Recognition properties of poly(vinylidene fluoride) hollow‐fiber membranes modified by levofloxacin‐imprinted polymers

Through the use of thermal polymerization, poly(vinylidene fluoride) (PVDF) hollow‐fiber membranes modified by a thin layer of molecularly imprinted polymers (MIPs) were developed for the selective separation of levofloxacin. To demonstrate the changes induced by thermal polymerization, PVDF hollow‐fiber membranes with different modification degrees by repeated polymerization were weighed. The total weight of the imprinted membranes increased by 14 μg/cm² after a five‐cycle polymerization. An increase in the membrane weight indicated the deposition of an MIP layer on the external surface of PVDF hollow‐fiber membranes during each polymerization cycle, which was also characterized by scanning electron microscopy. MIP membranes with different degrees of surface modification provided highly selective binding of levofloxacin. Both hollow‐fiber MIP membranes and nonimprinted membranes showed enhanced adsorption of levofloxacin and ofloxacin gradually with an increase in the modification degrees of PVDF hollow‐fiber membranes to a maximum value followed by a decrease. These results indicate that thermal polymerization indeed produces an MIP layer on the external surface of PVDF hollow‐fiber membranes and that it is feasible to control the permeability by repeated polymerization cycles. Different solvent systems in the permeation experiments were used to understand the hydrophobic interaction as one of the results of the binding specificity of MIP membranes. Selective separation was obtained by multisite binding to the template via ionic, hydrogen‐bond, and hydrophobic interactions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and morphology of platinum‐coated hollow‐fiber carbon membranes

Hollow‐fiber carbon membranes were prepared and used as support media for a platinum catalyst. The platinum metal was deposited onto the surface of the hollow‐fiber carbon membranes by three different techniques: solution coating with chloroplatinic acid, which is the commonly used technique; vapor deposition, involving the sublimation of the platinum metal; and magnetron sputter coating, the most effective method. The hollow‐fiber carbon membranes coated with a chloroplatinic acid solution were studied with scanning electron microscopy (SEM) and energy‐dispersive X‐ray analysis (EDAX). The platinum coating grew on the surface, unevenly, in the form of small crystals. The percentage of platinum on the surface was too low to be detected by EDAX. The high‐vacuum evaporation coating of the membranes with platinum was also studied with both SEM and EDAX. Again, because of the low percentage of platinum, EDAX did not reveal any platinum on the surfaces of the membranes. The magnetron sputter coating of platinum onto the membranes was performed and studied with SEM. The thickness of the coated platinum could be varied through variations in the coating time. The cavities observed in the micrographs were formed during the coating operations by the presence of dust particles on the membranes. An SEM micrograph of a hollow‐fiber carbon membrane, produced from a polyacrylonitrile‐based precursor, spun with a low amount of dimethyl sulfoxide in the bore fluid, and coated with platinum, showed a skin on the outside and a porous elongated structure inside the skin. The distance between the inner and outer skins contained fingerlike pores of various sizes. The largest pores were found near the inside skin, whereas the smallest pores were next to the outside skin. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1051–1058, 2003     

Effect of diluent on poly(ethylene‐co‐vinyl alcohol) hollow‐fiber membrane formation via thermally induced phase separation

Poly(ethylene‐co‐vinyl alcohol) hollow‐fiber membranes with a 44 mol % ethylene content were prepared by thermally induced phase separation. A mixture of 1,3‐propanediol and glycerol was used as the diluent. The effects of the ratio of 1,3‐propanediol to glycerol in the diluent mixture on the phase diagram, membrane structure, and membrane performance were investigated. As the ratio increased, the cloud point shifted to lower temperatures, and the membrane structure changed from a cellular structure due to liquid–liquid phase separation to a particulate structure due to polymer crystallization. Better pore connectivity was obtained in the hollow‐fiber membrane when the ratio of 1,3‐propanediol to glycerol was 50:50, and the membrane showed about 100 times higher water permeability than the membrane prepared with pure glycerol. For the prepared hollow‐fiber membrane, the solute 20 nm in diameter was almost rejected. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 219–225, 2005     

