Ramos Rivera, Gilberto

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    An evaluation of optical band gap in photovoltaic polymers for solar energy capture
    (2019-05-14) Ramos Rivera, Gilberto; Suleiman Rosado, David; College of Engineering; Bogere, Moses N.; Mina Camilde, Nairmen; Department of Chemical Engineering; Valentín Rullán, Ricky
    Organic solar cells are a very promising technology for use in the renewable energy field. Band gap measurements on liquid phase for different polymers were studied, and the possible radiation harvest and reasoning for band gap tendencies were established. Polymers were divided into 4 groups: commercial polymers (P3HT, Polyaniline and PTFE), SIBS related polymers, EGMEM, and PEEK, PTBAM and block polymers. Polymers were analyzed by UV-Visible spectrometry and with the Tauc’s method, direct and indirect band gaps were determined for them. Radiation harvest was approximated using the spectral data from ASTM AM 1.5 spectrum and a simple Matlab code. The best results were obtained for SIBS 88, PEEK and PTBAM polymers. Band gap values for these polymers are near values reported for PCBM, which may suggest a similar behavior and performance. Sulfonation, conjugation and structure of these polymers suggest them as good candidates to be acceptor materials on organic solar devices.
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    Synthesis and characterization of multi-ionic polymers with sulfonated units and blends for improved protective capabilities and energy efficient devices
    (2023-05-11) Ramos Rivera, Gilberto; Suleiman Rosado, David; College of Engineering; Bogere, Moses N.; Mina Camilde, Nairmen; Saliceti Piazza, Lorenzo; Department of Chemical Engineering; Valentín Rullán, Ricky
    Preparation and characterization of polymers with diverse ionic domains for use in methanol fuel cells and protective clothing against chemical agents was accomplished in this study. The techniques used to synthesize polymeric materials were condensation polymerization and radical polymerization, controlled by the transfer of atoms. The structures obtained by the methods used resulted in random polymers with ketone and sulfone units, copolymers with hydrophobic and hydrophilic blocks, and three-block copolymers combining amines, methacrylate, and polystyrene. Additionally, two chapters study the role of polymer mixtures in improving proton transport properties and water permeability across membranes. Characterizations for the materials studied included thermal stability, oxidative, proton conduction capacity, methanol permeability, breathability, and selectivity. These were carried out to understand how the structural variations caused by their ionic diversity affected the critical properties of the membranes used and how these could be optimized in future work. Among the major findings of this work was that the ion exchange capacity does not represent a crucial limitation for proton conduction if the polymer contains several ionic domains that interact effectively. Increasing the sulfonation of a polymer is not necessarily the way to improve proton conduction, but the right combination of ionic domains is. Another important contribution of this work is using the synthesis process before sulfonation. This process obtained a controlled and reproducible sulfonation in random polymer synthesis. This study showed that more conductive polymer membranes could be achieved for random sulfone polymers than for random ketone polymers. Finally, the role of polymeric mixtures was an important factor in improving the mechanical properties and transport of water through membranes because it provides more opportunities for interaction between hydrophilic groups.