Multicomponent Polymer Systems Research Articles

Surface modification strategies for multicomponent polymer systems. III: Effect of diblock copolymer‐modified rutile on the morphology and mechanical properties of LLDPE/PVC blends

Rutile pigment was surface-modified by the adsorption of various diblock copolymers and used as a component in two- and three-component polymer blends involving the incompatible pair of linear, low-density polyethylene (LLDPE) and poly(vinyl chloride) (PVC). Stress–strain analyses and electron microscopy show that the copolymer tethered to the rutile surface affects both mechanical and morphological properties of the blends. Inverse gas chromatography was used to evaluate dispersion surface energies and acid–base interaction parameters of the various solids. The mechanical and morphological characteristics of the blends can be rationalized by the concepts of acid–base and dispersion–force interaction. Of the copolymer modifiers used, the diblock based on polyisoprene and poly(4-vinyl pyridine) (PIP-P4VP) was best suited for use in LLDPE/PVC blends, ostensibly because of strong acid–base interaction between PVC and P4VP and mechanical interlocking between LLDPE and the PIP moiety. The properties of ternary blends were shown to be dependent on the method used for mixing the components. All mixing procedures used here resulted in time-dependent variations of mechanical properties, suggesting that none gave rise to equilibrium morphology in the compounds. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1891–1901, 2001

Solvent effects on polymer surface structure

AbstractThe surface modification of polymeric materials has been of great research interest in the last few years because of its importance in applications such as biomaterials and coatings. The bulk composition of polymeric materials often cannot provide the desired surface properties in these applications. For example, low‐surface‐energy materials can be obtained via the process of surface segregation. The properties of the solvents used in these processes are critical for surface formation in these polymers. Solvent properties such as polarity, volatility and specific interaction properties with the polymer material are important factors in the process of surface formation. The present paper reviews recent studies of solvent effects no surface segregation in multicomponent polymer systems. Copolymers, polymer blend and multicomponent polymer solution systems are discussed. Copyright © 2001 John Wiley & Sons, Ltd.

Solvent effects on polymer surface structure

The surface modification of polymeric materials has been of great research interest in the last few years because of its importance in applications such as biomaterials and coatings. The bulk composition of polymeric materials often cannot provide the desired surface properties in these applications. For example, low-surface-energy materials can be obtained via the process of surface segregation. The properties of the solvents used in these processes are critical for surface formation in these polymers. Solvent properties such as polarity, volatility and specific interaction properties with the polymer material are important factors in the process of surface formation. The present paper reviews recent studies of solvent effects no surface segregation in multicomponent polymer systems. Copolymers, polymer blend and multicomponent polymer solution systems are discussed. Copyright © 2001 John Wiley & Sons, Ltd.

Polymer Degradation Study by Factor Analysis of GPC-FT-IR Data

Factor analysis has been performed on gel permeation chromatography (GPC)-Fourier transform infrared (FT-IR) spectroscopic data sets for one control and two artificially aged, multicomponent polymer systems. This approach was utilized to provide insight into degradation chemistry and to obtain component spectra (factors) and their concentration profiles (scores). The results are evaluated in terms of the infrared spectra of the chemical species present, their concentration profiles, and the different aging environments. For the formulation of a poly(ester urethane) with added plasticizer, and stabilizer, the results demonstrate that chain scission and nitration of the poly(ester urethane) are dominant degradation pathways under radiolytic aging conditions. Thermal aging conditions induce some chain scission. In both aging studies, branching is shown not to be a dominant degradation pathway. However, because branching processes produce insoluble cross-linked material, this possibility was not further investigated in this study.

Surface modification strategies for multicomponent polymer systems. III: Effect of diblock copolymer‐modified rutile on the morphology and mechanical properties of LLDPE/PVC blends

AbstractRutile pigment was surface‐modified by the adsorption of various diblock copolymers and used as a component in two‐ and three‐component polymer blends involving the incompatible pair of linear, low‐density polyethylene (LLDPE) and poly(vinyl chloride) (PVC). Stress–strain analyses and electron microscopy show that the copolymer tethered to the rutile surface affects both mechanical and morphological properties of the blends. Inverse gas chromatography was used to evaluate dispersion surface energies and acid–base interaction parameters of the various solids. The mechanical and morphological characteristics of the blends can be rationalized by the concepts of acid–base and dispersion–force interaction. Of the copolymer modifiers used, the diblock based on polyisoprene and poly(4‐vinyl pyridine) (PIP‐P4VP) was best suited for use in LLDPE/PVC blends, ostensibly because of strong acid–base interaction between PVC and P4VP and mechanical interlocking between LLDPE and the PIP moiety. The properties of ternary blends were shown to be dependent on the method used for mixing the components. All mixing procedures used here resulted in time‐dependent variations of mechanical properties, suggesting that none gave rise to equilibrium morphology in the compounds. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1891–1901, 2001

