Fluorinated aromatic polyimides as high-performance electret materials.

In view of the increasing significance of technology-driven devices such as microelectromechanical systems, energy-harvesting devices, and organic field effect transistors, polymer electret materials with durable electret performance at elevated temperatures become more and more important. However, typical polymer electret materials lose their performance at elevated temperatures. To provide polymer materials with improved electret performance over a broad temperature range, a series of aromatic polyimides with different degree of fluorosubstitution is presented. Isothermal surface potential decay measurements at elevated temperatures reveal that minor differences in the chemical structure have a major influence on the electret behavior. The best performance is found for the polyimide containing a hexafluoroisopropylidene moiety in both the bisanhydride- and the diamine-based unit. Excellent long-term charge storage stability at 120 °C is observed. From the initial surface charge 94% remains after 24 h. This polyimide even tolerates short-term exposure of 30 s at 300 °C with almost no loss of performance. These findings demonstrate that this particular polyimide is suitable for device applications at elevated temperatures during fabrication and use.

Fast diffusion-limited lyotropic phase transitions studied in situ using continuous flow microfluidics/microfocus-SAXS.

Fast concentration-induced diffusion-limited lyotropic phase transitions can be studied in situ with millisecond time resolution using continuous flow microfluidics in combination with microfocus small-angle X-ray scattering. The method was applied to follow a classical self-assembly sequence where amphiphiles assemble into micelles, which subsequently assemble into an ordered lattice via a disorder/order transition. As a model system we selected the self-assembly of an amphiphilic block copolymer induced by the addition of a nonsolvent. Using microchannel hydrodynamic flow-focusing, large concentration gradients can be generated, leading to a deep quench from the miscible to the microphase-separated state. Within milliseconds the block copolymers assembly via a spinodal microphase separation into micelles, followed by a disorder/order transition into an FCC liquid-crystalline phase with late-stage domain growth and shear-induced domain orientation into a mesocrystal. A comparison with a slow macroscopic near-equilibrium kinetic experiment shows that the fast structural transitions follow a direct pathway to the equilibrium structure without the trapping of metastable states.

Association of pre-transplantation positron emission tomography/computed tomography and outcome in mantle cell lymphoma.

Positron emission tomography/computed tomography (PET/CT)-positive findings before autologous SCT (auto-SCT) are associated with inferior PFS and OS in patients with relapsed Hodgkin's and diffuse large B-cell lymphoma. We classified pre-transplant PET/CT performed before auto-SCT as positive or negative to evaluate the impact of pre-transplant PET/CT in mantle cell lymphoma (MCL). In 29 patients, 17 were PET/CT(-) and 12 were PET/CT(+). PET/CT(+) patients were younger (P=0.04), had lower MCL International Prognostic Index (MIPI, P=0.04) scores, but increased bulky adenopathy >5 cm (45% vs 13%, P=0.09). With a median follow-up of 27 months (range: 5-55 months), 7 patients relapsed (4 in the PET/CT(-) group and 3 in the PET/CT(+) group) with 2 deaths in the PET/CT(+) group without a documented relapse. The estimated 2-year PFS was 64% (95% confidence interval (CI): 0.30-0.85) vs 87% (95% CI: 0.57-0.97) in PET/CT(+) and PET/CT(-) patients, respectively (P=0.054). OS was significantly decreased in PET/CT(+) patients (P=0.007), with 2-year estimates of 60% (95% CI: 0.23-0.84) vs 100% in PET/CT(-) patients. A positive pre-transplant PET/CT is associated with a poor prognosis in patients with MCL. Additional factors may impact the prognostic value of PET/CT, as several PET/CT(+) patients remain in remission.