithine (PLO) films was performed for the first time on conductive substrates from aqueous and ethanol-water solutions. The deposition yield was monitored using a quartz crystal microbalance. The results demonstrated that the deposition yield can be varied by variation of the deposition time, voltage and polymer concentration in the solutions. It was shown that PLL and PLO provided stabilization and charging of hydroxyapatite (HA) nanoparticles in suspensions. Composite PLL-HA and PLO-HA films of controlled thickness were prepared by EPD. Electron microscopy investigations showed that the thickness of the PLL, PLO and composite films was varied in the range of 0-3 μm. The polymer and composite films can be used for biomedical applications.     

Physical aging of epoxy polymers and their composites

Exposure to extended periods of sub‐T_g temperatures causes physical changes in the molecular structure of epoxy resins and epoxy‐based materials to occur. These physical aging mechanisms include the reduction in free volume and changes to the molecular configuration. As a result, mechanical, thermodynamical, and physical properties are affected in ways that can compromise the reliability of epoxy‐based engineering components and structures. In this review, the physical changes in the molecular structure of epoxies are described, and the influence of these changes on the bulk‐level response is detailed. Specifically, the influence of physical aging on the quasistatic mechanical properties, viscoelasticity, fracture toughness, thermal expansion coefficient, volume relaxation, enthalpy relaxation, endothermic peak temperature, fictive temperature, and moisture/solvent absorption capability is reviewed. Also discussed are relationships between relaxation functions, crosslink density, composite reinforcement, and epoxy/copolymer blending and the physical aging response of epoxies. Finally, the concepts of thermal and mechanical rejuvenation are discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Equivalent dynamic thermoviscoelastic modeling of ionic polymers

Ionic polymers have attracted considerable attention due to their interesting sensing and actuating behavior which make them a proper choice for use in a wide range of applications including biomimetic robots and biomedical devices. The complicated electro‐chemo‐mechanical dynamics of ionic polymer actuators is a drawback for their applications in functional devices. Therefore, establishing a mathematical model which could effectively predict the actuators' dynamic behavior is of great interest. In this paper, a mathematical model, named equivalent dynamic thermoviscoelastic (EDT) model, based on thermal analogy and beam theory is proposed for dynamic analysis of bending‐type ionic polymer actuators. Then, the developed model is extended for analyzing the performance of the actuator in finite element software. The finite element analysis of the actuator enables consideration of material and geometric nonlinearities and facilitates modeling of functional devices based on the ionic polymer actuators. The proposed modeling approach is validated using experimental data. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation of organic-inorganic composites containing rod-like phthalocyanine polymers

Sol-gel polymerization of tetraethoxysilane in the presence of amphiphilic phthalocyanine polymer 2 produced organic-inorganic composites with the rod-like phthalocaynine polymers incorporated within ordered hexagonal channels.     

Thermal analysis of composites based on crystalline polymers and metals

Differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and infrared (IR) spectroscopy have been used to examine the chemical and physical changes (crystallinity, accumulation of oxygen-containing groups, etc.) during thermal oxidation of polyethylene, polypropylene and Penton contained in coatings and metalfilled films, taking into account the thickness of the polymer layer and catalytic activity of the metal.

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Zusammenfassung DSC, thermogravimetrische Analyse (TG) und infrarot (IR) Spektroskopie wurden zur Untersuchung der während der thermischen Oxidation von in Belägen und metallgefüllten Filmen enthaltenem Polyäthylen, Polypropylen und Penton stattfindenden chemischen und physikalischen Veränderungen (Kristallinität, Anhäufung stickstoffhaltiger Gruppen usw.) eingesetzt. Hierbei wurden die Stärke der Polymerschicht und die katalytische Aktivität des Metalls in Betracht genommen.

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New insight into modeling non-covalently imprinted polymers

Three series of polymers were carefully formulated with increasing amounts of template while keeping the polymer components constant. The number of binding sites (N) and the number average association constant (K(n)()) were calculated for each polymer in a series, using equations adapted from the literature describing molecularly imprinted polymers (MIPs). The trends of N and K(n)() for each series of polymers, which were graphed versus percent template, suggest multiple functional monomers in the binding sites of noncovalent MIPs. This new insight has implications for understanding the underlying mechanisms for the formation of binding sites in the MIPs studied.     

