Crystallization kinetical and morphological peculiarities in binary crystalline/crystalline polymer blends

A survey is presented on the crystallization kinetics and the morphology of miscible crystalline/crystalline polymer blends. There are only few corresponding systems. In them, however, a number of strange kinetic and structural phenomena can be observed: (i) spherulitic crystallization of the components side‐by‐side, (ii) “interpenetrating crystallization,” (iii) “interlocking spherulitic crystallization,” and (iv) “interfilling crystallization.” Cocrystallization is forbidden for crystallographic reasons. The blend partners grow instead in their own lamellar stacks, and mixed lamellar stacks are a seldom and questionable exception. They crystallize also usually stepwise and not simultaneously. Upon step crystallization, the crystallization of the second component is determined by its redistribution with crystallization of the former. Those composition inhomogeneities are an independent issue that arises also with the development of the morphology in crystalline/amorphous blends, and a corresponding survey is yielded, too. The blend poly (vinylidene fluoride)/poly‐β‐hydroxybutyrate is a convenient model system as it can show all of these morphological and kinetic features after suitable thermal treatment. Some of them are demonstrated in the present publication. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1917–1931, 2007     

Entropically driven phase separation of highly branched/linear polyolefin blends

Small‐angle neutron scattering (SANS) was used to examine the melt phase behavior of a heavily branched comb PEE polymer blended separately with two linear PEE copolymers. In this case, PEE refers to poly(ethylene‐r‐ethylethylene) with 10% ethylene units; therefore, the molecular architecture was the only difference between the two components of the blends. The molecular weights of the two linear random copolymers were 60 and 220 kg/mol, respectively. The comb polymer contained an average of 54 long branches, with a molecular weight of 13.7 kg/mol, attached to a backbone with a molecular weight of 10 kg/mol. Three different volume compositions (25/75, 50/50, and 75/25) were investigated for both types of blends. SANS results indicate that all the blends containing the lower molecular weight linear polymer formed single‐phase mixtures, whereas all the blends containing the high molecular weight linear polymer phase‐separated. These results are discussed in the context of current theories for polymer blend miscibility. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2965–2975, 2000     

Fractional crystallization behavior of PCL and PEG in blends

The crystallization behavior of poly(e-caprolactone)/poly(ethylene glycol) (PCL/PEG) blend was investigated by differential scanning calorimetry (DSC) and polarized microscopy (POM). Individual phase transition peaks in the DSC curves for both PEG and PCL in all the polymer blends with different PCL contents were observed. The crystallization and melting peak temperatures of PEG were at 41 and 65°C, respectively; while the crystallization and melting temperatures of PCL located at 28 and 56°C, respectively. In-situ POM results demonstrated that spherulites crystalline morphology was formed for both PCL and PEG homopolymers. In PEG/PCL blend, however, both the phase separation morphology and spherulitic morphology can be observed. In blends with 30 or 50 wt % PCL, the PCL component formed dispersed phase and crystallized at lower temperature. However, in blends with 70% PCL, the phase inversion behavior occurred. The continuous PCL phase crystallized at 35°C, while the PEG dispersed phase crystallized at a lower temperature. Fractional crystallization behavior of PEG and PCL was controlled by temperature. The spherulites growth rate of PEG was greatly influenced by temperature, instead of the content of PCL component in the PCL/PEG blends.     

Structure,morphology, and crystallization process of isotactic polypropylene/hydrogenated hydrocarbon resin blends

The structure, morphology, and isothermal and nonisothermal crystallization of isotactic polypropylene/low‐molecular‐mass hydrocarbon resin blends (iPP/HR) (up to 20% in weight of HR) have been studied, using optical and electron microscopy, wide‐ and small‐angle X‐ray and differential scanning calorimetry. New structures and morphologies can be activated, using appropriate preparation and crystallization conditions and blend composition. For every composition and crystallization condition, iPP crystallizes in α‐form, with a spherulitic morphology. The size of iPP spherulites increases with resin content, whereas the long period decreases. In the range of crystallization temperatures investigated, HR modifies the birefringence of iPP spherulites, favoring the formation of radial lamellae and changing the ratio between tangential and radial lamellae. Spherulitic radial growth rates, overall crystallization rates, and melting temperatures are strongly affected by resin, monotonically decreasing with resin content. This confirms miscibility in the melt between the two components of the blends. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3368–3379, 2004     

