Investigation on the miscibility of the blends of poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile)

The miscibility was investigated in blends of poly(methyl methacrylate) (PMMA) and styrene‐acrylonitrile (SAN) copolymers with different acrylonitrile (AN) contents. The 50/50 wt % blends of PMMA with the SAN copolymers containing 5, 35, and 50 wt % of AN were immiscible, while the blend with copolymer containing 25 wt % of AN was miscible. The morphologies of PMMA/SAN blends were characterized by virtue of scanning electron microscopy and transmission electron microscopy. It was found that the miscibility of PMMA/SAN blends were in consistence with the morphologies observed. Moreover, the different morphologies in blends of PMMA and SAN were also observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

Hydrolytic degradation of poly(l‐lactic acid)/poly(methyl methacrylate) blends

The hydrolytic degradation of poly(l ‐lactic acid)/poly(methyl methacrylate) (PLLA/PMMA) blends was carried out by the immersion of thin films in buffer solutions (pH = 7.24) in a shaking water bath at 60 °C for 38 days. The PLA/PMMA blends (0/100; 30/70; 50/50; 70/30; 100/0) were obtained by melt blending using a Brabender internal mixer and shaped into thin films of about 150 µm in thickness. Considering that PMMA does not undergo hydrolytic degradation, that of PLLA was followed via evolution of PLA molecular weight (recorded by size exclusion chromatography), thermal parameters (differential scanning calorimetry (DSC)) and morphology of the films (scanning transmission electron microscopy). The results reveal a completely different degradation pathway of the blends depending on the polymethacrylate/polyester weight ratio. DSC data suggest that, during hydrolysis at higher PMMA content, the polyester amorphous chains, more sensitive to water, are degraded before being able to crystallize, while at higher PLLA content, the crystallization is favoured leading to a sample more resistant to hydrolysis. In other words, and quite unexpectedly, increasing the content of water‐sensitive PLLA in the PLLA/PMMA blends does not mean de facto faster hydrolytic degradation of the resulting materials. © 2018 Society of Chemical Industry     

Reexamination of the miscibility of stereoregular poly(methyl methacrylate) with poly(vinyl phenol)

Previously, isotactic, atactic, and syndiotactic poly(methyl methacrylates) (PMMAs) (designated as iPMMA, aPMMA, and sPMMA) were mixed with poly(vinyl phenol) (PVPh) separately in tetrahydrofuran (THF) to make three polymer blend systems. According to calorimetry data, iPMMA was found to be miscible with PVPh; however, partial miscibility or immiscibility was found between aPMMA (or sPMMA) and PVPh. According to the article by C. J. T. Landry and D. M. Teegarden, Macromolecules, 1991, 24, 4310, THF is the reason for causing aPMMA and PVPh to phase separate, but 2‐butanone instead produces miscible blends. Therefore, in this article these three polymer systems were investigated again using 2‐butanone as solvent. Films were prepared under specific conditions to minimize the effect of aggregation in PMMA. The formation of hydrogen bonding between PMMA and PVPh and the attendant changes in the aggregation of PMMA segments were determined in the solid states by means of FTIR. Based on the results of calorimetry, iPMMA and aPMMA were found to be miscible with PVPh. For iPMMA/PVPh blends, different degrees of hydrogen bonding were observed based on DSC data and FTIR spectra when compared to previous study. An elevation of the glass transition temperatures (T_gs) of aPMMA/PVPh blends above weight average was detected and the T_g values were fitted well by the Kwei equation. But partial miscibility was still found between sPMMA and PVPh on account of the observation of two T_gs in most compositions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1425–1431, 2002     

Nonlinear phase‐separation behavior of poly(methyl methacrylate)/poly(styrene‐co‐maleic anhydride) blends

