Hybridization of poly(4-vinyl pyridine)-b-polystyrene-b-poly(4-vinyl pyridine) aggregates in dioxane/water solution

Self-assembly of binary blends of two triblock copolymers of poly(4-vinyl pyridine)-b-polystyrene-b-poly(4-vinyl pyridine), i.e., P4VP(43)-b-PS260-b-P4VP(43) (P1) and P4VP(43)-b-PS366-b-P4VP(43) (P2), in dioxane/water solution was studied. These two triblock copolymers individually tend to form vesicles (P2) and cylindrical micelles (P1) in dilute solution. It was found that copolymer components in the blend, sample preparation method, and annealing time had significant effect on hybridization aggregate morphology. By increasing P1 content in the copolymer blends, fraction of looped and stretched cylinders increased, while fraction of bilayers decreased. Nearly no bilayer was observed when P1 content was above 85 wt%.

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.

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.

Near-infrared polymer light-emitting diodes based on infrared dye doped poly(N-vinylcarbazole) film

Infrared light-emitting diodes possess potential applications in optical communication and safety detection. in this paper, we fabricated near-infrared light-emitting diodes possess potential applications in optical communication and safety detection. in this paper, we fabricated near-infrared polymer light-emitting diode employing a commercial near-infrared (NIR) organic dye as an emissive dopant dispersed within poly(N-vinylcarbazole) (PVK) by spin-casting method. The used device structure was indium tin oxide/3,4-polyethylene-dioxythiophene-polystyrene sulfonate/PVK: NIR dye/Al.

The effect of annealing treatment on performance of interdiffused organic photovoltaic devices

We fabricated the interdiffused organic photovoltaic devices, which composed of poly (2-methoxy-5-(2'-ethylhexyloxy)-1, 4-phenylenevinylene) (MEH-PPV) and buckminsterfullerene (C-60), by annealing treatment. After annealing, C60 diffused into the MEH-PPV layer, in consequence, MEH-PPV/C-60 interfacial area was increased and their interface became closer proximity. The results lead to reduce reverse-bias saturation current (J(s)), and increase the open-circuit voltage (V-OC) and the short-circuit current (J(SC)).

Effects of thermal annealing on polymer photovoltaic cells with buffer layers and in situ formation of interfacial layer for enhancing power conversion efficiency

We have investigated the effects of thermal annealing before and after cathode deposition on poly(3-hexylthiophene)(P3HT)/[6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend photovoltaic cells with different cathode buffer layers. The introduction of cathode buffer layer such as lithium fluoride (LiF) and calcium oxide (CaO) in pre-annealing cells can increase the open-circuit voltage (V-oc) and the power conversion efficiency (PCE). Post thermal annealing after cathode deposition further enhanced the PCE of the cells with LiF/Al cathode.

Multilayered core-shell structure of the dispersed phase in high-impact polypropylene

The multiphase morphology of high impact polypropylene (hiPP), which is a reactor blend of polypropylene (PP) with ethylene-propylene copolymer, was investigated by transmission electron microscopy, selected area electron diffraction, atomic force microscopy, and field-emission scanning electron microscopy techniques in conjunction with an analysis of the hiPP composition and chain structure based on solvent fractionation, C-13-NMR, and differential scanning calorimetry measurements.

Surface potential images of polycrystalline organic semiconductors obtained by Kelvin probe force microscopy

P-type copper phthalocyanine (CuPc) and n-type hexadecafluorophthalocyanina-tocopper (F16CuPc) polycrystalline films were investigated by Kelvin probe force microscopy (KPFM). Topographic and corresponding surface potential images are obtained simultaneously. Surface potential images are related with the local work function of crystalline facets and potential barriers at the grain boundaries (GBs) in organic semiconductors. Based on the spatial distribution of surface potential at GBs, donor- and acceptor-like trapping states in the grain boundaries (GBs) of p-CuPc and n-F16CuPc films are confirmed respectively.

Improved Melting Strength of Polypropylene by Reactive Compounding With Ultrafine Full-Vulcanized Polybutadiene Rubber (UFBR) Particles

Ultrafine full-vulcanized polybutadiene rubber (UFBR) in particle sizes of ca. 50-100 nm has been used for modifying mechanical and processing performances of polypropylene (PP), and PP-g-maleic anhydride (PP-MA) has been used as a compatibilizer for enhancing the interfacial adhesion between the two components. The results show that PP/UFBR possesses rheological behaviors such as highly branched PP when UFBR content in blends reaches 10 wt%, while in contrast, the much low content of UFBR combining small amount of PP-MA endows the material with rheological characteristics of high melt strength materials like highly branched PP.

