Nanostructure and crystallisation kinetics of poly(ethylene oxide)/poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) blends

Blends of poly(ethylene oxide) (PEO) and poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) (PVPh-HEM) were studied by means of synchrotron small and wide angle X-ray scattering (SAXS and WAXS, respectively) and by differential scanning calorimetry (DSC). The DSC measurements were used in the determination of the Flory–Huggins interaction parameter and also to study the isothermal and non-isothermal crystallisation kinetics of the PEO/PVPh-HEM blend. The interaction parameter, χ₁₂, was found to be negative (between −0.5 and −2.5, approximately) and presented a significant dependence on the blend composition, which is expected for a system with specific interactions such as hydrogen bonding. From the kinetic studies with Kissinger, Friedman and Avrami models, it was shown that crystallisation of PEO chains is slower in the blend than in the pure polymer, despite the decrease in the energy barrier to the crystallisation with the increase in PVPh-HEM concentration.

From the SAXS and WAXS profiles, the nanostructure of the blend was elucidated, exhibiting the formation of PEO lamellae even in the blends containing high concentrations of PVPh-HEM, which are non-crystalline (as observed by the WAXS profiles). The thickness of the PEO lamellae (R_c, approximately 8 nm) remains almost unchanged with the blend composition, while the crystalline peaks, observed at 19.78 and 23.98°, vanish, and the WAXS profile exhibits only a non-crystalline halo. For the non-crystalline blends with high concentrations of PVPh-HEM, PEO chains keep their crystalline structural memory.     

Miscibility and interactions in poly(n-propyl methacrylate)/poly(vinyl alcohol) blends

Poly(n-propyl methacrylate) (PPMA) is miscible with poly(vinyl alcohol) (PVA) over the whole composition range as shown by the existence of a single glass transition temperature in each blend. The interaction between PPMA and PVA was examined by Fourier transform infrared spectroscopy and solid-state nuclear magnetic resonance spectroscopy. The interactions mainly involve the hydroxyl groups of PVA and the carbonyl groups of PPMA. The measurements of proton spin-lattice relaxation time reveal that PPMA and PVA do not mix intimately on a scale of 1-3 nm, but are miscible on a scale of 20-30 nm. A small negative interaction parameter value has been obtained by melting point depression measurement.     

Graft copolymers of poly(methyl methacrylate) backbone and poly(propylene oxide-b-ethylene oxide) branches

Summary Two mono-functional macromonomers of poly (propylene oxide-b-ethylene oxide) were synthesized by reaction with methacryloyl chloride. The macromonomers have the same molecular weight and ratio of ethylene oxide and propylene oxide sequences. The reactive methacrylate group can be linked to the ethylene oxide (BuPPOPEO) or to the propylene oxide (BuPEOPPO). These macromonomers showed self-gelling in one week even at low temperature and under a dry atmosphere. Graft copolymers were obtained by reaction of these macromonomers with methyl methacrylate upon free-radical initiation and they were characterized by GPC, VPO, IR and ¹H NMR spectra.     

Spherulitic crystallization in blends of poly(ethylene oxide) and poly(methyl methacrylate)

The crystallization kinetics of binary blends of poly(ethylene oxide) and poly(methyl methacrylate) were investigated. The isothermal spherulitic growth rates were measured by means of a polarized light microscope. The temperature and composition dependence on the growth rates have been analysed. The temperature range studied was from 44° to 58°C. The introduction of poly(methyl methacrylate) into poly(ethylene oxide) resulted in a reduction of the spherulitic growth rate as the proportion of poly(methyl methacrylate) was increased from zero to 40% by weight. Results have been analysed using the theoretical equations of Boon and Azcue for the growth rate of polymer-diluent mixtures. The experimental results are in good agreement with this equation. The temperature coefficient is negative as is the case in the crystallization of bulk homopolymers.     

