Thermal Properties and Morphology of Poly(ethylene oxide)/Poly(n‐butyl methacrylate) Blends

Abstract

From the thermodynamic point of view, most of the high molar‐mass binary polymer blends are immiscible due to the entropic contribution to the free energy of mixing is relatively small. The miscibility of the systems on the molecular scale can be assessed by the thermal properties such as quantities of glass transition temperature (Tg) and change in heat capacity (ΔCp) of the polymers. For a semi‐crystalline polymer such as poly(ethylene oxide) (PEO), the crystallinity (X*) and the melting temperature (Tm) can also give some hints on the miscibility. Apart from the thermal properties, additional scientific findings such as morphology of the blends are needed as supplementary evidences to support the results. We focus on the PEO as the polymer host, blends with poly(n‐butyl methacrylate) (PnBMA) which were prepared using solution casting technique. Thermal properties of PEO/PnBMA polymer blends were investigated by modulated differential scanning calorimeter (MDSC) on the isothermal crystallized samples at 25 °C. Tg of PEO in the blends do not show significant variation with addition of PnBMA for entire composition range while for Tg of PnBMA in the blends, it is challenging to be estimated under the experimental condition due to the overlapping of the Tg of PnBMA and melting endotherm of PEO. Constancy of quantity Tg of PEO and ΔCp of PEO corresponding to the content of PEO in the blends suggest that PEO and PnBMA are immiscible for entire blend composition. X* and Tm of PEO in the blends show insignificant variation in PEO/PnBMA blends, when PEO as major component. This implies that these blends are immiscible under the experimental conditions as agreed with results of Tg and ΔCp. Spherulitic morphologies of PEO in the blends were studied by polarized optical microscopy (POM). PnBMA phase disperses randomly in PEO matrix when PEO in excess. The absence of significant change for the fibrillar spherulitic structures of PEO spherulites with addition of PnBMA (when PEO is the major component) suggests that immiscibility of PEO and PnBMA. Besides, the crystalline structure of PEO in PEO/PnBMA blends using X‐ray diffraction (XRD) reveals that the crystalline structure of PEO is not disturbed with the addition of PnBMA when PEO is in excess as the two distinct peaks of PEO do not shift as compared to neat PEO. Impedance spectroscopy (IS) studies show that the ionic conductivities (σDC) of the polymer blends at room temperature slightly increase with increasing of PEO with the order of magnitude of 10−11–10−10 S cm−1. This system serves as a potential polymer host as solid polymer electrolytes when added with inorganic salt.

Correlation of thermal, morphological and melt rheological properties of miscible poly(ethylene oxide)/poly(methyl acrylate) and immiscible poly(ethylene oxide)/poly(n‐butyl methacrylate) blends

“…4. This implies that these blends are immiscible under the experimental conditions, in agreement with the T g results in this study and similar observations recorded for immiscible blends in references 56 and 68. In general, in a blend including a semicrystalline polymer, the melting behaviour of the semicrystalline polymer is affected by the miscibility of the binary blend.…”

“…However, the constancy of T g values of PEO as a function of the mass fraction of PEO suggests that PEO and PnBMA are immiscible for the entire blend composition in the amorphous phase or in the melt state. A similar observation is noted in reference 56, where PEO is immiscible with PnBMA in the amorphous phase for isothermally crystallized blends at 25 °C from the melt. Alternatively, the assessment of immiscibility of PEO/PnBMA blends is suggested using Han plot analysis, which will be discussed in the section ‘Variation of viscoelastic moduli function with blend composition’ (Fig.…”

“…Hence, PEO spherulites formed in immiscible blends when PEO is in excess are very similar to the spherulites formed in neat PEO. Hence, there is no significant difference in T m values of PEO in the immiscible blends throughout the blend compositions compared to neat PEO 2,67,68 . In other words, the reduction in T m values of PEO in the binary blends may indicate the miscibility of the blends in the melt.…”

“…All polymers (PEO, PMA and PnBMA, Sigma‐Aldrich Chemical Co., St Louis, MO, USA) used were purified prior to use with the procedures described in references 50 and 56; the characteristics of the polymers are summarized in Table 1. PEO is used as the polymer host and the polyacrylates, i.e.…”

Thermal Properties and Morphological Studies of Poly(ethylene oxide) with the Addition of Salt or Nanofiller

“…Poly(ethylene oxide) (PEO) is one of the extensively studied polymers in developing new polymeric materials with enhanced properties designed for various scientific studies such as solid polymer electrolytes (SPEs) and composite polymer electrolytes (CPEs) for electrochemical energy storage devices, [1][2][3] packaging materials, [4,5] automotive industry, [6] and biomaterials for the medical industry and medical devices. [7][8][9] High molar mass PEO, which is the semicrystalline polymer with the crystallinity amount up to 70%, [10,11] is commonly employed as the polymer host for the previously mentioned applications. PEO carries longitudinal dipoles along the linear chain, which may benefit molecular interaction with additional component.…”