Biological, chemical and physical processes all affect the decomposition of municipal solid waste (MSW) in landfills as well as the behavior of trace waste components such as organics and metals. I am interested in all aspects of solid waste behavior in landfills and conduct research that ranges from fundamental studies of the microbial ecology of landfills to more applied studies on the effect of various industrial wastes on refuse decomposition and gas generation. Current research is focused on factors that contribute to the generation and accumulation of heat in landfills and the microbial ecology of anaerobic digestors during food waste decomposition.

I collaborate with Dr. Ranji Ranjithan in our department on research to identify optimal strategies for solid waste management in consideration of cost, energy consumption and environmental emissions using life-cycle analysis. Our team developed the Municipal Solid Waste Decision Support Tool (MSW-DST) in the late 1990s and, more recently, the Solid Waste Optimization Life-cycle Framework (SWOLF) in 2012. The foundation of our life-cycle tools is a set of process models that describe each aspect of the solid waste system from waste generation through collection, separation, recycling, combustion, biological treatment and landfill disposal. SWOLF has the capability to consider future changes to the solid waste system such as increased costs for energy, limits on greenhouse gas emissions and higher landfill diversion targets.

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Pattern Recognition by Copolymers
We have developed 3D self-consistent field theory and Monte Carlo simulation approaches to study the interplay between the spatial distribution of the surface chemical heterogeneities and the monomer sequence distribution in the copolymer. Our results demonstrate that when the chemically heterogeneous motifs on the substrate are detected by the copolymer adsorbing segments, the copolymers can transcript them with high fidelity into three dimensions. The way the surface pattern gets transferred is dictated by the monomer sequence distribution. Relative to alternating copolymer block copolymers are generally better in capturing the chemical pattern shape, “lifting it off” the substrate, and transcribing it into the bulk. Moreover, block copolymers with shorter adsorbing blocks are capable of better recognizing the substrate motifs. On the experimental front, we are developing simple chemical routes allowing us to control (to some extent) the sequence distribution of monomers in the copolymer.

Directed Assembly of Oligomers and Polymers on Elastomeric Substrates
We have pioneered a method for fabricating “mechanically assembled monolayers” (MAMs); structures that are built by combining self-assembly of surface grafting molecules with mechanical manipulation of the grafting points on the underlying elastic surface. We have shown that MAMs prepared by mechanically assembling semifluorinated alkanes posses long lasting barrier properties. We have also extended the MAMs technology to prepare polymer brushes with high grafting densities and with tunable physico-chemical properties by utilizing “mechanically assisted polymer assembly” (MAPA).

Molecular Gradients on Substrates
We are interested in preparing molecular density gradients on surfaces, based on vapor diffusion of organosilanes. Our primary interest in preparing theses structures and studying their properties is motivated by: (1) the ability of these gradients to form continuous molecular templates for assembly of polymers and non-polymer clusters (e.g., nanoparticles), (2) studying the mechanism of formation of self-assembled monolayers, and (3) utilizing the gradient substrates in multivariant studies of polymer interfacial behavior. We are also investigating the possibilities of using the molecular gradient substrates as novel means of controlling the motion of liquids and particles.

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Colloidal silica gels have tremendous potential as novel composite polymer electrolytes because of their mechanical stability, processability and high conductivity. Our effort focuses on determining shear-induced microstructural changes in flocculated fumed silica gels, and relating them to fractal dimensions. We also obtain scaling relationships (analogous to the Cox-Merz rule) between steady and dynamic shear for non-flocculated systems, and correlate colloidal interactions with rheology.

UV cross-linked polymers are increasingly being considered for a wide range of applications because of their environmentally-benign, solvent-free nature and their rapid (on-line) curing speed. We have developed new techniques to continuously monitor the cross-linking behavior of UV curable systems in situ in the rheometer and using FTIR spectroscopy. This enables us to correlate rheology with extent of reaction, and investigate the effects of temperature and monomer functionality on gel point, fractal dimension, reaction order, gelation mechanism, and kinetics of model polymers.

CO2-induced plasticization of polymers offers a novel route to enhance polymerization and processability and develop new systems. First, polymer swelling in the presence of high-pressure CO2 is being examined. Kinetic swelling experiments can be manipulated to provide information about CO2 solubility, diffusion coefficients, and free-volume expansion. Secondly, a high-pressure rheometer is being designed to measure viscosity of polymeric melts with dissolved high-pressure CO2. The ultimate objective is to correlate the swelling and rheological behavior of polymer melts in order to obtain a comprehensive understanding of CO2-induced plasticization in polymer melts.

Hydrophobically modified associative polymers (HASE) and polymer/surfactant complexes are of significant interest because of their potential use in many applications (e.g., coatings, flocculants for waste-water treatment). These materials exhibit a multitude of unusual phenomena with respect to physically entangled systems (sol-gel transition, shear thickening followed by extreme shear thinning, strain hardening), the underlying mechanisms of which remain poorly understood. Using rheology together with microscopy, we are probing the network topology and mode of chain coupling in these systems under different types of deformation, as well as the phase behavior and interaction mechanisms for surfactant/polymer interactions.

Enzymatic modification of water-soluble polymers, such as guar galactomannans, offer a novel and powerful way to develop polymers with tailored architecture and properties. These polymers can be used in application ranging from food additives to oil/gas production. We are studying the kinetics and mechanism of enzymatic hydrolysis using rheology, size exclusion chromatography and mathematical modeling. Of particular interest is the correlation between molecular changes and macroscopic properties as a function of temperature, enzyme concentration and type (side chain vs. main backbone cleavage). We are also interested in developing and characterizing novel blends of enzymatically modified guar with other polysaccharides.

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He obtained his Ph.D. in Paper and Imaging Science and Engineering from Western Michigan University, Kalamazoo, MI. He is a certified Lean Six Sigma (LSS) Black Belt. Dr. Pal research group is focused on developing sustainable and functional bioproducts, delivering top-class hygiene, smart packaging, and flexible electronics/3D printable materials and products that benefit society as well as the environment.

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In 2009, Dr. Pawlak took a scholarly leave to UNC Chapel Hill for a sabbatical in the Department of Biology. He has collaborated with numerous departments and universities. These activities have resulted in an interdisciplinary graduate program of study between the Forest Biomaterials and Microbiology departments at NC State University. Dr. Pawlak has served the University on numerous committees including: the Grievance Committee, the Evaluation of Teaching Committee, the Admissions Committee, and the University Budget Advisory Board. Dr. Pawlak is a member of the University Partnership Council and the Research Triangle Environmental Health Collaborative. He is a recognized expert in the field of paper physics and has served as a private consultant for more than 20 companies.

In addition to his active research program and university service, Dr. Pawlak instructs two undergraduate courses, and two graduate courses in the Department of Forest Biomaterials. He is also a recognized educator in the paper industry having instructed more 750 industrial professionals in continuing education workshops. Dr. Pawlak currently resides in Raleigh with his wife Leslie and three children.

Dr. Pawlak’s research focuses on the material science and material engineering of multiphase materials. Current research interests include porous fibrous web structures, foams made from natural materials, natural super-absorbents, enzymatic manipulation of material structure, natural nano-scale fiber composites, and novel application of rheological phenomenon.

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