Continuous Illumination of a Conjugated Polymer Causes Strong Enhancement of Photoluminescence.

We present measurements of absorbance and photoluminescence (PL) for films of poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) as a function of temperature (T) and time (t) of illumination. While having no detectable influence on absorbance of this conjugated polymer, our experiments clearly revealed that illumination of PDOPT caused a significant increase in the PL intensity (IPL(T,t)), that is, the emission probability of PDOPT. Without illumination, we always observed a decrease in IPL with time. An increase in IPL was only detectable when the sample was illuminated. Interestingly, while absorption and emission of photons occur on a time scale of nanoseconds, the here-reported changes in the emission probability were slow and occurred on a time scale of minutes to hours. The influence of illumination on changes in IPL(T,t) was qualitatively similar for slowly and rapidly crystallized PDOPT, that is, the degree of crystallinity was not decisive for the observation. The rate of the increase in IPL depended clearly on the power of the illumination light source. As a function of the illumination time, the change in IPL(T,t) was nonmonotonic and depended on sample temperature. We speculate that changes in polymer interactions caused by excited electronic states might have induced slow changes in polymer conformations.

Direct observation of backbone planarization via side-chain alignment in single bulky-substituted polythiophenes.

The backbone conformation of conjugated polymers affects, to a large extent, their optical and electronic properties. The usually flexible substituents provide solubility and influence the packing behavior of conjugated polymers in films or in bad solvents. However, the role of the side chains in determining and potentially controlling the backbone conformation, and thus the optical and electronic properties on the single polymer level, is currently under debate. Here, we investigate directly the impact of the side chains by studying the bulky-substituted poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) and the common poly(3-hexylthiophene) (P3HT), both with a defined molecular weight and high regioregularity, using low-temperature single-chain photoluminescence (PL) spectroscopy and quantum-classical simulations. Surprisingly, the optical transition energy of PDOPT is significantly (∼2,000 cm-1 or 0.25 eV) red-shifted relative to P3HT despite a higher static and dynamic disorder in the former. We ascribe this red shift to a side-chain induced backbone planarization in PDOPT, supported by temperature-dependent ensemble PL spectroscopy. Our atomistic simulations reveal that the bulkier 2,5-dioctylphenyl side chains of PDOPT adopt a clear secondary helical structural motif and thus protect conjugation, i.e., enforce backbone planarity, whereas, for P3HT, this is not the case. These different degrees of planarity in both thiophenes do not result in different conjugation lengths, which we found to be similar. It is rather the stronger electronic coupling between the repeating units in the more planar PDOPT which gives rise to the observed spectral red shift as well as to a reduced calculated electron-hole polarization.

Nickel Catalyst with a Hybrid P, N Ligand for Kumada Catalyst Transfer Polycondensation of Sterically Hindered Thiophenes.

A highly active nickel catalyst with a hybrid P,N ligand is successfully used for the first time for the polymerization of a thiophene monomer with sterically very demanding side groups. The performance of this catalyst is by far not achievable with commercially available standard catalysts. Polythiophenes with special side chain patterns can thus be made with predetermined molecular weight, low dispersity, and high regioregularity, which enable the preparation of various large crystalline superstructures for the investigation of anisotropic optoelectronic properties in the absence of π-π interactions.

Anisotropic Photophysical Properties of Highly Aligned Crystalline Structures of a Bulky Substituted Poly(thiophene).

The photophysical properties of a phenyl-substituted poly(thiophene), poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT), were studied as a function of polarization and degree of orientation of the crystalline structure. Under well-chosen controlled conditions, large-sized spherulitic crystals of PDOPT were successfully prepared from the melt. From polarized optical microscopy and X-ray diffraction, the molecular orientation of PDOPT within the spherulite was determined, indicating that the fastest growth direction of the spherulite was the a-axis. This implied that crystallization of PDOPT was directed by the packing of the side chains rather than the backbones, which are significantly separated. As the crystalline lamellae were all radially oriented, the local absorbance strongly depended on the polarization of the incoming light. Compared to randomly oriented crystals in a quenched and thus rapidly crystallized sample, PDOPT spherulites displayed red-shifted absorption and emission spectra, combined with a reduced photoluminescence quantum yield. Even for these markedly separated polymer backbones (1.47 nm), the reduced photoluminescence suggests an enhancement of interchain interactions of highly ordered bulky substituted polythiophene induced by crystallization.

Long term effects of comprehensive cardiac rehabilitation in an inpatient and outpatient setting.

OBJECTIVES: To compare the long-term effects of comprehensive outpatient versus inpatient rehabilitation with respect to morbidity and mortality, as well as to changes in physical performance and physical activity. DESIGN: A total of 163 consecutive patients were enrolled for comprehensive cardiac rehabilitation (CCR) following a recent coronary event, to outpatient or inpatient CCR according to treatment preference because randomisation was accepted by only 4 patients. CCR was six hours per day for 4 weeks and consisted of exercise training, education, psychological support, and nutritional and occupational advice. Examinations were before, after and 12 months after CCR. Primary outcome measures were event-free survival with or without interventions, EFS-I or EFS, respectively, 12 months after rehabilitation. RESULTS: Main patient characteristics were distributed equally in the cohorts. Results were adjusted by logistic regression for age, BMI, LV-function, exercise capacity and physical activity before the event. Adjusted EFS, EFS-I , overall survival and other morbidity outcome measures did not differ significantly. During CCR, physical activity was higher in outpatients, but this difference was not maintained in the follow up. Average physical activity was increased 12 month after CR with no difference between groups. CONCLUSION: Although influenced by patient preference, participation in either inpatient or outpatient CCR led to comparable results in terms of all-cause or cardiac overall survival, event-free survival and other secondary outcome measures like cardiac morbidity, physical performance and increased physical activity.

High-dose chemotherapy with autologous stem cell support in first-line treatment of aggressive non-Hodgkin lymphoma - results of a comprehensive meta-analysis.

BACKGROUND: Randomized controlled trials (RCTs) reported conflicting results on the impact of high-dose chemotherapy (HDCT) and autologous stem cell transplantation in the first-line treatment of patients with aggressive non-Hodgkin lymphoma (NHL). METHODS: We performed a systematic meta-analysis to assess the efficacy HDCT compared to conventional chemotherapy in aggressive NHL patients with regard to complete response (CR), overall survival (OS), event-free survival (EFS), toxicity, and impact of the age-adjusted International Prognostic Index (aaIPI) risk factors. We searched the Cochrane Library, MEDLINE and other databases (1/1990 to 1/2005). Hazard ratio (HR), relative risks (RR) and 95% confidence intervals (CIs) were calculated using the fixed effect model. RESULTS: Fifteen RCTs including 2728 patients were identified. HDCT improved CR when compared to conventional chemotherapy (RR 1.11, CI 1.04-1.18). Overall, there was no evidence for HDCT to improve OS (HR 1.05, 95% CI 0.92-1.19) or EFS (HR 0.92, 95% CI 0.80-1.05) when compared with conventional chemotherapy. However, subgroup analysis indicated OS differences (p=0.032) between good (HR 1.46, 95% CI 1.02-2.09) and poor risk (HR 0.95, 95% CI 0.81-1.11) patients. Conflicting results were reported for poor risk patients, where some studies reported improved and others reduced OS and EFS after HDCT. CONCLUSION: There was no evidence that HDCT improved OS and EFS in good risk NHL patients. The evidence for poor risk patients is inconclusive. HDCT should not be further investigated in good risk patients with aggressive NHL but high quality studies in poor risk patients are warranted.