Intermacromolecular complexation due to specific interactions. 7. Miscibility and complexation between poly(styrene-co-4-vinyl benzoic acid) and poly[n-butyl methacrylate-co-(4-vinylpyridine)]

The miscibility between poly(styrene-co-4-vinyl benzoic acid), that is, carboxylated PS (CPS), and polyfn-butyl methacrylate-co-(4-vinylpyridine)] (BVPy) was investigated using differential scanning calorimetry (DSC). The results showed that, when the 4-vinyl pyridyl content in BVPy was higher than about 5 mol%, the CPS/BVPy system exhibited miscibility for the carboxyl content in CPS as it varied from 1.6 to 20 mol%. Complexation between CPS and BVPy in non-aqueous solutions was studied by viscometry. It was found that, when the density of hydrogen bonding between the proton-donating and the proton-accepting polymers reached a certain level, an intermacromolecular complex would form as turbidity and/or precipitate in organic solutions such as 2-butanone and THF. Combining the results from DSC and viscometry in 2-butanone, an immiscibility-miscibility-complexation map for the CPS/BVPy system was obtained.     

Thermal Behaviors of Confined Triphenylmethyl Chloride Crystals in Various Molecular Weight Polystyrene

The thermal behaviors of polystyrene (PS)/triphenylmethyl chloride (TPCM) blends with different polymer molecular weights were investigated through differential scanning colorimetry (DSC). It was shown that when solvent content was lower than a critical composition, there was only a single amorphous phase in the blends. With increasing polymer concentration, both T_g and T_m could be detected in DSC curves, revealing that the blends were heterogeneous. The constant T_g of the amorphous phase indicated that the composition of the amorphous phase in the blends did not depend on the solvent concentration, and the T_m depression with decreasing PS content showed the decrease of TPCM crystallite size owing to geometric constraint by the polymer chains. On the basis of the Flory–Huggins theory, the interaction parameters between PS and TPCM in the blends were obtained; they showed that the PS/TPCM blends were not thermodynamically miscible with low polymer content. The Hoffmann-Weeks equation indicated that the crystals corresponding to the lower melting point were unstable. The unstable crystals in the blends were located in the interfacial regions between the crystalline solvent molecules and the amorphous phase. The heat capacity of the blends confirmed the geometric constraint on the crystallization of TPCM in the blends.     

Morphology and infrared spectroscopy of strongly interacting polymer blends: EVOH/copolyamide-6/6.9

The presence of aliphatic hydroxyl groups in poly(ethylene-co-vinylaleohol) (EVOH) suggests that these copolymers have the potential of forming miscible blends, within certain composition ranges, with a variety of polymers containing complementary functional groups. Hydrogen bonding in EVOH involves a wide variety of inter- and intramolecular species and plays an important role in the phase behavior of EVOH blends. Polymer blends of two random copolymers, EVOH with different ethylene contents and copolyamide-6/6.9 (COPA) at an approximately 1:1 comonomer ratio, were investigated using Fourier transform infrared (FTIR), near-IR, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) methods. The blends were found to be partially miscible due to intermolecular hydrogen bonding between the OH group of the EVOH and the amide group of the copolyamide. The EVOH-rich blends exhibit much lower miscibility compared with the copolyamide-rich blends.     

Study of Miscibility in Polymer Blends Obtained from Binary Inclusion Complexes of γ-Cyclodextrin and Polycarbonate/Poly(Ethylene Terephthalate)

In this work the synthesis and characterization of the nanostructure of polymer blends of polycarbonate (PC) and poly(ethylene terephthalate) (PET) obtained from their inclusion complexes with γ-cyclodextrin are reported. The blends prepared by this method present differences in their miscibility compared with those blends obtained by conventional methods like solution casting, coprecipitation, or melt blending. In order to understand the influence of molecular weight in the inclusion complex process, PCs of M_w = 64,000 and 28,000 g/mol were used. The analysis of the nanostructured blend by Fourier transform infrared (FTIR), ¹H-nuclear magnetic resonance (¹H-NMR), wide-angle X-ray diffraction (WAXD), differential scanning colorimetry (DSC), and thermogravimetric analysis (TGA) suggests the existence of specific intermolecular interactions between PC and PET that promote miscibility in this normally immiscible polymer blend. Studies by FTIR confirm that the miscibility found was not due to a transesterification reaction during DSC analysis. There were also differences in the morphology of the blends, observed by optical microscopy, obtaining a more homogeneous phase for blends formed in inclusion complexes. The results obtained strongly suggest an improvement in miscibility of the PC/PET blends.     

