Interfacial thickness in bilayers of poly(phenylene oxide) and styrenic copolymers

Estimates for the thickness of the interface between poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) and copolymers of styrene–acrylonitrile (SAN) and styrene–maleic anhydride (SMA) based on the theory of Helfand and Tagami are compared to neutron reflectivity (NR) measurements. Good agreement is found between the NR measurements and theoretical predictions that make use of a mean field binary interaction model and previously reported binary interaction energies. The techniques outlined in this work may be used to understand relationships between the mechanical properties of multiphase polymer blends and the fundamental thermodynamics of polymer interactions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3115–3125, 1998     

聚合物二元体系动态力学性能的估算

动态热机械分析是多相聚合物体系的一个重要研究手段.分析动态力学性能可以研究共混高聚物的相容性、复合材料的界面特性以及高分子运动机理等.本文综述了聚合物二元体系,即填充、纤维增强、共混体系动态力学性能的估算方法.在填充体系中,分别概述有无界面作用两种情况,当存在界面作用时,界面作用越强,模量越大,阻尼越小.对纤维增强体系,讨论了玻璃纤维有无取向的情况下模量和阻尼的估算.特别对于聚合物二元共混体系,分"海-岛"结构和双连续相两种情况,分别讨论了模量与阻尼的估算.     

Binary versus ternary interactions in a completely miscible three‐polymer blend system: Poly(ϵ‐caprolactone) with two different methacrylic polymers

A truly miscible ternary miscible blend consisting of poly(?‐caprolactone) (PCL), poly(phenyl methacrylate), and poly(benzyl methacrylate) (PBzMA) was discovered. The three‐polymer blend system was completely miscible within the entire composition range at ambient temperature up to about 150 °C, and ternary phase diagrams at increasing temperatures were characterized and interpreted. A ternary‐interaction model based on the modified Flory–Huggins expression was used to describe the phase diagrams with the individual binary interaction strengths. The model fitted well with the experimental‐phase diagram for the ternary blend system at T = 250 °C, where the binary PCL‐PBzMA blend system is on the critical points of phase separation. Interpretation of discrepancy between the model and experimental at other temperatures was handled with an empirical approach. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 747–754, 2002     

Influence of Competition Between Binary Pairwise Interactions on the Phase Behavior in Ternary Blends

There are three binary pairs in a ternary blend and competition exists among these pairwise interactions owing to the asymmetry of the interaction energies between these binary pairs, which will determine the overall phase behavior of the blend. The influence of molecular weight of the components on the asymmetry of the interactions was discussed based on a ternary copolymer blend poly(styrene-co-acrylonitile)/poly(styrene-comethylmethacrylate/poly(methyl methacrylate-co-acrylonitile) (SAN/SMMA/MAN). It has been demonstrated that the asymmetry of the interactions between different binary polymer pairs is driven not only by the difference of interaction parameters, i.e. the so-called Δξ effect, but also by the difference of chain length between different components in the mixture. If the two effects are coincident with each other, the asymmetry of the interactions will be intensified, promoting phase separation. On the other hand, the compatibility of the system may be improved remarkably as the two factors are in opposite directions. It implies that a miscible ternary blend may be available simply by exchanging the order of the molecular weight between the different components against the asymmetry direction caused by their corresponding interaction parameters, which is easier to do in many experimental conditions. © 1997 John Wiley & Sons, Ltd.     

Simulation of Polymer Aggregates as a Method to Investigate the Solvent Effect on Blend Complexation and the Relative Strength of H‐Bonding Groups in Blends

Simulations of polymer‐solvent and polymer‐polymer aggregates, in which the study of hydrogen bonding plays an important role, have been carried out with two blend systems. The aim was to examine the influence of the solvent on blend complexation and to compare the strength of different hydrogen bonds in a blend system. We quantified the strength of one hydrogen bond in the blend environments. For this we used the EVOCAP software, developed by our institute. It allows the building of large molecular aggregates with realistic and homogeneous densities, with an implemented positioning algorithm of the molecules under consideration and their excluded volume, and a charge equilibration method for the partial charge calculation. In the simulated aggregates the specific interaction energy of the hydrogen atom forming the hydrogen bond was a useful indicator for our studies. Through a direct correlation of this specific‐interaction energy with the strength of the hydrogen bond, we supported the experimental result that, in toluene, complex formation between poly(methyl methacrylate) (PMMA) and PSOH, a hydroxyl‐modified polystyrene, is possible, but not in tetrahydrofuran. Varying the proton‐donor polymer, also a hydroxyl‐modified polystyrene, in blends of poly(vinyl methyl ether) (PVME) with groups of different donor strength, we reconstructed the experimental row of increasing hydrogen‐bond strengths.     

