Chemical amplification in self-stiffening materials

Lai, Shuqi

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https://hdl.handle.net/2142/105874 Copy

Description

Title

Chemical amplification in self-stiffening materials

Author(s)

Lai, Shuqi

Issue Date

2019-06-26

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

Braun, Paul V

Doctoral Committee Chair(s)

Braun, Paul V

Committee Member(s)

• Moore, Jeffrey S
• Sottos, Nancy R
• Evans, Christopher M

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Chemical amplification
• sol-gel transition
• rheology
• self-stiffening

Abstract

Self-healing and self-stiffening materials represent bio-inspired materials which can recover and even improve their properties after a damage event ideally without human intervention. These materials are able to utilize a neutral or even harmful environmental stimulus generated in the damage event but very often require the stimulus to be above a threshold level to enable effective property recovery, which may not be always fulfilled especially in the early stage of a damage that leads to stimulus release. In this dissertation, an easily generalizable strategy was proposed to deal with the situation where an above-threshold stimulus is not available: a common self-healing or self-stiffening material can be endowed with the capability of chemical amplification to amplify the initially dilute or localized stimulus. Decoupling these two reactions largely simplifies requirements of synthesizing specific and sometimes complex functionality for sensitive response and allows for myriad combinations of reactions. In Chapter 2, an organic acid amplifier was first used to amplify a below-threshold acid trigger to constructive reactions of functional polymers. The low reactivity and stability of acid amplifier stimulated me to utilize base amplifiers as alternatives which show much better reactivity-stability balance than acid amplifiers. After monitoring of base amplification kinetics in solutions in the absence and presence of functional molecules in Chapter 3, the ability of using base amplification to amplify a dilute or localized base trigger to productive macroscopic material property changes was confirmed in Chapter 4. Base amplification allows for temporal control of gelation of a catechol-bearing polymer solution. A prototype self-stiffening material that is sensitive to a localized base trigger was constructed by incorporating base amplifier and FeCl3 into a catechol-containing polymeric matrix. Systematic studies were also conducted to clarify the effects of base amplifier and FeCl3 contents, shedding a light on designing a self-stiffening material with excellent stiffening performance. In Chapter 5, the feasibility of utilizing base amplification to accelerate base transport was explored in solid and organogel materials by tuning both reaction and diffusion components. Although a constant-velocity wave propagation (x∝t) was not achieved in current systems, a conceptual phase diagram was proposed and may serve as a guide for future research on the propagating chemical wave together with computation input. Chapter 6 pointed out challenges of transforming the prototype self-stiffening material to a practical one and proposed plausible solutions. Other promising applications of base amplifiers were also discussed for future work in this area.

Graduation Semester

2019-08

Type of Resource

text

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http://hdl.handle.net/2142/105874

Copyright and License Information

Copyright 2019 Shuqi Lai

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