Miscibility and phase behavior in blends of poly(hydroxyether of bisphenol A) with poly(ethylene oxide-co-propylene oxide)

The miscibility of poly(hydroxyether of bisphenol A) (phenoxy) with a series of poly(ethylene oxide-co-propylene oxide) (EPO) has been studied. It was found that the critical copolymer composition for achieving miscibility with phenoxy around 60°C is about 22 mol % ethylene oxide (EO). Some blends undergo phase separation at elevated temperatures, but there is no maximum in the miscibility window. The mean-field approach has been used to describe this homopolymer/copolymer system. From the miscibility maps and the melting-point depression of the crystallizable component in the blends, the binary interaction energy densities, B_ij, have been calculated for all three pairs. The miscibility of phenoxy with EPO is considered to be caused mainly by the intermolecular hydrogen-bonding interactions between the hydroxyl groups of phenoxy and the ether oxygens of the EO units in the copolymers, while the intramolecular repulsion between EO and propylene oxide units in the copolymers contributes relatively little to the miscibility. © 1993 John Wiley & Sons, Inc.     

Photodegradation of poly(methyl methacrylate)/ bisphenol A polycarbonate blends

Summary Poly(methyl methacrylate) [PMMA], Bisphenol A polycarbonate [BAPC] and its blends of different weight compositions irradiated under static vacuum conditions, were investigated by UV spectroscopy and gel permeation chromatography. Analysis indicated that photolysis of PMMA is retarded by blending with BAPC. This effect is attributed to photo products formed in the BAPC, most probably due to Fries rearrangement, that reduces the photodegradation of PMMA.     

Poly(ethylene oxide)/poly(methyl methacrylate) blends: Influence of tacticity of poly(methyl methacrylate) on blend structure and miscibility

The influence of different configurations of poly(methyl methacrylate) on the miscibility and superstructure of poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blends was examined using small-angle X-ray scattering and differential scanning calorimetry. The blends prepared by solution casting were isothermally crystallized at 48°C. The miscibility, the melting behaviour, the glass transition temperature and the structural parameters of the blends were strongly dependent on the tacticity and blend composition. The small-angle X-ray intensity profiles were analysed using a recently developed methodology. For the poly(ethylene oxide)/atactic poly(methyl methacrylate) (PEO/APMMA) and poly(ethylene oxide)/syndiotactic poly(methyl methacrylate) (PEO/SPMMA) blends, the long period and the amorphous and transition region thicknesses increased with increase of PMMA content, whereas for the poly(ethylene oxide)/isotactic poly(methyl methacrylate) (PEO/IPMMA) blends they are independent of composition. The structural properties of the blends were attributed to the presence of non-crystallizable material in the interlamellar or interfibrillar regions, depending on PMMA tacticity. From the glass transition and melting temperatures, it has been supposed that one homogeneous amorphous phase is present in the case of PEO/APMMA and PEO/SPMMA blends and that the PEO/IPMMA amorphous system is phase-separated. The free-volume contribution to the energy of mixing for the various tactic PMMAs is hypothesized to be responsible for the difference in mixing behaviour.     

Rheological properties of polystyrene and poly(methyl methacrylate) blends

Rheological properties of the polystyrene (PS) and poly(methyl methacrylate) (PMMA) blends were studied by Advanced Rheometric Expansion System (ARES). Storage modulus and loss modulus of the PS and PMMA blends were measured, and the interfacial tension of the PS and PMMA blends were obtained with various emulsion models by using the storage modulus and loss modulus of the blends. The value of interfacial tension estimated from the Palierne emulsion model was found to be 2.0 mN/m. Also, the interfacial tension between PS and PMMA was calculated by a theoretical model. The values of interfacial tension of the PS and PMMA blends obtained by the experiment and theoretical model were found to be in good agreement.     

Study of the non-isothermal crystallization of poly(ethylene oxide)/poly(methyl methacrylate) blends

Crystallization during cooling of a poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blend has been studied using differential scanning calorimetry. Five different cooling rates V_r have been used (namely 10, 5, 2.5, 1.25 and 0.625°C min⁻¹). The presence of PMMA for a given V_r reduces the overall PEO crystallization rate. This effect can be ascribed to reduction of the mobility of the crystallizable chains due to the presence of the amorphous component. It was found that in quasi-static conditions at lower V_r, when nucleation and growth processes are determined by a thermal mechanism alone, the experimental data for the pure PEO and the PEO/PMMA $\text{90}\text{10}$ and $\text{80}\text{20}$ blends agree quite well with the theoretical results obtained using the zero-order approximation of Ziabicki's theory. At higher V_r, in the case of the blends, athermal nucleation cannot be neglected, and then the same approximation does not fit the experimental results. The experimental data analysed showed no agreement with Ozawa's theoretical predictions.     

