Blends containing amphiphilic polymers IV. Poly(N‐1‐alkyl itaconamic acids) with poly(2‐vinylpyridine) and poly(4‐vinylphenol)

The phase behavior of blends containing Poly(N‐1‐alkyl itaconamic acids) (PNAIA) with Poly(2‐vinylpyrindine) (P2VPy) and Poly(4‐vinylphenol) (P4VPh) were analyzed by Diferential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR). Miscibility over the whole range of compositions is observed in both systems. All the blends show thermograms exhibiting distinct single glass transition temperatures (T_g), which are intermediate to those of the pure components. The Calorimetric Analysis using Gordon Taylor, Couchman, and Kwei treatments allows conclusion that interactions between the components is favorable to the miscibility. FTIR analysis of the blends suggests that the driving force for miscibility is hydrogen bonding formation. The variation of the absorptions of the carbonyl groups of PNAIA and the hydroxyl groups of P4VPh allows one to attribute the miscibility to weak acid base like interactions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1245–1250, 2002; DOI 10.1002/app.10453     

Miscibility and specific interactions in blends of poly(4-vinylphenol-co-methyl methacrylate)/poly(styrene-co-4-vinylpyridine)

The miscibility and phase behavior of poly(4-vinylphenol-co-methyl methacrylate) (PVPhMMA50) containing 50% of methyl methacrylate with random copolymers of poly(styrene-co-4-vinylpyridine) (PS4VPy) containing 5, 15, 30, 40, and 100% of 4-vinylpyridine, respectively, were investigated by differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). It was shown that for a composition of 4-vinylpyridine less than 30%, all blends of PVPhMMA50/PS4VPy are immiscible, characterized by the apparition of two glass transitions (T_g) over their entire composition range. However, above this composition, a single T_g has been observed in all the blends of PVPhMMA50 and PS4VPy. When the amount of vinylpyridine exceeds to 40% in PS4VPy, the obtained T_gs of PVPhMMA50/PS4VPy blends were found to be significantly higher than those observed for each individual component of the mixture indicating that these blends are able to form interpolymer complexes. FTIR analysis reveals the existence of preferential specific interactions via hydrogen bonding between the hydroxyl and pyridyl groups and intensifies when the amount of 4VPy is increased in PS4VPy copolymers. Furthermore, the quantitative FTIR study carried out for PVPhMMA50/PS4VPy blends was also performed for the vinylphenol and vinylpyridine functional groups. These results were also confirmed by SEM study. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Functionalization of lignin: Synthesis of lignophenol‐graft‐poly(2‐ethyl‐2‐oxazoline) and its application to polymer blends with commodity polymers

Lignophenol (LP)‐graft‐poly(2‐ethyl‐2‐oxazoline) (POZO) was prepared to reuse lignin, an industrial waste material, and to produce novel LP‐based polymer blends with poly(vinyl chloride) (PVC), poly(bisphenol A carbonate) (PC), polyvinylpyrrolidone (PVP), and polystyrene (PSt) as commodity polymers. The resulting graft polymer was soluble in various types of organic solvents such as chloroform, THF, acetone, and methanol, unlike LP. The miscibility of LP‐graft‐POZO with commodity polymers was measured by differential scanning calorimetry (DSC) to determine the glass transition temperatures (T_g). In the cases of the blends of LP‐graft‐POZO with PVC, PC, and PVP, the T_g values decreased during the second scan. Moreover, in the cases of the blends with PVC and PVP, the T_g values were not detected during the third scan. Therefore, it was inferred that LP‐graft‐POZO was miscible with PVC, PC, and PVP while forming single phases; in particular, the blends of LP‐graft‐POZO with PVC and PVP exhibited a secondary miscibility because the T_g values were not detected. Furthermore, the blend of LP‐graft‐POZO with PC exhibited better thermostability than LP and LP‐graft‐POZO. These results indicated that LP blended with POZO could be used as a polymer additive and as an adhesive to combine different polymers, organic–inorganic polymers, etc. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Miscibility and phase structure of binary blends of polylactide and poly(vinylpyrrolidone)

