Phase Behavior Of Binary Blends Research Articles

Bicontinuous microemulsion in binary blends of complementary diblock copolymers.

The phase behavior of binary blends of AB diblock copolymers of compositions f and 1 - f is examined using field-theoretic simulations. Highly asymmetric compositions (i.e., f ≈ 0) behave like homopolymer blends macrophase separating into coexisting A- and B-rich phases as the segregation is increased, whereas more symmetric diblocks (i.e., f ≈ 0.5) microphase separate into an ordered lamellar phase. In self-consistent field theory, these behaviors are separated by a Lifshitz critical point at f = 0.2113. However, its lower critical dimension is believed to be four, which implies that the Lifshitz point should be destroyed by fluctuations. Consistent with this, it is found to transform into a tricritical point. Furthermore, the highly swollen lamellar phase near the mean-field Lifshitz point disorders into a bicontinuous microemulsion (BμE), consisting of large interpenetrating A- and B-rich microdomains. BμE has been previously reported in ternary blends of AB diblock copolymer with its parent A- and B-type homopolymers, but in that system the homopolymers have a tendency to macrophase separate. Our alternative system for creating BμE is free of this macrophase separation.

Phase Behavior of Binary Blends of Diblock Copolymers: Progress and Opportunities.

The phase behavior of binary blends of diblock copolymers has been examined extensively in the past decades. Experimental and theoretical studies have demonstrated that mixing two different block copolymers provides an efficient and versatile route to regulate their self-assembled morphologies. A good understanding of the principles governing the self-assembly of block copolymer blends has been obtained from the study of A1B1/A2B2 diblock copolymer blends. The second (A2B2) diblocks could act synergistically as fillers and cosurfactants to regulate the domain size and interfacial properties, resulting in the formation of ordered phases not found in the parent (A1B1 or A2B2) diblock copolymer melts. The study of A1B1/A2B2 block copolymer blends further provides a solid foundation for future research on more complex block copolymer blends.

Complex Phase Behavior in Binary Blends of AB Diblock Copolymer and ABC Triblock Terpolymer

Blending block polymers with different block compositions provides an opportunity to create nanostructures that are not accessible from neat block copolymer melts. In this study, we investigate the equilibrium phase behavior in binary blends composed of an AB diblock copolymer and an ABC triblock terpolymer, using self-consistent field theory (SCFT). Blending these simple linear block polymers results in complex phase behaviors, including unusual core–shell network phases with asymmetric core and shell volume fractions and a new cylinder-in-O70 hybrid network phase. The phase diagrams with respect to segregation strength and blend composition reveal an unexpected morphological richness, including 15 ordered phases, illustrating the potential inherent in blending these relatively simple components.

Tuning conformational asymmetry in particle-forming diblock copolymer alloys.

Self-consistent field theory is employed to compute the phase behavior of binary blends of conformationally asymmetric, micelle-forming diblock copolymers with miscible corona blocks and immiscible core blocks (a diblock copolymer "alloy"). The calculations focus on establishing conditions that promote the formation of Laves phases by tuning the relative softness of the cores of the two different Laves phase particles via independent control of their conformational asymmetries. Increasing the conformational asymmetry of the more spherical particles of the Laves structure has a stabilizing effect, consistent with the expectations of increased imprinting of the Wigner-Seitz cells on the core/corona interface as conformational asymmetry increases. The resulting phase diagram in the temperature-blend composition space features a more stable Laves phase field than that predicted for conformationally symmetric systems. The phase field closes at low temperatures in favor of macrophase separation between a hexagonally-packed cylinder (hex) phase and a body-centered cubic phase. Companion calculations, using an alloy whose components do not produce a hex phase in the neat melt state, suggest that the Laves phase field in such a blend will persist at strong segregation.

Crystallization and phase behavior in mixture systems of anhydrous milk fat, palm stearin, and palm oil: Formation of eutectic crystals

The comparison between the crystallization and phase behavior of binary blends of anhydrous milk fat (AMF)/palm stearin (POs) and POs/palm oil (PO) was investigated. POs/POs blends showed good compatibility, while the compatibility of AMF/POs blends showed no ideal and was dominated by eutectic behavior. And the eutectic growth of blends was found to be a phenomenon that the triacylglycerol (TAG) of AMF grew on the peripheral of POs seed crystals. In binary blends, the addition of POs not only increased the liquid phase transition temperature but also induced the formation of β crystal forms in more than 70% POs. The addition of soybean oil to binary blends could improve the compatibility of the ternary system. It eventually provided potential formulations for the production of non-hydrogenated puff pastry margarine.