Miscibility and crystallization of poly(ethylene oxide) and poly(ε-caprolactone) blends

Blends of poly(ethylene oxide) (PEO) with poly(ε-caprolactone) (PCL), both semicrystalline polymers, were prepared by co-dissolving the two polyesters in chloroform and casting the mixture. Phase contrast microscopy was used to probe the miscibility of PEOB/PCL blends. Experimental results indicated that PEO was immiscible with PCL because the melt was biphasic. Crystallization of PEO/PCL blends was studied by differential scanning calorimetry and analyzed by the Avrami equation. The crystallization rate of PEO decreased with the increase of PCL in the blends while the crystallization mechanism did not change. In the case of the isothermal crystallization of PCL, the crystallization mechanism did not change, and the change in the crystallization rate was not very big, or almost constant with the addition of PEO, compared with the change of the crystallization rate of PEO.     

Degradation kinetics of poly(ethylene terephthalate) and poly (methyl methacrylate) blends

Summary Poly(ethylene terephthalate) PET and poly(methyl methacrylate) PMMA blends were made by melt mixing in a batch reactor. Three different weight ratios of PET : PMMA (25:75, 50:50 and 75:25) were chosen to study the effect of blend composition on the degradation kinetics. A relationship between the fractional volatiles evolved per unit time and the fraction of polymer degraded is established. The kinetic parameters for degradation were found using modified Avrami’s non-isothermal equation. Parameters like degradation rate constant (k) and order of degradation (n), were evaluated for the virgin polymers and the blends.     

Miscibility behavior and coil overlap in ionic blends of phenylated polytriphenylene oxide and poly(methyl methacrylate)

Blends of sulfonated phenylated polytriphenylene oxide and poly(methyl methacrylate‐co‐4‐vinyl pyridine) were examined by dynamic mechanical, Fourier transform infrared, and NMR techniques. A high degree of miscibility was evident from a single drop in a plot of the storage modulus versus the temperature. The presence of ionic moieties due to proton transfer from sulfonic acid to 4‐vinyl pyridine was confirmed by both NMR and IR spectroscopy studies. The coils were found to be close to one another in dimethyl sulfoxide‐d₆ because the aromatic shielding effect of the phenyl rings of the phenylated polytriphenylene oxide units was observed from the upfield shift of most of the protons of poly(methyl methacrylate) in the NMR spectrum. However, the absence of cross peaks in the nuclear Overhauser and exchange spectroscopy experiments suggested that the intermolecular distance between the chains had to be larger than 4 Å. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 728–733, 2003     

Tacticity effects on the miscibility behavior of poly(methyl methacrylate)/poly(ethylene oxide-b-dimethylsiloxane-b-ethylene oxide) blends

The miscibility of a triblock copolymer poly(ethylene oxide)-poly(dimethylsiloxane)-poly(ethylene oxide) with syndiotactic and isotactic poly(methylmethacrylate) wasstudied. Although isotactic poly(methyl methacrylate) (PMMA) was miscible with poly(ethylene oxide) (PEO) in the pure state, it was immiscible with the PEO end blocks in the copolymer. In comparison, the syndiotactic poly(methyl methacrylate) (sPMMA) was miscible with the PEO blocks as indicated by melting point depression, decrease in crystallinity, and slower rate of spherulite growth of PEO. When blends of the triblock copolymer were cooled to low temperatures, the poly(dimethylsiloxane) (PDMS) middle block which resided in the interlamellar region of PEO spherulites also crystallized; the development of PDMS crystals was clearly suppressed at high sPMMA contents.On leave from Union Chemical Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan     

Solvent effects on the miscibility of poly(methyl methacrylate)/poly(bisphenol a carbonate) blends