Morphological study of poly(vinylidene fluoride) asymmetric membranes: Effects of the solvent,additive, and dope temperature

Asymmetric poly(vinylidene fluoride) (PVDF) membranes were cast with commercial‐grade Kynar K760 polymer pellets and four different solvent systems: N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide, 1‐methyl‐2‐pyrrolidone, and triethyl phosphate. With a focus on the PVDF/DMAc system, the effects of various additives (i.e., ethanol, glycerol, lithium chloride, lithium perchlorate, and water) on the resulting membrane morphology were investigated. The membrane morphology was examined with scanning electron microscopy. The effect of the dope solution temperature on the membrane morphology was also studied for the various additives used. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1782–1789, 2004     

PEEKWC ultrafiltration hollow‐fiber membranes: Preparation,morphology, and transport properties

A series of hollow‐fiber membranes was produced by the dry–wet spinning method from PEEKWC, a modified poly(ether ether ketone) with good mechanical, thermal, and chemical resistance. The fibers were prepared under different spinning conditions, varying the following spinning parameters: polymer concentration in the spinning solution, height of the air gap, and bore fluid composition. The effect of these parameters on the water permeability, the rejection of macromolecules (using dextrane with an average molecular weight of 68,800 g/mol), and the morphology of the membranes was studied. The results were also correlated to the viscosity of the spinning solution and to the ternary polymer/solvent/nonsolvent phase diagram. The morphology of the cross section and internal and external surfaces of the hollow fibers were analyzed using scanning electron microscopy (SEM). All membranes were shown to have a fingerlike void structure and a skin layer, depending on the spinning conditions, varying from (apparently) dense to porous. Pore size measurements by the bubble‐point method showed maximum pore sizes ranging from 0.3 to 2 μm. Permeability varied from 300 to 1000 L/(h^?1 m^?2 bar) and rejection to the dextrane from 10 to 78%. The viscosity of polymer solutions was in the range of 0.2 to 3.5 Pa s. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 841–853, 2004     

Effects of mixed diluent compositions on poly(vinylidene fluoride) membrane morphology in a thermally induced phase‐separation process

The effects of a mixed diluent (MD) composition [dibutyl phthalate/dioctyl phthalate (DOP)] on poly (vinylidene fluoride) (PVDF) membrane morphology were investigated with scanning electron microscopy, and a bicontinuous morphology could be obtained with MD in a thermally induced phase‐separation process. The reasons for the morphology formation were explained according to the effect of MD on the phase diagrams. In addition, the effects of the PVDF concentration on the membrane morphology were examined. For the system with less DOP, the large spherulite morphology was obvious under all investigated concentrations, whereas no large spherulite structure existed in the membrane as the DOP content increased to concentrations other than 20%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of a graphene oxide additive and the conditions of membrane formation on the morphology and separative properties of poly(vinylidene fluoride) membranes

In this article, we present our study of the influence of a graphene oxide (GO) additive and the method of preparation on the properties of membranes. Poly(vinylidene fluoride) (PVDF)/GO membranes were obtained by an inverse phase method, which was conducted by two different methods. The first one was based on solvent evaporation, and the second method was a coagulation bath in distilled water. Our studies clearly showed that the introduction of the GO nanoadditive into the polymer membrane matrix played a major role in the pore process formation, and it also contributed to the reduction of the contact angle, and this led to an improvement in the hydrophilic properties of the obtained membranes. Furthermore, the PVDF/GO membrane preparation process had a direct influence on the thickness and porosity. Both of these factors had a direct influence on the transport properties of the membrane. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42789.     