Binary Blends of Diblock Copolymers: An Efficient Route to Complex Spherical Packing Phases

AbstractThe phase behavior of binary blends composed of AB and AB diblock copolymers is systematically studied using the polymeric self‐consistent field theory, focusing on the formation and relative stability of various spherical packing phases. The results are summarized in a set of phase diagrams covering a large phase space of the system. Besides the commonly observed body‐centered‐cubic phase, complex spherical packing phases including the Frank–Kasper A15, and the Laves C14, C15 phases could be stabilized by the addition of longer AB‐copolymers to asymmetric AB‐copolymers. Stabilizing the complex spherical packing phases requires that the added AB‐copolymers have a longer A‐block and an overall chain length at least comparable to the host copolymer chains. A detailed analysis of the block distributions reveals the existence of inter‐ and intra‐domain segregation of different copolymers, which depends sensitively on the copolymer length ratio and composition. The predicted phase behaviours of the AB/AB diblock copolymer blends are in good agreement with previous experimental and theoretical results. The study demonstrates that binary blends of diblock copolymers provide an efficient route to regulate the emergence and stability of complex spherical packing phases.

Thermal characterisation of metal stearate lubricant mixtures for polymer compounding applications

Metal stearate blends are potential lubricants and filler dispersants in polymer compounding. Therefore, the thermal phase behaviour of binary blends of calcium stearate and magnesium stearate with zinc stearate was investigated. Cooling curve studies indicated lower melting temperatures in both systems. X-ray diffraction studies revealed that this was due to the formation of solid solutions of variable composition rather than to eutectic formation. Rheology measurements showed that true fluidification only happened well above the apparent melting points established from cooling curves. Calcium carbonate filled polyethylene containing metal stearate mixtures showed lower melt viscosities than were achievable using only calcium- or magnesium stearate as the lubricant. These results suggest that metal stearate blends, in combination with a judiciously selected wax component, may offer advantages in lowering compound melt viscosity and facilitating better particle dispersion.

Beeswax Fractions Used as Potential Oil Gelling Agents

AbstractThe objective of this work was the fractionation of beeswax to investigate the phase behavior of binary blends of the fractions and their potential use as gelling agents in edible oleogels. We have extracted seven distinctive fractions, using preparative flash chromatography with eluents permitted to be used in the processing of food raw materials. The odor profile of the fractions was characterized. The high purity of collected fractions was shown through thin‐layer chromatography, Fourier‐transform infrared spectroscopy, and high‐performance liquid chromatography with an evaporative light scattering detector methods for hydrocarbons (94.8%), monoesters (97.6%), and mixed mono‐, di‐, and triesters fraction (98.7%). Free fatty acids and fatty alcohol fractions had lower purity which equals 82.6% and 39%, respectively. The analysis of the binary pseudo phase diagram revealed that all fractions combined with hydrocarbons express eutectic behavior. Combinations of all other fractions resulted in the formation of solid solutions. This study shows that the texture of oleogels can be improved by using a combination of various fractions of beeswax instead of native wax.

Visualized phase behavior of binary blends of coconut oil and palm stearin

The graded blends of coconut oil (CNO) and palm stearin (POs) phase behavior was studied in the present work, by using pulsed nuclear magnetic resonance (p-NMR), differential scanning calorimetry (DSC) and X-ray scattering (XRD). The kinetic phase diagram which was fitting to DSC data by polynomial equation (R > 0.95), indicated that the CNO-POs binary blends displayed monotectic behavior. The CNO-POs binary system displayed immiscible solid structures (β and β′ polymorphism) with the addition of POs in the range of 10–60%, beyond which it showed miscible solid structures (β polymorphism), respectively. Moreover, the presence of POs could elevate the liquid phase transition temperature and transform β′ polymorph into β. These variations in phase behavior were reflected in the morphology of the binary blends. Our findings not only broaden the application of CNO and POs with novel attributes, but also direct the production of high quality non-hydrogenated fat-containing products.