The miscibility, crystallization behavior, and component interactions of two binary blends, poly(L ‐lactide) (L ‐PLA)/poly(vinylpyrrolidone) (PVP) and poly(D ,L ‐lactide) (DL ‐PLA)/PVP, were studied with differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy. The composition‐dependent changes of the glass‐transition temperature (T_g) and degree of crystallinity (X_c) of the L ‐PLA phase indicated that L ‐PLA and PVP were immiscible over the composition range investigated. However, the sharp decrease of X_c with increasing PVP content in the second heating run demonstrated that the cold crystallization process of L ‐PLA was remarkably restricted by PVP. In DL ‐PLA/PVP blends, the existence of two series of isolated T_g's indicated that DL ‐PLA and PVP were phase‐separated, but evidence showed that there was some degree of interaction at the interface of the two phase, especially for the blends with low DL ‐PLA contents. FTIR measurements showed that there was no appreciable change in the spectra of L ‐PLA/PVP with respect to the coaddition of each component spectrum, implying the immiscibility of the two polymers. In contrast to L ‐PLA, the intermolecular interaction between DL ‐PLA and PVP was detected by FTIR; this was evidenced by the observation of a high‐frequency shift of the C?O stretching vibration band of PVP with increasing DL ‐PLA content, which suggested some degree of miscibility. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 973–979, 2003     

Miscibility and crystallization kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/ poly(methyl methacrylate) blends

The miscibility and crystallization kinetics of the blends of random poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(HB‐co‐HV)] copolymer and poly(methyl methacrylate) (PMMA) were investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that P(HB‐co‐HV)/PMMA blends were miscible in the melt. Thus the single glass‐transition temperature (T_g) of the blends within the whole composition range suggests that P(HB‐co‐HV) and PMMA were totally miscible for the miscible blends. The equilibrium melting point (T°_m) of P(HB‐co‐HV) in the P(HB‐co‐HV)/PMMA blends decreased with increasing PMMA. The T°_m depression supports the miscibility of the blends. With respect to the results of crystallization kinetics, it was found that both the spherulitic growth rate and the overall crystallization rate decreased with the addition of PMMA. The kinetics retardation was attributed to the decrease in P(HB‐co‐HV) molecular mobility and dilution of P(HB‐co‐HV) concentration resulting from the addition of PMMA, which has a higher T_g. According to secondary nucleation theory, the kinetics of spherulitic crystallization of P(HB‐co‐HV) in the blends was analyzed in the studied temperature range. The crystallizations of P(HB‐co‐HV) in P(HB‐co‐HV)/PMMA blends were assigned to n = 4, regime III growth process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3595–3603, 2004     

Miscible blends containing bacterial poly(3‐hydroxyvalerate) and poly(p‐vinyl phenol)

The miscibility of poly(3‐hydroxyvalerate) (PHV)/poly(p‐vinyl phenol) (PVPh) blends has been studied by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. The blends are miscible as shown by the existence of a single glass transition temperature (T_g) and a depression of the equilibrium melting temperature of PHV in each blend. The interaction parameter was found to be −1.2 based on the analysis of melting point depression data using the Nishi–Wang equation. Hydrogen‐bonding interactions exist between the carbonyl groups of PHV and the hydroxyl groups of PVPh as evidenced by FTIR spectra. The crystallization of PHV is significantly hindered by the addition of PVPh. The addition of 50 wt % PVPh can totally prevent PHV from cold crystallization. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 383–388, 1999     

Miscibility and crystallization behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/poly(vinyl acetate) blends

The miscibility and crystallization behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (P(HB‐co‐HV))/poly(vinyl acetate) (PVAc) blends have been investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that P(HB‐co‐HV)/PVAc blends were miscible in the melt over the whole compositions. Thus the blend exhibited a single glass transition temperature (T_g), which increased with increasing PVAc composition. The spherulitic morphologies of P(HB‐co‐HV)/PVAc blends indicated that the PVAc was predominantly segregated into P(HB‐co‐HV) interlamellar or interfibrillar regions during P(HB‐co‐HV) crystallization because of the volume‐filled spherulites. As to the crystallization kinetics study, it was found that the overall crystallization and crystal growth rates decreased with the addition of PVAc. The kinetics retardation was primarily attributed to the reduction of chain mobility and dilution of P(HB‐co‐HV) upon mixing with higher T_g PVAc. The overall crystallization rate was predominantly governed by the spherulitic growth rate and promoted by the samples treated with the quenched state because of the higher nucleation density. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 980–988, 2006     

Miscibility and intermolecular specific interactions in blends of poly(hydroxyether of bisphenol A) and poly(4-vinyl pyridine)

