G. N. Mahesh

Comparative studies on short‐chain and long‐chain crosslinking in polyurethane networks

Isocyanate terminated prepolymers were synthesises using poly(tetramethylene oxide) glycol of molecular weight 1 000 (PTMG 1000) and poly(propylene oxide) glycol of molecular weight 1 000 (PPG 1000 ) with tolylene-2,4-diisocyanate (TDI). The prepolymers were chain extended with N,N-bis(2-hydroxyethyl)isonicotinamide to form polyurethanes containing pyridine moieties. These polyurethanes were converted to cationomers by crosslinking with (a) 1,4-dibromobutane to form short-chain crosslinked polymers (SCCPs) and (b) bromine-terminated prepolymers to form long-chain crosslinked polymers (LCCPs). The cationomers were characterised by Fourier transform infrared spectroscopy, thermal and mechanical analysis. FTIR spectral results of SCCPs and LCCPs confirmed the quaternisation of heterocyclic nitrogen leading to crosslinking. Dynamic mechanical analysis showed better damping properties for LCCPs than SCCPs. The stress-strain mesurements showed higher elongation and lower tensile strength for LCCPs.

Synthesis and characterization of polyurethane–polyvinylbenzyl chloride multiblock copolymers and their cationomers using a polyurethane macroiniferter

Polyurethane iniferter prepared from isocyanate end capped prepolymer and 1,1,2,2-tetraphenyl-1,2-ethanediol, has been used to polymerize vinylbenzyl chloride to obtain polyurethane-polyvinylbenzyl chloride multiblock copolymers. Formation of the block copolymers proceeds with increase in both molecular weight and conversion with increasing polymerization time showing that the polymerization proceeds via a “living” radical mechanism. The block copolymers so obtained were converted into their cationomers by the treatment of triethylamine. The block copolymers and their cationomers have been characterized by FTIR, FTNMR, TGA, and DSC studies. The effect of thermal energy on the molecular weight of the macroiniferter in the absence of monomer has been studied in order to understand the mechanism of formation of the block copolymers.

Cast polyurethanes based on castor oil and fluorescein

Cast polyurethanes based on castor oil, fluorescein and tolylene diisocyanate have been synthesized. The polyurethanes were characterized by Fourier transform infrared spectroscopy. The thermal stabilities of the polymers were determined using a thermogravimetric analyser. From the differential scanning calorimetric analysis, change in the glass transition temperature of the soft segment was observed as the molar ratio and feed composition of the fluorescein were varied.

Segmented polyurethanes using fluorescein

Segmented Polyurethanes were prepared by chain extending the prepolymers based on poly(tetramethylene oxide)glycol and tolylene diisocyanate using fluorescein. The polymers were characterized using FTNMR and FTIR. Thermal stability of the polymers was studied using a thermogravimetric analyzer, and the glass transition temperature of the polymers was determined using a differential scanning calorimeter. Tensile strength and percentage of elongation of these segmented polyurethanes were evaluated using a Universal Testing Machine.

Investigations on polyurethane ionomers. II. 3,4-Dihydroxycinnamic acid-based anionomers

Polyurethanes of different compositions were synthesized by chain extending the prepolymer formed by the reaction of various polyols and diisocyanate with 3,4-dihydroxycinnamic acid. The polyurethanes were converted to their anionomers by treating with metal acetates. The polyurethanes were characterized using FTIR, FTNMR, TGA, and DSC analysis. The molecular weights of the polymers were determined using GPC. A detailed study of the effect of variation of molecular weight of the polyols and mol ratio of the various reactants on the glass transition temperature and molecular weight of the polyurethanes was made.

Polyurethane telechelic cationomers containing end functional 4-vinylpyridinium moieties

SummaryTelechelic polyurethane cationomers containing end functional 4-vinylpyridinium moieties have been synthesized by the reaction of 4-vinylpyridine on 2-bromoethanol terminated polyurethane. The polyurethanes were characterized by FTIR, FTNMR and DSC studies. The introduction of ionic groups into the polyurethane shifts the Tg to lower temperatures, the shift in Tg further increases with increase in ionic groups.

Polyurethane Microspheres as Drug Carriers

Polyurethane microspheres were prepared by reacting polyethylene glycol [PEG] (of different molecular weights) with different mole ratios of tolylene diisocyanate. A conventional drug was incorporated into the microspheres. The polyurethane microspheres were characterized by FTIR, optical microscopy and particle size analysis. The equilibrium fluid content of microspheres was determined in suitable buffer media. The release pattern of the drug entrapped inside the microspheres was monitored using a UV-VIS spectrophotometer.

Investigations on polyurethane anionomers using 3,4-dihydroxycinnamic acid. 1

Abstract Polyurethanes of different compositions were synthesized by chain extending the prepolymer formed by the reaction of poly(tetramethylene oxide)glycol and tolylene diisocyanate with 3,4-dihydroxycinnamic acid. The polyurethanes were characterized using Fourier transform infra-red and Fourier transform nuclear magnetic resonance spectroscopies. The molecular weights of the polymers were determined using gel permeation chromatography. The polyurethane anionomers showed typical polyelectrolyte behaviour. The glass transition temperatures of the polyurethanes and their anionomers were determined by differential scanning calorimetry. The thermal stabilities of the polymers were evaluated using a thermogravimetric analyser.

Novel Polyurethane Multiblock Copolymers and Their Zwitterionomers Using a Polyurethane Macroiniferter

Abstract Polyurethane-poly(4-vinylpyridine) multiblock copolymers have been prepared by the decomposition of a tetraphenylethane-based polyurethane macroiniferter in the presence of 4-vinylpyridine. The increase in the molecular weight and conversion with an increase in polymerization time proves the “living” radical mechanism. The polyurethane-poly(4-vinylpyridine) multiblock copolymers so obtained were converted into their zwitterionomers by treating with γ-propane sultone. Both block copolymers and their zwitterionomers have been characterized using spectral and thermal techniques.

Chain-extended polyurethane anionomers using fluorescin

Polyurethanes were synthesized by chain extension of isocyanate end-capped prepolymer based on poly(tetramethylene oxide) glycol and toluene diisocyanate using fluorescin. The polyurethanes were characterized using FT-IR and FT-NMR. The polyurethanes were converted to their anionomers by treatment with the respective metal acetates. To study the changes accompanying ionomer formation, especially in the soft segment, differential scanning calorimetry experiments were performed in the low temperature region. Thermal stabilities of the polymers and ionomers were studied using a thermogravimetric analyzer.