Molecular Visualization: Spreading Kinematics and Dynamics

University Of North Carolina At Chapel Hill, Chapel Hill NC

Investigators

Abstract

Spreading of thin polymer films on solid surfaces is of both fundamental and technological interest. During the last 20 years, significant experimental and theoretical studies have been carried out to understand the way fluids spread on surfaces. These have led to a macroscopic understanding of wetting; however, the molecular mechanism remains largely unknown. Thus, there is an apparent need for the development of experimental methods that are capable of visualization of individual molecules during spreading. It is proposed to develop an integrated system for monitoring molecular spreading based on a combination of AFM and fluorescent microscopy. It is also proposed to use branched polymer molecules as model systems that can be visualized by the chosen techniques. Four fundamental questions will be addressed in the project. (i) What is the conformation and packing of polymer chains confined to the surface plane? (ii) What is the spreading kinematics of polymer molecules in two dimensions and its correlation with the motion of the leading edge of the precursor film? (iii) What are the driving forces and dissipation channels, and their relative contribution to the wetting kinetics? (iv) What is the molecular pattern of the surface flow and its correlation with the surface structure of the substrate? This work will advance the fundamental understanding of the molecular mechanism of wetting and will also provide practical guidelines for manipulation of the molecular architecture to control the wetting kinetics. The project will also provide interdisciplinary research training for graduate and undergraduate students, since it combines fine polymer chemistry and advanced experimental techniques. An exceptional area of broader impact stems from the already established interactions with local high schools in form of regular scientific seminars and summer research at the UNC-Chapel Hill. In addition to the educational aspects, the project will reinforce collaborations in the Research Triangle Area including UNC, NCSU, and Duke University. Because of its innovative approach - investigation of material properties via visualization of individual molecules - this project will have broad impact on materials science and engineering in the area.