Molecular Dynamics Simulation of Polysulfone and Polystyrene-co-maleic Anhydride Blends Compatibility: A mesoscopic, Ewald Approach and Experimental Comparison

: 37 This work aims to use molecular modeling to envisage the compatibility of 38 Polysulfone (PSF) and Poly (styrene-co-maleic anhydride) (PSMA) polymers blend. 39 A blend-module was developed based on the molecular dynamics (MD) technique 40 compared to an experimental study. Molecular dynamics simulations were achieved 41 using the condensed phase-optimized molecular-potentials for atomistic simulation 42 studies (COMPASS) force field with atomic-based electrostatic. The PSF/PSMA 43 blend compatibility facets and thermodynamic Gibb’s free energy across ranges of 44 PSF/PSMA blend compositions were calculated. In doing so, the Flory Huggins chi 45 interaction paramet er of mixing (χ) and solubility parameters (δ) were computed from 46 298K and on increasing temperature to predict the miscibility of the polymers blend 47 in the amorphous cell model by atomistic simulations. It was found that the blend- 48 system is miscible using the interaction chi parameter of Florry Huggins at a 49 temperature above 400K. At higher time-step, mesoscopic simulations for PSF/PSMA 50 reached equilibrium and computed free energy. Mixing energy indicated the stability 51 of the PSF/PSMA polymer blend. The results of this work narrate to the Flory 52 Huggins theory enthalpy of mixing for binary blend polymers at 40 and 60 % PSMA. 53 Additionally, the kinetic phase of the miscibility/immiscibility of the PSF/PSMA 54 blend system's miscibility/immiscibility was examined using Differential Scanning 55 Calorimetry (DSC). The result confirms the good interaction between the two 56 polymers through the shift of glass transition temperature (Tg) values within 57 individual polymers Tg. It is crucial to investigate the miscibility of two different 58 polymers for a variety of polymer applications. The MD simulation provides a 59 powerful, accurate computational tool in the estimation of polymer compatibilities.

to achieve attractive membranes with desirable features such as antifouling, 91 hydrophilicity, and heavy metals rejection and compatibility of PSMA and with 92 polymers has the great technological and scientific interest to researchers to achieve 93 successful fabrication of membranes [20][21][22]. 94 This study aims to predict the compatibility/incompatibility of the PSF and PSMA by    [29].

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The CED computation can enable us to obtain the energy of mixing (ΔEmix) since the 206 Flory-Huggins model of this binary system is based on the thermodynamics of mixing 207 of the polymer/polymer system.

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Generally, the energy of mixing is expressed, as shown in Eq. (6) The terms that are in brackets represent cohesive energies of individual pure polymers (6) can also be 214 expressed in terms of free energy mixing, as shown in Eq. (7) 215 ln ln Whereby ∆G is the free energy of mixing (per mole), T is the reference absolute 217 temperature of the simulation (in Kelvin), R is the molar gas constant, and χ is the Ebb is the binding energy base-base pair, Ebs is a binding energy base-screen pair, Esb

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is the binding energy screen-base pair, and Ess is the binding energy screen-screen 243 pair. These are energies of interaction between two polymers and, together with the 244 interaction parameter (χ), can generate energy mixing.

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The blends-button is selected from the menu toolbar and then the menu's dropdown to In order to obtain the status of thermodynamics compatibility, the Gibbs free energy          PSF has a Tg of 163 °C, which is higher than pure PSMA having Tg of 137 °C.

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However, varying polymer concentration of polymer as indicated in Table 2, the Tg 342 values change and different from that pure PSF and pure PSMA. These differences can be due to many van der Waals interactions between two polymers that lose the 344 identity [53].      presented in Fig. 9. This plot can be further analyzed using the enthalpy of mixing by 478 Schneier's theory (at 298K), which will be discussed later in this study. However, as 479 the temperature increases, it is free to shift to the negative side at the similar 480 composition of PSMA. This is attributed to the temperature-dependent miscibility 481 behavior, as confirmed earlier in this work. Thus, the spinodal is linked to the coexistence region's separation into two phases,

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whereas the binodal links with the coexistence region in this phase diagram. In the 503 region between the spinodal and binodal, the polymer blend system is metastable.

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That is, the blend will separate only after sufficiently high fluctuation.

Gibb's Free energy graph -thermodynamic theory of compatibility
It is seen that the PSF/PSMA polymer blend is partially compatible. From 0.4 to 0.6 540 PSMA wt/wt, the enthalpy of mixing is higher than the limit of Flory Huggin's theory 541 (10 -3 cal/mol), which changes to the incompatibility on increase further PSMA weight 542 fraction turn to the compatible state. Therefore, from the Schneier equation 543 calculation, the system is partially compatible, which allows further investigation, 544 such as MD Simulations, compared to the experimental DSC approach. In Fig. 11. 545 From these (12, it is seen that Gibb's free energy is dependent on the enthalpy of 546 mixing calculated from the Schneier equation, the entropy of mixing and temperature 547 at which polymer blend system, higher temperature > 298 K as higher than 400K the 548 system is thermodynamically compatible with an increase pf PSMA polymer 549 composition in the blend system.