Quantitative viscoelastic spectroscopy of polymer films using Lorentz force actuated contact resonance atomic force microscopy

Bakir, Mete

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https://hdl.handle.net/2142/50413 Copy

Description

Title

Quantitative viscoelastic spectroscopy of polymer films using Lorentz force actuated contact resonance atomic force microscopy

Author(s)

Bakir, Mete

Issue Date

2014-09-16

Director of Research (if dissertation) or Advisor (if thesis)

King, William P.

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Quantitave Viscoelastic Spectroscopy
• Nanomechanical Characterization
• Block Copolymers Morphologies
• Multi-Frequency Atomic Force Microscopy (AFM)
• Cantilever Mathematical Modelling
• Contact Resonance Atomic Force Microscopy (AFM)

Abstract

This thesis presents development of a material metrology technique, which is shown to quantify viscoelastic properties of a polymer film within the glass transition region. Designed for nanoscale material characterization applications, heater integrated atomic force microscopy (AFM) cantilever operates in contact resonance mode actuated by externally induced Lorentz force. It is demonstrated that glass transition temperature (Tg) of polymethyl methacrylate (PMMA) film can be detected reproducibly by monitoring contact resonance frequency of the cantilever as a function of temperature. Also, the glass transition temperature is observed in the terms of differential change of cantilever electrical resistance and differential power consumption. Furthermore, employing a harmonic oscillator model to define tip-sample contact interactions, viscoelastic properties of contact stiffness, viscous damping coefficient and elastic modulus for the polymer film are measured as functions of temperature. In addition, multi-frequency actuation for contact resonance is demonstrated providing qualitative material properties. Besides, a mathematical approach is developed to model two-leg and V-shaped LCR cantilevers as in the form of rectangular beam. Finally, local viscoelastic measurements taken on 66-63K PS-PMMA lamellar block copolymer film are presented. Also, nanomechanical surface property mappings of both 37-37K PS-PMMA lamellar and 46-21K PS-PMMA cylindrical block copolymer morphologies are provided. The technique introduced in this work has vast potential to be employed for numerous nano-scale material applications, and eventually replace traditional macro-scale thermophysical material characterization technologies providing local, reproducible and non-destructive analyses.

Graduation Semester

2014-08

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http://hdl.handle.net/2142/50413

Copyright and License Information

Copyright 2014 Mete Bakir

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