The blends of poly(hydroxyether of bisphenol A) (phenoxy) with poly(4-vinyl pyridine) (P4VPy) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy. The single, composition-dependent glass transition temperature (T_g) was observed for each blend, indicating that the system is completely miscible. The sigmoid T_g-composition relationship is characteristic of the presence of the strong intermolecular specific interactions in the blend system. FTIR studies revealed that there was intermolecular hydrogen bonding in the blends and the intermolecular hydrogen bonding between the pendant hydroxyl groups of phenoxy and nitrogen atoms of pyridine ring is much stronger than that of self-association in phenoxy. To examine the miscibility of the system at the molecular level, the high resolution ¹³C cross-polarization (CP)/magic angle spinning (MAS) together with the high-power dipolar decoupling (DD) NMR technique was employed. Upon adding P4VPy to the system, the chemical shift of the hydroxyl-substituted methylene carbon resonance of phenoxy was observed to shift downfield in the ¹³C CP/MAS spectra. 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. In light of the proton spin-lattice relaxation parameters, it is concluded that the phenoxy and P4VPy chains are intimately mixed on the scale of 20-30 Å.     

Blends containing amphiphilic polymers. V. Compatibilization of N‐alkylitaconamic acid‐co‐styrene copolymers with interacting polymers

The phase behavior of blends containing N‐alkylitaconamic acid‐co‐styrene copolymers (NAIA‐co‐S) with poly(N‐vinyl‐2‐pyrrolidone) (PVP) of two different weight average molecular weights (M _w ), poly(2‐vinylpyridine) (P2VPy) and poly(4‐vinylpyridine) (P4VPy), was analyzed by differential scanning calorimetry and Fourier transform infrared spectroscopy. Copolymers containing 80% S are miscible with PVP₁₀, PVP₂₄, and P4VPy over the whole range of composition. In the case of blends with P2VPy, miscibility is observed only for the first three members of the series, i.e., NEIA‐co‐S, NPIA‐co‐S, and NBIA‐co‐S. For copolymers containing hexyl to dodecyl moieties, phase separation is observed in blends with P2VPy. Copolymers containing 50% S are miscible over the whole range of composition irrespective of the homopolymer and the length of the side chain of the itaconamic moiety of the copolymer. This behavior is interpreted in terms of steric hindrance, in the sense that the copolymers with long side chains are not able to interact with the nitrogen of P2VPy because of the position in the aromatic ring. The interactions between copolymers and homopolymers are discussed in terms of specific interactions like hydrogen bonds between the itaconamic moiety and the different functional groups of the homopolymers, together with the hydrophobic interaction, which cannot be disregarded. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2512–2519, 2006     

Glass‐transition temperature of poly(vinylidene fluoride)‐poly(methyl acrylate) blends: Influence of aging and chain structure

The glass‐transition temperature (T_g) of the poly(vinylidene fluoride) (PVF₂)‐poly(methyl acrylate) (PMA) blends increase with aging time. The T_g versus log(time) plots are straight lines whose slope values depend on the head to head (H–H) defect content of PVF₂ samples and on the composition of the blends. The values of polymer–polymer interaction parameters (χ) increase with an increase in the H–H defect of PVF₂ for a fixed composition of the blend. Consequently, the T_g of the blend decreases with an increase in the H–H defect of the PVF₂ sample. However, after aging for longer times this decrease of the T_g with H–H defects is lower than those of the unaged blends. The possible reasons are discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1541–1548, 2001     

Effect of in situ polymerization conditions of methyl methacrylate on the structural and morphological properties of poly(methyl methacrylate)/poly(acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene)‐g‐styrene) PMMA/AES Blends

In this study, the structural and morphological properties of poly(methyl methacrylate)/poly(acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene‐g‐styrene) (PMMA‐AES) blends were investigated with emphasis on the influence of the in situ polymerization conditions of methyl methacrylate. PMMA‐AES blends were obtained by in situ polymerization, varying the solvent (chloroform or toluene) and polymerization conditions: method A—no stirring and air atmosphere; method B—stirring and N₂ atmosphere. The blends were characterized by infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). The results showed that the PMMA‐AES blends are immiscible and present complex morphologies. This morphology shows an elastomeric dispersed phase in a glassy matrix, with inclusion of the matrix in the elastomer domains, suggesting core shell or salami morphology. The occlusion of the glassy phase within the elastomeric domains can be due to the formation of graft copolymer and/or phase inversion during polymerization. However, this morphology is affected by the polymerization conditions (stirring and air or N₂ atmosphere) and by the solvent used. The selective extraction of the blends' components and infrared spectroscopy showed that crosslinked and/or grafting reactions occur on the elastomer chains during MMA polymerization. The glass transition of the elastomer phase is influenced by morphology, crosslinking, and grafting degree and, therefore, T_g depends on the polymerization conditions. On the other hand, the behavior of T_g of the glassy phase with blend composition suggests miscibility or partial miscibility for the SAN phase of AES and PMMA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Miscibility enhancement on the immiscible poly (vinyl pyrrolidone) and poly (ethyl methacrylate) with poly (vinyl phenol)

