Synthesis, thermal and solar cell application of novel hyperbranched polyurethanes containing azomethine and aryl-ether connectivities

Abstract

methylidene]aminophenoxyhexylgbenzene-1,3-dicarboxylate -a novel A 2 diol monomer -and a series of new blocked isocyanates (B 3 monomers) were synthesized in high yield and their structures were confirmed. Using these monomers, different hyperbranched polyurethanes (HBPUs) containing azomethine and aryl-ether connectivities were prepared via an A 2 þ B 3 approach. All possible parameters were varied to study their effect on molecular weight build-up. The effects of concentrations of A 2 and B 3 and the A 2 : B 3 monomer ratio were well reflected in the molecular weight of the polymer. The structure of the B 3 monomer was also found to have a significant effect on the molecular weight. The polymers were characterized by Fourier transform infrared, proton nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction and impedance spectroscopy. All the polymers registered unusual sub-T g ; and they invariably underwent decomposition at three distinct stages with significantly improved thermal stability at initial stage. The ionic conductivity of HBPU increased remarkably upon doping with KI and I 2 . The dye-sensitized solar cell fabricated using this polymer as electrolyte yielded an overall conversion efficiency of 3.5% upon illumination with visible light.

Photophysical, Electrochemical, Thermal and Morphological Properties of Polyurethanes Containing Azomethine Bonding

“…Moreover, various derivatives of PAMs, such as poly(azomethine-ether)s (16), poly(azomethinesulfone)s (17) and poly(azomethine-ester)s (18), have been synthesized and reported in the literature. Polyurethane containing azomethine, which are also known as poly(azomethine-urethane)s, have also been reported in the literature (19,20), and their thermal stability (21), semicrystalline behavior (22), non-linear optical (23) and electrochemical properties (24), solar cell (25) and ion sensor applications (26,27) have been clarified. To the best of our knowledge, there is not too much paper in the literature on polyurethanes containing azomethine.…”

Performance of novel hyperbranched poly(aryl‐ether‐urea)s doped with N3‐dye in nanocrystalline DSSC

“…Among the two doped polymers, the end‐group modified polymer (M‐HBPEU) shows very high ionic conductivity of 4.1 × 10 −2 S/cm and this range is closer to the conductance of ionic liquids. Moreover, this value is found to be higher than that of doped hyperbranched polyurethanes reported recently for DSSC applications . Such a remarkably high conductivity of doped polymer electrolyte conforming that there is effective ion mobility in the aryl‐ether‐urea skeleton of the polymer chain.…”

“…Besides, these lone pair electrons can readily interact with the metal cations added and hence increase the conductivity and the performance of DSSCs. These polyureas are expected to show better cell performance than the polymers reported in our previous work, because of the presence systems, the two aromatic rings are separated by oxygen atom of ether linkage or by urea linkage instead of alkyl groups; the presence of alkyl groups restricts the conjugation length and ionic conductance.…”

“…For this study, the skeleton of the polymer was designed in such a way that the lone pairs of electrons present in the carbonyl oxygen, ether oxygen, and nitrogen of urea groups readily interact with the metal cations added, which could increase the performance of the DSSCs. The cell operation mechanism has been described in our previous report . The current–voltage characteristics of the photovoltaic cell based on HBPEU/I − /I 3 − /N3‐dye are presented in Figure and the performance parameters of the cells are summarized in Table .…”

“…The presence of ionic conductivity in combination with good thermal stability is an important requirement for a material to be used for photovoltaic devices. Recently, we reported hyperbranched poly(aryl‐ether‐urethane)s and hyperbranched polyurethanes containing azomethine and aryl‐ether connectivity for solar cell applications …”