The nonlinear phase‐separation behavior of poly(methyl methacrylate)/poly(styrene‐co‐maleic anhydride) (PMMA/SMA) blends over wide appropriate temperature and heating rate ranges was studied using time‐resolved small‐angle laser light scattering. During the non‐isothermal process, a quantitative logarithm function was established to describe the relationship between cloud point (T_c) and heating rate (k) as given by T_c = Alnk + T₀, in which the parameter A, reflecting the heating rate dependence, is much different for different compositions due to phase‐separation rate and activation energy difference. For the isothermal phase‐separation process, an Arrhenius‐like equation was successfully applied to describe the temperature dependence of the apparent diffusion coefficient (D_app) and the relaxation time (τ) of the early stage as well as the late stage of spinodal decomposition (SD) of PMMA/SMA blends. Based on the successful application of the Arrhenius‐like equation, the related activation energies could be obtained from D_app and τ of the early and late stages of SD, respectively. In addition, these results indicate that it is possible to predict the temperature dependence of the phase‐separation behavior of binary polymer mixtures during isothermal annealing over a range of 100 °C above the glass transition temperature using the Arrhenius‐like equation. © 2012 Society of Chemical Industry     

Nonisothermal crystallization kinetics of poly(ethylene terephthalate) and poly(methyl methacrylate) blends

The nonisothermal crystallization kinetics of poly(ethylene terephthalate) (PET) and poly(methyl methacrylate) (PMMA) blends were studied. Four compositions of the blends [PET 25/PMMA 75, PET 50/PMMA 50, PET 75/PMMA 25, and PET 90/PMMA 10 (w/w)] were melt‐blended for 1 h in a batch reactor at 275°C. Crystallization peaks of virgin PET and the four blends were obtained at cooling rates of 1°C, 2.5°C, 5°C, 10°C, 20°C, and 30°C/min, using a differential scanning calorimeter (DSC). A modified Avrami equation was used to analyze the nonisothermal data obtained. The Avrami parameters n, which denotes the nature of the crystal growth, and Z_t, which represents the rate of crystallization, were evaluated for the four blends. The crystallization half‐life (t_½) and maximum crystallization (t_max) times also were evaluated. The four blends and virgin polymers were characterized using a thermogravimetric analyzer (TGA), a wide‐angle X‐ray diffraction unit (WAXD), and a scanning electron microscope (SEM). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3565–3571, 2006     

Crystallization behavior and mechanical properties of poly(ethylene oxide)/poly(L‐lactide)/poly(vinyl acetate) blends

Poly(vinyl acetate) (PVAc) was added to the crystalline blends of poly(ethylene oxide) (PEO) and poly(L ‐lactide) (PLLA) (40/60) of higher molecular weights, whereas diblock and triblock poly(ethylene glycol)–poly(L ‐lactide) copolymers were added to the same blend of moderate molecular weights. The crystallization rate of PLLA of the blend containing PVAc was reduced, as evidenced by X‐ray diffraction measurement. A ringed spherulite morphology of PLLA was observed in the PEO/PLLA/PVAc blend, attributed to the presence of twisted lamellae, and the morphology was affected by the amount of PVAc. A steady increase in the elongation at break in the solution blend with an increase in the PVAc content was observed. The melting behavior of PLLA and PEO in the PEO/PLLA/block copolymer blends was not greatly affected by the block copolymer, and the average size of the dispersed PEO domain was not significantly changed by the block copolymer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3618–3626, 2001     

Miscibility and phase structure of binary blends of poly(L‐lactide) and poly(vinyl alcohol)