Principles of theoretical description of microstructure of linear condensation polymers

Key ideas of general original approach to the theoretical consideration of monomer sequence distribution problem are formulated for linear condensation heteropolymers showing either isomerism due to different fashions of monomer unit alternation in macromolecules of a copolymer or constitutional isomerism resulting from different orientation of asymmetric monomer units in polymers.     

Design,synthesis and properties of molecular composites of rod-like polymers

Processing and performance of fiber reinforced polymers suffer from problems related to the heterogeneous nature of the composites. The strong impact of the nature of the interface between fibers and matrix adds to the complication of the field. Consequently many attempts have been made to reduce the cross-section of the reinforcing fibers to molecular dimensions and to increase the compatibility between the rod-like molecules or bundles of molecules and the isotropic matrix of ordinary flexible polymers. All such attempts have failed, mainly for reasons of thermodynamics which predict immiscibility of rods and coils on the molecular level. A possibility to create structures in which molecular rods are embedded in a continuous matrix of flexible chain segments exists nevertheless.¹ Rod-like backbone structures decorated with a skin of flexible side chains of moderate length in terms of the number of carbon atoms (typically C₆ - C₁₈-side chains) have been synthesized and tested for the spontaneous formation of molecular composites. Some of the materials built along this principle can be processed by solution casting or even melt extrusion. The academically more interesting materials can be built up layerwise by a modified Langmuir-Blodgett technique. The latter process gives rise to monodomain textures which allow for straight-forward testing of the mechanical properties by optical means (Brillouin-spectroscopy) and by piezoquartz-techniques. Hairy-rod macromolecules can also be synthesized which contain crosslinkable side chains. Thus, after formation of layered, oriented structures, these can be crosslinked photochemically or by curing. The result is a network, which is unidirectionally reinforced by the rod-like macromolecules. These novel types of networks can serve as membranes by which size exclusion is achieved via control of the distance between adjacent backbone molecules in the matrix. Recent synthetic advances in the field have concentrated on hairy-rod macromolecules based on cellulose alkyl ethers and on derivatives of poly-(p-phenylene). The latter materials serve as examples of systems which can be processed by casting and extrusion processes. Due to their excellent thermal stability relevant data on the rheological and mechanical-dynamical data have become available. These data serve to document the unique behavior of the hairy-rod macromolecules as bulk materials.     

Theoretical consideration and modeling of self‐healing polymers

Bioinspired self‐healing polymers have attracted more and more interests. Imparting self‐healing ability to existing polymers or developing new polymeric materials capable of self‐healing is considered to be a solution for improving their long term stability and durability. This article reviews achievements in the field of theoretical researches on re‐establishment of bonding between broken surfaces of self‐healing polymers from microscopic and macroscopic point of view. Chains interaction, mechanical models related to healing procedures and effect of healing, design of novel self‐healing composite systems, and so forth are summarized and analyzed in detail. Both thermoplastics and thermosets are included to offer a comprehensive knowledge framework of the smart function. The scientific challenges are also highlighted, which are related to the production of more advanced self‐healing polymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Combination of electrostrictive polymers composites and electrets for energy harvesting capability

More recently, the development of electrostrictive polymers has generated novel opportunities for high‐strain actuators. At present, the investigation of using electrostrictive polymers for energy harvesting is beginning to show potential for this application. Basically, the relative energy gain depends on the current induced by the mechanical strain and frequency. The aim of the present experimental work is to study the composites on the basis of terpolymer P(VDF–TrFE–CFE) filled with low concentrations of copper (Cu) powders. The scanning electron microscopy was performed essentially to verify the dispersion of the fillers within the polymeric matrix. The obtained results showed a relatively homogeneous dispersion for the microsized fillers and the existence of agglomerates for their nanosized counterparts. On the other hand, our experimental data show that the harvested power as well as the current is significantly important for nano‐Cu fillers with respect to micro‐Cu fillers by a factor of 45.9% in the case of the hybridization of electrostrictive polymers and electrets. Copyright © 2014 John Wiley & Sons, Ltd.     

