Rigidity effect on phase behavior of symmetric ABA triblock copolymers: A Monte Carlo simulation

The phase behavior of symmetric ABA triblock copolymers containing a semiflexible midblock is studied by lattice Monte Carlo simulation. As the midblock evolves from a fully flexible state to a semiflexible state in terms of increase in its persistence length, different phase behaviors are observed while cooling the system from an infinite high temperature to a temperature below T-ODT (order-disorder transition temperature). Within the midblock flexibility range we studied (l(p)/N-c <= 0.105), a lamellar structure is formed at equilibrium state as the situation for fully flexible chains. The fraction of bridge chain is evaluated for the lamellar structures. We find that the increase in midblock rigidity indeed results in the increase in bridge chain fraction within the range from 44.9% to 51.8%.

Molecular weight dependence of phase Behavior of PEO/P(EO-b-DMS) blends: Application of Sanchez-Lacombe lattice fluid theory

Molecular weight dependence of phase separation behavior of the Poly (ethylene oxide) (PEO)/Poly(ethylene oxide-block-dimethylsiloxane) (P(EO-b-DMS)) blends was investigated by both experimental and theoretical methods. The cloud point curves of PEO/P(EO-b-DMS) blends were obtained by turbidity method. Based on Sanchez-Lacombe lattice fluid theory (SLLFT), the adjustable parameter, epsilon*(12)/k (quantifying the interaction energy between different components), was evaluated by fitting the experimental data in phase diagrams. To calculate the spinodals, binodals, and the volume changes of mixing for these blends, three modified combining rules of the scaling parameters for the block copolymer were introduced.

The phase behavior of comblike block copolymer A(m+1)B(m)/homopolymer A mixtures

The phase behaviors of comblike block copolymer A(m+1)B(m)/homopolymer A mixtures are studied by using the random phase approximation method and real-space self-consistent field theory. From the spinodals of macrophase separation and microphase separation, we can find that the number of graft and the length of the homopolymer A have great effects on the phase behavior of the blend. For a given composition of comblike block copolymer, increasing the number of graft does not change the macrophase separation spinodal curve but decreases the microphase separation region. The addition of a small quantity of long-chain homopolymer A increases the microphase separation of comblike block copolymer/homopolymer A mixture.

Phase transition behavior and molecular orientation of oligo(9,9 '-dioctylfluorene-alt-bithiophene)

A novel conjugated oligomer, oligo(9,9'-dioctylfluorene-alt-bithiophene) (OF8T2), was found to exhibit a unique phase transition between crystalline and liquid-crystalline states, and a liquid-crystalline glass was easily generated, offering better TFT device performance. In thin films, upon annealing the OF8T2 molecules oriented preferentially with their planes of conjugation being normal to the substrate, and both film thickness and annealing temperature were critical to the film morphology and the molecular orientation. When the OF8T2 film was deposited on a rubbed polyimide surface and annealed, the molecules aligned their long axes along the rubbing direction.

Effect of shear on the crystallization behavior of glass bead filled polypropylene

Linkam CSS450 optical shearing stage, wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering(SAXS) were used to investigate the effect of shear on crystal structure and crystallization morphology of the glass bead filled polypropylene( PP). The results indicate that the glass bead worked as nucleating agent for the glass bead filled PP, compared with pure PP it restrained the formation of beta-crystal after shear treatment. When the mean size of glass bead is smaller(4 mu m) shear rate had less effect on the formation of beta-crystal of PP obviously.

Critical behavior of brittle-ductile transition of polymers

We report that the brittle-ductile transition of polymers induced by temperature exhibits critical behavior. When t close to 0, the critical surface to surface interparticle distance (IDc) follows the scaling law: IDc proportional to t(-v) where t = 1 - T/T-BD(m) (T and T-BD(m) are the test temperature and brittle-ductile transition temperature of matrix polymer, respectively) and v = 2/D. It is clear that the scaling exponent v only depends on dimension (D). For 2, 3, and 4 dimension, v = 1, 2/3, and 1/2 respectively. The result indicates that the ID, follows the same scaling law as that of the correlation length (xi), when t approach to zero.

