We synthesized a highly crystalline DPP-based polymer, DPPBTSPE, which contained 1,2-bis(5-(thiophen-2-yl)selenophen-2-yl)ethene as a planar and rigid electron donating group. High- and low-molecular weight (MW) DPPBTSPE fractions were collected by Soxhlet extraction and were employed to investigate their unique charge transport properties in macroscopic films and single crystalline polymer nanowire (SC-PNW), respectively. The low-MW polymer could provide well-isolated and high aspect ratio SC-PNWs, in which the direction of π-π stacking was perpendicular to the wire growing axis. The field effect transistors made of SC-PNWs exhibited remarkably high carrier mobility of 24 cm(2) V(-1) s(-1). In addition, phototransistors (PTs) made of SC-PNW showed very high performance in terms of photoresponsivity (R) and photoswitching ratio (P). The average R of the SC PNW-based PTs were in the range of 160-170 A W(-1) and the maximum R was measured at 1920 A W(-1), which is almost three orders higher than that of thin film-based PT device.

SynopsisSorption isotherms and diffusion coefficients of water in a 0.3-mil Kapton polyimide film at 30,45, and W C are reported. The data are well described by the dual mode sorption and transport models at low activities. At high penetrant activities, clustering of water is suggested by a Zimm-Lundberg analysis of the sorption data and the fact that the diffusion coefficient for water decreases with increasing external vapor activity. The effect of temperature on the diffusion coefficients at infinite dilution and the dual mode sorption parameters kD, b, and Ch are presented and discussed. The magnitude of the activation energy of the diffusion coefficient at infinite dilution, 5.4 kcal/mol, is smaller than the corresponding activation energy in more flexible chain polymers, perhaps suggesting that rather small backbone motions are associated with diffusion of water through the Kapton matrix. The predictions for the isosteric enthalpy of sorption from the dual mode model are presented and compared with the values determined from graphical analysis of the sorption isotherms performed independently without reference to the dual mode sorption model.

The first demonstration of polymer nanowire (PNW) crystals based on a diketopyrrolopyrrole-based copolymer (i.e., PDTTDPP), and their application to field-effect transistors (FETs) is reported. Remarkably, transmission electron microscopy and selected area electron diffraction analyses of the PNW reveal its single-crystalline (SC) nature. FETs fabricated of a SC PNW exhibit a maximal charge carrier mobility of ≈7.00 cm(2) V(-1) s(-1) , which is almost one order of magnitude higher than that of the thin-film transistors made of the same polymer (PDTTDPP).

SynopsisA comparison of water sorption and diffusion behavior in 2 mil, as-received, Kapton @ film, and in otherwise identical but hygrothermally aged samples, suggests chemical differences between the samples. These differences can be related to known polyimide chemistry and the specific history encountered by the samples. Although the sorption isotherms are similar for an as-received 0.3 mil sample studied earlier and for the as-received 2 mil samples studied here, the diffusion coefficient of water in the as-received 2 mil sample is approximately 300% larger than in the as-received 0.3 mil sample. This large effect is believed to be related to the presence of small, paracrystalline aggregates with large aspect ratios. Differences in orientation measured by birefringence for the two samples suggest that the bamer properties of Kapton@ are strongly affected by the detailed morphological organization of the ordered aggregates. Comparison of the sorption isotherms for the as-received and hygrothermally aged 2-mil films suggests a significant increase in the hydrophillic nature of the aged film. This change is consistent with an apparent chemical reaction between water and uncyclized amic acid residues in the film. The tendency for water to cluster in as-received Kaptono is essentially eliminated by the chemical modification associated with hygrothermal aging. The hygrothermal aging produces a dramatic reduction in the water vapor diffusion coefficient at low vapor activities but a rather modest change at high activities.

A new tellurophene-based π-conjugated polymer, PDTDPPTe, was synthesized. PDTDPPTe exhibits a smaller optical band gap (E(g)(opt) = 1.25 eV) than thiophene-based PDTDPPT (E(g)(opt) = 1.30 eV). Thin-film transistors comprising PDTDPPTe displayed outstanding performance (μ(max) = 1.78 cm(2) V(-1) s(-1), I(on)/I(off) = 10(5-6)).

Diketopyrrolopyrrole (DPP)-based conjugated polymer PDTDPPQT was synthesized and was used to perform epitaxial polymer crystal growth on removable 1,3,5-trichlorobenzene crystallite templates. A thin-film transistor (TFT) was successfully fabricated in well-grown large spherulites of PDTDPPQT. The charge carrier mobility along the radial direction of the spherulites was measured to be 5.46-12.04 cm(2) V(-1) s(-1), which is significantly higher than that in the direction perpendicular to the radial direction. The dynamic response of charge transport was also investigated by applying a pulsed bias to TFTs loaded with a resistor (∼20 MΩ). The charge-transport behaviors along the radial direction and perpendicular to the radial direction were investigated by static and dynamic experiments through a resistor-loaded (RL) inverter. The RL inverter made of PDTDPPQT-based TFT operates well, maintaining a fairly high switching voltage ratio (Vout(ON)/Vout(OFF)) at a relatively high frequency when the source-drain electrodes are aligned parallel to the radial direction.

A new bitellurophene-based π-conjugated polymer (PDPPBTe) was synthesized and its semiconducting property was utilized for detecting Br2. The PDPPBTe polymer exhibited a highly sensitive response to Br2, which was indicated by a significant variation of the drain current in thin-film transistors.

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