Copolymers comprising 2,7-carbazole and bis-benzothiadiazole units for bulk-heterojunction solar cells.

On the basis of theoretical considerations of the intramolecular charge transfer (ICT) effect, we have designed a series of donor (D)-acceptor (A) conjugated polymers based on bis-benzothiadiazole (BBT). A PPP-type copolymer of electron-rich 2,7-carbazole (CZ) and electron-deficient BBT units poly[N-(2-decyltetradecyl)-2,7-carbazole-co-7,7'-{4,4'-bis-(2,1,3-benzothiadiazole)}] (PCZ-BBT), a PPV-type copolymer poly[N-(2-decyltetradecyl)-2,7-carbazolevinylene-co-7,7'-{4,4'-bis-(2,1,3-benzothiadiazolevinylene)}] (PCZV-BBTV), and a tercopolymer based on carbazole, thiophene, and BBT poly[N-(2-decyltetradecyl)-2,7-(di-2-thienyl)carbazole-co-7,7'-{4,4'-bis-(2,1,3-benzothiadiazole)}] (PDTCZ-BBT) have been synthesized to understand the influence of BBT acceptor structure and linkage on the photovoltaic characteristics of the resulting materials. Both the HOMO and LUMO of the resulting polymers are found to be deeper-lying than those of benzothiadiazole-based polymers. The measured electrochemical band gaps (eV) are in the following order: PDTCZ-BBT (1.65 eV) < PCZV-BBTV (1.69 eV) < PCZ-BBT (1.75 eV). All the polymers provide a photovoltaic response when blended with a fullerene derivative as an electron acceptor. The best cell reaches a power conversion efficiency of 2.07 % estimated under standard solar light conditions (AM1.5G, 100 mW cm(-2)). We demonstrate for the first time that BBT-based polymers are promising materials for use in bulk-heterojunction solar cells.

Spontaneous flexor tendon rupture in the palm.

Spontaneous flexor intratendinous ruptures are rare and incompletely understood. They occur within the substance of the tendon, and in the absence of underlying pathological processes or direct trauma. We present an unusual case of spontaneous flexor digitorum profundus tendon rupture in the palm.

A rare and life-threatening cause of epistaxis.

Epistaxis is a potentially life-threatening condition that can compromise a patient's airway, breathing and circulation. Early recognition of underlying bleeding diatheses that are amenable to medical therapy is imperative in order for timely treatment and to reduce morbidity. We present a case in which acquired haemophilia was diagnosed in an 83-year-old man presenting with seemingly uncomplicated epistaxis. The patient suffered multisite haemorrhages and haemodynamic compromise before definitive management with monoclonal antibody therapy. The case highlights the difficulties in managing this rare condition. It also emphasises the importance of clotting assay analysis in patients who present with epistaxis in the absence of an underlying anticoagulant.

The ischaemic ECG: is it all in the head?

Acute cerebrovascular events including ischaemic stroke and subarachnoid haemorrhage are known to be associated with left ventricular dysfunction and significant electrocardiographic abnormalities that can mimic cardiac ischaemia. The authors present a case in which an intracerebral haemorrhage was diagnosed during the treatment of pneumonia in a 62-year-old woman, with repolarisation abnormalities on the ECG acting as the key diagnostic clue in the absence of clinical or radiological evidence of ventricular dysfunction. The pneumonia was treated without complication, and there were no long-term respiratory, cardiac or neurological sequelae. Diagnostic cardiac imaging, including angiography at follow-up, confirmed the absence of significant coronary artery disease, suggesting a non-coronary aetiology for these ECG changes. The authors emphasise that when presentation is atypical for acute coronary syndrome, non-specific ECG changes could point to a primary cerebrovascular pathology, even in the absence of neurological or cardiac symptoms.

A simple route toward the synthesis of bisbenzothiadiazole derivatives.

A simple and efficient route toward the synthesis of 4,4'-bis(2,1,3-benzothiadiazole) and 7,7'-dibromo-4,4'-bis(2,1,3-benzothiadiazole) has been developed. Oligomers were synthesized with bisbenzothiadiazole units either at the periphery or core, and each oligomer was characterized by X-ray crystallography. Both crystal structures display supramolecular interactions between the conjugated backbones, although the former, bearing two bisbenzothiadiazole units, has extended interactions within layers that engage all of the thiadiazole rings.