Experimental investigation of the effects of different chemical absorbents on wetting and morphology of poly(vinylidene fluoride) membrane

Membrane wetting is of one the most important factor that affects the CO₂ absorption efficiency in membrane contactors due to the increase of mass transfer resistance. In this study, the effects of different absorbents on the wettability of poly(vinylidene fluoride) membranes were investigated. Four absorbents including monoethanolamine, potassium carbonate–piperazine (PZ), potassium carbonate–monoethanolamine, and methyldiethanolamine–PZ were applied to investigate the effects of different absorbents on membrane wetting. Membrane properties before and after contact with absorbents were investigated using methods of thermogravimetric analysis, Fourier transform infrared spectroscopy, electron scanning microscope, and contact angle measurements. The results revealed that methyldiethanolamine and mixed absorbents containing methyldiethanolamine caused the most morphological changes in membrane. The results showed that reduction percentages of contact angle for water, K2CO3/PZ, K2CO3/MEA, MEA, and MDEA/PZ solutions were 14.52, 16.9, 21.19, 23.7, and 28.33, respectively, after 30 days immersion. The results also showed that potassium carbonate–PZ solution caused the least change in membrane wettability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45543.     

Effect of the exposure time on the structure and performance of hydrophobic polydimethylsiloxane–poly(vinylidene fluoride) membranes via a non‐solvent‐induced phase separation process in a clean room

The objective of this study was to investigate the effects of the exposure time on the properties and permeability of polydimethylsiloxane (PDMS)–poly(vinylidene fluoride) (PVDF) blend hydrophobic microporous membranes, which were fabricated via a non‐solvent‐induced phase separation process at 25 °C and 60% relative humidity in a clean‐room circumstance. For the prepared PDMS–PVDF membranes, the membrane morphologies were observed by scanning electron microscopy. Crystalline structures were observed by X‐ray diffraction. Pore structures were analyzed by membrane porosity and mean pore size. Hydrophobicity was measured by contact angle measurement, and the mechanical properties were characterized by tensile strength testing. Our study results show that with increasing exposure time from 10 to 110 s, all of the membranes showed a similar pore structure: a spongelike substrate layer with a thin realm of fingerlike structures under the top surface. Phase separation between PDMS and PVDF occurred. The membrane porosity and mean pore radius decreased, and the membrane thickness increased. The membrane hydrophobicity decreased, and the mechanical properties first increased and then decreased. In addition, vacuum membrane distillation experiments were conducted. With the increase in the exposure time from 10 to 110 s, the membrane permeate flux decreased from 16.54 to 6.65 kg m⁻²·h⁻¹, and the salt rejection was higher than 99.9%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43842.     

Preparation and characterization of antifouling poly(vinylidene fluoride) blended membranes

Poly(vinylidene fluoride) (PVDF) membranes have been widely used in microfiltration and ultrafiltration because of their excellent chemical resistance and thermal properties. However, PVDF membranes have exhibited severe membrane fouling because of their hydrophobic properties. In this study, we investigated the antifouling properties of PVDF blended membranes. Antifouling PVDF blended membranes were prepared with a PVDF‐g‐poly(ethylene glycol) methyl ether methacrylate (POEM) graft copolymer. The PVDF‐g‐POEM graft copolymer was synthesized by the atom transfer radical polymerization (ATRP) method. The chemical structure and properties of the synthesized PVDF‐g‐POEM graft copolymer were determined by NMR, Fourier transform infrared spectroscopy, and gel permeation chromatography. To investigate the antifouling properties of the membranes, we prepared microfiltration membranes by using the phase‐inversion method, which uses various PVDF/PVDF‐g‐POEM concentrations in dope solutions. The pure water permeabilities were obtained at various pressures. The PVDF/PVDF‐g‐POEM blended membranes exhibited no irreversible fouling in the dead‐end filtration of foulants, including bovine serum albumin, sodium alginate, and Escherichia coli broth. However, the hydrophobic PVDF membrane exhibited severe fouling in comparison with the PVDF/PVDF‐g‐POEM blended membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of poly(vinyl chloride)/polystyrene/poly(ethylene glycol) hollow‐fiber ultrafiltration membranes

