Summary: A probability model, based on the “in‐out” recursive analysis, is developed for obtaining the average molecular weights of star polymers formed by connecting polydispersed primary chains onto a multifunctional coupling agent. The average properties and the polydispersity index of the formed star polymers can be described as a function of the reaction conversion and the average properties of the polydispersed primary chains without the knowledge of the whole distribution. The results indicate that, although PI of the resulting star polymers might increase at the intermediate conversion for the higher functionalities of the core molecules, the resulting star polymers generally have narrower molecular weight distributions at the complete conversion compared to the initial polydispersed polymer chains.
A schematic illustration of the star polymer formation. 相似文献
Non-contact atomic force microscopy (AFM) was employed following emersion to examine Au nanoclusters deposited from aqueous mixtures of HF and 10−4 M KAu(CN)2 onto Si(111). As the HF concentration is increased, the growth rates both parallel and perpendicular to the substrate of the approximately oblate Au hemispheroids increase. AFM images were obtained for times at which previously reported in situ second harmonic generation signals from the interface reach a maximum. At the time when the second harmonic enhancement is maximized during deposition from 0.500 (5.00) M HF, the Au nanoclusters have an average diameter of 94 (109) nm and an average height of 3.6 (9.5) nm. These cluster diameters can be understood qualitatively by the shift of the plasmon resonance due to depolarization as the cluster size increases, causing the resonant second harmonic enhancement at 532 nm to pass through a maximum at cluster diameters in the range 90–110 nm. 相似文献
