Imide‐functionalized naphthodithiophene based donor‐acceptor conjugated polymers for solar cells

Donor‐acceptor conjugated polymers containing a new imide‐functionalized naphthodithiophene (INDT) as the acceptor unit and a 2,2'‐bithiophene with varied substituents as the donor unit have been synthesized. The bandgaps of these polymers depend strongly on the dihedral angle of the 2,2'‐bithiophene unit. The 3,3'‐dialkoxy substitution (polymers PDOR / PBOR ) leads to near planar bithiophene conformation due to the well‐known S–O short contact, while the 3,3'‐dialkyl substitution (polymer PDR ) results in significant twisting due to the steric effect. Consequently PDOR / PBOR shows the lowest bandgap of 1.82/1.85 eV while PDR has a bandgap of 2.38 eV. Bulk‐heterojunction solar cells of the polymer/fullerene blends have been fabricated. Preliminary results show that PBOR gives the best device performance with power conversion efficiencies as high as 2.45% in air without any thermal annealing treatment, indicating the promising potential of INDT‐containing conjugated polymers for efficient solar cells. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3818–3828     

Polyaniline‐tailored electromechanical responses of the silver/epoxy conductive adhesive composites

In this article, the electromechanical properties of silver‐in‐epoxy conductive adhesives with the polyaniline (PANI) micron particles as cofillers have been investigated. PANI is a conductive polymer and has a moderate conductivity in between those of silver and epoxy. It was found that PANI can be used to tailor both the adhesive's electrical contact resistance and its relaxation behavior; however, the effects of adding PANI were complex. The addition of small amount of PANI (2 wt %) dramatically increased the contact resistance; it might block the electrical contacts among silver flakes and was not able to form a continuous path among themselves. The addition of more PANI showed a moderate increase in contact resistance, which increased with the weight fraction of PANI from 6 to 15 wt %. Interdependent behavior of compressive strain and relaxation in electrical contact resistance is characterized to evaluate the origin of this relaxation. The addition of PANI made the relaxation in electrical contact resistance more sensitive to the compressive strain and the electromechanical coupling to deviate from the linear relationship. These research findings provide insights into the way to use PANI to tailor the electromechanical properties of the adhesive bonds or joints in the development of advanced functional devices. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013, 51, 1448–1455     

Conductive and optical properties of PPV modified by N+ ion implantation

In this article, a soluble poly[2‐methoxy‐5‐(3′‐methyl)butoxy]‐p‐phenylene vinylene (MMB‐PPV) was synthesized by dehydrochlorination reaction and the MMB‐PPV film was implanted by nitrogen ions (N⁺) with the ion dose and energy in the range of 3.8 × 10¹⁵ to 9.6 × 10¹⁶ ions/cm² and 15–35 keV, respectively. The surface conductivity, optical absorption, optical band gap (E_g) of modified MMB‐PPV film were studied, and the third‐order nonlinear optical susceptibility (χ⁽³⁾) as well as its environmental stability of modified MMB‐PPV film were also measured by degenerate four‐wave mixing system. The results showed that the surface conductivity of MMB‐PPV film was up to 3.2 × 10^?2 S when ion implantation was performed with the energy of 35 keV at an ion dose of 9.6 × 10¹⁶ ions/cm², which was seven order of magnitude higher than that of the pristine film. UV‐Vis absorption spectra demonstrated that the optical absorption of MMB‐PPV film was enhanced gradually in the visible region followed by a red shift of optical absorption threshold and the E_g value was reduced from 2.12 eV to 1.59 eV with the increase of ion dose and energy. The maximum χ⁽³⁾ value of 2.45 × 10^?8 esu for modified MMB‐PPV film was obtained with the ion energy of 20 keV at an ion dose of 3.8 × 10¹⁶ ions/cm², which was almost 33 times larger than that for pristine film. In comparison to the reduction of 17% in the χ⁽³⁾ value of pristine MMB‐PPV film, the maximum χ⁽³⁾ value of 2.45 × 10^?8 esu for modified MMB‐PPV film decreased by over 5.3% when they had been exposed under the same ambient conditions for 90 days. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2072–2077, 2010     

Photoinitiated alternating copolymerization of dialkyl maleates and fumarates with vinyl ethers

A systematic study of the free radical photoinitiated alternating crosslinking copolymerizations of dialkyl maleates and furmarates with multifunctional vinyl ethers was carried out. The photocopolymerizations were fast and highly efficient when carried out using a variety of α‐cleavage photoinitiators. The effects of the structures of the both the unsaturated esters and the vinyl ether monomers were examined. Dialkyl maleates were observed to be more reactive than the corresponding fumarate esters. The photopolymerization rates of several of these comonomer pairs were compared with standard diacrylate and dimethacrylate monomers. A range of different physical properties can be obtained by varying the length of the alkyl chain on alcohol portion of the unsaturated ester monomer. Prospects for the use of these comonomer systems in UV curable coatings, adhesives, printing inks, and composites are discussed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

LK property for σ-ideals

An ideal J of subsets of a Polish space X has (LK) property whenever for every sequence (An) of analytic sets in X, if lim supn∈HAn∉J for each infinite H then _?n∈G∉J for some infinite G. In this note we present a new class of σ-ideals with (LK) property.     

A model of hysteresis with two inputs

We formulate and analyze a new model of vector hysteresis for the case of two-input signals. We prove the essential mathematical properties of this model and we present the solutions to two identification problems connected with our model.     

Prey-predator systems with intertwined basins of attraction

In this article, we show the existence of intertwined basins of attraction for a class of prey-predator systems, which improves the extant results by deleting some crucial and hard testing conditions.     

Density versions of Schur's theorem for ideals generated by submeasures

We characterize ideals of subsets of natural numbers for which some versions of Schur's theorem hold. These are similar to generalizations shown by Bergelson (1986) in [1] and Frankl, Graham and Rödl (1990) in [7]. Additionally, we prove a generalization of an iterated version of Ramsey's theorem.     

Spaces of idempotent measures of compact metric spaces

We investigate certain geometric properties of the spaces of idempotent measures. In particular, we prove that the space of idempotent measures on an infinite compact metric space is homeomorphic to the Hilbert cube.     

Effect of the Si/Ce molar ratio on the textural properties of rare earth element cerium incorporated mesoporous molecular sieves obtained room temperature

Rare earth Ce-incorporated MCM-41 mesoporous molecular sieves (CeMCM-41) were synthesized via a direct and nonhydrothermal method at room temperature from sodium silicate and ammonium cerium (IV) nitrate as raw materials. Cetyltrimethyl ammonium bromide (CTAB) was used as a template. The resultant samples were characterized by means of powder X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance ultraviolet–visible spectroscopy (UV–vis) and N₂ physical adsorption, respectively. The effect of the Si/Ce molar ratio on the crystalline structure and textural properties of CeMCM-41 was also investigated. The experimental results show that ordered CeMCM-41 mesoporous molecular sieves were successfully synthesized at room temperature and the resultant mesoporous materials have specific surface areas in the range of 594–1369 m²/g and average pore sizes in the range of ca. 2.5–2.8 nm. It has been found that the structural properties are strongly related to the amounts of cerium incorporation. When the cerium content increased in the samples, the intensity of the peak (1 0 0) was gradually reduced, and the surface area and structural regularity were diminished.