Hollow‐fiber ultrafiltration (UF) membranes were prepared from blends of poly(vinyl chloride) (PVC) and polystyrene (PS) with a dry/wet phase inversion method. Poly(ethylene glycol) (PEG) and N,N‐dimethylacetamide were used as the additive and solvent, respectively. The effects of the PEG concentration in the dope solution as an additive on the cross sections and inner and outer surface morphologies, permeability, and separation performance of the hollow fibers were examined. The mean pore size, pore size distribution, and mean roughness of both the inner and outer surfaces of the produced hollow fibers were determined by atomic force microscopy. Also, the mechanical properties of the hollow‐fiber membranes were investigated. UF experiments were conducted with aqueous solutions of poly(vinyl pyrrolidone) (PVP; K‐90, M_w = 360 kDa). From the results, we found that the PVC/PS hollow‐fiber membranes had two layers with a fingerlike structure. These two layers were changed from a wide and long to a thin and short morphology with increasing PEG concentration. A novel and until now undescribed shape of the nodules in the outer surfaces, which was denoted as a sea‐waves shape, was observed. The outer and inner pore sizes both increased with increasing PEG concentration. The water permeation flux of the hollow fibers increased from 104 to 367 L m^?2 h^?1 bar^?1) at higher PEG concentrations. The PVP rejection reached the highest value at a PEG concentration of 4 wt %, whereas at higher values (from 4 to 9 wt %), the rejection decreased. The same trend was found also for the tensile stress at break, Young's modulus, and elongation at break of the hollow fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 989‐1004, 2013     

Effect of Tween 80 on morphology and performance of poly(L‐lactic acid) ultrafiltration membranes

Poly(L‐lactic acid) (PLLA) ultrafiltration (UF) membrane was fabricated by immersion precipitation method using Tween 80 as an additive. Membrane structure was characterized by scanning electron microscopy (SEM), porosity and pore size measurement, and atomic force microscopy (AFM). Membrane performance was evaluated by pure water flux, molecular weight cut‐off, and tensile test. It was found that the addition of Tween 80 into the casting solution significantly increased the permeability and molecular weight cut‐off of membrane. Tensile test confirmed that the as‐prepared PLLA membranes exhibited acceptable mechanical properties for ultrafiltration. Further, the role of Tween 80 in the process of membrane formation was analyzed and proposed. The addition of Tween 80 favored the formation of larger pores by interrupting the polymer chain entanglement and improving the miscibility between solvent and coagulant. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44428.     

Preparation of polyvinylamine/polysulfone composite hollow‐fiber membranes and their CO2/CH4 separation performance

Fixed‐carrier composite hollow‐fiber membranes were prepared with polyvinylamine (PVAm) as the selective layer and a polysulfone ultrafiltration membrane as the substrate. The effects of the PVAm concentration in the coating solution, the number of coatings, and the crosslinking of glutaraldehyde and sulfuric acid on the CO₂ permeation rate and CO₂/CH₄ selectivity of the composite membranes were investigated. As the PVAm concentration and the number of coatings increased, the CO₂/CH₄ selectivity increased, but the CO₂ permeation rate decreased. The membranes crosslinked by glutaraldehyde or sulfuric acid possessed higher CO₂/CH₄ selectivities but lower CO₂ permeation rates. For the pure feed gas, a composite hollow‐fiber membrane coated with a 2 wt % PVAm solution two times and then crosslinked with glutaraldehyde and an acid solution in sequence had a CO₂ permeation rate of 3.99 × 10^?6 cm³ cm^?2 s^?1 cmHg^?1 and an ideal CO₂/CH₄ selectivity of 206 at a feed gas pressure of 96 cmHg and 298 K. The effect of time on the performance of the membranes was also investigated. The performance stability of the membranes was good during 6 days of testing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1885–1891, 2006     

Durable adhesives based on electrospun poly(vinylidene fluoride) fibers

Herein, the fabrication of poly(vinylidene fluoride) (PVDF) fibrous membrane using electrospinning is reported and its use for dry‐adhesive applications is demonstrated. The shear and normal adhesion performance of the samples was investigated using an Instron tensile tester and an atomic force microscope (AFM) respectively. For shear adhesion measurements, the electrospun membrane was finger pressed on to a glass slide and pulled in shear mode using a tensile tester. The thickness of the electrospun membrane was varied and the effect of thickness on shear adhesion was investigated. The shear adhesion strength increased when the thickness of the samples was reduced. Shear adhesion strength of a 200 µm thick sample was determined to be approximately 0.165 N/cm. For normal adhesion measurements, a flat tipless cantilever was used to indent the sample and then retract back to measure the pull‐off force. High shear adhesion strength and normal pull‐off force recorded are attributed to the fine size of the fibers that conform to the asperities present on the surfaces of the glass slide and the AFM cantilever. The durability of the adhesive was also verified by repeating the AFM adhesion measurements over 1000 consecutive attachment–detachment cycles. The pull‐off force was seen to be constant over 1000 attachment–detachment cycles. Our results indicate that these electrospun fibrous membranes can potentially be used as reusable dry‐adhesives. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44393.     

