Carbon‐13 Fourier‐transform spectra (67.88 MHz) of 1,2‐polybutadienes (PBDs) (I–IV) were obtained. The triad and pentad intensities were calculated for the olefinic methylene carbon (C‐1). Bernoullian and first‐order Markov‐chain propagation statistics were tested to fit the experimental data. The pentad placements for the olefinic methine carbon (C‐2) were also assigned using the data calculated for the C‐1 carbon. Fine‐structure splitting due to placements higher than pentads was observed for both C‐1 and C‐2 carbons in PBD samples III and IV.
Several new polybenzimidazoles (PBIs) and N‐phenyl PBIs were synthesized by high temperature solution polycondensation techniques. Three different tetramine hydrochlorides and one N‐phenyl tetramine hydrochloride were condensed independently with p‐phenylenedioxydiacetic acid (PDDA), 2,2′‐[isopropylidene bis(p‐phenyleneoxy)] diacetic acid (bisacid A2) and 2,2′‐[sulfonyl bis(p‐phenyleneoxy)] diacetic acid (bisacid S) in polyphosphoric acid (PPA) at high temperatures. The polymers were obtained in 55–65% yield with inherent viscosities in the range 0.58–0.96 dL/g. Four model benzimidazoles (MBI) were also synthesized to confirm the formation of polybenzimidazoles. The PBIs and MBIs were characterized by infrared spectroscopy and elemental analysis. The properties of the polymers such as solubility, density, crystallinity, and thermal, thermoxidative, and isothermal stabilities were studied.
Investigations are carried out to have a systematic comparison of the acidic properties and catalytic activities of single oxide TiO2, SiO2, Al2O3, their binary oxides and the ternary oxide TiO2–SiO2–Al2O3. The acidity distributions are measured by using butylamine titration technique and the test reactions selected for the catalytic activity measurements are alkylation of toluene with 2-propanol and the dehydration of 2-propanol. The single oxides have only low acid strength and are not at all active in catalyzing the alkylation reaction, but are marginally active in the dehydration of 2-propanol. However the binary oxides SiO2–TiO2 and Al2O3–TiO2 of 10% by weight of TiO2 are found to contain very strong acid sites Ho≤−8.2 and are highly active catalysts in both the test reactions. But TiO2–SiO2–Al2O3 of 10% by weight of TiO2 showed the highest acid amount and the highest activity in the aikylation and dehydration reactions compared to the binary oxides. The acid amount and the catalytic activity of the ternary oxide increased with the increase of TiO2 content upto 50 mol% of TiO2 and then decreased. The ternary oxide containing 80 mol% of TiO2 is rich in weak acid sites. The increase of TiO2 content does not affect the selectivity.
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