Temperature and molecular weight dependence of interfacial tension between immiscible polymer pairs by the square gradient theory combined with the Flory–Orwoll–Vrij equation-of-state theory

Interfacial tension between immiscible polymer pairs was predicted by using a square gradient theory in conjunction with the Flory–Orwoll–Vrij equation-of-state expression for the free energy of mixing. The contact interaction parameter was determined by fitting the equation-of-state theory to experimental cloud points taken from the literature, and the square gradient coefficient was estimated from the relation derived from a scattering function. The modified square gradient theory could successfully predict both the magnitude and temperature dependence of interfacial tension between polystyrene and poly(methyl methacrylate), although no adjustable parameters were used in calculating interfacial tension. The molecular weight dependence of interfacial tension was also successfully predicted. The contribution of free volume on interfacial tension is analyzed for two systems: polystyrene/poly(methyl methacrylate) and polystyrene/poly(dimethyl siloxane) blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2683–2689, 1998     

Flory状态方程理论研究PS/PMMA/SAN相行为

将改进的Flory状态方程理论(EOS)引入含“分子内链段排斥性相互作用”的高分子共混物中,研究含无规共聚物的三元共混体系聚苯乙烯(PS)/聚甲基丙烯酸甲酯(PMMA)/聚苯乙烯-丙烯腈(SAN)无规共聚物的相行为,建立相应的适用于含无规共聚物三元共混体系Spinodal方程.用PS、PMMA、PAN的特征参数及其链段间相互作用参数分别计算相应共聚物的特征参数,由二元相互作用模型计算均聚物-共聚物间的相互作用能参数.在运用EOS理论研究三元均聚物共混体系相行为基础上,进一步预测PS/PMMA/SAN体系的相行为,计算并绘制不同温度下的Spinodal曲线并进行实验验证,理论计算与实验结果吻合.结果表明,EOS理论可以克服经典平均场理论的缺陷,成功描述含分子内排斥作用共混体系相行为与共聚物组成及温度之间的关系.     

Theoretical equation of state of polymer blends: The poly(2,6-dimethyl-1,4-phenylene ether)–polystyrene pair

A recent theory of multicomponent fluids is applied for the first time to a compatible binary polymer blend. Good accord between the experimental pressure-volume-temperature measurements over the whole range of compositions by Zoller and theoretical predictions obtains. In particular, satisfactory predictions of high pressure from low-pressure information result. From the interplay between experiment and theory, the scaling quantities and thus the characteristic self- and cross interaction parameters are derived. The excess volumes are discussed and estimates of excess enthalpies presented. The theory predicts the actual enthalpy of the components or mixtures once the scaling parameters have been determined by means of volume-temperature data at atmospheric pressure. Enthalpy measurements to test these predictions are highly desirable.     

Analysis and evaluation of biobased polyester of PTT/PBAT blend: thermal,dynamic mechanical,interfacial bonding,and morphological properties

Novel blends were prepared from biobased poly(trimethylene terephthalate) (PTT) and poly(butylene adipate‐co‐terephthalate) (PBAT) using a twin screw extrusion process as a function of different weight ratios. Thermal stability, mechanical, and interfacial properties of PTT/PBAT blends were investigated using a thermogravimetric analyzer and mechanical analyzer. Phase behavior and surface morphology of the blends were characterized using scanning electron microscopy. Interfacial bonding value of the PTT/PBAT blend was evaluated from the Pukanszky empirical relationship. Viscoelastic properties of PTT/PBAT blends were investigated using the dynamic mechanical analyzer. PTT/PBAT blend exhibited higher thermal stability than the neat PTT matrix. The entire blend showed better interfacial adhesion between the matrixes. Storage and loss modulus of the PTT/PBAT blend reduces with increasing PBAT content. PTT/PBAT blend exhibited higher impact energy than the neat PTT matrix, because of its flexible and amorphous nature of PBAT polymer and increasing toughness. Copyright © 2016 John Wiley & Sons, Ltd.     

