DPD Study On Different Topological Structure Of Nano-particle/Diblock Copolymer

Compared with nanosphere, nanochain and nanorod with different topological structure will lead to more complicated phase behavior and mechanical behavior in the polymer matrix owing to that the orientational entropy generated by anisotropy, when the diblock copolymer assembled with the nano-particles. The self-assembly structure of the A3B7 diblock copolymer will be destroyed by the mixture models of nanochains/A3B7, nanorods/A3B7 and nanoparticles/A3B7, and the A3B7 can form a cylinder structure by self-assembly. The internal mechanism of the phase behavior was studied by the entropy and enthalpy of model system which guided by the orientational entropy. The stress-strain curve of nano-composite materials has been simulated which can guide the application in practice. The phase behavior and mechanical behavior in the self-assembly of the diblock and the nano-particles has been studied in detail by the Dissipative Particle Dynamics (DPD) method. This paper has been divided into four chapters.The research development of the application of the computer simulation in the polymer science has been studied, which includes the self-assembly of the nanospheres, nanocube, nanorod and nanochain, and the overview of the DPD method.The effect of the concentration, length, flexibility of the nanoparticles on the self-assembly, when the nanoparticles with different topological structure (nanoparticles, nanorods and nanochains) self-assembled with the diblock copolymer, has been introduced in detail. The cylinder structure of the A3B7 and the lamellar structure of the A5B5 will be destroyed by nanoparticles, when the nanoparticles reach to a certain level of concentration. The cylinder structure will be formed by the self-assembly of the nanochain and A3B7 with more addition of the nanochain. When more nano-particles were added, the phase diagram is disorder. Furthermore, the self-assembly behavior of nanochain/A3B7 is not only associated with the length of the nanochain, the flexibility of the nanochain is also a main effect factor. The result showed that the cylinder structure of the composites cannot be formed by the self-assembly of the A3B7 and the nanochain with a short-chain-length, but the nanochain with medium-chain (the k=4 or k=8) and long-chain (the k=8 or k=12).The effect of the elongation rate, the concentration, length and flexibility of the nano-particles and stress direction on the stress-strain curve, when the nanoparticles with different topological structure (nanoparticles, nanorod and nanochain) self-assembled with the diblock copolymer, has been studied in detail. The result showed that the Young modulus, yield stress and tensile strength of the copolymer increases with an increase of stretching rate, when the elongation rate is reasonable. The rigidity and anti-stretching properties increase with an increase of the concentration of the nano-particles. The mechanical properties of the composites will be improved effectively with an appropriate length of the nanochain, when the length of the nanochain is reasonable. The effect of the flexibility of the nanochain on the mechanical properties of composites has been discussed as the fourth factor. The effect of the nanoparticles on the improvement of the rigidity of composites has been studied, and the result showed that the reinforcing effect of the nanorod is best, the reinforcing effect of nanochain is second-best, and the reinforcing of nano-particles is worst. Furthermore, the flexibility of the nanochain has an great effect on the Young modulus of the composites, and the rigidity of the nano-composites materials increase with an increase of the rigidity of the nanochain. The effect of tensile direction on the tensile properties has been studied. The result showed that the tensile properties of the nano-composites with the tensile direction, which is parallel to the alignment direction of the nanochain, is better than the tensile properties of the nano-composites with the tensile direction, which is perpendicular to the alignment direction of the nanochain.The summary and expectation of the article has been introduced in the chapter four.