Effects of the oriented mesophase on the cold crystallization of syndiotactic polystyrene and its blend with poly(2,6‐dimethyl‐1,4‐phenylene oxide)

The effects of molecular orientation on the crystallization and polymorphic behaviors of syndiotactic polystyrene (sPS) and sPS/poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) blends were studied with wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry. The oriented amorphous films of sPS and sPS/PPO blends were crystallized under constraint at crystallization temperatures ranging from 140 to 240°C. The degree of crystallinity was lower in the cold‐crystallized oriented film than in the cold‐crystallized isotropic film. This was in contrast to the case of the cold crystallization of other polymers such as poly(ethylene terephthalate) and isotactic polystyrene, in which the molecular orientation induced crystallization and accelerated crystal growth. It was thought that the oriented mesophase was obtained in drawn films of sPS and that the crystallization of sPS was suppressed in that phase. The WAXD measurements showed that the crystal phase was more ordered in an sPS/PPO blend than in pure sPS under the same annealing conditions. The crystalline order recovered in the cold‐crystallized sPS/PPO blends in comparison with the cold‐crystallized pure sPS because of the decrease in the mesophase content. The crystal forms depended on the crystallization temperature, blend composition, and molecular orientation. Only the α′‐crystalline form was obtained in cold‐crystallized pure sPS, regardless of molecular orientation, whereas α′, α″, and β′ forms coexisted in the cold‐crystallized sPS/PPO blends prepared at higher crystallization temperatures (200–240°C). The β′‐form content was much lower in the oriented sPS/PPO blend than in the isotropic blend sample at the same temperature and composition. It was concluded that the oriented mesophase suppressed the crystallization of the stable β′ form more than that of the metastable α′ and α″ forms during the cold crystallization of sPS/PPO blends. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1665–1675, 2003     

Rheological and thermal study of delayed crystallization in poly(butylene terephthalate)/ethylene‐co‐ethyl acrylate blends

The effects of the composition and resulting morphology on the crystallization and rheology of blends containing poly(butylene terephthalate) (PBT) and an ethylene‐co‐ethyl acrylate (EEA) copolymer, two immiscible polymers, were studied over the entire range of volume fractions. Differential scanning calorimetry (DSC) thermograms recorded during cooling showed important differences, mainly in terms of the PBT crystallization temperatures, depending on the blend composition. In addition to the classical crystallization peaks of PBT and EEA, a third crystallization peak appeared for blends containing less than 60% PBT. This peak was attributed to a delayed crystallization of PBT. This phenomenon was examined in terms of homogeneous crystallization. Linear viscoelastic measurements allowed the delayed crystallization behavior in these polymer blends to be displayed. Indeed, the variation of the storage modulus with the temperature showed increasing steps during cooling. These sudden increases appeared at temperatures very close to those at which the crystallization peaks were observed in the DSC experiments. This behavior was verified for different blend compositions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 714–721, 2004     

Crystalline Morphology and Crystallization Kinetics of Melt-miscible Crystalline/Crystalline Polymer Blends of Poly（vinylidene fluoride） and Poly（butylene succinate-co-24mol% hexamethylene succinate）

Poly（vinylidene fluoride） （PVDF） and poly（butylene succinate-co-24 mol% hexamethylene succinate） （PBHS）, both crystalline polymers, formed melt-miscible crystalline/crystalline polymer blends. Both the characteristic diffraction peaks and nonisothermal melt crystallization peak of each component were found in the blends, indicating that PVDF and PBHS crystallized separately. The crystalline morphology and crystallization kinetics of each component were studied under different crystallization conditions for the PVDF/PBHS blends. Both the spherulitic growth rates and overall isothermal melt crystallization rates of blended PVDF decreased with increasing the PBHS composition and were lower than those of neat PVDF, when the crystallization temperature was above the melting point of PBHS component. The crystallization mechanism of neat and blended PVDF remained unchanged, despite changes of blend composition and crystallization temperature. The crystallization kinetics and crystalline morphology of neat and blended PBHS were further studied, when the crystallization temperature was below the melting point of PBHS component. Relative to neat PBHS, the overall crystallization rates of the blended PBHS first increased and then decreased with increasing the PVDF content in the blends, indicating that the preexisting PVDF crystals may show different effects on the nucleation and crystal growth of PBHS component in the crystalline/crystalline polymer blends.     