Bead-bead interaction parameters in dissipative particle dynamics: relation to bead-size, solubility parameter, and surface tension

Dissipative particle dynamics (DPD) is a mesoscale modeling method for simulating equilibrium and dynamical properties of polymers in solution. The basic idea has been around for several decades in the form of bead-spring models. A few years ago, Groot and Warren established an important link between DPD and the Flory-Huggins chi-parameter theory for polymer solutions. We revisit the Groot-Warren theory and investigate the DPD interaction parameters as a function of bead size. In particular, we show a consistent scheme of computing the interfacial tension in a segregated binary mixture. Results for three systems chosen for illustration are in excellent agreement with experimental results. This opens the door for determining DPD interactions using interfacial tension as a fitting parameter.     

Interfacial Properties of Asymmetric Polymer Mixtures

Using a Monte‐Carlo simulation of a continuous space Rod Bead Model the interface properties of systems of flexible polymer chains with different sizes of monomers are investigated. An immiscible polymer blend in the strong segregation state is modeled by a double sandwich system of chains differing by an factor of two in the size of the beads and the interfacial tension is calculated by a virial theorem method. The simulation data are compared to self‐consistent mean field and experimental data. The results show that the simulation data agree very satisfactory with mean‐field results. The interfacial tension decreases for asymmetric systems in comparison to symmetric systems with comparable volume contents of monomers and interaction strengths due to a decrease of the effective interaction. The parameters of the investigated systems are close to the properties of PS, PMMA and PI melts. A comparison with experimental results yields a very good agreement with data for PS/PMMA and less satisfactory for PS/PI. Additionally to the interfacial tension we have studied the interfacial width, the deformation of polymer chains near the interface, distributions of chain ends, monomer densities and distributions of centers of mass of chains.

Snapshot of a typical configuration for chains with different monomer sizes and equal number of monomers per chain.     

Viscoelastic behavior of polypropylene/nitrile rubber thermoplastic elastomer blends: Application of Kerner's models for reactively compatibilized and dynamically vulcanized systems

The viscoelastic properties of binary blends of nitrile rubber (NBR) and isotactic polypropylene (PP) of different compositions have been calculated with mean‐field theories developed by Kerner. The phase morphology and geometry have been assumed, and experimental data for the component polymers over a wide temperature range have been used. Hashin's elastic–viscoelastic analogy principle is used in applying Kerner's theory of elastic systems for viscoelastic materials, namely, polymer blends. The two theoretical models used are the discrete particle model (which assumes one component as dispersed inclusions in the matrix of the other) and the polyaggregate model (in which no matrix phase but a cocontinuous structure of the two is postulated). A solution method for the coupled equations of the polyaggregate model, considering Poisson's ratio as a complex parameter, is deduced. The viscoelastic properties are determined in terms of the small‐strain dynamic storage modulus and loss tangent with a Rheovibron DDV viscoelastometer for the blends and the component polymers. Theoretical calculations are compared with the experimental small‐strain dynamic mechanical properties of the blends and their morphological characterizations. Predictions are also compared with the experimental mechanical properties of compatibilized and dynamically cured 70/30 PP/NBR blends. The results computed with the discrete particle model with PP as the matrix compare well with the experimental results for 30/70, 70/30, and 50/50 PP/NBR blends. For 70/30 and 50/50 blends, these predictions are supported by scanning electron microscopy (SEM) investigations. However, for 30/70 blends, the predictions are not in agreement with SEM results, which reveal a cocontinuous blend of the two. Predictions of the discrete particle model are poor with NBR as the matrix for all three volume fractions. A closer agreement of the predicted results for a 70/30 PP/NBR blend and the properties of a 1% maleic anhydride modified PP or 3% phenolic‐modified PP compatibilized 70/30 PP/NBR blend in the lower temperature zone has been observed. This may be explained by improved interfacial adhesion and stable phase morphology. A mixed‐cure dynamically vulcanized system gave a better agreement with the predictions with PP as the matrix than the peroxide, sulfur, and unvulcanized systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1417–1432, 2004     

A new method of stabilization and characterization of the interface in binary polymer blends by irradiation: A positron annihilation study

