Person:
Meredith, J. Carson

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    Advances in Cellulose Nanomaterial Utilization in Renewable Materials
    (Georgia Institute of Technology, 2022-04-05) Meredith, J. Carson
    This talk will review several recent advances in utilizing cellulose nanocrystals (CNCs) in commodity materials applications. The talk will focus on developments relevant to the coatings industry, particularly waterborne coatings utilized in latex paints as well as those useful as barrier coatings for packaging materials. Waterborne acrylic latexes are found in a large variety of commercial coating and paint products, but most of these products continue to contain volatile organic solvents (VOCs). I will present recent work that demonstrates who CNCs can be used as additives to waterborne acrylic formulations to displace the use of VOCs. Notably, because CNCs enable the development of hardness in otherwise soft acrylics, the VOC is no longer needed to enable film formation during the early drying stage. We have investigated two modes of addition of CNC: addition direct to the aqueous phase after the latex is produced and addition to the monomer phase prior to polymerization. In the latter case, the latex is then produced after CNC is dispersed in monomer droplets, by miniemulsion polymerization. This presentation will also feature research on the utilization of CNC dispersions as coatings on conventional polymer films such as PET and cellulose acetate, in order to impart high oxygen barrier properties to these films.
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    Raw Data for the Elastic Modulus of Sporopollenin
    (Georgia Institute of Technology, 2017-10-27) Qu, Zihao ; Meredith, J. Carson
    Sporopollenin, the polymer comprising the exine (outer solid shell) of pollens, is recognized as one of the most chemically- and mechanically-stable naturally-occurring organic substances. The elastic modulus of sporopollenin is of great importance to understanding the adhesion, transport, and protective functions of pollen grains. In addition, this fundamental mechanical property is of significant interest in using pollen exine as materials for drug delivery, reinforcing fillers, sensors, and adhesives. Yet, the literature reports of sporopollenin modulus are very limited. We provide the first report of the elastic modulus of sporopollenin of pollen particles from three plant species: ragweed (Ambrosia artemisiifolia), pecan (Carya illinoinensis) and Kentucky bluegrass (Poa pratensis). Modulus was determined with atomic force microscopy by using direct nanomechanical mapping of the pollen shell surface. The moduli were atypically high for noncrystalline organic biomaterials, with average values of 16 ± 2.5 GPa (ragweed), 9.5 ± 2.3 GPa (pecan) and 16 ± 4.0 GPa (Kentucky bluegrass). The amorphous pollen exine has a modulus exceeding all non-crystalline biomaterials, such as lignin (6.7 GPa) and actin (1.8 GPa). In addition to native pollens, we have investigated the effects of exposure to a common preparative acid-base chemical treatment and elevated humidity on modulus. Acid-base treatment reduced the ragweed modulus by up to 58% and water vapor exposure at 90% relative humidity reduced the modulus by 54% (pecan) and 72% (Kentucky bluegrass).
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    Combinatorial measurement technology for cell interactions at polymer surfaces
    (Georgia Institute of Technology, 2009-06-05) Meredith, J. Carson
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    Effect of substrate-polymer interactions on polymer thin film dewetting
    (Georgia Institute of Technology, 2008-06-02) Meredith, J. Carson
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    High-Throughput Screening of Advanced Polymeric Materials
    (Georgia Institute of Technology, 2008-02-12) Meredith, J. Carson
    In this talk Professor Meredith reviewed recent advances in the high-throughput screening of polymers for advanced materials. Two applications were reviewed: proton exchange membranes (PEM) and biomaterials for cell adhesion and growth. After decades of research the essential requirements of successful PEMs are understood reasonably well. But still, even with design information available, there are millions of potential candidate materials: more than can be reasonably evaluated experimentally. A new approach for searching this space of materials more efficiently would lead to PEMs with significantly better performance-to-price characteristics. This talk reviewed a combinatorial screening system that integrates synthesis of sample libraries based on composition gradients, high-throughput screening of conductivity, mechanical properties, and transport properties. A significant challenge encountered in high-throughput research and development of organic and polymeric materials is the reproducible preparation of combinatorial libraries with programmed variations in composition. A number of examples of discrete and gradient library preparation techniques have been presented in the literature, which were reviewed in this talk. The application of these novel techniques to polymeric biomaterials was also covered. The HTS protocol has been utilized to discover microphase-separated patterns that enhance cell attachment and proliferation for osteoblasts (bone). Informatics processing and models that enable optimization of large materials data sets was also discussed in reference to biomaterials screening.