Effect of the preparation conditions on the morphology and performance of poly(imide) hollow fiber membranes

Poly(imide) (PI) hollow fiber membranes were prepared by using classical phase inversion process. Effects of different external coagulation bath temperatures (ECBT) and various bore flow rates (BFR) on the morphology and separation performance of the membranes were studied. Cross‐section, inner and outer structures were characterized by using scanning electron microscope and atomic force microscopy (AFM). Mean pore size, pore size distribution, and mean roughness of the PI hollow fibers surfaces were estimated by AFM. It was found that the hollow fibers morphology composed of sponge‐like and finger‐like structures with different ECBT and BFR. A circular shape of the nodules with different sizes was observed in the outer surface of the PI hollow fibers. Mean pore size of the outer surface increases with increasing ECBT and BFR. The important result observed in this study is that the ECBT clearly has the largest effect on hollow fiber PI membrane roughness compared with the BFR. Pure water permeability of the PI hollow fibers was improved with increase of ECBT and BFR. The solute rejection (R%) was reduced when the ECBT and BFR was increased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40428.     

Preparation of poly(4‐methyl‐1‐pentene) asymmetric or microporous hollow‐fiber membranes by melt‐spun and cold‐stretch method

Poly(4‐methyl‐1‐pentene) (PMP) hollow fibers were prepared and fabricated into gas separation or microporous membranes by the melt‐spun and cold‐stretched method. PMP resin was melt‐extruded into hollow fibers with cold air as the cooling medium. The effects of take‐up speed and thermotreatment on the mechanical behavior and morphology of the fibers were investigated. Scanning electronic microscope (SEM) photos were used to reveal the geometric structure of the section and surface of the hollow fibers. It was found that the original fiber had an asymmetric structure. A “sandwich” mode was used to describe the formation of this special fine structure. And a series of PMP hollow‐fiber membranes were prepared by subsequent drawing, and it was found that there was a “skin–core” structure on the cross section of these hollow‐fiber membranes. Asymmetric or microporous PMP hollow‐fiber membranes could be obtained by controlling posttreatment conditions. The morphology of these membranes were characterized by SEM, and the gas (oxygen, nitrogen, and carbon dioxide) permeation properties of the membranes was measured. The results indicate that the annealing time of the original fiber and the stretching ratio were the key factors influencing the structure of the resulting membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2131–2141, 2006     

Study of crystallization behavior of neat poly(vinylidene fluoride) and transcrystallization in carbon fiber/poly(vinylidene fluoride) composite under a temperature gradient

The crystallization behavior of poly(vinylidene fluoride) (PVDF) and transcrystallization in carbon fiber (CF)/PVDF composite were investigated under a temperature gradient. The crystallization temperature (T_c) was controlled in the range of 110–180 °C. For neat PVDF, the results showed that exclusive γ phase formed at T_c above 164 °C, but coexisted with α phase at T_c ranging from 137 to 160 °C. The promotion of γ phase to nucleation of α phase at low T_c was observed for the first time. For CF/PVDF composite, a cylindrical transcrystalline (TC) layer formed on the surface of CF when T_c was between 137 and 172 °C. The TC layer was exclusively composed of γ phase at T_c above 164 °C. The hybrid nucleation was dominated by γ phase though some α phase nuclei emerged on the surface of CF when T_c was in the range of 144–160 °C. As T_c decreased, competition between the hybrid nucleation of α and γ phase became more intense. The γ phase nuclei was soon circumscribed by the rapidly developed α phase when T_c was below 144 °C. Furthermore, some α phase nuclei were induced at the surface of the γ phase TC layer, and developed into α phase TC layer when T_c was in the range of 146–156 °C, which resulted in a doubled TC layer of α and γ phase at the interface of the composite. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43605.     