Infrared studies on the molecular interactions of polymer blends: polystyrenes and polycarbonates systems

Fourier—transform infrared (FT-IR) with digital subtraction method has been applied to investigate the molecular interactions of immiscible polystyrene (PS)/bisphenol A polycarbonate (PC) blends and miscible PS/tetra-methyl PC (TMPC) blends. The FT-IR results show that there are no interactions for PS/PC, and the miscibility of PS/TMPC blends is mainly due to the intermolecular interaction between the phenyl ring of PS and the carbonate group of TMPC. The phenyl ring band of PS is linearly shifted to higher wave number with increasing concentration of TMPC, and the bandwidth at half maximum intensity of the carbonyl band of TMPC is linearly decreased with increasing concentration of PS. The amplitude of the interactional bands is decreased with increasing temperature consistent with LCST behavior of the blend. The miscibility of PS/TMPC and immiscibility of PS/PC has also been discussed in terms of local free-volume, self-interactions, and intermolecular interactions based on the chemical structures of PC and TMPC. Furthermore, the immiscibility behavior for blends of methyl-substituted PS and TMPC, and blends of PS and halogen-substituted PC has been explained in terms of intra and intermolecular interactions caused by steric and/or induction effects.     

A Study on Compatibility and Properties of POE/PS/SEBS Ternary Blends

Ethylene‐α‐olefin copolymer (POE)/polystyrene (PS)/poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS) blends were prepared via melt blending in a co‐rotating twin‐screw extruder. The effects of SEBS copolymer on the morphology and rheological and mechanical properties of the blends were studied. Scanning electron microscopy (SEM) photos showed that the addition of SEBS copolymer resulted in finer dispersion of PS particles in the POE matrix and better interfacial adhesion between POE and PS compared with POE/PS blends, which exhibited a very coarse morphology due to the immiscibility between them. Interestingly, the tensile strength increased from 12.5 MPa for neat POE to 23.5 MPa for the POE/PS/SEBS (60/10/30) blend, whereas the tensile strengths of POE/PS (85.7/14.3) blend and POE/SEBS (66.7/33.3) blend were only 10.5 and 16.5 MPa, respectively. This indicates that both SEBS copolymer and PS have a synergistic reinforcing effect on POE. Dynamic mechanical thermal analysis (DMTA) and dynamic rheological property measurement also revealed that there existed some interactions between POE and SEBS as well as between SEBS and PS. DMTA results also showed that the storage modulus of POE increased when PS and SEBS were incorporated, especially at high temperature, which means that the service temperature of POE was improved.     

Preferential surface segregation of homopolymer and copolymer blend films

Surface film properties of the homopolymers polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(butyl methacrylate) (PBMA) and the copolymer poly(methyl methacrylate)-co-poly(butyl methacrylate) (PMMA-co-PBMA) and their blends with PS have been examined by atomic force microscopy (AFM) and contact angle measurements. The total and the Lifshitz-van der Waals, acid and base components of the surface free energy together with the work of adhesion and its components, the cohesive energy density and the solubility parameters of the homopolymer, copolymer and blend films were determined. Films of about 3 μm were considered. The results are discussed in terms of surface migration mechanisms based on surface free energy and solubilities of the polymers in the solvent, toluene in this paper. AFM imaging and contact angles revealed surface enrichment at the air polymer interface of PBMA for both the PS/PBMA blend and the copolymer PMMA-co-PBMA, whereas the PS/PMMA and PS/PMMA-co-PBMA blend film surfaces show island-like phase-separated structure of typical size 27.4-86.5 nm in diameter and 6.9-15.6 nm in height for PS/PMMA, while for PS/ PMMA-co-PBMA film surface the typical size is 49.6-153.3 nm in diameter and 1.6-14.2 nm in height.     

COMPATIBILIZATION OF POLY(ETHYLENE OXIDE)/POLY(STYRENE) BLENDS: EFFECT OF THE MOLECULAR WEIGHT OF THE COMPATIBILIZER

The effect of the molecular weight and concentration of the compatibilizer maleic acid-alt-styrene copolymer (MAaS) on the compatibility behavior of incompatible poly(ethylene oxide)/poly(styrene) (PEO/PS) blends was studied by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). PEO with [Mbar] _w = 100,000 (PEO₁₀₀) and PS with [Mbar] _w = 225,000 (PS₂₂₅) were used for this study. DSC measurements showed two T _g values that were shifted relative to those of the pure components. This result should be indicative that MAaS acts as a compatibilizer for the blend. Diminishing of the spherulitic growth rate G was observed as the content and molecular weight of MAaS increased in the blend. This result was confirmed by morphological analysis, by which it was possible to observe that the amorphous component diminished its droplike domains. Contact angle measurements suggest that the wettability of PEO drops on a PS/MAaS surface are larger in the system containing MAaS as the compatibilizer.     

