We have studied the electronic states of closely stacked InAs/GaAs quantum dots (QDs) with a 4.0-nm spacer layer using linearly polarized photoluminescence (PL) and time-resolved PL measurements. An increase in the stacking-layer number (SLN) leads to an increase in the linear polarization anisotropy in the (001) plane; the [−110]-polarization component becomes dominant. These SLN-dependent polarization characteristics result from the valence-band mixing induced by the vertically coupled electronic states. The PL spectrum of the stacked QDs shows clear blueshifts with an increase in the excitation power because of the band filling. In addition, the radiative recombination lifetime has been found to obey the T 1/2 dependence, which directly confirms the one-dimensional translational motion of excitons in the closely stacked QDs.

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A series of poly[(tetraethyldisilanylene)(2,5-thienylenes) n ] (1−5) with n = 1−5 were synthesized. The NiCl2(dppe)-catalyzed Grignard coupling of 1,2-bis(5-bromothien-2-yl)tetraethyldisilane (6) and 1,2-bis(5‘-bromo-2,2‘-bithien-5-yl)tetraethyldisilane (7) with 1 equiv of Mg afforded polymer 2 (M w = 53 000, 75% yield) and 4 (M w = 29 500, 97% yield), respectively, while similar reaction of the di-Grignard reagent obtained from 6 and 7 with 1 equiv of 2,5-dibromothiophene afforded the respective polymers 3 (M w = 47 000, 77% yield) and 5 (M w = 17 000, 78% yield). The sodium condensation of 2,5-bis(chlorodiethylsilyl)thiophene afforded polymer 1 (M w = 20 000, 32% yield). Irradiation of polymers 1−5 with a low-pressure mercury lamp resulted in cleavage of the silicon−silicon bonds, but the reactivity decreased with an increase in the number of thienyl units. When the films of polymers 2−5 were doped with FeCl3 vapor, conductivities of doped films were determined to be 10-5−10-3 S cm-1 (in vacuo).

Radical copolymerization behavior of alkyl cyclobutenecarboxylate‐derivatives 4‐6 and related norbornene‐derived compounds 7–9 is described. A variety of alkyl cyclobutenecarboxylates fused with cycloaliphatic framework (4–6) were prepared by [2 + 2] cycloaddition of five, six, and eight‐membered cycloolefins with alkyl propiolates [alkyl = Me, 2‐hydroxyethyl, and 3‐γ‐butyrolactonyl (γ‐BL)]. The fused cyclobutenecarboxylates 4–6 were radically copolymerized with n‐butyl acrylate (nBA) to afford random copolymers, and terpolymerized with alkyl methacrylates with bulky ester groups [alkyl = γ‐BL and 3‐(3‐methyladamantyl)]. The cyclobutane‐containing bicyclic framework incorporated in the resulting polymer backbone contributes to raising Tg of resulting copolymers. Similar results were obtained when a mixture of related norbornene‐derived compounds were used as monomers with an apparently enhanced Tg‐raising effect in the copolymerization with nBA. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2716–2724

The radical copolymerization of alkyl 2-norbornene-2-carboxylates, 1a-c, with alkyl (meth)acrylates, to produce copolymers with norbornane in the main chain, is described here. g-Butyrolactone-and hydroxy group-containing norbornene-based monomers (1b and 1c, respectively) were freshly synthesized, and their radical copolymerization behavior with n-butyl acrylate was examined. Methyl 2-norbornene-2-carboxylate, 1a, and the new monomers, 1b and 1c, were employed as comonomers for radical terpolymerization with lactone-and adamantane-containing (meth)acrylates to produce copolymers that could be applied as new, more chemically robust 193-nm photoresist materials. The dissolution rate of the spin-coated copolymer films after exposure to a photoacid generator, a significant characteristic in the photoresist application, was measured for various exposure doses of 193-nm ArF laser light under standard conditions in an aqueous alkaline solution.