Browsing by Author "Lawrence, Mathias B."

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    D.C. conductivity behaviour of poly(vinyl alcohol)-based ferrogels: role of borax and carbonyl iron
    (Springer Nature, 2019) Lawrence, Mathias B.; Joseph, Jaison; Phondekar, Karesh; Moodi, Kiran
    The d.c. conductivity of poly(vinyl alcohol) hydrogels and ferrogels, cross-linked with borax, has been studied using two-probe resistance measurement method as a function of cross-linker and dopant concentrations. The availability of charge carriers (i.e. unbound borate ions and free sodium ions) in these matrices is seen to vary with cross-linker and dopant concentrations. Increase in borax concentration leads to the rise in d.c. conductivity values. Enhancement in the carbonyl iron dopant proportions, at unchanged borax concentrations, causes a decrease in the conductivity. This behaviour is explained on the basis of structural modifications introduced within the network matrix owing to the variations in cross-linker and dopant concentrations.
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    Spectroscopic, thermal and sorption characterization of poly(vinyl alcohol)-borax hydrogels with incorporated turmeric
    (Springer Nature, 2025) Lawrence, Mathias B.; Joseph, Jaison
    In this work, three sets of poly(vinyl alcohol) hydrogels, cross-linked using borax, with incorporated turmeric have been synthesized. Their water content, spectroscopic, thermal and sorption properties have been studied, as functions of borax and turmeric concentrations. The water content of the hydrogels decreases due to the presence of turmeric. The Fourier Transform Infra-red (FT-IR) and Raman spectroscopic measurements confirm the incorporation of turmeric in the matrices. Turmeric does not chemically bond with the polymer hydrogel network but is confined to the solvent phase within the pores. The presence and concentration of turmeric significantly affect the adsorption of water molecules onto the polymer backbone. Glass transition temperature and solvent uptake are affected by the concentration of borax and turmeric in the matrices. The sorption behaviour obeys the second-order kinetic model. The observed modifications in properties are caused by the structural re-arrangement of the polymer chains and the re-organization of borate cross-links due to the presence of turmeric.
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    Swelling and DC Conductivity Behaviour of Gelatin-Based Ferrogels
    (Springer Nature, 2021) Lawrence, Mathias B.; Joseph, Jaison; Usapkar, Twinkle; Azavedo, Firman
    Gelatin-based systems have great potential in bio-medical applications. Here, we report the solvent uptake and DC conductivity of glutaraldehyde-crosslinked gelatin hydrogels and ferrogels. Both the parameters are found to depend on cross-linker (glutaraldehyde) and dopant (carbonyl iron) concentrations. Higher cross-linker proportions cause decrease in solvent uptake, equilibrium swelling ratio and DC conductivity. Solvent uptake is seen to increase while equilibrium swelling ratio and DC conductivity decrease with dopant concentration in the ferrogels. The solvent uptake and DC conductivity behaviour of the studied systems are explained on the basis of variations in pore size and polymer segmental mobility which, themselves, are functions of cross-linker and dopant concentrations. The diffusion process in the hydrogels and ferrogels obeys the second-order kinetic model.