New methods for stabilizing the interface of partially miscible and immiscible binary polymer blends and characterizing such an interface are described here. Interfacial modifications in four binary polymer blend systems namely PS/PMMA, PVC/EVA, PP/NBR, and PVC/SAN were induced by e‐beam and microwave irradiation. These changes have been characterized in terms of free volume measured by Positron lifetime technique and DSC as supplementary to free volume data. The changes observed in free volume parameters upon irradiation could not be connected to the changes at the interface and also not specific to composition of the blend. Owing to this limitation, we exploited the usefulness of hydrodynamic interaction parameter α derived from the very same free volume data to monitor the changes at the interface. The present results demonstrated that α is effective in revealing the changes at the interface and can be used to characterize the interfacial properties in partially miscible and immiscible polymer blends. Further, the results clearly show that microwave irradiation is a better route to stabilize the interface of a partially miscible or immiscible blend if its component polymers contain polar groups. E‐beam irradiation seems to be better route if the component polymers of the blend contain no polar groups. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 619–632, 2009     

Chirality Discrimination at Binary Organic|Water Interfaces Monitored by Interfacial Tension Measurements with Preliminary Comparison with Molecular Dynamics Simulations

Chirality discrimination at a binary toluene (organic)/water(aqueous) interface between R- or S-Tol-BINAP (2,2′-Bis(di-p-tolylphosphino)-1,1′-binaphthyl) molecules and the water-soluble serine chiral specie is examined for the first time, using a combination of interfacial tension measurements and molecular dynamic simulations. Experimental interfacial measurements exhibit a clear chirality-controlled difference when a homochiral versus a heterochiral enantiomeric pairs are introduced at the interfaces. The related molecular dynamics simulations support the experimental results and provide further molecular insight of intermolecular interactions at the interfaces. The results indicate that interfacial tension measurements can capture the preferential interactions which exist between different pairs of enantiomers at the binary interfaces, opening up a new way for probing chirality discrimination at liquid-liquid interfaces.     

Miscibility of poly(ϵ-caprolactone) and of poly(styrene-co-acrylonitrile) with poly(styrene-co-acrylic acid)

The miscibility of poly (?-caprolactone) (PCL) with poly (styrene-co-acrylic acid) (SAA) and of poly (styrene-co-acrylonitrile) (SAN) with SAA was examined as a function of the comonomer composition in the copolymers. For PCL/SAA blends it was found that PCL is miscible with SAA within a specific range of copolymer compositions. Segmental interaction energy densities were evaluated by analysis of the equilibrium melting point depression and application of a binary interaction model. The results suggest that the intramolecular repulsion in SAA copolymer plays an important role in inducing the miscibility. Additionally, the critical AA content in SAA for the blend to be homogeneous was predicted by correlating the segmental interaction energy densities with the binary interaction model. For SAN/SAA blends, it was also found that SAA is miscible with SAN within a specific range of copolymer compositions. From the binary interaction model, segmental interaction energy denisties between different monomer units were estimated from the miscibility map and were found to be positive for all pairs, indicating that the miscibility of the blends is due to the strong repulsion in the SAA copolymers.     

Interactions between Hydrophobically Modified Associating Polyacrylamide and Cationic Surfactant at the Water‐Octane Interface: Interfacial Dilational Viscoelasticity and Relaxation Processes

The interfacial dilational viscoelastic properties of hydrophobically associating block copolymer composed of acrylamide (AM) and a low amount of 2‐ethylhexyl acrylate (EHA) (<1.0 mol%) with a hydrolyzed degree of about 1.5–2.0% at the octane‐water interfaces were investigated by means of two methods: the interfacial tension response to sinusoidal area variations (oscillating barriers method) and the relaxation of an applied stress (interfacial tension relaxation method) respectively. The influence of cationic surfactant cetyl trimethylammonium bromide (CTAB) on the dilational viscoelastic properties was studied. The results obtained by oscillating barriers method showed that dilational modulus decreased moderately with the increase of CTAB concentration. The results obtained by interfacial tension relaxation measurements showed that two main relaxation processes exist in the interface at 7,000 ppm polymer concentration: one is the fast process involving the exchange of hydrophobic blocks between the proximal region and distal region in the interface; the other is the slow relaxation process involving conformational changes of polymer chain in the interface. By adding CTAB, the slow process changed obviously due to the strong electrostatic interaction between oppositely charged surfactant and hydrolyzed part of polymer chain. Only when the CTAB concentration was close to the “equal charge point,” the associations formed mainly by the hydrophobic interaction like that in SDS/polymer system appeared and the characteristic time of fast process decreased obviously. The information of relaxation processes obtained from interfacial tension relaxation measurements can explain the results from dilational viscoelasticity measurements very well.     