Properties of ultrahighly filled composites based on polymers and ground rubber

The stress-strain and strength properties of ultrahighly filled composites based on thermoplastic polymers and ground rubber wastes are studied. The content of the elastic filler is higher than 70 wt%. As is shown, introduction of minor amounts of the plastic polymer, which serves as the binder for the filler particles, makes it possible to improve the strength properties of ultrahighly filled composites and to prepare materials of a desired thickness. A correlation between the stress-strain properties of the plastic polymer-rubber systems and the effective viscosity of the matrix polymer is established. When a polymer with homogeneous deformation and good adhesion to the elastic filler is used as the matrix, the resultant composites are characterized by properties close to those of vulcanized rubbers. A new method is proposed for processing of ground rubber wastes and preparation of materials that are similar to hard rubbers.     

Micromechanical modeling of the deformation kinetics of semicrystalline polymers

The mechanical behavior of semicrystalline polymers is strongly dependent on their crystallinity level, the initial underlying microstructure, and the evolution of this structure during deformation. A previously developed micromechanical constitutive model is used to capture the elasto‐viscoplastic deformation and texture evolution in semicrystalline polymers. The model represents the material as an aggregate of two‐phase layered composite inclusions, consisting of crystalline lamellae and amorphous layers. This work focuses on adding quantitative abilities to the multiscale constitutive model, in particular for the stress‐dependence of the rate of plastic deformation, referred to as the slip kinetics. To do that, the previously used viscoplastic power law relation is replaced with an Eyring flow rule. The slip kinetics are then re‐evaluated and characterized using a hybrid numerical/experimental procedure, and the results are validated for uniaxial compression data of HDPE, at various strain rates. A double yield phenomenon is observed in the model prediction. Texture analysis shows that the double yield point in the model is due to morphological changes during deformation, that induce a change of deformation mechanism. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1297–1310, 2011     

Micromechanical modeling of anisotropic behavior of oriented semicrystalline polymers

Some manufacturing processes of polymeric materials, such as injection molding or film blowing, cause the final product to be highly anisotropic. In this study, the mechanical behavior of drawn polyethylene (PE) tapes is investigated via micromechanical modeling. An elasto‐viscoplastic micromechanical model, developed within the framework of the so‐called composite inclusion model, is presented to capture the anisotropic behavior of oriented semicrystalline PE. Two different phases, namely amorphous and crystalline (both described by elasto‐viscoplastic constitutive models), are considered at the microstructural level. The initial oriented crystallographic structure of the drawn tapes is taken into account. It was previously shown by Sedighiamiri et al. (Comp. Mater. Sci. 2014, 82, 415) that by only considering the oriented crystallographic structure, it is not possible to capture the macroscopic anisotropic behavior of drawn tapes. The main contribution of this study is the development of an anisotropic model for the amorphous phase within the micromechanical framework. An Eindhoven glassy polymer (EGP)‐based model including different sources of anisotropy, namely anisotropic elasticity, internal stress in the elastic network and anisotropic viscoplasticity, is developed for the amorphous phase and incorporated into the micromechanical model. Comparisons against experimental results reveal remarkable improvements of the model predictions (compared to micromechanical model predictions including isotropic amorphous domains) and thus the significance of the amorphous phase anisotropy on the overall behavior of drawn PE tapes. © 2019 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 378–391     

Molecular modeling and thermoanalytical studies of thermophysical properties of some polymers

The results of computational modeling and experimental data on some thermophysical properties of selected polymers were compared. Different engineering polymers, e.g. polycarbonates and terephthalate polyesters, were considered and their glass transition temperatures and thermal stabilities were determined, by using thermoanalytical methods, e.g. DSC and TG. Measurements were carried out with Perkin-Elmer DSC 7 and TGA 7 instruments. Molecular modeling and computer calculations were performed at the Interdisciplinary Computer Modeling Center (ICM) of Warsaw University, using a Cray El 98 computer and the Insight II software of BIOSYM Technologies Inc. Reasonably good agreement was found between the experimental and calculated values of the glass transition temperatures of the investigated polymers, e.g. for poly(butylene terephthalate)T _g (calc.)=74C andT _g (experim.)=70C. Discrepancies were observed for the temperature of half decompositionT _d,1/2, some of them can be explained by effects of polymer molecular weight and/or char-forming effects.Polymer modeling computations were performed at the Interdisciplinary Computer Modeling Center (ICM) of the Warsaw University, where a CRAY EL 98 computer and the software of BIOSYM Technologies, Inc. were used.     

