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Chemistry Seminar Series: Li XiExport this event to calendar

Wednesday, April 18, 2018 — 2:30 PM EDT

Physical chemistry of polymer materials via molecular simulation: from engineered plastics or bio-nanomaterials

Li Xi
Assistant Professor
Department of Chemical Engineering
McMaster University

Wednesday, April 18, 2018
2:30 p.m.
C2 361 (Reading Room)

Host:  Jean Duhamel

Abstract:  Atomistic molecular modeling and simulation is a widely-used tool for probing the physicochemical properties and interactions of materials. Its application in polymer systems faces many unique challenges. Two projects in this area that we recently started will be discussed.

The first project focuses on the modeling of a synthetic and amorphous polymer: poly(vinyl chloride) (PVC) plasticized with phthalate compounds. PVC is the third most produced plastic on the market. Pure PVC is rigid and brittle at room temperature. Introduction of certain small-molecule additives – plasticizers – can adjust its properties for easier processing and better materials performance. Phthalates are the most commonly used plasticizers but they tend to migrate out of the polymer matrix over time, leading to the gradual deterioration of materials performance and contamination of the environment. Recent discovery of their potential health hazards has led to increasing governmental regulations on their usage in many consumer products. Development of safer and more stable alternative plasticizers requires better understanding of the relationship between their chemical structure and performance. In this project, molecular models are developed for the reliable prediction of plasticizer performance. Insight into the effects of molecular design will also be discussed.

The second project focuses on the modeling of a biological and crystalline polymer -- cellulose nanocrystal (CNC) – and its interaction with cellulose derivatives. CNC is a nano-sized crystal of cellulose produced from, e.g., wood pulps and cotton fibers. Its unique properties and abundance from natural resources have attracted much attention and its application is explored in many different areas. Recent studies on their applications in interfacial systems – such as gel formation and emulsion stabilization – revealed that CNC becomes significantly more effective when used together with certain polymers, suggesting nontrivial polymer-CNC interactions. In this project, molecular models are built to study the adsorption of two polymers – cellulose and methyl cellulose – on CNC surfaces for better understanding of such interactions. The effects of surface morphology and salt addition on the adsorption will also be discussed.

Refreshments provided

All welcome

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