Modelling polymers with side chains: MEH-PPV and P3HT

Modelling polymers with side chains is always a challenge once the degrees of freedom are very high. In this study, we present a successful methodology to model poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylenevinylene] (MEH-PPV) and poly[3-hexylthiophene] (P3HT) in solutions, taking into account the influence of side chains on the polymer conformation. Molecular dynamics and semi-empirical quantum mechanical methods were used for structure optimisation and evaluation of optical properties. The methodology allows to describe structural and optical characteristics of the polymers in a satisfactory way, as well as to evaluate some usual simplifications adopted for modelling these systems. Effective conjugation lengths of 8-14.6 and 21 monomers were obtained for MEH-PPV and P3HT, respectively, in accordance with experimental findings. In addition, anti/syn conformations of these polymers could be predicted based on intrinsic interactions of the lateral branches. © 2013 Copyright Taylor and Francis Group, LLC

Molecular modeling of low bandgap diblock co-oligomers with pi-bridges for applications in photovoltaics

CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULORecently, the diblock co-oligomers concept, a new design method to obtain conjugated organic compounds for varied applications in photovoltaics was proposed. These materials combines the interesting properties of extended systems and the versatility of small molecules, leading to low bandgap materials with improved properties, such as adjustable open circuit voltages and promising optical responses. Aiming to evaluate possible improved routes for the design of such materials, in this report we present a study on the effect of pi-bridges incorporation on the properties of diblock co-oligomers. Six different p-bridges were inserted between polythiofene (Th) and polypyrrol (Py) oligomers with five units, following the structure [Th](5)-[pi-bridge]-[Py](5). The geometry optimization and optical absorption studies were carried out in the density functional theory (DFT) and time dependent-DFT (TD-DFT) frameworks, respectively, using the B3LYP correlation-exchange functional and 6-31G(d, p) basis set. The results point out that compounds with improved opto-electronic properties can be obtained by an appropriated choice of the pi-bridges. The possible improvements are associated with the higher delocalization of the pi-systems on the molecules, reduction of the effective optical/electronic bandgaps, high optical transition probability between the new highest occupied and lowest unoccupied molecular levels (HOMO-LUMO), optimized charge transport properties and reduced exciton dissociation energies.1521219CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO448310/2014-788881.068492/2014-0123038.004680/2015-012012/21983-02014/20410-12016/18499-

Effect of vegetarian soy diet on hyperlipidaemia in nephrotic syndrome

Nephrotic patients with persistent proteinuria also have various lipid abnormalities that may promote atherosclerosis and more rapid progression of renal disease. We aimed to find out whether dietary manipulation can correct the hyperlipidaemia found in these patients. After a baseline control period of 8 weeks on their usual diets, 20 untreated patients with chronic glomerular diseases, stable long-lasting severe proteinuria (5.9 [SD 3.4] g/24 h) and hyperlipidaemia (mean serum cholesterol 8.69 [3.34] mmol/l) ate a vegetarian soy diet for 8 weeks. The diet was low in fat (28% of total calories) and protein (0.71 [0.36] g/kg ideal body weight daily), cholesterol free, and rich in monounsaturated and polyunsaturated fatty acids (polyunsaturated/saturated ratio 2.5) and in fibre (40 g/day). After the diet period the patients resumed their usual diets for 8 weeks (washout period). During the soy-diet period there were significant falls in serum cholesterol (total, low-density lipoprotein, and high-density lipoprotein) and apolipoproteins A and B, but serum triglyceride concentrations did not change. Urinary protein excretion fell significantly. The concentrations of all lipid fractions and the amount of proteinuria tended to return towards baseline values during the washout period. We do not know whether the favourable effect of this dietary manipulation on proteinuria was due to the qualitative or quantitative modifications of dietary protein intake or was a direct consequence of the manipulation of dietary lipid intake