含无规共聚物三元共混体系SMMA-PMMA-SAN相行为

含无规共聚物共混体系的相容性研究正在成为近年来的研究热点 ,因为相容的驱动力来自共聚物分子内不同单体链段间的排斥性相互作用 [1～ 3] .目前研究这类体系还主要采用过份简化的 F- H平均场理论 ,用旨在克服平均场理论缺陷的 Flory状态方程 ( EOS)理论仅局限于研究二元共聚物共混体系[4～ 8] .与三元共混体系相比 ,用 EOS理论预测含两个无规共聚物三元体系相行为尚需确定共聚物 -共聚物间的二元参数 sj/si,Xij和 Qij.若用 Ax B1- x和 Cy D1- y分别代表共聚物 1和 2 ,则 A,B,C,D代表相应共聚物中的单体单元 ,x,y分别是 1和 2的共…     

“Volume‐Preserving” Conformational Rheological Models for Multi‐Component Miscible Polymer Blends Using the GENERIC Formalism

A family of conformational rheological models for multi‐component miscible polymer blends is developed using a modified form of the Poisson bracket formulation. Two conformation tensors called c ₁ and c ₂ are introduced to show the orientation of the first and the second components of a blend, respectively. The mobility tensor and the energy function for each blend component are expressed in terms of these conformation tensors. The interaction effects are also included by energy expressions. The predictions of this family of “volume‐preserving” models are illustrated for a Hookean‐type energy function and several expressions of the modified mobility tensors. The results are illustrated for material functions in transient (start‐up and relaxation) and steady shear flows. The predictions are compared with experimental data taken from the literature for a miscible polymer blend. Study of the model sensitivity to its parameter shows that model predictions can cover a wide range of rheological behavior generally observed for multi‐component miscible polymer blends in steady and transient shear flows.

Experimental data and model predictions for steady shear viscosity for HDPE/LDPE blends.     

Mechanical behavior and wrinkling patterns of phase-separated binary polymer blend film

The wrinkling of phase-separated binary polymer blend film was studied through combining the Monte Carlo (MC) simulation for morphologies with the lattice spring model (LSM) for mechanical properties. The information of morphology and structure obtained by use of MC simulation is input to the LSM composed of a three-dimensional network of springs, which allows us to determine the wrinkling and the mechanical properties of polymer blend film, such as strain, stress, and Young’s modulus. The simulated results show that the wrinkling of phase-separated binary polymer blend film is related not only to the structure of morphology, but also to the disparity in elastic moduli between polymers of blend. Our simulation results provide fundamental insight into the relationship between morphology, wrinkling, and mechanical properties for phase-separated polymer blend films and can yield guidelines for formulating blends with the desired mechanical behavior. The wrinkling results also reveal that the stretching of the phase-separated film can form the micro-template, which has a wide application prospect.     

Liquid phase demixing in ferroelectric/semiconducting polymer blends: An experimental and theoretical study

This article describes a combined experimental and theoretical study on nanophase structure development as a result of liquid phase demixing in solution‐cast blends of the organic semiconductor poly(9,9′‐dioctyl fluorene) (PFO) and the ferroelectric polymer poly(vinylidene fluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)). Blend layers (200 nm) are prepared by spin coating a 1:9 (w/w) PFO:P(VDF‐TrFE) blend solution in a common solvent on a poly(ethylenedioxy thiophene)/poly(styrene sulfonate) substrate. Owing to the pronounced incompatibility between the two polymers, a strong phase‐separated morphology is obtained, characterized by disk‐like nanodomains of PFO embedded in a P(VDF‐TrFE) matrix, as revealed by scanning electron microscopy. By varying the processing conditions, we find the average domain size and standard deviation to increase with spinning time. The considerable increase in domain size suggests the coarsening process not to be impeded by a steep rise in viscosity. This indicates solvent evaporation to be only moderate within the experimental time frame. The evolution of the observed phase morphology is modeled using ternary diffuse interface theory integrated with a modified Flory–Huggins (FH) treatment of the homogeneous (bulk) free energy of mixing, to account for significant molecular differences between the active blend components. Using calculated FH interaction parameters, the model confirms the phase separation to occur via spinodal decomposition of the blend solution during spin coating, as suggested by experimental observations. The simulated phase morphologies as well as the modeled trends in domain growth and standard deviation compare favorably with the experimental data. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1255–1262, 2011