Tetragonal phase of cylinders self-assembled from binary blends of AB diblock and (A'B)n star copolymers.

The phase behavior of binary blends composed of AB diblock and (A'B)n star copolymers is studied using the polymeric self-consistent field theory, focusing on the formation and stability of the stable tetragonal phase of cylinders. In general, cylindrical domains self-assembled from AB-type block copolymers are packed into a hexagonal array, although a tetragonal array of cylinders could be more favourable for lithography applications in microelectronics. The polymer blends are designed such that there is an attractive interaction between the A and A' blocks, which increases the compatibility between the two copolymers and thus suppresses the macroscopic phase separation of the blends. With an appropriate choice of system parameters, a considerable stability window for the targeted tetragonal phase is identified in the blends. Importantly, the transition mechanism between the hexagonal and tetragonal phases is elucidated by examining the distribution of the two types of copolymers in the unit cell of the structure. The results reveal that the short (A'B)n star copolymers are preferentially located in the bonding area connecting two neighboring domains in order to reduce extra stretching, whereas the long AB diblock copolymers are extended to further space of the unit cell.

Phase behavior of binary blends of PP/PP‐g‐AA: limitations of the conventional characterization techniques

AbstractIn this study, miscibility/immiscibility issues of a binary blend consisting of polypropylene (PP) and acrylic acid grafted polypropylene (PP‐g‐AA) were investigated using rheometry, DSC, dynamic mechanical and thermal analysis (DMTA), AFM and time‐of‐flight secondary‐ion mass spectrometry (ToF‐SIMS). Phase separation analysis of such blend systems is a challenge and complex due to chemically similar components as well as the low value of acrylic acid groups in the graft copolymer. Thus, it is crucial to determine if the present blend shows some degree of miscibility or develops co‐continuous morphology between the components. The analysis of rheometrical, DSC and DMTA results indicated no sensitivity of these classical techniques for detecting the miscibility or immiscibility of such a system. However, AFM data effectively detected dispersed‐phase domains corresponding to the PP‐g‐AA rich phase. The results, for the first time, indicated that the start of phase separation occurs at a critical copolymer concentration between 2 and 5 wt%. Furthermore it was observed that, as the PP‐g‐AA content increases, the size and continuity of the dispersed phase increase and reach a highly continuous morphology. Additionally, ToF‐SIMS chemical imaging was carried out to aid in the interpretation of the AFM data. © 2016 Society of Chemical Industry

Phase Behavior of Binary Blends of Four Different Waxes

AbstractThe objective of this study was to investigate the phase behavior of binary blends of four waxes—beeswax (BW), paraffin wax (PW), sunflower wax (SFW), and rice bran wax (RBW)—using differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Blends of BW/PW, RBW/PW, SFW/PW, SFW/RBW, SFW/BW, and RBW/BW were crystallized in a DSC, and their melting behavior was used to build binary phase diagrams. The microstructure of the crystalline networks formed in these blends was analyzed using PLM. BW/PW, SFW/PW, SFW/BW, and RBW/BW blends showed eutectic phase behavior, while RBW/SFW showed continuous solid solution and the RBW/PW blend showed monotectic behavior. Results from the box‐counting fractal dimension (Db) measurement of crystal morphology showed higher Db values for the 20 and 80 % wax blends, irrespective of crystallization temperature or wax type. Db values of single waxes decrease as temperature increases.

Self-Assembly of Binary Mesocrystals from Blends of BABCB Multiblock Copolymers and ABC Triblock Copolymers

The phase behavior of binary blends composed of BABCB-type pentablock terpolymers and ABC-type triblock copolymers is investigated using the self-consistent field theory in the grand canonical ensemble. Specifically, the study is focused on how the simpler copolymers regulate the phase behavior of two sphere-forming multiblock copolymers of the type B1AB2CB1 and AB2CB3. For certain compositions, these two multiblock copolymers self-assemble to form mesocrystalline phases composed of binary A and C spheres with the ZnSC and ReO3 structures, respectively. It is discovered that the addition of symmetric ABC triblocks or AB diblocks to the two multiblock copolymers leads to the formation of different binary crystalline phases including symmetric binary crystalline phase of NaCl type for the A/C-component symmetric blends and asymmetric Cu2O, SnI4, TiO2, and CaF2 phases for the A/C-component asymmetric blends. In particular, the binary mesocrystals of the Cu2O and SnI4 structures observed in the blends of the tail-symmetric B1AB2CB1 terpolymers and the AB diblock copolymers are new stable phases which have not been observed in the B1AB2CB3 terpolymers melts. The theoretical results demonstrate that blending of block copolymers with specially designed multiblock terpolymers could provide an efficient route to fabricate binary mesocrystals.

