@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 {46151,
	title = {Structure-property relations in regenerated cellulose fibers: comparison of fibers manufactured using viscose and lyocell processes},
	journal = {Cellulose},
	volume = {26},
	year = {2019},
	month = {APR},
	pages = {3655-3669},
	type = {Article},
	abstract = {<p>Regenerated cellulose fibers are produced using two industrially dominant technologies: the viscose and lyocell processes. Here, we compare commercially available fibers, prepared using the viscose and lyocell processes. Single fibers are subjected to a variety of mechanical deformations to obtain stress-strain, stress relaxation and stress recovery data. These are fitted to a phenomenological model, whose parameters are interpreted in terms of the fiber semicrystalline microstructure. This simple model does not incorporate the complexities of semicrystalline microstructure. Rather, it represents structure in a semicrystalline polymer fiber in terms of an elastic crystalline phase that coexists with a viscoelastic Voigt-like glassy amorphous phase. Lyocell fibers are characterized by higher values of crystalline modulus relative to viscose. Lyocell fibers also have a higher amorphous phase modulus and a wider relaxation spectrum than viscose, suggesting that amorphous and crystalline phases are dispersed in close connectivity in lyocell. Viscose and lyocell fibers exhibit qualitative similarities in their mechanical response. On stretching, there is a transition in the stress-strain curve from a low strain elastic response at a critical value of strain. This critical strain has been incorrectly attributed to yielding of the fiber. We establish that this critical value corresponds to an apparent yield. When subjected to strains higher than this apparent yield point, the fibers develop a memory of the mechanical deformation. This memory decays slowly, logarithmically with time and is lost over about a day as the fiber structure transitions back to the original as spun fiber. Finally, we demonstrate that on wetting the fibers with water, there is an increase in the apparent yield strain for viscose fibers, but not for lyocell. We interpret these results in terms of the semicrystalline microstructure of the fibers.</p>
},
	keywords = {mechanical properties, Model, Regenerated cellulose, Yielding},
	issn = {0969-0239},
	doi = {10.1007/s10570-019-02352-w},
	author = {Sharma, Aakash and Nagarkar, Shailesh and Thakre, Shirish and Kumaraswamy, Guruswamy}
}
