Examination of miscibility at molecular level of poly(hydroxyether of bisphenol A)/poly(N-vinyl pyrrolidone) blends by cross-polarization/magic angle spinning 13C nuclear magnetic resonance spectroscopy

The miscibility of poly(hydroxyether of bisphenol A) (phenoxy) and poly(N-vinyl pyrrolidone) (PVP) was investigated by differential scanning calorimetry (DSC) and high-resolution solid-state nuclear magnetic resonance (NMR) techniques. The DSC studies showed that the phenoxy/PVP blends have a single, composition-dependent glass transition temperature (T_g). The S-shaped T_g-composition curve of the phenoxy/PVP blends was reported, which is indicative of the strong intermolecular hydrogen-bonding interactions. To examine the miscibility of the system at molecular level, high-resolution solid-state ¹³C nuclear magnetic resonance (NMR) technique was employed. Upon adding phenoxy to system, the chemical shift of carbonyl carbon resonance of PVP was observed to shift downfield by 1.6 ppm in the ¹³C cross-polarization (CP)/magic angle spinning (MAS) together with the high-power dipolar decoupling (DD) spectra when the concentration of phenoxy is 90 wt %. The observation was responsible for the formation of intermolecular hydrogen bonding. The proton spin-lattice relaxation time T₁(H) and the proton spin-lattice relaxation time in the rotating frame T_1ρ(H) were measured as a function of the blend composition. The T₁(H) result was in good agreement with the thermal analysis, i.e., the blends are completely homogeneous on the scale of 20 ∼ 30 nm. The six results of T_1ρ(H) further indicated that the blends were homogeneous on the scale of 40 ∼ 50Å. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2291–2300, 1998     

Thermodynamic parameters of the interaction of cellulose ethers with low-molecular-mass liquids

The thermodynamic analysis of the interaction of methyl cellulose, cyanoethyl cellulose, cyanoethyl hydroxyethyl cellulose, and hydroxyethyl cellulose with low-molecular-mass liquids is performed via the method of static sorption. A correlation is found between the thermodynamic parameters and the chemical structures of the components.     

Morphology and micromechanical behaviour of styrene/butadiene block copolymers and their blends with polystyrene

The correlation between the morphology and the deformation mechanism in styrene/butadiene block copolymers having modified architecture and in blends with homopolymer polystyrene (hPS) was studied. It was demonstrated that the morphology formation in the block copolymers is highly coupled with their molecular architecture. In particular, the micromechanical behaviour of a star block copolymer and its blends with polystyrene was investigated by using electron microscopy and tensile testing. A homogeneous plastic flow of polystyrene lamellae (thin layer yielding) was observed if the lamella thickness was in the range of 20 nm. The deformation micromechanism switched to the formation of craze-like deformation zones when the average PS lamella thickness changed to about 30 nm and more.     

Phase behaviour and miscibility window in UCST-type blends of poly(styrene-co-acrylonitrile) and tetramethylbisphenol A oligosulfones

The pressure–volume–temperature (PVT) behaviour of styrene–acrylonitrile (SAN) random copolymers and of tetramethylbisphenol A oligosulfones (TMOS) was studied using the Flory–Orwoll–Vrij (FOV) as well as the Sako–Wu–Prausnitz (SWP) equation-of-state (EOS). It was found that the SWP EOS is superior to the FOV theory in describing the PVT behaviour of the polymers, especially in the high-pressure range. Furthermore, blends comprising TMOS and SAN copolymers of varying acrylonitrile content were studied by means of cloud point measurements and differential scanning calorimetry. The system shows pronounced miscibility-window behaviour, i.e. the miscibility depends strongly on the copolymer composition. At the edges of the miscibility window, UCST (upper critical solution temperature) behaviour was observed and discussed in terms of the FOV EOS. The cloud point curves were exceptionally broad and could be reproduced neither by the Flory–Huggins nor by the FOV theory. However, taking the polydispersity of both components into account, the calculation of correct phase diagrams was possible using the FOV theory. Exchange energy parameters between the polymers, X_AB, were obtained from fitting the critical points of the phase diagrams. Additionally, segmental exchange energy parameters X_i/j of the components were calculated.     

