@article {46013,
	title = {Effect of electrostatic interactions on structure and mechanical properties of ice templated colloid-polymer composites},
	journal = {Journal of Physics D-Applied Physics},
	volume = {52},
	year = {2019},
	month = {MAY },
	pages = {214002},
	type = {Article},
	abstract = {<p>When an aqueous dispersion of negatively charged colloids, cationic polymer and crosslinker is frozen and the polymer is allowed to crosslink in the frozen state, we obtain a self-standing macroporous composite foam. This material is soft, despite the high concentration of colloids and yet is remarkably elastic to large compressive strains. In these macroporous composites, the pore walls comprise colloidal particles held within a crosslinked polymer network. Here, we investigate the effect of varying colloid- polymer interactions in pre-fabricated macroporous composites on their microstructure and mechanical properties. During preparation of the composite, cationic polymer adsorbs on the negatively charged colloids. We tune the surface charge of particles embedded in a macroscopic monolith by immersing the composites in water maintained at different pH. In this way, we tune polymer-particle interactions in the composite. We observe a sudden increase in interparticle distance and swelling of composite when pH is decreased below the particle{\textquoteright}s isoelectric point. Correspondingly, we observe reduction in Young{\textquoteright}s and shear moduli, compression strength and macroscopic energy dissipation. We did not observe any pH dependent changes in pure polymer sponges (prepared by ice templating and crosslinking a polymer solution that does not contain colloidal particles). Therefore, the pH dependent structural and mechanical property changes arise from the composite structure rather than purely from the crosslinked polymer. We believe that the reduction in mechanical stiffness when the polymer-particle interaction becomes repulsive is because of the reduction in interfacial contacts between particle and polymer. Therefore, the mechanical stiffness of ice templated composite is strongly influenced by interactions between the polymer and particle surface.</p>},
	keywords = {colloid, electrostatic interaction, ice templating, mechanical properties, Polymer},
	issn = {0022-3727},
	doi = {10.1088/1361-6463/ab0b7b},
	author = {Suresh, Karthika and Kumaraswamy, Guruswamy}
}
@article {47353,
	title = {Highly compressible ceramic/polymer aerogel-based piezoelectric nanogenerators with enhanced mechanical energy harvesting property},
	journal = {Ceramics International},
	volume = {47},
	year = {2021},
	month = {JUN },
	pages = {15750-15758},
	type = {Article},
	abstract = {<p>Ceramic piezoelectric materials have orders of magnitude higher piezoelectric coefficients compared to polymers. However, their brittleness precludes imposition of large strains in mechanical energy harvesting applications. We report here that ice templating affords low bulk modulus lead-free aerogel piezoelectric nanogenerators (PENG) with unprecedented combination of flexibility and high piezoelectric response (voltage and power density). A modified ice templating protocol was used to fabricate piezoelectric nanocomposites of surface modified BaTiO3 (BTO) nanoparticles in crosslinked polyethylene imine. This protocol allowed incorporating a significantly high fraction of BTO particles (up to 83 wt \%) in the aerogel, while retaining remarkably high compressibility and elastic recovery up to 80\% strain. The output voltage, at an applied compressive force of 20 N (100 kPa), increased with BTO loading and a maximum output voltage of 11.6 V and power density of 7.22 ?W/cm2 (49.79 ?W/cm3) was obtained for PENG aerogels containing 83 wt\% BTO, which is orders of magnitude higher than previously reported values for foam-based piezoelectric energy harvesters. The BTO/PEI PENGs also showed cyclic stability over 900 cycles of deformation. PENGs with higher porosity showed better elastic recovery and piezoelectric properties than lower porosity and higher BTO content aerogels. To the best of our knowledge, this is the first report to demonstrate the piezoelectric properties of high ceramic content aerogels having very high compressibility and elastic recovery.</p>},
	keywords = {Ceramic polymer aerogels, energy harvesting, ice templating, piezoelectric},
	issn = {0272-8842},
	doi = {10.1016/j.ceramint.2021.02.147},
	author = {Ram, Farsa and Suresh, Karthika and Torris, Arun and Kumaraswamy, Guruswamy and Shanmuganathan, Kadhiravan}
}