Miscibility and crystallization behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) and methoxy poly(ethylene glycol) blends

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHB‐HHx) and methoxy poly(ethylene glycol) (MPEG) blends were prepared using melt blending. The single glass transition temperature, T_g, between the T_gs of the two components and the negative χ value indicated that PHB‐HHx and MPEG formed miscible blends over the range of compositions studied. The Gordon–Taylor equation proved that there was an interaction between PHB‐HHx and MPEG in their blends. FTIR supported the presence of hydrogen bonding between the hydroxyl group of MPEG and the carbonyl group of PHB‐HHx. The spherulitic morphology and isothermal crystallization behavior of the miscible PHB‐HHx/MPEG blends were investigated at two crystallization temperatures (70 and 40 °C). At 70 °C, melting MPEG acted as a noncrystalline diluent that reduced the crystallization rate of the blends, while insoluble MPEG particles acted as a nucleating agent at 40 °C, enhancing the crystallization rate of the blends. However, no interspherulitic phase separation was observed at the two crystallization temperatures. The constant value of the Avrami exponent demonstrated that MPEG did not affect the three‐dimensional spherulitic growth mechanism of PHB‐HHx crystals in the blends, although the MPEG phase, such as the melting state or insoluble state, influenced the crystallization rate of the blends. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2852–2863, 2006     

Synthesis,crystallization, and morphology of star‐shaped poly(ε‐caprolactone)

Six‐arm star‐shaped poly(ε‐caprolactone) (sPCL) was successfully synthesized via the ring‐opening polymerization of ε‐caprolactone with a commercial dipentaerythritol as the initiator and stannous octoate (SnOct₂) as the catalyst in bulk at 120 °C. The effects of the molar ratios of both the monomer to the initiator and the monomer to the catalyst on the molecular weight of the polymer were investigated in detail. The molecular weight of the polymer linearly increased with the molar ratio of the monomer to the initiator, and the molecular weight distribution was very low (weight‐average molecular weight/number‐average molecular weight = 1.05–1.24). However, the molar ratio of the monomer to the catalyst had no apparent influence on the molecular weight of the polymer. Differential scanning calorimetry analysis indicated that the maximal melting point, cold crystallization temperature, and degree of crystallinity of the sPCL polymers increased with increasing molecular weight, and crystallinities of different sizes and imperfect crystallization possibly did not exist in the sPCL polymers. Furthermore, polarized optical microscopy analysis indicated that the crystallization rate of the polymers was in the order of linear poly(ε‐caprolactone) (LPCL) > sPCL5 > sPCL1 (sPCL5 had a higher molecular weight than both sPCL1 and LPCL, which had similar molecular weights). Both LPCL and sPCL5 exhibited a good spherulitic morphology with apparent Maltese cross patterns, whereas sPCL1 showed a poor spherulitic morphology. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5449–5457, 2005     

Ringed spherulites in ternary polymer blends of poly(<Emphasis Type="Italic">ε</Emphasis>-caprolactone), poly(styrene-<Emphasis Type="Italic">co</Emphasis>-acrylonitrile), and polymethacrylate

The relationship between ringed spherulite morphology, crystallization regimes/kinetics, and molecular interactions in miscible ternary blends of poly(-caprolactone) (PCL), poly(benzyl methacrylate) (PBzMA), and poly(styrene-co-acrylonitrile) (SAN) was investigated by using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). The interactions resulted in the deviation of both experimental and calculated T_gs and formation of the specific morphology of the spherulitic structure. Ring-banded spherulites were observed in the PCL/PBzMA/SAN ternary blends. The width of ring bands changed with the blend ratio and the crystallization temperature. Additionally, both composition and wt% of AN in the SAN copolymer had an apparent effect on the morphology of PCL spherulites. Both the crystallization structure of lamellae and molecular interactions greatly influenced the ring bands of PCL spherulites. Furthermore, by using the Flory–Huggins approximation, the depression of the melting point showed that interactions in the PCL/PBzMA/SAN-17 blend were greater than in the PCL/PBzMA/SAN-25 blend. In the ternary blends, the great molecular interactions between amorphous and crystalline polymer resulted in better homogeneity and a larger band period of the extinction rings in the PCL spherulites.     