Blends of cellulose ester/phenolic polymers – chemical and thermal properties of blends with polyvinyl phenol

A series of miscible cellulose ester/poly (vinyl phenol) (CE/PVP) blends containing a latent formaldehyde source were prepared. Due to the low molecular weight of the PVP, the maximum PVP content ID the films was 50 wt %. The blends were then thermally cross-linked ID an attempt to create semi-interpenetrating polymer networks (semi-IPN). The blends were characterized with differential scanning calorimetry, swelling experiments, pyrolysis molecular beam mass spectrometry (py-MBMS), and Fourier transform infrared (FTIR) spectroscopy. The results from the swelling experiments, py-MBMS and FTIR showed that the PVP component did react with the formation of methylene bridges. Blends that contained 50% PVP and high levels of formaldehyde formed semi-IPN structures.     

Solvent effects on the formation of nanoparticles and multilayered coatings based on hydrogen-bonded interpolymer complexes of poly(acrylic acid) with homo- and copolymers of N-vinyl pyrrolidone

The formation of hydrogen-bonded interpolymer complexes between poly(acrylic acid) and poly(N-vinyl pyrrolidone) as well as amphiphilic copolymers of N-vinyl pyrrolidone with vinyl propyl ether has been studied in aqueous and organic solutions. It was demonstrated that introduction of vinyl propyl ether units into the macromolecules of the nonionic polymer enhances their ability to form complexes in aqueous solutions due to more significant contribution of hydrophobic effects. The complexation was found to be a multistage process that involves the formation of primary polycomplex particles, which further aggregate to form spherical nanoparticles. Depending on the environmental factors (pH, solvent nature), these nanoparticles may either form stable colloidal solutions or undergo further aggregation, resulting in precipitation of interpolymer complexes. In organic solvents, the intensity of complex formation increases in the following order: methanol < ethanol < isopropanol < dioxane. The multilayered coatings were developed using layer-by-layer deposition of interpolymer complexes on glass surfaces. It was demonstrated that the solvent nature affects the efficiency of coating deposition.     

Transition from miscibility to immiscibility in blends of poly(methyl methacrylate) and styrene-acrylonitrile copolymers with varying copolymer composition: a DSC study

The glass transition and the structural relaxation processes have been studied in blends of poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile (SAN) copolymers with different acrylonitrile (AN) contents. The 50/50 wt.% blend of PMMA with the SAN copolymer containing 30 wt.% of AN is immiscible, while blends with copolymers containing between 13 and 26 wt.% of AN are miscible. Thus the upper limit of miscibility is between 26 and 30 wt.% of AN. The temperature dependence of the relaxation times of the conformational rearrangements of polymer chains around the glass transition have been determined in the blends and pure components by modelling DSC thermograms obtained after different thermal histories in each sample. The slope in the Arrhenius diagram logτ vs 1/T around the glass transition temperature is significantly smaller in the blend which is closer to the upper limit of miscibility than in the other miscible blends in which SAN copolymer contains less AN. The change of slope can be ascribed to a distribution in the glass transition temperatures of the different rearranging regions, reflecting the appearance of a microheterogeneity in the blend that cannot be detected as a double glass transition in the blend.     

Phase behavior of tetramethylpolycarbonate blends with styrene‐based methacrylate copolymers and their interaction energies

The miscibility of tetramethylpolycarbonate (TMPC) blends with styrenic copolymers containing various methacrylates was examined, and the interaction energies between TMPC and methacrylate were evaluated from the phase‐separation temperatures of TMPC/copolymer blends with lattice‐fluid theory combined with a binary interaction model. TMPC formed miscible blends with styrenic copolymers containing less than a certain amount of methacrylate, and these miscible blends always exhibited lower critical solution temperature (LCST)‐type phase behavior. The phase‐separation temperatures of TMPC blends with copolymers such as poly(styrene‐co‐methyl methacrylate), poly(styrene‐co‐ethyl methacrylate), poly(styrene‐co‐n‐propyl methacrylate), and poly(styrene‐co‐phenyl methacrylate) increase with methacrylate content, go through a maximum, and decrease, whereas those of TMPC blends with poly(styrene‐co‐n‐butyl methacrylate) and poly(styrene‐co‐cyclohexyl methacrylate) always decrease. The calculated interaction energy for a copolymer–TMPC pair is negative and increases with the methacrylate content in the copolymer. This would seem to contradict the prediction of the binary interaction model, that systems with more favorable energetic interactions have higher LCSTs. A detailed inspection of lattice‐fluid theory was performed to explain such phase behavior. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1288–1297, 2002     

Insight into the interaction of the microwave radiation with droplets of interest in analytical chemistry