Multiscale modeling and simulation methods with applications to dendritic polymers

Dendrimers and hyperbranched polymers represent a novel class of structurally controlled macromolecules derived from a branches-upon-branches structural motif. The synthetic procedures developed for dendrimer preparation permit nearly complete control over the critical molecular design parameters, such as size, shape, surface/interior chemistry, flexibility, and topology. Dendrimers are well defined, highly branched macromolecules that radiate from a central core and are synthesized through a stepwise, repetitive reaction sequence that guarantees complete shells for each generation, leading to polymers that are mono-disperse. This property of dendrimers makes it particularly natural to coarsen interactions in order to simulate dynamic processes occurring at larger length and longer time scales. In this paper, we describe methods to construct 3-dimensional molecular structures of dendrimers (Continuous Configuration Boltzmann Biased direct Monte Carlo, CCBB MC) and methods towards coarse graining dendrimer interactions (NEIMO and hierarchical NEIMO methods) and representation of solvent dendrimer interactions through continuum solvation theories, Poisson–Boltzmann (PB) and Surface Generalized Born (SGB) methods. We will describe applications to PAMAM, stimuli response hybrid star-dendrimer polymers, and supra molecular assemblies crystallizing to A15 colloidal structure or Pm6m liquid crystals.     

Molecular modeling of polymers, 14 quantitative structure-property relationship analyses of multicomponent systems containing polymers

One general class of polymer modeling applications involves materials which are large, in terms of molecular degrees of freedom, and poorly defined in terms of composition and morphology. Such materials are often multicomponent with respect to number of distinct polymers, fillers, additives, etc. Two obstacles limit the modeling of these materials. First, one normally does not have any idea about the key physicochemical molecular properties governing the system. Second, the functional dependence of the target properties of the material upon the key physicochemical molecular properties is usually totally unknown. Torsion angle unit (TAU) theory, a molecular decomposition technique, permits an arbitrarily large number of physicochemical properties to be computed in an open-ended fashion, and thus addresses the first problem. Genetic function approximation (GFA) analysis tackles the second problem by efficiently exploring any desired number of functional relationships between target properties and physicochemical molecular properties. Case studies of (TAU theory)-(GFA analysis) applications to estimate glass, Tg, and crystal-melt, Tm, transition temperatures will be described.     

Stable nonequilibrium composites based on liquid-crystalline polymers and cadmium selenide nanoparticles

On the basis of copolymers of 4-methoxyphenyl-4-(6-(acryloyloxyhexyloxy)benzoate with 4-(6-acryloyloxyhexyloxy)benzoic acid, nonequilibrium composites containing nanoparticles (quantum dots) of cadmium selenide at concentrations many times higher than their solubility limit in the liquid-crystalline phase are synthesized. In the resulting material, the polymer matrix undergoes the transition to the liquidcrystalline state before separation into phases with concentrations of nanoparticles corresponding to thermodynamically equilibrium values. Under common conditions, the composites are stable for at least several months.     

Synthesis,properties and molecular modeling of functional hyperbranched polymers and dendrimers

The design, synthesis, properties and molecular modeling of fully conjugated dendritic molecules and conjugated hyperbranched polymers are described. It has been shown that conjugated hyperbranched molecules are much more soluble than their linear analogues while maintaining all the properties characteristic of conjugated polymers. It was found that the use of polymeric solid support in hyperbranched polymerization allows to control molecular weight and degree of branching (DB). The molecular modeling of hyperbranched conjugated molecules reveals that hyperbranched structure of conjugated molecules affects significantly neither their stability nor the conjugation. On the other hand the terminal groups affect appreciably the electronic structure of conjugated hyperbranched molecules.