Preparation and Properties of Polylactide/Poly(ethylene-co-octene)/nano-SiO2 Ternary Composites

Polylactide (PLA)/poly(ethylene-co-octene)(POE) blends with various contents of nano-SiO₂ were prepared via melt mixing. The structure and properties of the PLA/POE/nano-SiO₂ ternary composites were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), rheometry, and tensile testing. The particle size of the dispersed POE phase first decreased with increasing nano-SiO₂ content and then remained constant. Nano-SiO₂ played an important role in the heterogeneous nucleation of PLA, which resulted in an increase of the crystallinity of PLA. The synergistic effect of both POE and nano-SiO₂ can significantly improve the toughness, strength, and modulus of PLA. When the ratio of PLA/POE/nano-SiO₂ was 90/10/0.5, PLA/POE/nano-SiO₂ composite had the best comprehensive properties.     

Calorimetric study of blend miscibility of polymers confined in ultra-thin films

Miscibility in blends of polystyrene and poly(phenylene oxide) (PS/PPO) confined in thin films (down to 6 nm) was investigated using a recently developed sensitive differential alternating current (AC) chip calorimeter. Comparison of composition dependence of glass transition in thin films with common models should provide information on miscibility. This study focuses on the blend system polystyrene and poly(phenylene oxide) (PS/PPO) because it is thought as a miscible model system in the whole composition range. Furthermore, its local dynamic heterogeneity is already identified by dynamic mechanic thermal analysis (DMTA) and solid state NMR techniques. For this blend, we find that even for the thinnest films (6 nm, corresponding to about half of PPO’s radius of gyration R _g) only one glass transition is observed. The composition dependence of T _g is well described by the Fox, Couchman or Gordon-Taylor mixing law that are used for the miscible bulk blends. Although there is a contradicting result on whether T _g decreases with decreasing film thickness between our calorimetric measurements and Kim’s elipsometric measurements on the same blend (Kim et al. Macromolecules 2002, 35, 311–313), the conclusion that the good miscibility between PS and PPO remains in ultrathin films holds for both studies. Finally, we show that our chip calorimeter is also sensitive enough to study the inter-layer diffusion in ultrathin films. PS chain in a thin PS/PPO double layer that is prepared by spin coating PPO and PS thin film in tandem will gradually diffuse into the PPO layer when heated above T _g of PS, forming a PS_xPPO_100−x blend. However, above the PS_xPPO_100−x blend, there exists an intractable pure PS like layer (∼30  nm in our case) that does not diffuse into the blend beneath even staying at its liquid state over 10 hours.     

Microhardness Studies of the Interphase Boundary in Rubber‐Softened Glassy Polymer Blends Prepared with/without Compatibilizer

Abstract

The interphase boundary of incompatible polymer blends such as poly(methyl methacrylate) (PMMA)/natural rubber (NR) and polystyrene (PS)/NR, and of compatible blends such as PMMA/NR/epoxidized NR (ENR) and PS/NR/styrene–butadiene–styrene (SBS) block copolymer, where ENR and SBS were used as compatibilizers, was studied by means of microindentation hardness (H) and microscopy. Cast films of neat PMMA and PS, and blended films of PMMA/NR, PS/NR, PMMA/NR/ENR, and PS/NR/SBS were prepared by the solution method using a common solvent (toluene). Hardness values of 178 and 173 MPa were obtained on the surfaces of the neat PMMA and PS, respectively. After the inclusion of soft phases, the binary (incompatible) and the ternary (compatible) blend surfaces show markedly lower H‐values. Scanning electron and optical microscopy reveal a clear difference at the phase boundary of the surface of compatible (smooth boundary) and incompatible (sharp boundary) blends. The compatibilized blends were characterized by using microhardness measurements, as having the thinnest phase boundary (～30 µm), while incompatible blends were shown to present a boundary of about 60 µm. The hardness values indicate that the compatibilizer is smoothly distributed across the interface between the two blend components. Results highlight that the microindentation technique, in combination with microscopic observations, is a sensitive tool for studying the breadth and quality of the interphase boundary in non‐ or compatibilized polymer blends and other inhomogeneous materials.     

