ABSTRACT:The application of cashew nut shell liquid (CNSL) and CNSL-based polymers in the burgeoning microelectronics industry is rare. "High ortho" alternating and semialternating tailor-made novolac copolymers based on CNSL and m-cresol and/or p-cresol and have been made and successfully used as photoresists for microlithography. The microstructure of one of the representative m-cresol copolymer is exhaustively elucidated based on 1-D and 2-D NMR techniques. Incorporation of different monomers in the resin backbone has been quantitatively estimated based on an improved NMR methodology. The lithographic performance of photoresists using novolac resins based on cardanol (fractionated CNSL) and diazonaphthoquinone ester was also evaluated.

Fictionalizations (fullerenes, CNTs & grapheme) help overcome the limitation of nanocarbon materials, making them soluble. Recently the emphasis has shifted to make water soluble Fullerenes (FWS). Much work has been documented showing the use of FWS in treating cancer (e.g. breast cancer), tumors, arthritis, Parkinson's, Influenzas & HIV-AIDS. Even an aqueous nasal spray to combat Alzheimer's has been advocated. A recent US patent shows that FWS is a powerful Radical Oxygen Scavenger (ROS) and thus shows anti-oxidant activity. FWS have been used in X-ray imaging, as MRI Contrast Agents (MRI-CA), to make solar cells and are expected to help produce nano-devices and biosensors.

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The photochemistry of 4-methoxycarbonylphenyl azide (2a), 2-methoxycarbonylphenyl azide (3a) and 2-methoxy-6-methoxycarbonylphenyl azide (4a) were studied by ultrafast time-resolved infrared (IR) and UV-vis spectroscopies in solution. Singlet nitrenes and ketenimines were observed and characterized for all three azides. Isoxazole species 3g and 4g are generated after photolysis of 3a and 4a, respectively, in acetonitrile. Triplet nitrene 4e formation correlated with the decay of singlet nitrene 4b. The presence of water does not change the chemistry or kinetics of singlet nitrenes 2b and 3b, but leads to protonation of 4b to produce nitrenium ion 4f. Singlet nitrenes 2b and 3b have lifetimes of 2 ns and 400 ps, respectively, in solution at ambient temperature. The singlet nitrene 4b in acetonitrile has a lifetime of about 800 ps, and reacts with water with a rate constant of 1.9 × 108 L·mol−1·s−1 at room temperature. These results indicate that a methoxycarbonyl group at either the para or ortho positions has little influence on the ISC rate, but that the presence of a 2-methoxy group dramatically accelerates the ISC rate relative to the unsubstituted phenylnitrene. An ortho methoxy group highly stabilizes the corresponding nitrenium ion and favors its formation in aqueous solvents. This substituent has little influence on the ring-expansion rate. These results are consistent with theoretical calculations for the various intermediates and their transition states. Cyclization from the nitrene to the azirine intermediate is favored to proceed towards the electron-deficient ester group; however, the higher energy barrier is the ring-opening process, that is azirine to ketenimine formation, rendering the formation of the ester-ketenimine to be less favorable than the isomeric MeO-ketenimine.

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Photoactive compounds, such as diazonaphthoquinone (DNQ) esters, blended with novolac resins, solvents and certain additives, serve as photoresists. These are used for printing of electronic circuits at the micron or sub-micron level. Patterns are generated based on changes in the physical and chemical properties of the exposed and unexposed photoresist surfaces (printed circuit boards). The huge polarity change between the exposed and unexposed photoresists is exploited in the technique of microlithography. It is believed that the large polarity difference is due to acid formation in the exposed photoresist by a photochemical reaction of DNQ on exposure to light. However, it has also been suggested that in the unexposed part of a photoresist, the novolac resin undergoes an azo coupling reaction with DNQ, leading to an increase in the molecular weight of the resin, rendering it more insoluble in base. The protons in the para positions of the m-cresol units incorporated in the novolac resin are believed to take part in this azo coupling reaction with DNQ. In this paper, we propose a novel mechanism of action of positive photoresists in the unexposed part of photoresists for dissolution inhibition using molecular modelling, 1 H NMR, 13 C NMR and DEPT-135 NMR spectroscopic techniques. Our results enable us to propose that the diazo group of DNQ attacks the methylene bridges rather than the aromatic moiety of the resin. This mechanism explains the pattern formation observed using even p-cresol-based resins, where no free para positions are present in the aromatic ring.

ABSTRACT:The elucidation of the exact microstructure of polymers is always a challenging task. The range of molecular weights and uncontrolled polymerization leading to branching necessitates the development of better analytical methodologies. An improved methodology is presented for quantitatively estimating the microstructure of novolac resins and the percent incorporation of different monomers therein. An analysis is used that is based on the fully relaxed 1 H-NMR spectrum in combination with the results of twodimensional heteronuclear single quantum correlation, double quantum filtered correlation spectroscopy, and total correlation spectroscopy.

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