Blend films of poly(L ‐lactide) (PLLA) and poly(vinyl alcohol) (PVA) were obtained by evaporation of hexafluoroisopropanol solutions of both components. The component interaction, crystallization behavior, and miscibility of these blends were studied by solid‐state NMR and other conventional methods, such as Fourier transform infrared (FTIR) spectra, differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction (WAXD). The existence of two series of isolated and constant glass‐transition temperatures (T_g's) independent of the blend composition indicates that PLLA and PVA are immiscible in the amorphous region. However, the DSC data still demonstrates that some degree of compatibility related to blend composition exists in both PLLA/atactic‐PVA (a‐PVA) and PLLA/syndiotactic‐PVA (s‐PVA) blend systems. Furthermore, the formation of interpolymer hydrogen bonding in the amorphous region, which is regarded as the driving force leading to some degree of component compatibility in these immiscible systems, is confirmed by FTIR and further analyzed by ¹³C solid‐state NMR analyses, especially for the blends with low PLLA contents. Although the crystallization kinetics of one component (especially PVA) were affected by another component, WAXD measurement shows that these blends still possess two isolated crystalline PLLA and PVA phases other than the so‐called cocrystalline phase. ¹³C solid‐state NMR analysis excludes the interpolymer hydrogen bonding in the crystalline region. The mechanical properties (tensile strength and elongation at break) of blend films are consistent with the immiscible but somewhat compatible nature of these blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 762–772, 2001     

Radiational hardening of poly(vinylidene fluoride)–poly(methyl methacrylate)–polystyrene ternary blends

Specimens of poly(vinylidene fluoride) (PVDF)–poly(methyl methacrylate) (PMMA)–polystyrene (PS) polyblends with different weight percentage ratios of the three polymers were prepared with the solution cast technique. The effect of γ irradiation on the Vicker's microhardness was studied. Among the three pure polymers, PVDF, PMMA, and PS, the γ irradiation imparted crosslinking in PVDF, thereby causing radiational hardening. In the cases of PMMA and PS, the effect of irradiation exhibited a predominance of both the scissioning and crosslinking processes in different ranges of doses. Moreover, at a dose of 5 Mrad, in both PMMA and PS, maximum radiational crosslinking was observed. The effect of γ irradiation seemed to stabilize beyond 15 Mrad in PVDF and beyond 20 Mrad in PMMA and PS. Microhardness measurements on ternary blends of PVDF, PMMA, and PS revealed that the blend with low contents of PMMA, that is, up to 5 wt %, yielded softening, whereas increasing the content of PMMA beyond 5 wt % produced a hardened material because of radiational crosslinking, and a higher content of PMMA in the blend facilitated this crosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3107–3111, 2004     

Characterization of the mechanical and thermal properties and morphological behavior of biodegradable poly(L‐lactide)/poly(ε‐caprolactone) and poly(L‐lactide)/poly(butylene succinate‐co‐L‐lactate) polymeric blends

Two series of biodegradable polymer blends were prepared from combinations of poly(L ‐lactide) (PLLA) with poly(?‐caprolactone) (PCL) and poly(butylene succinate‐co‐L ‐lactate) (PBSL) in proportions of 100/0, 90/10, 80/20, and 70/30 (based on the weight percentage). Their mechanical properties were investigated and related to their morphologies. The thermal properties, Fourier transform infrared spectroscopy, and melt flow index analysis of the binary blends and virgin polymers were then evaluated. The addition of PCL and PBSL to PLLA reduced the tensile strength and Young's modulus, whereas the elongation at break and melt flow index increased. The stress–strain curve showed that the blending of PLLA with ductile PCL and PBSL improved the toughness and increased the thermal stability of the blended polymers. A morphological analysis of the PLLA and the PLLA blends revealed that all the PLLA/PCL and PLLA/PBSL blends were immiscible with the PCL and PBSL phases finely dispersed in the PLLA‐rich phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modification of polycarbonate by adding poly(L‐lactide)

In this study, the blend of polycarbonate (PC)/poly(L‐lactide) (PLLA) (70/30) was prepared through the conventional extrusion‐injection‐molding process. The morphology of the blend was characterized using scanning electron microscope. Both differential scanning calorimetry and wide angle X‐ray diffraction were used to investigate the crystallization behavior of PLLA component in the blend. The mechanical and thermal properties of the blend were comparatively investigated, and the hydrolytic degradation ability of the material was also evaluated. The results show that the dispersed‐PLLA particles are in the amorphous state in the PC matrix. Although the blend is immiscible, the rigid PLLA particles exhibit the toughening and reinforcement effects on PC simultaneously. Specifically, the heat‐distortion temperature of the blend is comparable to that of pure PC. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Conductive blends of polyaniline with plasticized poly(methyl methacrylate)