The miscibility behavior of ternary blends of poly (vinyl phenol) (PVPh)/poly (vinyl pyrrolidone) (PVP)/poly (ethyl methacrylate) (PEMA) was investigated mainly with calorimetry. PVPh is miscible with both PVP and PEMA on the basis of the single T_g observed over the entire composition range. FTIR was used to study the hydrogen bonding interaction between the hydroxyl group of PVPh and the carbonyl group of PVP and PEMA at various compositions. Furthermore, the addition of PVPh is able to enhance the miscibility of the immiscible PVP/PEMA and eventually transforms it into a miscible blend, especially when the ratio between PVP/PEMA is 3:1, probably because of favorable physical interaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1205–1213, 2006     

Synthesis and evaluation of interaction parameters of synthetic elastin‐derived polypentapeptide with poly(vinylpyrrolidone) in solution and solid phase

The parent repeating sequence of elastin, poly(GVGVP) has been synthesized by solution phase method and characterized by 13C and ¹H‐NMR spectroscopy. The poly(GVGVP) and poly(vinyl pyrrolidone) (PVP) interactions have been examined in solution phase by the viscometric method at 24 °C. The interaction parameters such as α, β, µ, and Δ[η]_m indicated the miscible nature of poly(GVGVP)/PVP blends. Immiscibility occurred when the quantity of poly(GVGVP) is lesser than 60%. In the solid phase, Fourier transform infrared spectroscopic scrutiny of the thin films of poly(GVGVP)/PVP blends indicated the presence of strong intermolecular interaction such as hydrogen bonds linking the blend components. This result was further supported by glass transition temperature (T_g), scanning electron microscopic, and X‐ray diffraction studies. The blending of poly(GVGVP) with PVP may provide an opportunity to produce new materials for potential biomedical applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46699.     

Polymer blends of stereoregular poly(methyl methacrylate) and poly(styrene‐co‐p‐hydroxystyrene)

Isotactic, atactic, and syndiotactic poly(methyl methacrylates) (PMMAs) (designated as iPMMA, aPMMA, and sPMMA) were mixed with poly(styrene‐co‐p‐hydroxystyrene) (abbreviated as PHS) containing 15 mol % of hydroxystyrene separately in 2‐butanone to make three polymer blend systems. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were used to study the miscibility of these blends. The three polymer blends were found to be miscible, because all the prepared films were transparent and there was a single glass transition temperature (T_g) for each composition of the polymers. T_g elevation (above the additivity rule) is observed in all the three PMMA/PHS blends mainly because of hydrogen bonding. If less effective hydrogen bonding based on the FTIR evidence is assumed to infer less exothermic mixing, sPMMA may not be miscible with PHS over a broader range of conditions as iPMMA and aPMMA. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 431–440, 1999     

Glass‐transition and melting behavior of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) blends

The glass‐transition temperatures and melting behaviors of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) (PET/PEN) blends were studied. Two blend systems were used for this work, with PET and PEN of different grades. It was found that T_g increases almost linearly with blend composition. Both the Gibbs–DiMarzio equation and the Fox equation fit experimental data very well, indicating copolymer‐like behavior of the blend systems. Multiple melting peaks were observed for all blend samples as well as for PET and PEN. The equilibrium melting point was obtained using the Hoffman–Weeks method. The melting points of PET and PEN were depressed as a result of the formation of miscible blends and copolymers. The Flory–Huggins theory was used to study the melting‐point depression for the blend system, and the Nishi–Wang equation was used to calculate the interaction parameter (χ₁₂). The calculated χ₁₂ is a small negative number, indicating the formation of thermodynamically stable, miscible blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 11–22, 2001     

The phase behavior and thermal stability of blends of poly(styrene‐co‐methacrylic acid)/poly(styrene‐co‐ 4‐vinylpyridine)

