Muthiahpillai Palanichamy

Novel microporous hypercross-linked conjugated quinonoid chromophores with broad light absorption and CO2 sorption characteristics

We have discovered formation of hypercross-linked conjugated quinonoid chromophores (polymers) with broad light absorption characteristics during cross-linking of aromatic monomers, such as benzene, naphthalene, anthracene, phenanthrene and 1,3,5-trimethyl benzene with 1,3,5-trioxane in the presence of an FeCl3 catalyst. The para or ortho –CH2 groups that bridge aromatic monomers were dehydrogenated during polymerization to form the quinonoids. The quinonoid chromophores were confirmed by their DRS-UV Vis and FTIR spectra. We have also discovered similar such quinonoid chromophores in the hypercross-linked polymers of aromatic monomers, reported from 1970 onwards by different research groups. The polymers were synthesized by similar experiments with an FeCl3 catalyst, and brown colored. As all the polymers bear low band gaps, they strongly absorb light covering the wavelength range of 1000 to 200 nm. Most of the hypercross-linked polymer matrices carry microporous spheres of about 1 to 5 μm diameter and showed 6–7% CO2 sorption. The polymers with their low band gaps will inspire research on semiconductors, solar cell devices, UV stabilizers/absorbers and infrared absorbers/detectors, molecular sensors and academic study.

A new strategy to synthesize hypercross-linked conjugated polystyrene and its application towards CO2 sorption

Polystyrene is cross-linked to generate micropores for sorption applications. Herein, we report, hypercross-linking of polystyrene in the presence of Friedel-Crafts catalyst, FeCl3 without a cross-linker. For comparison, polystyrene was also hypercross-linked with a cross-linker, dimethoxy methane with the same catalyst. The cross-linking and de-hydrogenation of cross-links to quinonoid formation were confirmed by FT-IR and 13C-NMR techniques. The hyper cross-linked polymers (HCPs) were also characterized by TGA, DRS-UV, SEM, Raman, BET and CO2 sorption techniques. All the HCPs showed a maximum of 5 weight % CO2 sorption at 25 oC and 1 atm. The same polymers could also be applied for the sorption of other air pollutants.

Microporous Hypercross-linked Conjugated Quinonoid Chromophores of Anthracene: Novel Polymers for CO 2 Adsorption

Microporous hypercross-linked conjugated quinonoid chromophores represent a novel class of amorphous polymers, synthesized by the reaction of anthracene with dimethoxy methane in the presence of FeCl3 catalyst. Their N2 adsorption isotherms confirm their microporous nature. Diffuse reflectance UV-Visible (DRS UV-Vis) spectroscopy confirms their matrix built with the conjugated quinonoids by their broad light absorption characteristics extending from 1000 nm to 200 nm with the absorbance maximum close to 400 nm. The catalyst cross-linked anthracene with -CH2- bridges and subsequently dehydrogenating them to form quinonoids. Their Fourier transform infrared (FTIR) spectra showed their characteristic quinonoid vibrations between 1600 and 1700 cm−1. The synthesis of polymers was carried out at 30, 40, 50, 60, 70 and 80 °C, but the quinonoid content of the polymer obtained at 80 °C was higher than that of the others. Their scanning electron microscopy (SEM) images showed microspheres of 1 to 5 μm size built with tiny particles. Their surfaces were not smooth. The polymer synthesized at 80 °C showed 5.1 wt% CO2 sorption at 25 °C and 0.1 MPa, but when it was recross-linked, the CO2 sorption increased to 8 wt%. Hence, hypercross-linked conjugated quinonoid chromophores of anthracene are good for sorption of CO2.

Drug Release Evaluation of Mesoporous TiO2: A Nano Carrier for Duloxetine

Mesoporous TiO2 was synthesized solvothermally, but its XRD pattern proved little randomly arranged mesopores. Its DRS-UV-Vis spectrum showed characteristic band gap excitation just below 400 nm and oxygen to metal charge transfer close to 250 nm. It was loaded with the model drug duloxetine (DX) by wet method. Locked-in drug within the mesopores of TiO2 was confirmed by XRD, DRS-UV-Vis and FT-IR techniques. About 11% loading of drug was verified by UV-Vis spectroscopy. The study of drug release showed two stages of burst release between 0 and 12 h and beyond that slow extended release of DX occurred. The total burst release was equal to 20%, and even at the end of 40 h the total release was equal to 90%. Hence, mesoporous TiO2 was established as a viable, biocompatible DX reservoir for its controlled release. The same mesoporous TiO2 could be convenient for the release of potentially toxic drugs which require small and extended dose.

Polyimides: Synthesis, Characterization and Its Application to CO2 Adsorption

Polyimides were synthesized using 3,3′,4,4′-biphenyltertracarboxylic dianhydride, (BPDA), tetraethylenepentamine (TEPA) and tris(2-aminoethyl)amine (TAEA) and tested for CO2 adsorption. They were characterized by FT-IR, TGA, DSC and BET techniques. The polyimides were thermally stable upto 400 °C. The polyimide, P2 with significant amount of TEPA and TAEA exhibited higher CO2 adsorption of about 6 wt% at 30 °C than others. The polyimide with only TEPA or TAEA exhibited lower CO2 adsorption. Hence, presence of both the amines is important for high CO2 uptake.

Mesoporous Co(III) bis(tetrazolate) Framework for CO2 Adsorption

Mesoporous Co(III) bis(tetrazolate) metal organic framework was prepared by the reaction of cobalt (III) nitrate and tetrazole in water. The crystalline nature of the material was verified by its X-ray diffraction pattern. Its Fourier transform-infrared spectrum showed absence of N-H stretching vibration proving nitrogen coordination with cobalt. Its non-electrolytic nature was verified by its insolubility in water. Its surface area, pore size and pore volume were 543 m2/g, 4.9 nm and 0.67 cm3/g respectively. Its thermogravimetric analysis showed stability up to 250 °C. Its mesopore provided an opportunity to examine its CO2 uptake, and it was nearer to 6 wt%. This study revealed potential for other metal based tetrazolate derivatives for CO2 sorption.

CO2 Sorption on Carbon Balls Derived from Covalent Organic Polymer

Carbon balls were synthesized by carbonizing covalent organic polymer (COP) derived from cyanuryl chloride and 1,4-di(1H-tetrazol-5-yl)benzene at 400, 500 and 600 °C. The COP and derived carbon were characterized by FT-IR, SEM and TGA techniques. The SEM images of the carbon revealed ball like morphology with smooth surface. The CO2 uptake was tested at 30 °C and 1 atm, and a maximum of about 10 wt% was obtained with the carbon derived at 500 °C carbonization.

AlSBA-1 Molecular Sieves: Synthesis, Characterization and Catalytic Application

Aluminum containing mesoporous molecular sieves, AlSBA-1 (nSi/nAl = 2, 5, 10 and 15) was synthesized hydrothermally using the template, cetyltriethylammonium bromide. They were characterized by XRD, BET, SEM and FT-IR. All the XRD patterns showed characteristic reflections of the three dimensional space group Pm3n. The catalytic activity was tested for the synthesis of 7-methoxy-4-methyl coumarin via Pechmann condensation of 3-methoxyphenol and ethyl acetoacetate. The reaction parameters, temperature, time, feed ratio, catalyst were optimized in order to obtain high conversion and product selectivity. Among the AlSBA-1 molecular sieves, AlSBA-1(2) exhibited higher activity than others.