Polyaniline (PANI) protonated with camphorsulfonic acid (CSA) and three different poly(alkylene phosphates) (PAPs) (where alkylene = pentylene, hexylene, or nonylene) was used in the fabrication of conductive polyaniline–poly(methyl methacrylate) (PMMA) blends. The lowest percolation threshold (f_p = 0.041 wt %) was obtained for the PANI(CSA)_0.5–PMMA blend plasticized with 35 wt % of dibutyl phtalate (DBPh). This blend is also very resistant against the deprotonation of its conductive phase in basic solutions of pH = 9. In the case of blends prepared with the use of PAPs as PANI dopants, the percolation threshold strongly depends on the length of the hydrophobic spacer (alkylene group) in the dopant. The percolation threshold decreases in the order PPP > PHP > PNP, whereas the resistance against deprotonation in basic solutions decreases in the following inverse order: PNP > PHP > PPP. This last observation can be rationalized by increasing contribution of hydrophobic segments in the polymeric dopant, when going from PPP to PNP, which renders polyaniline more resistance toward the penetration by aqueous basic solutions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 471–479, 1999     

Miscible blends of biobased poly(lactide) with poly(methyl methacrylate): Effects of chopped glass fiber incorporation

Poly(lactide) (PLA) and poly(methyl methacrylate) (PMMA) are melt compounded with chopped glass fiber using laboratory scale twin‐screw extrusion. Physical properties are examined using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), tensile testing, impact testing, X‐ray computed tomography (CT) scanning, and field emission scanning electron microscopy (FE‐SEM). Molecular weight is determined using gel permeation chromatography (GPC). Miscibility of the blends is implied by the presence of a single glass transition temperature and homogeneous morphology. PLA/PMMA blends tend to show positive deviations from a simple linear mixing rule in their mechanical properties (e.g., tensile toughness, modulus, and stress at break). The addition of 40 wt % glass fiber to the system dramatically increases physical properties. Across all blend compositions, the tensile modulus increases from roughly 3 GPa to roughly 10 GPa. Estimated heat distortion temperatures (HDTs) are also greatly enhanced; the pure PLA sample HDT increases from 75 °C to 135 °C. Fiber filled polymer blends represent a sustainable class of earth abundant materials which should prove useful across a range of applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44868.     

Kinetics of phase separation of poly(styrene‐co‐methyl methacrylate) and poly(styrene‐co‐acrylonitrile) blends

The phase behavior and kinetics of phase separation for blends of the random copolymer poly(styrene‐co‐methyl methacrylate) (SMMA) and poly(styrene‐co‐acrylonitrile) (SAN) were studied by using small‐angle laser light scattering. The partially miscible SMMA/SAN blends undergo spinodal decomposition (SD) and subsequent domain coarsening when quenched inside the unstable region. For blends of SMMA and SAN, the early stages of the phase separation process could be observed, unlike a number of other blends where the earliest stages are not visible by light scattering. The process was described in terms of the Cahn–Hilliard linear theory. Subsequently, a coarsening process was detected and the time evolution of q_m at the beginning of the late stages of phase separation followed the relationship q_m∝t^?1/3, corresponding to an evaporation–condensation mechanism. Self‐similar growth of the phase‐separated structures at different timescales was observed for the late stage. Copyright © 2004 Society of Chemical Industry     

Melt electrospinning from poly(L‐lactide) rods coated with poly(ethylene‐co‐vinyl alcohol)