Influence of hyperbranched against linear architecture on crystallization behavior of poly(ε‐caprolactone)s in binary blends with poly(vinyl chloride)

Nonisothermal and isothermal crystallization behaviors of the hyperbranched poly(ε‐caprolactone) (HPCL)/poly(vinyl chloride) (PVC) and linear poly(ε‐caprolactone) (LPCL)/(PVC) blends were characterized with various blend composition such as 100/0, 95/5, 90/10, and 80/20, respectively. HPCL was synthesized through polycondensation of AB₂ macromonomer while LPCL and PVC were commercially purchased. The architectural characterization performed on ¹H NMR spectra revealed that HPCL consisted of about 3 AB₂ units and the linear segments consisted of 25 ε‐CL units. Through the nonisothermal crystallization analyses by modified Avrami approach with DSC crystallization exotherms, it was found that the crystallization rate was retarded by the increase in the noncrystallizable component (PVC) in the blends. This is in good agreement with the results of the isothermal crystallization analyses where time resolved small angle light scattering (SALS) and polarized optical microscopy (POM) were used. The effect of molecular architectural difference between HPCL and LPCL on the crystallization of their binary blends with PVC was elucidated by comparing the crystallization kinetic parameters. Both the nonisothermal and isothermal crystallization analyses showed that the crystallization rates of HPCL/PVC blends was faster than LPCL/PVC blends at given blend compositions. The faster crystallization of the HPCL/PVC blends is ascribed to the two specific architectural characteristics of HPCL; the branched structure and the incorporated long linear segments. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 577–589, 2007     

Crystallization and phase morphology of injection‐molded isotactic polypropylene (iPP)/syndiotactic polypropylene (sPP) blends

The crystallization and phase morphology of the injection‐molded isotactic polypropylene (iPP)/syndiotactic polypylenen (sPP) blends were studied, focusing on the difference between the skin layer and core layer. The distribution of crystallinity of PPs in the blends calculated based upon the DSC results shows an adverse situation when compared with that in the neat polymer samples. For 50/50 wt % iPP/sPP blend, the SEM results indicated that a dispersed structure in the skin layer and a cocontinuous structure in the core layer were observed. A migration phenomenon that the sPP component with lower crystallization temperature and viscosity move to the core layer, whereas the iPP component with higher crystallization temperature and viscosity move to the skin layer, occurred in the iPP/sPP blend during injection molding process. The phenomenon of low viscosity content migrate to the low shear zone may be due to the crystallization‐induced demixing based upon the significant difference of crystallization temperature in the sPP and iPP. This migration caused the composition inhomogeneity in the blend and influenced the accuracy of crystallinity calculated based upon the initial composition. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2948–2955, 2007     

Molecular transport of aromatic hydrocarbons through nylon‐6/ethylene propylene rubber blends: Relationship between phase morphology and transport characteristics

Molecular transport of aromatic hydrocarbons through nylon/ethylene propylene rubber (EPR) blend has been investigated in the temperature range of 25 to 65 °C. The effect of blend ratio on the transport behavior was studied in detail. Nylon/EPR‐50/50 blend shows the lowest uptake among all the systems studied. This behavior is related to blend morphology, density, and crystallinity of the blend composition. The transport property was correlated with the extent of interfacial adhesion in the blends. The effects of temperature and penetrant size on the sorption behavior were examined. Thermodynamic and Arrhenius parameters were evaluated from the diffusion data. Theoretical and experimental diffusion results were compared. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2136–2153, 2000     

Morphology development during isothermal crystallization. I. Isotactic and atactic polypropylene blends