Phase Behavior of Binary Blends of Diblock Copolymer/Homopolymer Confined in Spherical Nanopores

Binary blends of a diblock copolymer (AB) and an incompatible homopolymer (C) confined in spherical cavities are studied using a simulated annealing technique. The phase behavior of the blends is examined for four typical cases, representing the different selectivity of the pore surface to the A, B, and C species. The internal morphology of the spherical polymeric particles is controlled by the homopolymer volume fraction, the degree of confinement, and the composition of the copolymer. Inside a particle, the homopolymers segregate to form one or, under some conditions, two domains; thus, the homopolymers may act as an additional controlling parameter of the shape and symmetry of the copolymer domain. A rich array of confinement-induced novel diblock copolymer morphologies is predicted. In particular, core-shell particles with the copolymers as the shell wrapping around a homopolymer core or a copolymer-homopolymer combined core and Janus-like particles with the copolymers and the homopolymers on different sides are obtained.

Phase Behavior of Rod–Coil Diblock Copolymer and Homopolymer Blends from Self-Consistent Field Theory

The phase behavior of binary blends of rod-coil diblock copolymers and coil or rod homopolymers is studied by the self-consistent field theory (SCFT). The rod blocks are modeled as wormlike chains and the corresponding SCFT equations are solved using a hybrid method, in which the orientation-dependent functions are discretized on a unit sphere, while the positional space-dependent functions are treated using a spectral method. Phase diagrams of the blends are constructed as a function of the homopolymer volume fraction and phase segregation strength. It is discovered that the phase behavior of the system depends on the flexibility of the homopolymers. The addition of coil-homopolymers stabilizes the smectic phases. Low-molecular weight coil-homopolymers tend to mix with the coil-blocks, whereas high-molecular weight coil-homopolymers are mostly localized at the center of the coil-domains. On the other hand, the addition of rod-homopolymers strongly affects the orientation ordering of the system, leading to transitions between monolayer smectic-C, monolayer smectic-A and bilayer smectic-A phases.

Phase Behavior of Binary Blends of Block Copolymers Having Hydrogen Bonding

Phase behavior of binary blends consisting of high molecular weight polystyrene-block-poly(2-vinylpyridine) copolymer (PS-b-P2VP) and low molecular weight polystyrene-block-poly(4-hydroxystyrene) copolymer (PS-b-PHS) was investigated by using small-angle X-ray scattering and transmission electron microscopy. Both PS-b-P2VP and PS-b-PHS exhibited lamellar microdomain over the entire experimental temperatures up to 300 °C. When the weight fraction of PS-b-PHS in the blend was less than 0.1, the lamellar microdomains were maintained. However, with increasing amount of PS-b-PHS, the microdomains in the blends were transformed to hexagonally packed (HEX) cylindrical microdomains and body-centered cubic (BCC) spherical microdomains. On the other hand, when a relatively high molecular weight of PS-b-PHS was used, the BCC spherical microdomains were not observed even at a large weight fraction of PS-b-PHS in the blend, but HEX cylindrical microdomains were formed. The phase behaviors observed experimentally were rationalized by the results of the self-consistent mean-field theory. Based on the theoretical results, some of the PS-b-PHS dissolves into P2VP microdomains and thereby increases the effective volume of P2VP/PHS phase because of hydrogen bonding between P2VP and PHS blocks. In the case of smaller molecular weight of PS-b-PHS, the dissolved amount is significant because the favorable interactions of P2VP/PHS chains becomes dominant over the relatively small enthalpic penalty between PS/P2VP in the P2VP microdomains as well as the gain of the translational entropy of the PS-b-PHS chains. The increase in the effective volume of the PHS/P2VP phase leads to a transformation of the microdomains in the blends from lamellar to HEX cylindrical microdomains and BCC spherical microdomains. On the other hand, when a relatively higher molecular weight of PS-b-PHS was used, the effective volume of the P2VP/PHS phase was not increased greatly because of a large enthalpic loss arising from the contact between PS/P2VP as well as a small gain in the translational entropy. Consequently, only lamellar and HEX cylindrical microdomains are observed.

