Browsing by Author "Leon, Valeria"

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    The effect of the shape, concentration and iron content of silica nanorods on the Phase Separation of the thermo-responsive polymer, Poly(N-isopropyl acrylamide)
    (2021-09) Chibambo, Nondumiso O; Neal, Christopher A; Leon, Valeria; Quan, Michelle; Calabrese, Michelle
    A polymer’s macroscopic properties can be manipulated and enhanced using nanoparticles. Shear, magnetic and electric fields can further increase this enhancement to improve the polymer’s tensile strength, thermal and electrical conductivity, as well as color and optical activity. The use of thermo-responsive polymers with nanorods allows the researcher to control and manipulate these macroscopic properties and introduce complex flow and optical properties. This serves as a basis for flexible electronics which have grown in popularity and relevance in recent years. The purpose of this research is to synthesize silica nanorods with various aspect ratios, and to determine how their shape, concentration and iron content can be controlled.
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    Supporting data for Tuning the thermodynamic, optical, and rheological properties of thermoresponsive polymer solutions via silica nanoparticle shape and concentration
    (2022-12-08) Neal, Christopher A P; Leon, Valeria; Quan, Michelle C; Chibambo, Nondumiso O; Calabrese, Michelle A; c-neal@umn.edu; Neal, Christopher A P; University of Minnesota, Twin Cities Calabrese Research Lab
    In this work, differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), turbidimetry, and oscillatory rheology were utilized to examine interactions between NPs, PNIPAM, and water and to track changes in phase separation and mechanical properties due to NP concentration and shape. Data presented in this set include raw data files for aforementioned techniques as well as SEM micrographs of silica nanoparticles and thermo-gravimetric analysis (TGA) data for nanoparticle characterization. Through the analysis in the supported manuscript, we found that NP addition reduces phase separation enthalpy (from DSC data) due to PNIPAM-NP hydrogen bonding interactions, the degree to which depends on polymer content. While NP addition minorly impacts thermodynamic (from DSC data) and optical (from turbidimetry data) properties, rheological transitions and associated rheological properties (both from rheology data) are dramatically altered with increasing temperature, and depend on NP quantity, shape, and polymer molecular weight. Thus NP content and shape can be used to finely tune transition temperatures and mechanical properties for applications in stimuli-responsive materials.