Morphology development during isothermal crystallization in equal molecular weight isotactic polypropylene (iPP) and atactic polypropylene (aPP) blends was studied with time‐resolved simultaneous small‐angle X‐ray scattering (SAXS) and wide‐angle X‐ray scattering methods with synchrotron radiation. The final long period obtained after crystallization at 115 °C was nearly independent of blend composition up to 50 wt % aPP but showed an increase in the 80 wt % aPP blend. At a high crystallization temperature (137.5 °C), the increase in the final long period with aPP content was significant, and the evolution of iPP crystallinity was also affected. However, at low crystallization temperatures, the additive decrease of the crystallinity and the constant melting point with increasing aPP content suggest that the crystallizability and crystal morphology of iPP is not a strong function of aPP. The iPP/aPP blends showed a strong low‐angle SAXS upturn as a function of composition, which suggests the segregation of aPP on size scales larger than the lamellar spacing. A detailed analysis of the SAXS patterns indicates that aPP disrupts the ordering within the lamellar stacking. The results are generally consistent with predominantly interfibrillar incorporation of the aPP diluent within the microstructure, with only modest interlamellar incorporation dependent on the crystallization temperature. The findings can be attributed to the partial miscibility/mixing of the aPP and iPP components in the blend before crystallization, depending on the crystallization undercooling. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2580–2590, 2000     

Viscoelastic properties and interfacial tension of polystyrene–polyethylene blends

The linear viscoelastic properties of polystyrene polyethylene (PS/PE) blends have been investigated in the molten state. For concentrations of the dispersed phase equal to 30 vol %, the blends exhibited a droplet‐matrix morphology with a volume‐average diameter of 5.5 μm for a 70/30 PS/PE blend at 200 °C and 14.7 μm for a 30/70 PS/PE blend at 230 °C. Enhanced elasticity (G′) for both blends, in the terminal zone, compared to the modulus of the matrix (PS and PE, respectively) was observed. This is related to the deformation of the droplets in the matrix phase and hence to the interfacial forces between the blend components. The results for these uncompatibilized blends are shown to be in agreement with the predictions of the emulsion model of Palierne. These predictions were used to obtain the interfacial tension between PS and PE, which was found to be between 2 and 5 mN/m at 200 °C and 4 ± 1 mN/m at 230 °C. Independent interfacial tension measurements using the breaking‐thread method resulted in a value of 4.7 mN/m and 4.1 mN/m at 200 °C and 230 °C for the respective blends. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1359–1368, 2000     

Surface segregation of highly branched polymer additives in linear hosts

Entropy‐driven segregation of various branched and hyperbranched polymeric additives in chemically similar linear polymer hosts is studied using self‐consistent (SCF) mean‐field lattice simulations. The simulations account for the effect of molecular architecture on local configurational entropy in the blends, but ignores the effect of architecture on local density and blend compressibility. Star, dendrimer, and comb‐like additives are all found to be enriched at the surface of chemically identical linear host polymers. The magnitude of their surface excess increases with increased number of chain ends and decreases with increased segmental crowding near the branch point. Provided the number of arms and molecular weight of the branched additives are maintained constant, we find that the simplest branched architecture, the symmetric star, exhibits the strongest preference for the surface of binary polymer blends. We show that a single variable, here termed the “entropic driving force density,” controls the relative surface affinities of branched additives possessing a wide range of architectures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1788–1801, 2008     