Rheological Technique as a Sensitive Method to Characterize the Chain Diffusion across the Interface between Polystyrene and Carbon Black Filled Polystyrene

The mutual diffusion process and interphase development taking place at the interface between disks of polystyrene (PS) and carbon black filled polystyrene (CB-PS) in the molten state were investigated by a small-amplitude, oscillatory shear, rheological technique. The rheological method was employed to probe the thermorheological complexity of these polymer disks. It was found that the dynamic complex shear modulus, G*(t), increased with the time of contact in two time regimes at a fixed frequency. The time of transition between the two regimes was observed to be close to the time needed for the transition from the Rouse mode to the reptation mode. The results showed that the content of the carbon black and the temperature affected the slope of the G*(t) – t curve. Scanning electron microscopy revealed the interface disappeared when the diffusion process was complete.     

Maleic Acid–alt–Styrene Copolymer as Compatibilizer for Poly(Ethylene Oxide)-Poly(Styrene)Blends

Maleic acid-alt-styrene (MAaS) copolymer with number-average molecular weight [Mbar] _n = 2500 was used as a compatibilizer in blends of poly(ethylene oxide) (PEO) and poly(styrene) (PS). PEO with weight-average molecular weight [Mbar] _w = 10⁵ (PEO₁₀₀) and two PS samples with [Mbar] _w = 9 × 10⁴ and 4 × 10⁵, respectively (PS₉₀ and PS₄₀₀, respectively) were used. A depression of the melting temperature T _m of PEO in blends containing MAaS relative to pure PEO and PEO/PS blends was observed. The melting enthalpy ΔH _m for the PEO/PS blends containing MAaS was lower than those of pure PEO and PEO/PS blends without compatibilizer. The crystallization kinetics of PEO and the blends were studied by differential scanning calorimetry (DSC) at different crystallization temperatures T _c. Flory-Huggins interaction parameters χ₁₂ for the blends were estimated. Their values are in good agreement with those obtained for similar systems and suggest that the free energy of mixing ΔG _mix should be negative. Polarized optical microscopy shows differences in the macroscopic homogeneity of the blends containing compatibilizer that could be attributed to a compatibilization process.     

Stimuli-responsive poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) triblock copolymers and complexation with poly(acrylic acid) at low pH

The self-organization of the double hydrophilic triblock copolymer poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide), PEO-b-P2VP-b-PEO, was investigated in dilute aqueous solution under several experimental conditions using turbidimetry, as well as static and dynamic light scattering. As a result of the temperature-sensitive properties of the end PEO blocks and the p H-responsive properties of the middle P2VP block, the formation of large star-like micellar nanostructures is observed at high p H, while at low p H, but in the presence of salt and at high temperature, flower-like micelles are formed. Moreover, the viscosimetric and dynamic light scattering studies at low p H revealed that micelle-like nanostructures are formed upon mixing the triblock copolymer with poly(acrylic acid), PAA, due to hydrogen bonding interpolymer complexation.     

Effect of Solvent on the Miscibility of Polystyrene/Poly(Styrene-Co-Acrylonitrile) Blends at Different Temperatures

The effect of solvent and temperature on the miscibility of polystyrene (PS) and poly (styrene-co-acrylonitrile) (PSAN) was examined by the dilute-solution viscometry (DSV) method. The extent of miscibility of different PS/PSAN blend compositions (30/70, 50/50, and 70/30) in chloroform (CHCl₃) and N, N- dimethyl formamide (DMF) was discussed in terms of the signs of various viscosity (ΔB, μ, Δ[η], α, and β) parameters. Based on the sign convention of these interaction parameters, partial miscibility in DMF and almost immiscibility in CHCl₃ was indicated for the examined blend. The data obtained from the DSV method were then correlated with the ones obtained through density and refractive index measurements; good agreement was obtained. The study also revealed a relatively greater influence of temperature and composition on the miscibility of the blend in DMF than in CHCl₃.     

Miscibility,Morphology, and Thermal Properties of Poly(Trimethylene Terephthalate)/Polycarbonate

Abstract

Poly(trimethylene terephthalate)/polycarbonate (PTT/PC) blends were prepared by melt blending and rapid quenching in ice water. The miscibility and thermal properties were investigated using differential scanning calorimeter (DSC) and dynamic mechanical analysis (DMA). The blend's morphologies were investigated using scanning and transmission electron microscopies. Both DSC and DMA results suggested that PTT and PC were very limited, partially miscible pairs. The melting point, melt crystallization, and cold crystallization exotherms in the blends of PTT were depressed by the presence and amount of PC. When the PC content was <50 wt%, PC spherical particles were found to distribute evenly in the PTT matrix; at 50–60 wt%, the two‐phase structures were close to being bicontinuous. At higher PC content, PTT formed a string‐like texture in the PC matrix. The PTT spherulitic morphologies in PTT/PC blends were found to be very sensitive to PC and PC content. When the PC content was ≥60 wt%, the blends crystallized as an agglomeration of tiny PTT crystals.     

