Description of the nanostructured morphology of [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM) by XRD, DSC and solid-state NMR.

PCBM or [6,6]-phenyl-C(61)-butyric acid methyl ester is nowadays still one of the most successful electron acceptors for plastic bulk heterojunction (BHJ) photovoltaic devices. In this study, a set of complementary techniques, i.e. solid-state NMR, XRD and DSC, is proposed as a fast and sensitive tool to screen the morphology of PCBM specimens with different preparation histories. Based on proton NMR relaxation decay time values, an interval can be derived that situates the average crystal dimensions and which can further be refined on the basis of XRD patterns and DSC thermograms.

Development of starch-based pellets via extrusion/spheronisation.

A modified starch (high-amylose, crystalline and resistant starch) was evaluated as an alternative excipient to microcrystalline cellulose for pellets prepared via extrusion/spheronisation. Theophylline anhydrous (25%, w/w) was used as a model drug. A binder was necessary to obtain an acceptable yield and the addition of sorbitol improved the surface properties of the pellets. A surface response design with three formulation variables (binder, sorbitol and water level) and one process variable (spheronisation speed) was used to optimise the process and to evaluate pellet yield, sphericity (aspect ratio and two-dimensional shape factor, e(R)), size (mean Feret diameter), friability and disintegration properties. Mixer torque rheometry and solid-state NMR revealed a significant influence of sorbitol on wet mass consistency and pellet properties. A high pellet yield (>90%), acceptable sphericity (AR<1.2), low friability (<0.01%), fast disintegration (<10 min) and complete drug release in less than 20 min for all formulations, demonstrated the potential of this modified starch in formulations intended for extrusion/spheronisation.