Crystallization behavior of a thermoplastic polyimide derived from 3,3 ',4,4 '-oxydiphthalic dianhydride and 4,4 '-oxydianiline

Nonisothermal and isothermal crystallization kinetics of an aromatic thermoplastic polyimide derived from 3,3',4,4'-oxydiphthalic dianhydride and 4,4'-oxydianiline have been investigated by means of differential scanning calorimetry (DSC) and wide-angle X-ray diffraction. The results for nonisothermal crystallization study showed that a weak melting peak appeared during the first heating process, whereas no crystallization peak appeared in the DSC curve during the subsequent cooling process. On the other hand, the study for the isothermal crystallization in the temperature range of 260-330 degrees C showed that a new exothermic peak appeared at lower temperature for the samples crystallized for 100 min at 300 degrees C.

Dewetting behavior of polystyrene film filled with (C6H5C2H4NH3)(2)PbI4

The dewetting behavior of thin (about 30 nm) polystyrene (PS) films filled with different amount of (C6H5C2H4NH3)(2)PbI4 (PhE-PbI4) on the silicon substrate with a native oxide layer was investigated. For different additive concentrations, PhE-PbI4 showed different spatial distributions in the PS films, which had a strong influence on the film wettability, dewetting dynamics, and mechanism. With 0.5 wt % additive, PhE-PbI4 formed a noncontinuous diffusion layer, which caused a continuous hole nucleation in the film. With about 1 wt % additive, a continuous gradient distribution layer of PhE-PbI4 formed in the film, which inhibited the dewetting.

Effect of interfacial roughness on dewetting behavior of polystyrene/poly(methyl methacrylate) bilayer film

The dewetting behavior of polystyrene (PS) film on poly(methyl methacrylate) (PMMA) sublayer was investigated by changing the short-range roughness of the PMMA sublayer systemically. When the bilayer film was heated to the temperature above both Tgs, the protuberances formed in both layers to reduce the system energy. By tracing the dewetting process of the PS up-layer, the dewetting velocity was found to increase with the roughness of the sublayer.

The electrochemical behavior of a system with a limited number of molecules

In this paper, based on Einstein relationship between diffusion and random walk, the electrochemical behavior of a system with a limited number of molecules was simulated and explored theoretically. The transition of the current vs time responses from discrete to continuous was clearly obtained as the number of redox molecules increased from 10 to 10(6).

Infrared spectroscopic study on thermal behavior of Langmuir-Blodgett films of octadecyl ammonium octadecanoate and octadecylammonium octadecanoate-d(35)

Langmuir-Blodgett (LB) films of octadecylammonium octadecanoate (C(18)H(37)j7NH(3)(+)C(17)H(35)COO(-),ODASA) and octadecylammonium octadecanoate-d(35) (C18H37+NH3+C17D35COO-, ODASA-d(53)) were prepared and their thermal behaviors were investigated by variable-temperature Fourier transform infrared transmission spectroscopy. It was found that the two hydrocarbon chains of ODASA molecule in LB films are highly ordered while that protonated (H) chain in ODASA-d(35) is partially disordered with some gauche conformers introduced at room temperature.

The release behavior of doxorubicin hydrochloride from medicated fibers prepared by emulsion-electrospinning

The release behavior of a water-soluble small molecule drug from the drug-loaded nanofibers prepared by emulsion-electrospinning was investigated. Doxorubicin hydrochloride (Dox), a water-soluble anticancer agent, was used as the model drug. The laser scanning confocal microscopic images indicated that the drug was well incorporated into amphiphilic poly(ethylene glycol)-poly(L-lactic acid) (PEG-PLA) diblock copolymer nanofibers, forming "core-sheath" structured drug-loaded nanofibers.

Weak epitaxy growth and phase behavior of planar phthalocyanines on p-sexiphenyl monolayer film

We systematically investigated the weak epitaxy growth (WEG) behavior of a series of planar phthalocyanine compounds (MPc), i.e., metal-free phthalocyanine (H2PC), nickel phthalocyanine (NiPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), iron phthalocyanine (FePc); cobalt phthalocyanine (CoPc), grown on a p-sexiphenyl (p-6P) monolayer film by selected area electron diffraction (SAED) and atomic force microscopy (AFM). Two types of epitaxial relations, named as incommensurate epitaxy and commensurate epitaxy, were identified between phthalocyanine compounds and the substrate of the p-6P film.

Ion-Responsive Behavior of Ionic-Liquid Surfactant Aggregates with Applications in Controlled Release and Emulsification

We propose a simple but efficient, rapid, and quantitative ion-responsive micelle system based on counter-anion exchange of a surfactant with an imidazolium unit. The ion-exchange reaction results in the amphiphilic-to-hydrophobic transition of the imidazolium salt, leading to the destruction of the micelles, which has been successfully applied to control led release and emulsification.