Stratification processes in thermoplastic olefins monitored by step-scan photoacoustic FT-IR spectroscopy

In this study we utilized step-scan photoacoustic Fourier transform IR (SS-PA-FT-IR) spectroscopy to examine surface/interfacial properties of thermoplastic olefins (TPOs). This approach, combined with 2D FT-IR correlation analysis, allowed us to determine stratification processes in TPOs. These studies showed that the talc and polypropylene (PP) crystalline phase in TPO stratifies within the first 6–30 μm from the surface. Specifically, the PP crystalline phase exists at about 6.5 μm from the surface and its content diminishes at 7.1 μm, followed by reappearance around 11.3 μm, and becomes more prevalent upon approaching the bulk of TPO. Talc concentration levels show a similar pattern of change with depth across the interface, although absolute concentration levels differ from those of crystalline PP. These studies also demonstrated that SS-PA-FT-IR is a powerful tool in surface analysis, in particular for surface/interfacial analysis of multi-component polymeric systems.

Detailed mechanistic modeling of polymer degradation: application to polystyrene

The degradation of polystyrene was modeled at the mechanistic level using population balance equations formulated via the method of moments. Five degradation models of varying complexity were developed. For all models, the conversion among the species was described using typical free radical reaction types, including hydrogen abstraction, mid-chain β-scission, end-chain β-scission, 1,5-hydrogen transfer, radical addition, bond fission, radical recombination, and disproportionation. The five models differed in their resolution of the structural characteristics of the “dead” and “live” polymeric species and whether they explicitly tracked low molecular weight species. The most complex model included over 4500 reactions and tracked 93 polymeric and low molecular weight species, both dead and live species. To facilitate model construction, programs were developed using the programming language Perl to assemble population balance equations from specific reaction mechanism input. The intrinsic kinetic parameters (a frequency factor and activation energy for each reaction) were obtained from previous modeling work in which the decomposition of a polystyrene mimic was described at the mechanistic level (Woo, Ph.D. dissertion, Northwestern University, 1999; Woo and Broadbelt, 1998, Catal. Today 40, 121) to link reactivity directly to structure. As the complexity of the models increased to include branching reactions and branched species, the model predictions improved. The separation between M n and M w observed experimentally was reproduced well for the three most complex models. The general modeling framework established may be easily extended to other single-component and multicomponent polymeric systems.

Characterization of Multi-Phase and Multi-Component Polymer Systems Using the Atomic Force Microscope

Recent advances have been made on two fronts regarding the capability of the atomic force microscope (AFM) to characterize the mechanical response of polymers. Phase imaging with the AFM has emerged as a powerful technique, providing contrast enhancement of topographic features in some cases and, in other cases, revealing heterogeneities in the polymer microstructure that are not apparent from the topographic image. The enhanced contrast provided by phase images often allows for identification of different material constituents. However, while the phase changes of the oscillating probe are associated with energy dissipation between the probe tip and the sample surface, the relationship between this energy dissipation and the sample properties is not well understood.As the popularity of phase imaging has grown, the capability of the AFM to measure nanoscale indentation response of polymers has also been explored. Both techniques are ideal for the evaluation of multi-phase and multi-component polymer systems.

On the relationship between microhardness and glass transition temperature of some amorphous polymers

On the basis of microhardness (H) data measured at room temperature only for a number of polymers in the glassy state, a linear correlation between H and the glass transition temperature Tg has been found (H = 1.97Tg − 571). By means of this relationship, the deviation of the H values from the additivity law for some multicomponent and/or multiphase polymeric systems can be accounted for. The latter usually contains a liquidlike soft component and/or phase with Tg below room temperature. A completely different deformation mechanism in comparison to systems with Tg above room temperature is invoked. A novel expression for the hardness of polymers in terms of crystallinity of the single components and/or phases, the Tg values, and the mass fraction of each component is proposed. This expression permits the calculation of (i) the room-temperature H value of amorphous polymers, mainly containing single bonds in the main chain, provided Tg is known, and of (ii) the contribution of the soft liquidlike components (phases) to the hardness of the entire multiphase system. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1413–1419, 1999