A strategy of fabricating exfoliated thermoplastic polyurethane/clay nanocomposites via introducing maleated polypropylene

By reducing the attraction between the platelets of octaclecylammonium chloride modified montmorillonite (OMMT-C18) via pre-intercalation of maleated polypropylene (MAPP), OMMT-C18 was exfoliated in thermoplastic polyurethane (TPU) matrix during melt-mixing. Wide angle X-ray diffraction, transmission electron microscopy and thermogravimetric analysis were used to investigate the microstructure of TPU nanocomposites. Three factors (including introducing sequence, the kind and the content of MAPP) showed important effects on the dispersion degree of OMMT-C18 in TPU matrix. The results confirmed that the pre-intercalation of MAPP was necessary for the exfoliation of OMMT-C18; however, the role of MAPP in TPU nanocomposites was different from that in polypropylene nanocomposites.

Novel NIR-absorbing conjugated polymers for efficient polymer solar cells: effect of alkyl chain length on device performance

Three low bandgap conjugated polymers, i.e., PDTPBT-C8, PDTPBT-C6 and PDTPBT-C5, which consist of alternating N-alkyl dithieno[3,2-b: 2',3'-d] pyrrole and 2,1,3-benzothiadiazole units and carry 1-octylnonyl, 1-hexylheptyl and 1-pentylhexyl as side chains, respectively, were synthesized. These polymers show strong absorption in the wavelength range of 600-900 nm with enhanced absorption coefficient as the length of alkyl chain decreases. The film morphology of the polymers and 1-(3-methoxycarbonyl) propyl-1-phenyl-[6,6]-C-61 (PCBM) blends is also dependent on the alkyl chain length. As the length decreases, the film becomes more uniform and the domian size decreases from 400-900 nm for PDTPBT-C8 to similar to 50 nm for PDTPBT-C5.

Combined Effects of Hot Curing Conditions and Reaction Heat on Rubber Vulcanization Efficiency and Vulcanizate Uniformity

A mathematical model of the chemical kinetics of silicone rubber Vulcanization is developed, with the thermal effects being computed using the increment method, and the hot Vulcanization process estimated with the finite element method. The results show that the reaction heat of rubber vulcanization is important for energy saving, and that a proper curing medium temperature is important when considering both vulcanization efficiency and vulcanizate uniformity. The results also indicate that increases in the forced convective heat transfer coefficient have no significant effect above a certain level. The validity of the numerical model is indirectly proven by comparison with existing data.

Simulation of Banded Spherulite Patterns by Coupled Logistic Map Lattice Model in Three Dimensions

Banded spherulite patterns are simulated in three dimensions by means of a Coupled Logistic map lattice model. The patterns obtained by numerical calculation are consistent with those in experiments. The simulation results also indicate that the hand spacing is decreased with the increase of parameter mu in the Logistic map and increased with the increase of the coupling parameter e for cube lattices, and increased with the increase of the thickness of the lattice for polymer film, which is quite similar to the results in some experiments. Spiral pattern in three dimensions is also shown in this paper, which helps us understand the form of banded spherulite in polymers.

Investigation of the dewetting inhibition mechanism of thin polymer films

The mechanism of inhibition of polymer film dewetting is investigated by adding a star comb-like polymer, four-arm P(S-ran-VB-g-PMMA), to PS film and PMMA film on different substrates. It is found that the mechanism of inhibition of polymer film dewetting is kinetic in nature, and is related to the miscibility between the additional compound and the polymer film. On addition to the miscible system [four-arm P(S-ran-VB-g-PMMA) and PMMA], the star comb-like polymers can increase the resistant force of dewetting with hole growth and inhibit the dewetting process of the thin polymer film by enrichment in the rim.

Simulation Study of Aggregate Morphologies Formed by ABC Linear Triblock Copolymers in a Selective Solvent Through the Self-Consistent Field Theory

The effect of the hydrophobic properties of blocks B and C on the aggregate morphologies formed by ABC linear triblock copolymers in selective solvent was studied through the self-consistent field theory. Five typical micelles, such as core-shell-corona, hamburger-like, segmented-wormlike, were obtained by changing the hydrophobic properties of blocks B and C. The simulation results indicate that the shape and size of micelle are basically controlled by the hydrophobic degree of the middle block B, whereas the type of micelle is mainly determined by the hydrophobic degree of the end block C.