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New pH-sensitive polyaspartamide derivatives were synthesized by grafting 1-(3-aminopropyl)imidazole and/or O-(2-aminoethyl)-O'-methylpoly(ethylene glycol) 5000 on polysuccinimide for application in intracellular drug delivery systems. The DS of 1-(3-aminopropyl)imidazole was adjusted by the feed molar ratio, and the structure of the prepared polymer was confirmed using FT-IR and 1H NMR spectroscopy. Their pH-sensitive properties were characterized by light transmittance measurements, and the particle size and its distribution were investigated by dynamic light scattering measurements at varying pH values. The pH-sensitive phase transition was clearly observed in polymer solutions with a high substitution of 1-(3-aminopropyl)imidazole. The prepared polymers showed a high buffering capacity between pH 5 and 7, and this increased with the DS of 1-(3-aminopropyl)imidazole. The pH dependence of the aggregation and de-aggregation behavior was examined using a fluorescence spectrometer. For MPEG/imidazole-g-polyaspartamides with a DS of 1-(3-aminopropyl)imidazole over 82%, self aggregates associated with the hydrophobic interactions of the unprotonated imidazole groups were observed at pH values above 7, and their mean size was over 200 nm, while the aggregates of polymers were dissociated at pH values below 7 by the protonation of imidazole groups. These pH-sensitive polyaspartamide derivatives are potential basic candidates for intracellular drug delivery carriers triggered by small pH changes.

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In this work, Al–Si was synthesized via a sol–gel process and introduced in poly 2,2′‐m‐(phenylene)‐5,5′‐bibenzimidazole (PBI). As a result, a series of five Al–Si/PBI composite (ASPBI) membranes (0, 3, 6, 9, and 12 wt%) were developed and characterized for application in high temperature polymer electrolyte membrane fuel cells (HT‐PEMFCs). The chemical and morphological structure of ASPBI membranes were analyzed by Fourier transform infrared spectroscopy, X‐ray diffractometer, and scanning electron microscopy. According to the doping level test and thermogravimetric analysis, as the concentration of Al–Si increased, the doping level increased up to 475% due to the affinity and interaction between Al and phosphoric acid (PA). Moreover, the proton conductivity, current density at 0.6 V, and maximum power density of ASPBI membranes increased up to 0.31 S cm−1, 0.320 A cm−2, and 0.370 W cm−2, respectively, because the increased concentration of Al–Si allows the membranes to hold more PA. Alternatively, as the amount of Al–Si increased, the tensile strength of PA‐doped and ‐undoped membranes decreased. This was caused by both excess PA and aggregation, which can cause serious degradation of the membrane and induce cracks. Furthermore, the PA‐doped and ‐undoped ASPBI12 had the lowest tensile strength of 11.6 and 77.2 MPa. The improved proton conductivity and single cell performance of ASPBI membranes implies that these membranes are possible candidates for HT‐PEMFC applications. However, further studies seeking to enhance the compatibility between PBI and Al–Si and optimize the amount of filler should be performed. POLYM. COMPOS., 38:87–95, 2017. © 2015 Society of Plastics Engineers