Surface modification strategies for multicomponent polymer systems,VI:acid–base interactions as a strategy for interfacial modification in immiscible polymer blends

Three copolymers with different emulsification efficacies were used as potential interface modifiers for an immiscible blend of linear low density polyethylene (LLDPE) and poly(vinyl)chloride (PVC). The specific interaction between blend components and the modifying copolymers was determined by measurements of interfacial tension and by inverse gas chromatographic (IGC) data, characterizing the acid–base properties of the polymers. Additional information on modifier effectiveness was obtained from blend morphology data. Acid–base pair interaction parameters, computed from IGC results, predicted the modifying potential of the two copolymers which emulsified the system, and were consistent with the morphology and interfacial tension results. IGC, however, did not distinguish between the emulsification qualities of the two good modifiers. The best of the three modifiers (P4VP-PIP) also increased the impact strength of the modified LLDPE/PVC system. The results indicate that specific (acid–base) interactions at component interfaces may represent a promising strategy for the choice of emulsifying agents for some immiscible polymer blends.

The mutual effect of absorption of biologically active substances and microstructure of native cellulose matrix on the properties of resulting compounds

AbstractIn order to obtain multicomponent polymer systems exhibiting biological activity microcrystalline cellulose was used as a matrix for biologically active compounds, such as dimethylbenzylalkylammonium chloride, poly‐N‐vinylpyrrolidone, copolymer of N‐vinylpyrrolidone and crotonic acid, and complex of dimethylbenzylalkylammonium chloride with copolymer of N‐vinylpyrrolidone and crotonic acid. Adsorption interaction of microcrystalline cellulose with these was studied under various conditions. Adsorption isotherms of compounds of polymer nature are of similar character and are described by the Freundlich equation. The isotherms of dimethylbenzylalkylammonium chloride are described by the Langmuir equation. Characteristics of the resulting compounds were obtained using XPS and IR Fourier spectroscopy, WAXS, and SEM. Chemical interaction between microcrystalline cellulose and dimethylbenzylalkylammonium chloride takes place. This interaction leads to a new labile morphological cellulose structure accessible to penetration, which is confirmed at a morphological level by SEM.

The effect of quaternary ammonium base adsorbates on the molecular and morphological structure of microcrystalline cellulose

In order to obtain multicomponent polymer systems exhibiting biological activity, microcrystalline cellulose was used as a matrix for biologically active compounds, such as dimethylbenzylalkylammonium chloride, poly- N-vinylpyrrolidone, copolymer of N-vinylpyrrolidone and crotonic acid, and polymer complex of dimethylbenzylalkylammonium chloride with copolymer of N-vinylpyrrolidone and crotonic acid. Adsorption interaction of microcrystalline cellulose with these compounds was studied under various conditions. Adsorption isotherms of compounds of polymer nature are of similar character and are described by the Freundlich equation. The isotherms of the low molecular weight compound dimethylbenzylalkylammonium are described by the Langmuir equation. Characteristics of the resulting compounds were obtained using X-ray photoelectron and infrared Fourier spectroscopy, wide-angle X-ray diffractometry and scanning electron microscopy. Chemical interaction between microcrystalline cellulose and dimethylbenzylalkylammonium chloride takes place. This interaction leads to a new labile morphological cellulose structure accessible to penetration, which is confirmed at a morphological level by scanning electron microscopy.

Quantitative measurements of spherical particle size distribution in a phase separated matrix

In many multicomponent polymeric blend systems micro-phase separation takes place to form dispersed phases within a continuous matrix phase. The mechanical and physical properties of this type of material are often dependent on the number, size, interspacing and volume fraction of the dispersed phase particles. These morphological parameters can be estimated once a correct three-dimensional distribution is established. The use of microscopy for the quantitative study of these parameters presents difficulties arising from the fact that it provides only two-dimensional information. Several statistical treatments to convert two-dimensional distributions to three-dimensional distributions have been developed. These methods were tested with known systems by a computer simulation. Error analysis for estimated distributions as well as suggestions of experimental procedures to more quantitatively deal with this problem are discussed. ©

Surface modification strategies for multicomponent polymer systems. V. Interaction states and mechanical properties of LLDPE/PVC blends with corona‐modified rutile pigment

