| Summary: | 碩士 === 國立中央大學 === 化學工程與材料工程研究所 === 96 === The osmotic pressure Π and virial coefficients ( B2 and B3 ) of linear and star polymers in good solvents are studied by dissipative particle dynamics simulations.
The dependence of the osmotic pressure on the concentration c is directly caculated by considering two reservoirs separated by a semi-
permeable, fictitious membrane. For linear polymers with chain length N, our simulation results confirm the scaling relations that B2 ~ N3ν in the dilute regime and Π ~ c2.70 in the semi-dilute regime. The exponent is greater than 9/4 due to the nature of soft beads. For star polymers, the scaling relations become B2 ~ Rg3 in dilute regime and Π λcα in semi-dilute regime. Both the prefactor λ and exponent α vary with the arm number but is independent of the arm length. As the arm number is increased, the exponent may rise from 2.7 to 3.07, which is qualitatively consistent with the experimental result.
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