The idea of heating aerosols by applying a microwave field has recently been taken up again for liquid sample introduction in atomic spectrometry. Heating of the droplets can take place directly, because of microwave energy absorption by the droplets themselves, or indirectly, as a result of heat transmission from the radiated parts of the system to the droplets by conduction, convection or thermal radiation. There is some degree of discrepancy among the specialists on this subject, i.e., about the contribution of each of these mechanisms to the temperature of the aerosol. Some of them state that there is no direct coupling between the microwave radiation and the droplets, only indirect heating. However, we claim that both ways of heating occur. In this work we support our point of view on the basis of the existing bibliographical background, a theoretical analysis and our own experimental results.     

Molecular interpretation of miscibility in polyamide-6 blends with alkali ionomers of sulfonated polystyrene

Blends of polyamide-6 with lithium ionomers of 9.8 and 5.4 mole percent sulfonated polystyrene, formed by combining solutions of these polymers, are miscible over a wide compositional range, but those with the equivalent sodium ionomers are not. The molecular origin of this difference is addressed by studying the far infared and infrared spectra of the blends and pure materials to follow changes in the interactions between the cations and their surroundings, and changes in the interactions between functional groups. Based on analysis of these spectra, a molecular level interpretation of the blending is proposed. The initial step involves both the interaction of one amide carbonyl with an Li⁺ ion and simultaneous hydrogen bonding between an amide N? H and a sulfonate group. This eventually leads to formation of an Li(>CO)⁺_n(n ～ 4) entity while the sulfonates are converted to the acid form through hydrogen bonding to the amide N? H groups. The Na⁺ ion does not interact strongly enough with the amide groups to leave its sulfonate environment to a significant extent. © 1995 John Wiley & Sons, Inc.     

Insight into understanding the evolution of the epitaxy crystallization in isotactic polypropylene and polyethylene blends

In this article, epitaxial structures have been successfully obtained in the isotactic polypropylene (iPP)/polyethylene (PE) blends by an accessible injection molding methods. By studying a series of iPP/PE blends, the evolution of the epitaxial growth of PE lamellae on the oriented iPP lamellae has been detailedly discussed via wide‐angle X‐ray diffraction, small‐angle X‐ray scattering, scanning electron microscopy and differential scanning calorimetry. Unexpectedly, the exactly epitaxial angles between peculiarly arranged PE lamellae and oriented PP lamellae are all larger than the classical epitaxy theory value of 50°, and it even increases gradually with increasing PP content. It is inferred that the special crystallization of PE is the consequence of joint construction of the oriented PP crystals and the continuous intense shear field provided by pressure vibration injection molding. The epitaxial structures play a positive role in the interfacial connection between two components; thus, the mechanical properties of the blends are improved. This work provides an insight understanding on the formation mechanism of the epitaxy crystallization under shear field. Copyright © 2017 John Wiley & Sons, Ltd.     

Estimating the parameters of the microheterogeneous structure of metal melts according to viscometric experimental data in terms of the absolute reaction rate theory

The temperature dependences of the viscosity of microheterogeneous metal melts are analyzed in terms of the Frenkel–Eyring theory. Using viscometric experimental data, the sizes of dispersed particles in metal melts whose components undergo eutectic and monotectic interactions are numerically estimated.     

Insight into molecular interactions and solvation properties of methylammonium perchlorate in acetonitrile-dimethylsulfoxide binary mixtures: Compressibility,viscometric and dissolution thermodynamic studies

Densities (ρ), ultrasonic velocities (u) and viscosities (ƞ) of Methylammonium perchlorate (CH₃NH₃ClO₄) in binary solvent mixtures of Acetonitrile (AN) and Dimethylsulfoxide (DMSO) containing 0.0, 0.20, 0.40, 0.60, 0.80 and 1.0 ​mol fraction of DMSO at various temperatures ranging from 298K–328K at atmospheric pressure, have been measured. From the experimental data important parameters, namely, apparent molal volume (V_Φ), isentropic compressibility (K_s), limiting apparent molal isentropic compressibility (K^o_s,ɸ), A and B-viscosity coefficients from Jones-Dole equation, B/V_ɸ^o values and viscous flow related thermodynamic properties have been derived. Interpretation of the obtained thermodynamic parameters was done with regards to solute-solvent and solute-solute interactions and structure breaking and making potential of the solutes in solution. To evaluate the extent of preferential solvation, K^o_s,ɸ values and B-coefficients for the electrolytes have been further split up into the contribution of individual ion (K^o_s,ɸ± and B_± values) by reference electrolyte method.     

