Multi-scale Simulation Of Polymer Membrane Consisted Of PMMA-Calixarene

Multi-scale simulation is performed to study the polymer membrane consists of PMMA-Calixarene. The residual solvents' influence on the micro structure of the polymer was studied. The multi-scale simulation includes meso, micro and quantum scale.Mesoscopic structure of polymer membrane contains small amount of solvent was simulated by using dissipative particle dynamic (DPD) method. In this method the polymer chain is represented using a coarse-gained model. The calculated cutoff distance is roughly 0.76nm. The interaction parameters of Flory-Huggins theory are estimated by calculating the cohesive energy between different components. When the system reaches equilibrium, a mesoscopic structure and concentration distribution of each component was obtained. Inside the polymer, the chloroform (CHCl₃) was found to aggregate around the Calixarene group, the tetrahydrofuranz (THF) molecules to stick together and H₂O molecules evenly distributed troughout the film.Atomistic structure of the polymer membrane is generated by mapping atoms to the concentration profile of each component in the meso-scale structure through Hybrid Monte Carlo technique. Then, a molecular dynamics simulation is performed. The self-diffusion coefficients of solvent molecules are calculated with respect to the solvent content. The results show that the the chloroform (CHCl₃) aggregated around the Calixarene group may exist in the form of cluster. With the increasing of solvent content, the clusters become larger and the self-diffusion coefficients are also larger.The first proton dissociation energy form the hydroxyle groups of the Calixarene in the polymer is calculated using both Density Function Theory (DFT) and empirical quantum methods. PBE exchange-correlation function and DNP basis set in DFT was used to calculate the first proton dissociation energy with MMA chain length less than 4. Then AM1, PM3, AM1* of empirical quantum method was chosen to calculate the same energy of the polymer with MMA chain length larger than 4, less than 8. The results show that among empirical quantum calculation methods, PM3 seems more suitable for this polymer system. Simulation results suggest that the PMMA makes the dissociation easier up to 8 MMA. Calculation results indicate that the stereo tacticity of the polymer has strong influences on the dissociation energy. In addition, solvents such as chloroform may help reduce the disassociation energy.