Macromorphology of polypropylene homopolymer tacticity mixtures

The macromorphology of isotactic/atactic (iPP/aPP) and isotactic/syndiotactic (iPP/sPP) polypropylene mixtures is examined by optical microscopy. The spherulitic macrostructure of equimolecular weight [weight‐average molecular weight (M_w) = 200k] iPP/aPP blends is volume‐filling to very high aPP concentrations when the crystallization temperature is 130 °C. Similar spherulitic macrostructures (spherulite size and volume‐filling nature) are observed for iPP homopolymer and a 50/50 iPP/aPP blend at low crystallization temperatures (115–135 °C). At higher crystallization temperatures (140–145 °C), a equimolecular weight (M_w = 200k) 50/50 iPP/aPP blend exhibits nodular texture that blurs the spherulitic boundaries. Double temperature jump experiments show that the nodular texture is due to melt phase separation that develops prior to crystallization. The upper critical solution temperature (UCST) of a 50/50 iPP/aPP blend (M_w = 200k) lies below 155 °C, and the blend is miscible at conventional melt processing temperatures. The UCST behavior is controlled by the blend molecular weight and aPP microstructure. aPP microstructures containing increased isospecific sequencing (although still noncrystalline) exhibit a reduced tendency for phase separation in 50/50 mixtures (M_w = 200k) and the absence of nodular texture at low undercoolings (140–145 °C). Equimolecular weight (M_w = 200k) 50/50 iPP/sPP mixtures exhibit phase‐separated texture at all crystallization temperatures. The size scale of the phase‐separated texture decreases with decreasing crystallization temperature because of a competition between crystallization and phase separation from a melt initially well mixed from the initial solution blending process. Extended melt annealing experiments show that the 50/50 iPP/sPP mixture (M_w = 200k) is immiscible in the melt at conventional melt processing temperatures. The iPP/sPP pair shows a much stronger tendency for phase separation than the iPP/aPP polymer pair. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1947–1964, 2000     

Mechanical behavior of films of miscible polyamide 6/polyamide 6I‐6T blends

The deformation behavior of miscible PA6/aPA blends films under uniaxial and biaxial tensile drawing has been investigated in relation to blend composition. Whatever be the composition, the initial crystalline structure is ill‐ordered and no evidence of spherulitic morphology was shown. At temperatures beyond the activation of the viscoelastic α relaxation, a ductility improvement upon addition of aPA has been revealed in both uniaxial and biaxial stretching. The decrease in the yield stress with increasing aPA content mainly originates from the reduction in crystal fraction. Regarding the observed evolution in ultimate drawability and strain hardening upon addition of aPA, the latter component of the blend is considered to act as a diluent of the macromolecular network, and the experimental data are fairly well accounted for according to Graessley's theory. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1690–1701, 2006     

Morphology engineering of a novel poly(L‐lactide)/poly(1,5‐dioxepan‐2‐one) microsphere system for controlled drug delivery

Morphology is presented as a powerful tool to control the in vitro degradation and drug release characteristics of novel drug delivery microspheres prepared from homopolymer blends of 1,5‐dioxepan‐2‐one, DXO, and L ‐lactide, L‐LA. Their performance in this respect was compared to analogous P(L‐LA‐co‐DXO) microspheres. Blends formed denser and less porous microspheres with a higher degree of matrix crystallinity than copolymers of corresponding L‐LA:DXO composition. The morphology differences of blends and copolymers, further adjustable by means of component ratio, are shown to have a vital impact on the in vitro performance. Sustained drug delivery was obtained from both copolymers and blends. Molecular weight loss was retarded and diffusion‐mediated release was inhibited in the latter case, further delaying the release process. The effects of storage on the physicochemical properties of these systems were evaluated under desiccated and moist conditions for 5 months. Storage‐induced physicochemical changes, such as matrix crystallization and molecular weight decrease, were accelerated at higher relative humidities. P(L‐LA‐co‐DXO) demonstrated higher moisture sensitivity than a PLLA‐PDXO blend of corresponding composition. The more crystalline and dense morphology of blend microspheres may thus be considered an improvement of the storage stability. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 786–796, 2000     

Effect of low contents of a polyaniline derivative on the crystallization and electrical properties of blends with PVDF

The effect of low levels of poly(o‐methoxyaniline) (POMA) on the crystallization, morphology, and electrical characteristics of blends with poly(vinylidene fluoride) (PVDF) were studied by infrared spectroscopy, AC electrical measurements, and optical microscopy. Undoped POMA has a strong effect in increasing the α‐phase and decreasing the β‐phase content of PVDF in blends crystallized from solution. For blends melt crystallized, doped POMA promotes much greater homogeneity than undoped POMA. Interestingly, doped POMA promotes the nucleation and growth of unringed PVDF spherulites, whereas undoped POMA hinders it. The doping state of the POMA was also extremely important in determining the electrical behavior of the blend. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1219–1224, 1999