Blends of atactic or syndiotactic poly(methyl methacrylate) (designated as aPMMA or sPMMA) and poly(bisphenol A carbonate) (PC) were prepared from solution casting. Tetrahydrofuran (THF) and chloroform were used as solvent. Experimental results indicated that the as‐cast blends from THF were quite different from the chloroform‐cast ones. After film preparation, THF‐cast blends did not show any visible phase separation. However, chloroform‐cast blends formed a phase‐separated structure. The as‐cast PC from either solvent was not completely amorphous, and had a melting point at 239–242°C, indicating a certain degree of crystallinity. In contrast, the quenched samples of aPMMA/PC blends prepared from the two solvents behaved virtually the same. They both showed aPMMA dissolves better in PC, but PC solubility in aPMMA is very little. Using sPMMA instead of aPMMA to blend with PC, different results were obtained. The quenched sPMMA/PC blends cast from THF showed only one T_g. However, immiscibility (i.e., two T_gs) was found in the same blend system when cast from chloroform. THF was believed to cause the observation of single T_g due to the following kinetic reason. sPMMA and PC were still trapped together even after THF removal in a homogeneous, but nonequilibrium state below the glass transition. Therefore, the quenched sPMMA/PC blends were not truly thermodynamically miscible. From the results of aPMMA or sPMMA with PC, increasing syndiotacticity seemed to improve the miscibility between PMMA and PC. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2842–2850, 2001     

Miscibility of poly(methoxymethyl methacrylate) and poly(methylthiomethyl methacrylate) with poly(methyl methacrylate)

Summary Poly(n-propyl methacrylate) is known to be immiscible with poly(methyl methacrylate) (PMMA). However, we have found that poly(methoxymethyl methacrylate) is miscible with PMMA, indicating the importance of ether oxygen atoms in achieving miscibility. On the other hand, poly(methylthiomethyl methacrylate) is immiscible with PMMA.     

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     

A polymeric solid electrolyte based on a binary blend of poly(ethylene oxide), poly(methyl vinyl ether-maleic acid) and LiClO4

A new polymeric solid electrolyte based on a PEO/PMVE-MAc blend, complexed with LiClO₄, was obtained and characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), polarized light optical microscopy, electrochemical impedance and cyclic voltammetry. DSC traces indicated miscibility for all the PSE samples. Crystallinity was suppressed for samples with LiClO₄ concentrations higher than 2.5 wt%. FTIR associated with DSC studies indicated that there is a preferential formation of complexes PEO/Li⁺/PMVE-MAc in all PSE samples studied here. The ionic conductivity of PSE reaches a maximum of about 10⁻⁵ S/cm at ambient temperature and 7.5 wt% LiClO₄. The electrochemical stability window is 4.5 V and associated with the other characteristics, make the PSE studied here suitable for applications in ‘smart-windows’, batteries, sensors, etc.     

Gas chromatographic determination of the interaction parameter of poly(ethylene oxide)/poly(methyl methacrylate) blends

Inverse gas chromatography (IGC) has been used to investigate thermodynamic miscibility of a molten poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blend. Toluene, benzene, and chloroform have been employed as probes in pure and mixed stationary phases of these polymers. Experimental measurements have been taken over a narrow range of temperatures because of the high PMMA glass transition temperature as well as the degradation of the PEO. The interaction parameter χ₂₃ determined at 150°C is slightly negative and dependent on the interacting probe, as has been also noted in previous chromatographic studies on polymer-polymer miscibility. The last section is devoted to a model calculation, using Flory's equation of state theory. Different χ₂₃-concentration curves have been simulated, with the interaction energy parameter X₂₃ as an adjustable parameter.     

Study of the morphology of poly(butylene succinate)/poly(ethylene oxide) blends using hot-stage atomic force microscopy

Blends of poly(butylene succinate) (PBS) and poly(ethylene oxide) (PEO) were cast into films, melted, and crystallized. A number of PBS/PEO blend compositions, ranging from 85/15 to 20/80 were used. The PBS, with a higher melting point, always crystallizes first, providing a scaffold on which the PEO would crystallize. AFM phase and height images were made at room temperature and at higher temperatures, as the PEO melted, allowing one to determine the morphology and location of the PEO. It was found that at low PEO concentrations (below 15 w/o) the PEO resides preferentially between PBS lamellae. This interlamellar PEO does not crystallize, except under extreme undercooling. At higher concentrations, larger amorphous domains exist within the PBS crystalline scaffold and PEO can crystallize in these domains. Two unexpected phenomena are observed: (1) the reversible exuding of PEO from interlamellar spaces to the surface for crystallization and (2) an unusual orientation of PEO lamellae within amorphous domains in the PBS scaffold.     

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.