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Sijia Huang, PhD

Lawrence Livermore National Laboratory

 

Friday, September 16, 2022

9:30 AM

102 Benedum Hall

 

Photopolymers by Design

 

Abstract

Conventional thermosetting photopolymers have been broadly implemented across industrial settings such as automotive, composite materials, with an emerging focus on additive manufacturing. To date, materials for most of these applications are based on (meth)acrylate or epoxy chain growth photopolymerizations. However, those chemistries are generally limited due to the chain-growth polymerization mechanism. Introducing alternative step-growth polymerizations, especially those based on click chemistry, as a means for photopolymerization is highly desirable as it broadens the range of mechanical performance.

Herein, in this talk, I will explore several unique features of step-growth photopolymerizations: 1) A detailed kinetic study of the thiol-Michael click chemistry will be discussed. I will introduce a fundamental investigation in the kinetic parameters of three commonly used thiol and vinyl functional monomers. Those kinetic parameters can well describe the kinetic behavior of the thiol-Michael reaction as well as enable accurate prediction of the relative reactivity and selectivity in the multicomponent system. This powerful kinetic tool can further predict the photopolymerization behavior and guide researchers to choose the monomers by design. 2) Exploring the fundamental difference between step-growth and chain-growth polymerization, I will introduce a state-of-art, tough photopolymers with voxel-controlled mechanical properties. The different polymerization mechanisms of three reaction stages yield disparate crosslink densities and viscoelastic properties. As a result, our materials possess Young’s Moduli spanning over three orders of magnitude (400 kPa < E0.2-1% < 1.6 GPa) with smooth transitions between soft and stiff regions. This unique chemistry platform unlocks many possibilities to design tough and multi-responsive materials with intricate architectures. Together, these demonstrations highlight how rational polymer design can be used to create materials with appropriate kinetic characteristic and material properties.

Bio-Sketch

Sijia Huang is a Lawrence fellow in Material Engineering Division at Lawrence Livermore National Laboratory working on designing recyclable and sustainable polymers for additive manufacturing. Prior to joining LLNL in October 2020, she graduated with her B.S degree in Chemical Engineering from the University of Minnesota-Twin Cities in 2011, and with her Ph.D degree in chemical engineering from the University of Colorado-Boulder in 2020. Her research at CU-Boulder with Prof. Christopher N. Bowman focused on the photopolymerization kinetics and recyclable polymers enabled by dynamic covalent bonds. After graduate school, Sijia worked as a research consultant at Flextouch Investment LLC, which concentrated on the development of next-generation materials for flexible flat panel displays. 

Event Details

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