Poly(vinyl chloride) hollow‐fiber membranes for ultrafiltration applications: Effects of the internal coagulant composition

Poly(vinyl chloride) (PVC) hollow‐fiber membranes were spun by a dry/wet phase‐inversion technique from dopes containing 15 wt % PVC to achieve membranes with different pore sizes for ultrafiltration (UF) applications. The effects of the N,N‐dimethylacetamide (DMAc) concentration in the internal coagulant on the structural morphology, separation performance, and mechanical properties of the produced PVC hollow fibers were investigated. The PVC membranes were characterized by scanning electron microscopy, average pore size, pore size distribution, void volume fraction measurements, and solubility parameter difference. Moreover, the UF experiments were conducted with pure water and aqueous solutions of poly(vinyl pyrrolidone) as feeds. The mechanical properties of the PVC hollow‐fiber membranes were discussed in terms of the tensile strength and Young's modulus. It was found that the PVC membrane morphology changed from thin, fingerlike macrovoids at the inner edge to fully spongelike structure with DMAc concentration in the internal coagulant. The effective pores showed a wide distribution, between 0.2 and 1.1 μm, for the membranes prepared with H₂O as the internal coagulant and a narrow distribution, between 0.114 and 0.135 μm, with 50 wt % DMAc. The results illustrate that the difference in the membrane performances was dependent on the DMAc concentration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of the coagulation‐bath temperature on the phase‐separation process of poly(vinylidene fluoride)‐graft‐poly(N‐isopropylacrylamide) solutions and membrane structures

A poly(vinylidene fluoride)‐graft‐poly(N‐isopropylacrylamide) (PVDF‐g‐PNIPAAm) copolymer was synthesized, and flat‐sheet membranes were prepared via the phase‐inversion method with N,N‐dimethylformamide (DMF) as the solvent and water as the coagulation bath. The effects of the coagulation‐bath temperature on poly(vinylidene fluoride) (PVDF)/DMF/water and PVDF‐g‐PNIPAAm/DMF/water ternary systems were studied with phase diagrams. The results showed that the phase‐separation process could be due to the hydrophilicity/hydrophobicity of poly(N‐isopropylacrylamide) at low temperatures, and the phase‐separation process was attributed to crystallization at high temperatures. The structures and properties of the membranes prepared at different coagulation‐bath temperatures were researched with scanning electron microscopy, porosity measurements, and flux measurements of pure water. The PVDF‐g‐PNIPAAm membranes, prepared at different temperatures, formed fingerlike pores and showed higher water flux and porosity than PVDF membranes. In particular, a membrane prepared at 30°C had the largest fingerlike pores and greatest porosity. The water flux of a membrane prepared in a 25°C coagulation bath showed a sharp increase with the temperature increasing to about 30°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Miscibility and morphology of poly(vinylidene fluoride)/poly[(vinylidene fluoride)‐ran‐trifluorethylene] blends

This study presents an investigation of the effect of the different crystalline phases of each blend component on miscibility when blending poly(vinylidene fluoride) (PVDF) and its copolymer poly[(vinylidene fluoride)‐ran‐trifluorethylene] [P(VDF–TrFE)] containing 72 mol % of VDF. It was found that, when both components crystallized in their ferroelectric phase, the PVDF showed a strong effect on the crystallinity and phase‐transition temperature of the copolymer, indicating partial miscibility in the crystalline state. On the other hand, immiscibility was observed when both components, after melting, were crystallized in their paraelectric phase. In this case, however, a decrease in crystallization temperatures suggested a strong interaction between monomers in the liquid state. Blend morphologies indicated that, in spite of the lack of miscibility in the crystalline state, there is at least miscibility between PVDF and P(VDF–TrFE) in the liquid state, and that a very intimate mixture of the two phases on the lamellar level can be maintained upon crystallization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1362–1369, 2002