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Wu N.,Qingdao University of Science and Technology | Wu N.,Key Laboratory of Molecular Engineering of Polymers | Yang P.,Qingdao University of Science and Technology
Acta Polymerica Sinica | Year: 2010

The crystallization and the phase morphology of polypropylene/poly (methy methacrylate) (PP/ PMMA) incompatible blends were studied by using polarizing microscopy and discrepancy microscopy. Polypropylene-g-malaie anhydride (PP-g-MAH) was used as a compatibilizer for PP/PMMA blends,the results from the polarized micrographs showed that PP crystalline form became incomplete and PP crystal size decreased because of the crystallization of PP conquering more energy barrier. The results showed that the compatibility of PP and PMMA phases became better, and the interface areas between PP and PMMA phases became unclear in the PP/PMMA/PP-g-MAH blends. When the MAH graft yield of PP-g-MAH was increased, the size distribution of PMMA phase became uniform and the size of PMMA phase decreased. When the graft yield of PP-g-MAH was 2. 41 wt% and the concentration of PP-g-MAH in PP/PMMA/PP-g-MAH blends was 4.71 wt%, the size of PMMA dispersed phase showed a minimum value. PP-g-MAH was a reactive compatibilizer, on the one hand, PP segments of PP-g-MAH and PP homopolymer were crystallized together ; on the other hand,the acid anhydride groups of MAH were linkaged with the ester groups of PMMA by covalence. The conformation of PP-g-MAH in the interface between PP and PMMA phases decreased the whole system entropy and improved the compatibility of PP/PMMA blends. PP/PMMA and PP/PMMA/PP-g-MAH blend was isothermal crystallized at 130°C. The polarized micrographs showed that the PP crystallization for the PP/ PMMA blend exhibited the characteristics of homogeneous nucleation; and PP crystal size for PP/PMMA blends was larger than that for PP/PMMA/PP-g-MAH blend. PMMA phase size for PP/PMMA blend after isothermal crystallization at 130°C was obviously larger than the corresponding PMMA phase size under nonisothermal crystallization. Source


Xu Y.,Key Laboratory of Molecular Engineering of Polymers | Xu Y.,Fudan University | Li W.,Key Laboratory of Molecular Engineering of Polymers | Li W.,Fudan University | And 5 more authors.
Physical Chemistry Chemical Physics | Year: 2011

The phase behaviors of A(BC)nBA′ linear multiblock terpolymers are investigated using the pseudo-spectral method of self-consistent field theory by varying the volume fractions of different blocks. The relative stability among the lamellae-in-lamellae structures with different BC internal layers is tuned by the volume fraction of the two long tails. A larger A volume fraction favors the formation of structures with fewer BC thin layers. When the volume fraction of A is increased further, a hierarchical cylinder phase can be formed because of the effect of the spontaneous curvature and vice versa. The separation between B and C significantly reduces the phase regime of the cylinder, especially for the case of small A volume fraction. © the Owner Societies 2011. Source


Li W.,Key Laboratory of Molecular Engineering of Polymers | Li W.,Fudan University | Qiu F.,Key Laboratory of Molecular Engineering of Polymers | Qiu F.,Fudan University | And 3 more authors.
Macromolecules | Year: 2010

The ordering dynamics of directed self-assembly of cylinder-forming diblock copolymers is studied by cell dynamics simulations. The directing field, mimicking chemically or topologically patterned substrates, is in the form of hexagonally arranged potential wells attractive to minority blocks. Time evolution of the defect concentration is used to characterize the ordering dynamics of the self-assembled cylindrical structures of the block copolymers. When the period of the external potential, Ls, is a small integer multiple of the cylinder-to-cylinder distance, Lo, of the block copolymer microphase, the defect concentration decays exponentially. The defect annihilation becomes slower as Ls is increased, and eventually, the exponential decay law is broken. When the ratio Ls/L0 is a square root of an integer, large polycrystalline grains with different orientations are observed. The results are consistent with available experimental and theoretical results. © 2010 American Chemical Society. Source


Li W.,Key Laboratory of Molecular Engineering of Polymers | Xie N.,Key Laboratory of Molecular Engineering of Polymers | Xie N.,Fudan University | Qiu F.,Key Laboratory of Molecular Engineering of Polymers | And 4 more authors.
Journal of Chemical Physics | Year: 2011

The ordering kinetics of directed assembly of cylinder-forming diblock copolymers is investigated by cell dynamics simulation of the time-dependent Ginzburg-Landau theory. The directing field, mimicking chemically or topologically patterned surfaces, is composed of a rectangular array of potential wells which are attractive to the minority blocks. The period of the templating fields is commensurate with the hexagonal lattice of the block copolymer domains. The ordering kinetics is described by the time evolution of the defect concentration, which reveals that the rectangular field of [1 m] for a given density multiplication has the best directing effect, and the reversed case of [m 1] has the worst. Compared with a hexagonal directing field, the rectangular field provides a better directing efficiency for a fixed high density multiplication. The difference of the directing effect can be understood by analyzing the ordering mechanisms in the two types of directing fields. The study reveals that the rectangular pattern is an alternative candidate to direct block copolymer assembly toward large-scale ordered domains. © 2011 American Institute of Physics. Source


Xu Y.,Key Laboratory of Molecular Engineering of Polymers | Xu Y.,Fudan University | Li W.,Key Laboratory of Molecular Engineering of Polymers | Li W.,Fudan University | And 5 more authors.
Journal of Physical Chemistry B | Year: 2010

The phase behaviors of multiblock terpolymer A(BC)nB (or A(BC)n) with equal volume fractions of A and compositional symmetric (BC)nB (or (BC)n) are investigated by using the pseudospectral method of the self-consistent mean field theory. These terpolymers can self-assemble into hierarchical lamellar phases of perpendicular or parallel lamellae within lamellae, and the number of B/C thin layers in the parallel phase can be varied. The relative stability among these hierarchical lamellar phases can be tuned by the three interaction parameters of ΞABN, ΞACN, and ΞBCN. Two-dimensional phase diagrams, the cross sections of the three-dimensional phase diagram, are determined in our calculations. Our conclusion that the perpendicular phase is stable only in the case of ΞACN ≪ ΞABN < ΞBCN is consistent with experimental observations by Bates's group. In addition, our results suggest that the existence of the perpendicular phase is generic in both types of terpolymers: A(BC)nB and A(BC) n, with different values of n, even for the special case of A(BC)n, that is, an ABC linear terpolymer. © 2010 American Chemical Society. Source

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