Rodlike poly(L ‐lactide) (PLLA) samples coated with poly(ethylene‐co‐vinyl alcohol) (EVOH) were made. Fibers were produced from these rodlike samples by using a melt electrospinning system equipped with a laser irradiating device, and the effects of EVOH content and the processing parameters of the melt electrospinning on fiber diameters were investigated. We also studied the fiber formation mechanism from the rods during the laser melt electrospinning process. The following conclusions were reached: (i) coating of EVOH on PLLA rods has a remarkable effect on decreasing fiber diameter from 3 μm to around 1 μm; (ii) increases in the electric field strength and temperature of spinning space decrease the average diameter of fibers produced from pure PLLA rods, and longer collector distance leads to lager PLLA fiber diameter; and (iii) the migration of PLLA component from the core to the surface of electrospun fibers takes place during the fiber formation process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Morphology and property changes of immiscible polycarbonate/poly(L‐lactide) blends induced by carbon nanotubes

Blends of polycarbonate (PC)/poly(l ‐lactide) (PLLA) have great potential in applications ranging from packaging materials to consumer electronics. However, research into these blends is relatively limited compared with that into other polyesters. In this work, different contents of functionalized multiwalled carbon nanotubes (FMWCNTs) were introduced into PC/PLLA blends. The crystallization and melting behaviors of the nanocomposites were investigated using differential scanning calorimetry. The morphology of the nanocomposites and the dispersion states of the FMWCNTs were investigated using scanning electron microscopy, transmission electron microscopy and rheological measurements. The results showed that all samples were in the amorphous state during the injection‐molding process. Although the co‐continuous morphology features of samples was not changed, the presence of the FMWCNTs noticeably induced an increase of phase domains of PC, which was suggested to be the result of the formation of a percolated FMWCNT network structure. The electrical resistivity of the nanocomposites was greatly reduced when the content of FMWCNTs was increased to 2 wt%. The determination of mechanical properties showed that the addition of FMWCNTs facilitated an improvement of the fracture resistance. Another exciting aspect of this research was that the hydrolytic degradation ability of the blends was further improved by adding the FMWCNTs.     

Feather‐like morphology of poly(methyl methacrylate)/poly(ethylene oxide) blends: The effect of cooling rate and poly(methyl methacrylate) content

The effect of cooling rate on the crystallization morphology and growth rate of poly(ethylene oxide) (PEO) and PEO/poly(methyl methacrylate) (PMMA) blends has been observed by Hot Stage Polarized Microscopy (HS‐POM). The isothermal crystallization kinetics study was carried out by differential scanning calorimetry (DSC). The spherulite morphology has been observed for the neat PEO with molecular weight of 6000 g/mol. By adding of PMMA with molecular weight of 39,300 g/mol, the growth fronts become irregular. With the increasing of PMMA content, the irregularity of growth front becomes more obvious, and the feather‐like morphology can be observed. When PMMA content is 60%, the spherulite is seriously destroyed. This phenomenon is more obvious for the slow cooling process. Based on the measurement of spherulite, the growth rate curves were obtained. According to the curves, it can be seen that the growth rate decreases with the increasing of PMMA content, and the growth rate during the slow cooling process is higher than that of the fast cooling process. The isothermal crystallization experiment indicates that the crystallization rate decreases dramatically with the increasing of PMMA content. And the Avrami parameter n was obtained, which is non‐integral and less than 3. Finally, it can be concluded that the higher value of n can be obtained for the condition with low crystallization rate. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41705.     

Poly(para‐dioxanone)/poly(D,L‐lactide) blends compatibilized with poly(D,L‐lactide‐co‐para‐dioxanone)