Effect of Polydispersity on the Phase Behavior of Polystyrene (PS)/Poly (Vinyl Methyl Ether) (PVME)

The thermodynamics and kinetics of phase separation in partially miscible blends of poly (vinyl methyl ether) (PVME) and two kinds of polystyrene (PS) with the same weight average molecular weight but different polydispersity were studied. The miscibility of PS/PVME with the monodisperse PS was better than that of PS/PVME with the polydisperse PS. Different morphology was observed for the two kinds of PS/PVME (10/90) blends during the nonisothermal phase separation process. The blend with monodisperse PS presented a co-continuous structure while the blend with polydisperse PS presented a viscoelastic phase separated network structure at a quench depth of 29°C. With increase of the heating rate, the increase of cloud point of PS/PVME (30/70) with polydisperse PS was smaller than that of PS/PVME (30/70) with monodisperse PS. During the isothermal phase separation of the critical composition (20/80) of PS/PVME with a quench depth of 30°C, it was found that the phase morphology of the two kinds of blends was nearly the same at the early stage of phase separation. However, as the dispersed phase, an approximately spherical droplet structure was observed in the blend with monodisperse PS at the late stage of phase separation, which did not appear in the blend with polydisperse PS.     

Characterization of ion transport property in hot-press cast solid polymer electrolyte (SPE) films: [PEO: Zn(CF3SO3)2]

Characterization of ion transport property in dry solid polymer electrolyte (SPE) films: [PEO: Zn(CF₃SO₃)₂] in different salt wt% ratio has been reported. SPE films have been prepared by a hot-press casting procedure. Salt concentration dependent conductivity study at room temperature identified SPE film: [90PEO: 10 Zn(CF₃SO₃)₂] as optimum conducting composition (OCC) with σ _rt ~ 1.09 × 10⁻⁶ S/cm which is approximately three orders of magnitude higher than that of pure PEO host (σ _rt ~ 3.20 × 10⁻⁹ S/cm). The reason attributed for σ _rt enhancement has been the increase in degree of amorphous phase in polymeric host after salt complexation. This has been confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), and polarized optical microscopy (POM) analysis. To evaluate the usefulness of SPE OCC film in all-solid-state-battery applications, ion transport property has been characterized in terms of basic ionic parameters viz. ionic conductivity (σ) and total ionic (t _ion)/cation (t ₊) transport numbers. Mechanism of ion transport has been explained by temperature dependent conductivity measurements and the activation energy (E _a) has been computed by least square linear fitting of “log σ − 1/T” Arrhenius plot.

     

End group effect on surface and interfacial segregation in PS-PMMA blend thin films

Thin films of polystyrene (PS)/poly (methyl methacrylate) (PMMA) blends with different end groups were investigated using ToF-SIMS and AFM. PS with -OH and -NH₂ end groups were blended in toluene solvent with pure PMMA homopolymer, and PMMA having anhydride end group. The ToF-SIMS spectra of PS-OH/PMMA resembled that of pure PS-PMMA blends showing an increase of PMMA intensity after annealing. On the contrary, the PS-NH₂ blended with PMMA showed an increase in PS intensity on the surface after annealing. The ToF-SIMS spectra were similar to that of a pure PS-PMMA di-block copolymer. These results indicate copolymer formation at the surface. The PS-NH₂ with PMMA-anhydride blend spectra showed very slight changes in spectra before and after annealing and the AFM images revealed spinodal bi-continuous structures on the surface before and after annealing. The copolymer formation is found to occur in the as-cast film itself and not after thermal treatment.     

Morphological Aspects of In-Situ Compatiblized Binary Polymer Blends With Variable Viscosity Ratios of Components

The in-situ compatiblized binary polymer blend polypropylene(PP)/polystyrene(PS)/ anhydrous aluminum chloride(AlCl₃) was selected as a model system of a reactive polymer blend to investigate the effect of viscosity ratio of components at a constant shear rate on the phase morphological behavior in in-situ compatibilized systems. The results showed that the well-known interfacial compatibilization effect was related to variations of viscosity ratios of components in the reactive PP/PS blends with different contents of AlCl₃ catalyst. The phase morphology evolution of the in-situ compatiblized reactive blend was determined by both the interfacial compatibilization and the variation of the viscosity ratio of components under the fixed mixing conditions, which showed characteristics obviously different from and much more complex than those in binary polymer blends generally compatiblized by added compatiblizers. The results implied that the variation of the viscosity ratio of components should be checked carefully and taken into account if necessary, when the phase morphology of binary polymer blends is investigated, especially in complex in-situ compatiblized reactive polymer blends.