Surface modification strategies for multicomponent polymer systems. V. Interaction states and mechanical properties of LLDPE/PVC blends with corona‐modified rutile pigment

Surface modification strategies for multicomponent polymer systems. V. Interaction states and mechanical properties of LLDPE/PVC blends with corona-modified rutile pigment

Rutile pigment with preadsorbed monomers of acrylamide (AM) or acrylic acid (AA) has been treated in air corona discharges at various input power levels for times from 30–120 s. Inverse gas chromatographic data showed that the treatments reduced dispersive surface energies and significantly altered the acid/base interaction potential of the surfaces. Inferred is the corona-activated synthesis of oligomeric or polymeric structures anchored to the pigment surface. XPS analyses report modifications in the chemical structure of pigment surfaces, which are consistent with the suggested consequence of corona treatment. When incorporated into LLDPE and PVC host polymers, compounds with the corona-modified rutiles have better mechanical properties than analogues with untreated pigment, notable being improved elastic moduli, yield stresses, and stress/strain relationships at break. AM-modified rutiles were preferable to AA-modified versions in this regard. The addition of treated pigments to immiscible LLDPE/PVC (75/25) blends resulted in similar benefits to mechanical properties, AM pretreatment again being preferred. Stronger acid-base interaction at contacts between corona-modified rutiles and the PVC component is an apparent reason for improved mechanical properties. Speculatively also, AM pretreatments lead to attached chains of sufficient length to entangle with the LLDPE, further strengthening the interphase and relevant bulk properties. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1597–1604, 1998

Molecular theory of solutions and blends of heteropolymers. I. Thermodynamics of amorphous multicomponent polymer systems

On the basis of a variational principle a quantitative theory is developed enabling a thermodynamic description in terms of mean field approximation of heteropolymer mixtures of macromolecules with an arbitrary distribution for both degree of polymerization and composition. Rather simple general equations are derived to calculate compositions and volume fractions of spatially homogeneous macroscopic phases as well as to find the cloud-point curve, spinodal, and critical points. Potentialities of general theory are illustrated for copolymers synthesized by traditional methods.

Nanostructured conducting polymer composites — superparamagnetic particles in conducting polymers

Methods of preparation and the properties of polymer composites with superparamagnetic nanoparticles are reviewed and discussed. Multicomponent polymer systems with nanoparticles of metal oxides can be tailored to exhibit, besides good magnetic properties and transparency, also good adhesion (polymers and copolymers of various types), film forming and processing properties. An interesting feature of polymer composites with nanosized superparamagnetic particles is that, in all cases reported, the measured magnetization considerably deviates from the values calculated or measured for bulk iron oxides (e.g. single crystals). No definite explanation of this discrepancy exists. The studies on a selected system: polyaniline/iron oxide particles help to resolve this question because interactions between the matrix and iron oxide nanoparticles can be studied under different conditions and at different stages of structure formation.

FT-IR Imaging of the Interface in Multicomponent Systems Using Optical Effects Induced by Differences in Refractive Index

For phase-separated multicomponent polymeric systems, characterization of the interface between the components is particularly challenging. We have observed an optical effect in the infrared that can be used to image the interface specifically. This method yields images of the interfaces based on the interfaces showing apparent absorption arising from changes in refractive index at frequencies far from the specific frequencies associated with the components of the mixture. This method has been applied to multicomponent samples of polymer-dispersed liquid crystals where the nature of the interface can be specifically altered by the application of an electric potential across the sample. Effects of this optical phenomenon on spectra from such multicomponent systems are discussed, and factors that complicate quantitative analysis of data from interfacial regions have been pointed out.

高分子系多相構造：分子設計・制御・応用 高分子多成分系の構造制御

高分子系多相構造：分子設計・制御・応用 高分子多成分系の構造制御

Remarks on the structure and validity of the Cahn—Hilliard—Cook theory in multicomponent polymer systems

The accuracy of the linear Cahn—Hilliard—Cook (CHC) theory in matrix form (multicomponent description) is scrutinized by comparing its exact macroscopic derivation with its phenomenological derivation based on the linear Markov process assumption. The effect of the coupling of density modes to those which are not directly observed is examined. The influence of the initial state on the accuracy of the CHC theory is discussed. Interpretation of scattering experiments using a bimodal description of transients is presented in detail. As an application, the possible effect of coupling to viscoelastic modes on transients is analysed.