The hydrogen bonding and miscibility behaviors of poly(styrene‐co‐methacrylic acid) (PSMA20) containing 20% of methacrylic acid with copolymers of poly(styrene‐co‐4‐vinylpyridine) (PS4VP) containing 5, 15, 30, 40, and 50%, respectively, of 4‐vinylpyridine were investigated by differential scanning calorimetry, thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). It was shown that all the blends have a single glass transition over the entire composition range. The obtained T_gs of PSMA20/PS4VP blends containing an excess amount of PS4VP, above 15% of 4VP in the copolymer, were found to be significantly higher than those observed for each individual component of the mixture, indicating that these blends are able to form interpolymer complexes. The FTIR study reveals presence of intermolecular hydrogen‐bonding interaction between vinylpyridine nitrogen atom and the hydroxyl of MMA group and intensifies when the amount of 4VP is increased in PS4VP copolymers. A new band characterizing these interactions at 1724 cm⁻¹ was observed. In addition, the quantitative FTIR study carried out for PSMA20/PS4VP blends was also performed for the methacrylic acid and 4‐vinylpyridine functional groups. The TGA study confirmed that the thermal stability of these blends was clearly improved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of molecular weight on phase structure of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) blends

The phase structure of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) (PET/PEN) blends was studied in relation to the molecular weight. The samples were prepared by both solution blends, which showed two glass‐transition temperatures (T_g), and melt blends (MQ), which showed a single T_g, depending on the composition of the blends. The T_g of the MQ series was independent of the molecular weight of the homopolymer, although the degree of transesterification in the blends was affected by the molecular weight. The MQ series showed two exotherms during the heating process of a differential scanning calorimetry scan. The peak temperature and the heat flow of the exotherms were affected by the molecular weight of the homopolymers. The strain‐induced crystallization of the MQ series suggested the independent crystallization of PET and PEN. Based on the results, a microdomain structure of each homopolymer was suggested. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2428–2438, 2005     

Miscibility enhancement on the immiscible binary blend of poly(vinyl acetate) and poly(vinyl pyrrolidone) with bisphenol A

The miscibility behavior and hydrogen bonding of ternary blends of bisphenol A (BPA)/poly(vinyl acetate) (PVAc)/poly(vinyl pyrrolidone) (PVP) were investigated by using differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). The BPA is miscible with both PVAc and PVP based on the observed single T_g over the entire composition range. FTIR was used to study the hydrogen-bonding interaction between the hydroxyl group of BPA and the carbonyl group of PVAc and PVP at various compositions. Furthermore, the addition of BPA is able to enhance the miscibility of the immiscible PVAc/PVP binary blend and eventually transforms into miscible blend with single T_g, when a sufficiently quantity of the BPA is present due to the significant Δχ and the ΔK effect.     

Compatibility of poly(butadiene‐co‐acrylonitrile) with poly(L‐lactide) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

Poly(L ‐lactide) (PLLA) and poly(3‐hydrobutyrate‐co‐3‐hydroxyvalerate) (PHBV) were blended with poly(butadiene‐co‐acrylonitrile) (NBR). Both PLLA/NBR and PHBV/NBR blends exhibited higher tensile properties as the content of acrylonitrile unit (AN) of NBR increased from 22 to 50 wt %. However, two separate glass transition temperatures (T_g) appeared in PLLA/NBR blends irrespective of the content of NBR, revealing that PLLA was incompatible with NBR. In contrast, a single T_g, which shifted along with the blend composition, was observed for PHBV/NBR50 blends. Moreover NBR50 suppressed the crystallization of PHBV, indicating that PHBV was compatible with NBR50. Decrease of both elongation modulus and stress at maximum load was less significant and increase of elongation at break was more pronounced in PHBV/NBR50 blends than in PLLA/NBR50 blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3508–3513, 2004     

Melt rheology of poly(ϵ‐caprolactone)/poly(styrene‐co‐acrylonitrile) blends

Dynamic viscoelastic properties for miscible blends of poly(?‐caprolactone) (PCL) and poly(styrene‐co‐acrylonitrile) (SAN) were measured. It was found that the time–temperature superposition principle is applicable over the entire temperature range studied for the blends. The temperature dependency of the shift factors a_T can be expressed by the Williams–Landel–Ferry equation: log a_T = ?8.86(T ? T_s)/(101.6 + T ? T_s). The compositional dependency of T_s represents the Gordon–Taylor equation. The zero‐shear viscosities are found to increase concavely upward with an increase in weight fraction of SAN at constant temperature, but concavely downward at constant free volume fraction. It is concluded that the relaxation behavior of the PCL/SAN blends is similar to that of a blend consisting of homologous polymers. It is emphasized that the viscoelastic functions of the miscible blends should be compared in the iso‐free volume state. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2037–2041, 2001