Phase Behavior of Binary Blends of Diblock Copolymers

The phase behavior of binary blends of a long symmetric AB diblock copolymer and a short asymmetric AB diblock copolymer is studied using the self-consistent mean-field theory. The investigation focuses on blends with different short diblocks by constructing phase diagrams over the whole blending compositions and a large segregation regime. The influences of the chain length ratio (R) of the long and short diblock copolymers on their miscibility and on the stability of various ordered structures are explored. The theoretical results reveal that the blends have a much more complex phase behavior than each constituent copolymer. With the increase of the volume fraction of the short diblocks in the blends, multiple transitions from a long-period lamellar phase to phases with nonzero interfacial curvatures including cylindrical and spherical phases, and finally to a short-period lamellar phase or disordered phase, are predicted. In particular, consistent with experiments, the theory predicts that the cylindrical phase is stabilized over a wide blending compositions region in the strong segregation region, even though the two constituent diblock copolymers are both lamella-forming. When the ratio R is large enough, macrophase separation occurs over a wide range of blending compositions in a relatively strong segregation regime. Various coexisting phases, including those of lamellar and disorder, lamellar and cylindrical, cylindrical and cylindrical, cylindrical and disorder, spherical and disorder, and cylindrical and spherical, are predicted. In addition, the density profiles of the typical ordered structures are presented in order to understand the self-organization of the different copolymer chains.

Tacticity effects on glass transition and phase behavior in binary blends of poly(methyl methacrylate)s of three different configurations

Using optical and scanning electron microscopies, dynamic mechanical analysis, and differential scanning calorimetry, this study investigated effects of tacticity in PMMAs on the phase behavior in three pairs of binary blends comprising any two of isotactic-, syndiotactic-, and atactic-PMMAs. Miscibility was confirmed for all three binary blends (i.e., aPMMA/iPMMA, aPMMA/sPMMA, and iPMMA/sPMMA); however, the Tgvs. composition relationships for the aPMMA/iPMMA blend differ significantly. Configurational tacticity may lead to subtle differences in molecular interactions in the tactic polymers; and in turn such difference in the interactions causes variation in the glass transition and phase behavior in these three blends. This study also points out that the miscibility nature in iPMMA/sPMMA may constitute a prerequisite condition (necessary but not sufficient) for its tendency in forming complexes.

STUDY OF THE PHASE BEHAVIOR OF BINARY BLENDS OF SYMMETRIC LONG AND NEARLY SYMMETRIC SHORT DIBLOCK COPOLYMERS

The phase behavior of binary blends of symmetric long diblock copolymers and nearly short symmetric diblock copolymers with different ratio of chain lengths is studied using the self-consistent field theory.The occurrence of order-order transition,disorder-order transition and regions of order-disorder coexistence has been examined.Comparisons are also made with the theoretical study of the binary blend of symmetric long and short diblock copolymers and experiments on the similar systems.The effects of the short nearly symmetric diblock copolymer on the symmetric long diblock copolymer in their blends were analyzed.

Phase Behavior of Binary Blends of High Molecular Weight Diblock Copolymers with a Low Molecular Weight Triblock

Binary blends of four different high molecular weight poly(styrene-b-isoprene) (SI) diblock copolymers with a lower molecular weight poly(styrene-b-isoprene-b-styrene) (SIS) triblock copolymer were prepared, and their morphology was characterized by transmission electron microscopy and ultra-small-angle X-ray scattering. All the neat block copolymers have nearly symmetric composition and exhibit the lamellar morphology. The SI diblock copolymers had number-average molecular weights, Mn, in the range 4.4 × 105−1.3 × 106 g/mol and volume fractions of poly(styrene), ΦPS, in the range 0.43−0.49, and the SIS triblock had a molecular weight of Mn ∼ 6.2 × 104 g/mol with ΦPS = 0.41. The high molecular weight diblock copolymers are very strongly segregating, with interaction parameter values, χN, in the range 470−1410. A morphological phase diagram in the parameter space of molecular weight ratio (R = Mndiblock/1/2Mntriblock) and blend composition was constructed, with R values in the range between 14 and 43, wh...