The effect of poly(D ,L ‐lactide‐co‐para‐dioxanone) (PLADO) as the compatibilizer on the properties of the blend of poly(para‐dioxanone) (PPDO) and poly(D ,L ‐lactide) (PDLLA) has been investigated. The 80/20 PPDO/PDLLA blends containing from 1% to 10% of random copolymer PLADO were prepared by solution coprecipitation. The PLADO component played a very important role in determining morphology, thermal, mechanical, and hydrophilic properties of the blends. Addition of PLADO into the blends could enhance the compatibility between dispersed PDLLA phase and PPDO matrix; the boundary between the two phases became unclear and even the smallest holes were not detected. On the other hand, the position of the T_g was composition dependent; when 5% PLADO was added into blend, the T_g distance between PPDO and PDLLA was shortened. The blends with various contents of compatibilizer had better mechanical properties compared with simple PPDO/PDLLA binary polymer blend, and such characteristics further improved as adding 5% random copolymers. The maximum observed tensile strength was 29.05 MPa for the compatibilized PPDO/PDLLA blend with 5% PLADO, whereas tensile strength of the uncompatibilized PPDO/PDLLA blend was 14.03 MPa, which was the lowest tensile strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of polystyrene/poly(methyl methacrylate) blends by compressed fluid antisolvent technique

Submicron polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends were generated by the precipitation with a compressed antisolvent (PCA) technique. The generation of PS/PMMA blends was carried out by spraying a solution containing PS and PMMA into a precipitator. The blends without coalescence were observed to only be generated when both vapor and liquid CO₂ existed in the precipitator combined with appropriate total polymer concentration in solution, molecular weights (Mws) of PS and PMMA, mass ratio of PS to PMMA, flow rates of CO₂ and polymer solution, and liquid CO₂ level in the precipitator. Two Mws of PS, 144,000 and 44,000, and two Mws of PMMA, 85,000 and 36,000, were used in this study. It was found that the blends could be easier to generate using a higher PS Mw, a lower PMMA Mw, and a higher mass ratio of PS to PMMA. Toluene with a solubility parameter smaller than that of tetrahydrofuran (THF) was found to be the more appropriate solvent for generating spherical PS/PMMA submicron blends. The SEM and TEM images show that the spherical PS/PMMA core/shell blends could be generated at a temperature of 298 K, a pressure of 6.41 MPa, a liquid CO₂ level of 1/2 of the precipitator, a CO₂ flow rate of 2000 mL/min, a solution flow rate of 5 or 10 mL/min, and a total polymer concentration of 0.72 wt% for a PS Mw of 144,000, a PMMA Mw of 36,000, and a PS/PMMA mass ratio of 9/1. Individual and spherical PS and PMMA particles or spherical PS particles partially covered by a PMMA films, however, were generated when the liquid CO₂ level was of 1/8 or lower in the precipitator. A possible mechanism for the formation of core-shell blend was proposed.     

Configurational effects on the crystalline morphology and amorphous phase behavior in poly(3‐hydroxybutyrate) blends with tactic poly(methyl methacrylate)

Poly(3‐hydroxybutyrate) (PHB) blends with two tactic poly(methyl methacrylate)s [PMMAs; isotactic poly(methyl methacrylate) (iPMMA) and syndiotactic poly(methyl methacrylate) (sPMMA)], being chiral/tactic polymer pairs, were investigated with regard to their crystalline spherulite patterns, optical birefringence, and amorphous phase behavior with polarized optical microscopy and differential scanning calorimetry. The PHB/sPMMA and PHB/iPMMA blends exhibited upper critical solution temperatures of about 225 and 240°C, respectively, on the basis of the results of thermal analysis and phase morphology. The interactions of two constituents in the blends (PHB/iPMMA or PHB/sPMMA) were measured to be insignificantly different for the PHB/sPMMA and PHB/iPMMA blends. However, syndiotacticity in PMMA exerted a prominent effect on the alteration of the PHB spherulite morphology, whereas, by contrast, isotacticity in PMMA had almost no effect at all. At high sPMMA contents (e.g., 30 wt %) in the PHB/sPMMA blend, the spherulites were all negatively birefringent and ringless when they were crystallized at any crystallization temperature between 50 and 90°C. That is, not only was the original ring‐banded pattern in the neat PHB spherulites completely disrupted, but the optical sign was also reverted completely from positively to negatively birefringent in the sPMMA/PHB blend; this was not observed in the iPMMA/PHB one. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013