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Molecular Simulation of the Miscibility for Polymer Blends

Author: XueZhaoJun
Tutor: ZhuangQiZuo
School: East China University of Science and Technology
Course: Polymer Chemistry and Physics
Keywords: Molecular Simulation Miscibility Flory - Huggis RDF
CLC: O631.3
Type: Master's thesis
Year: 2012
Downloads: 186
Quote: 1
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Abstract


Polymer blend of poly(2,6 - dimethyl - 1,4 - phenylene ether)(PPE) and poly(styrene-co- acrylonitrile) (SAN), which has broad commercial interest, has limited miscibility. Atriblock terpolymer, polystyrene - block - polybutadiene - block - poly(methyl methacrylate) (SBM), is often used as compatibilizer to improve the miscibility of PPE/SAN. In this work, dissipative particle dynamics and molecular dynamics of Material Studio were used to study the essentials that influence miscibility of the blend systems, and then Flory-Huggins parameter v, radial distribution function (RDF) and morphologies are analyzed. It shows that the blends with more content of styrene in SAN (above 90 wt%), whose mass percentage is 60%, are best miscible. For the systems of PPE/SAN added with SBM, the miscibility increases and then decreases with the increase of SBM content. A longer chain of styrene (S) in SBM leads to wrapped structure of PMMA by PB, wrapped by PS, resulting in decrease of the miscibility. From studies and simulation ofχand RDF, the best blend system for commercial and industrial use is the one with mass ratio of PPE/SAN/SBM 36/54/10, in which S content in SAN is above 90 wt%. For SBM, the ratio of chain length styrene (S)/butadiene (B) is less than 1, while B and M are the same in chain length.High impact polystyrene (HIPS) is a kind of thermoplastic with good impact, which is considered to derive from the biphase of microstructure studied with SEM, etc. In this paper, the influence of polystyrene (PS)/polybutadiene (PB) graft structure to the behavior of HIPS was studied through molecular simulation. The analysis of Flory - Huggis parameterχand radial distribution function (RDF) shows that the blend system of PS/PB has the best miscibility when the mass ratio of PS/PB is 60/40. In the toughening process, however, the graft copolymer PB - g - S is formed. For the PS/PB - g - S system with the same repeat unit of PS, PB - g - S chains with two grafts (PB - g - S(G=2)) are better than PB - g - S chains with one graft (PB - g - S(G=1)) in miscibility.

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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers > The chemical nature of polymers
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