Properties of blends of methyl cellulose and carboxymethyl cellulose with different degrees of ionization in solutions and solids

The rheological properties of dilute and moderately concentrated aqueous solutions of methyl cellulose with carboxymethyl cellulose having different degrees of ionization, were examined. The solvent vapor sorption method was applied to examine the compatibility of the polymers in the solid state and elucidate how the amount of nonionized carboxy groups in carboxymethyl cellulose affects its compatibility with methyl cellulose.     

Effect of selected structural parameters of styrene–butadiene block copolymers on their compatibilization efficiency in polystyrene/polybutadiene blends

The effects of the block length and block number of linear styrene–butadiene (S–B) block copolymers on their compatibilization efficiency in blending polystyrene with polybutadiene were studied. For this purpose, two sets of model S–B copolymers and both homopolymers were prepared by anionic polymerization. Diblocks, triblocks, or pentablocks of S–B copolymers were blended with these homopolymers, and the structures and some end‐use properties of the blends were determined. The supramolecular structure (determined by small‐angle X‐ray scattering), morphology (determined by transmission and scanning electron microscopy), and stress‐transfer characteristics (impact and tensile strengths) of the blends were chosen as criteria for the compatibilization efficiency of the copolymers used. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2612–2623, 2002     

Polymer-polymer miscibility in blends of a new poly(aryl ether ketone) with poly(ether imide)

Polymer miscibility was found for a blend system comprising of a new poly(aryl ether ketone) and a poly(ether imide). Phase homogeneity was preliminarily confirmed using optical and scanning electron microscopy, indicating that the scales of phase homogeneity in the blends were beyond the resolution limits of either microscopy. A composition-dependent, single glass transition temperature (T_g) in the PAEK/PEI blends within the full range of composition was observed using differential scanning calorimetry (DSC). The thermal transition breadth also suggests that the scales of mixing are fine and uniform.     

Self-assembly of amphiphilic ABC star triblock copolymers and their blends with AB diblock copolymers in solution: self-consistent field theory simulations

The self-assembled morphologies of amphiphilic ABC star triblock copolymers consisting of hydrophilic A blocks and hydrophobic B and C blocks and the blends with their counterpart linear AB diblock copolymers in solution are investigated by 2D real-space implementation of self-consistent field theory (SCFT) simulation. The star triblock copolymers self-assemble in solution to form various micellar structures from hamburger, to segmented wormlike, to toroidal segmented micelles, and finally to vesicles with simultaneously increasing hydrophobic lengths of blocks B and C. When the length of hydrophobic blocks B and C is asymmetric, specific bead-on-string worm micelles are found. Particularly, when the star ABC triblock copolymer is in a strong segregation regime and both B and C blocks are strongly hydrophobic, quite long segmented wormlike micelles are obtained, which had not been found in previously investigated diblock and linear ABC triblock copolymers solution. Additionally, raspberry micelles with beads dispersed on the core also occur in the strong segregation regime of bulk star ABC triblock copolymers. Furthermore, the aggregate morphology of ABC star triblock copolymers is strongly influenced by the addition of linear AB diblock copolymers. The most significant feature is that the long segmented worms will become shorter, to form hamburger micelles with the addition of AB diblock copolymers. These simulations are in good agreement with the experimental findings by Lodge's group.     

Mercapto-modified copolymers in polymer blends, 1. Functionalization of EPDM with mercapto groups and its use in NBR/EPDM blends

Ethylene-propylene-diene rubber (EPDM) was reacted with thioacetic acid in the presence of 2,2′-azoisobutyronitrile (AIBN), giving rise to thioacetate-modified EPDM (EPDMTA). The extent of the incorporation was studied as a function of both thioacetic acid and AIBN concentration and reaction time. The products were analyzed by FTIR spectroscopy, sulfur content, and ¹H NMR spectroscopy. The hydrolysis of EPDMTA in a NaOH methanolic solution resulted in mercapto-modified EPDM (EPDMSH). The addition of 5 wt.-% of this functionalized copolymer to a sulfur-vulcanized nitrile rubber (NBR)/EPDM (70 : 30 wt.-%) blend accelerated the vulcanization process as indicated by oscillating disk rheometer analysis. In addition, an improvement of mechanical and ageing properties was also observed.