@article{jani_farias_jain_houston_velev_santiso_hsiao_khan_2024, title={Isothermal Titration Calorimetry Reveals Entropy-Driven Bisphenol A Epoxy Resin Adhesion to Metal Oxide Surfaces}, volume={1}, ISSN={["1520-5835"]}, url={https://doi.org/10.1021/acs.macromol.3c02440}, DOI={10.1021/acs.macromol.3c02440}, abstractNote={Polymer-coated metals are ubiquitous in multiple industries as a corrosion protection strategy. Particularly in food and beverage packaging, bisphenol A (BPA)-based epoxy coatings provide an excellent barrier and strong adhesion to metals. There is, however, a need to design safer, alternative coatings with similar adhesion as BPA-epoxies due to environmental and health concerns associated with BPA. Limited critical information exists on epoxy-metal interactions and the effect of interfacial functional group concentration on overall adhesion due to the constraints of most experimental methods, which typically probe the interface only within a few nanometers in situ. Herein, we use isothermal titration calorimetry (ITC) and molecular dynamics simulations to characterize the thermodynamics of epoxy-metal oxide binding in the liquid phase and identify the influence of epoxy resin structure and metal oxide surface chemistry in dictating the binding process. Across a series of epoxy resins and three metal oxides, we reveal a previously unreported dominant role of entropy in the binding process, primarily facilitated by the release of bound solvent molecules from the epoxy/metal interface with possible contributions from dispersive OH–π interactions between the benzene rings of the resin and the –OH groups on the metal oxide surface. Enthalpy-favored hydrogen bonding between the –OH groups of the resin and the metal oxide plays a supporting role in the binding, with its participation dependent on the interfacial –OH group concentration. ITC therefore offers key molecular insights into the relative functional group contributions to the adhesion mechanism and informs the rational design of next-generation polymer coatings.}, journal={MACROMOLECULES}, author={Jani, Pallav K. and Farias, Barbara V. and Jain, Rakshit Kumar and Houston, Katelyn R. and Velev, Orlin D. and Santiso, Erik E. and Hsiao, Lilian C. and Khan, Saad A.}, year={2024}, month={Jan} }
 @article{sarker_jani_hsiao_rojas_khan_2023, title={Interacting collagen and tannic acid Particles: Uncovering pH-dependent rheological and thermodynamic behaviors}, volume={650}, ISSN={0021-9797}, url={http://dx.doi.org/10.1016/j.jcis.2023.06.209}, DOI={10.1016/j.jcis.2023.06.209}, abstractNote={Biomaterials such as collagen and tannic acid (TA) particles are of interest in the development of advanced hybrid biobased systems due to their beneficial therapeutic functionalities and distinctive structural properties. The presence of numerous functional groups makes both TA and collagen pH responsive, enabling them to interact via non-covalent interactions and offer tunable macroscopic properties.The effect of pH on the interactions between collagen and TA particles is explored by adding TA particles at physiological pH to collagen at both acidic and neutral pH. Rheology, isothermal titration calorimetry (ITC), turbidimetric analysis and quartz crystal microbalance with dissipation monitoring (QCM-D) are used to study the effects.Rheology results show significant increase in elastic modulus with an increase in collagen concentration. However, TA particles at physiological pH provide stronger mechanical reinforcement to collagen at pH 4 than collagen at pH 7 due to the formation of a higher extent of electrostatic interaction and hydrogen bonding. ITC results confirm this hypothesis, with larger changes in enthalpy, |ΔH|, observed when collagen is at acidic pH and |ΔH| > |TΔS| indicating enthalpy-driven collagen-TA interactions. Turbidimetric analysis and QCM-D help to identify structural differences of the collagen-TA complexes and their formation at both pH conditions.}, journal={Journal of Colloid and Interface Science}, publisher={Elsevier BV}, author={Sarker, Prottasha and Jani, Pallav K. and Hsiao, Lilian C. and Rojas, Orlando J. and Khan, Saad A.}, year={2023}, month={Nov}, pages={541–552} }
 @article{adhikari_jani_hsiao_rojas_khan_2021, title={Interfacial Contributions in Nanodiamond-Reinforced Polymeric Fibers}, volume={125}, ISSN={["1520-5207"]}, url={https://doi.org/10.1021/acs.jpcb.1c03361}, DOI={10.1021/acs.jpcb.1c03361}, abstractNote={We study the interfacial energy parameters that explain the reinforcement of polymers with nanodiamond (ND) and the development of mechanical strength of electrospun ND-reinforced composites. Thermodynamic parameters such as the wettability ratio, work of spreading and dispersion/aggregation transition are used to derive a criterion to predict the dispersibility of carboxylated ND (cND) in polymeric matrices. Such a criterion for dispersion (Dc) is applied to electrospun cND-containing poly(vinyl alcohol) (PVA), polyacrylonitrile (PAN), and polystyrene (PS) fiber composites. The shifts in glass transition temperature (ΔTg), used as a measure of polymer/cND interfacial interactions and hence the reinforcement capability of cNDs, reveal a direct correlation with the thermodynamic parameter Dc in the order of PAN < PS < PVA. Contrary to expectation, however, the tensile strength of the electrospun fibers correlates with the Dc and ΔTg only for semicrystalline polymers (PAN < PVA) while the amorphous PS displays a maximum reinforcement with cND. Such conflicting results reveal a synergy that is not captured by thermodynamic considerations alone but also factor in the contributions of polymer/cND interface stress transfer efficiency. Our findings open the possibility for tailoring the interfacial interactions in polymer-ND fiber composites to achieve maximum mechanical reinforcement.}, number={36}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, publisher={American Chemical Society (ACS)}, author={Adhikari, Prajesh and Jani, Pallav K. and Hsiao, Lilian C. and Rojas, Orlando J. and Khan, Saad A.}, year={2021}, month={Sep}, pages={10312–10323} }