Typher Yom
Advisor: Prof. Mark Losego

will defend a doctoral thesis entitled,

Assembling and Understanding Precursor-Polymer Couples for Vapor Phase Infiltration 

On

Tuesday, September 29 at 11:00 a.m.
J. Erskine Love Room 295

and

Virtually via Teams at https://teams.microsoft.com/meet/212996889118737?p=kSrPGsUv0UlCQZfuw

Committee

Prof. Mark Losego – School of Materials Science and Engineering (advisor)

Prof. Seung Soon Jang – School of Materials Science and Engineering

Prof. Antonio Facchetti – School of Materials Science and Engineering

Prof. Shucong Li – School of Materials Science and Engineering

Prof. Ryan Lively – School of Chemical and Biomolecular Engineering

Abstract

Hybrid organic-inorganic materials present a new frontier of materials that show properties that are distinct from – and sometimes superior to – the properties of their individual components. These materials have far-reaching applications, from renewable energy to catalysis and electronics manufacturing. One process by which we can create these hybrid materials is through vapor phase infiltration (VPI) of polymers. In VPI, the inorganic exists as a vapor precursor that is diffused within the polymer bulk, embedding itself into the matrix and distributing itself evenly throughout the polymer. However, this process is still a fairly young process, and there is much to understand about this process.

With the rise of machine learning and computational methods to determine material properties and physical phenomena, it is possible to predict outcomes of any combination of precursor and polymer. However, to do so, experimental datasets are required to provide a foundation to build a predictive model. The first part of this work involves the creation of a survey that collects the empirical outcomes of the infiltration of 3 polymers into 12 polymers at 3 different temperatures, bringing a total of 108 precursor-polymer-temperature combinations. The degree of infiltration will be determined by SEM-EDX and XRF, creating a standardized semi-quantitative set of data to which future researchers in the VPI field can build upon and use as a reference guide.

Digging deeper into this survey, we then investigated the infiltration of diethylzinc, a zinc oxide precursor, into poly (methyl methacrylate) (PMMA). Prior studies have shown that DEZ does not form a hybrid material with PMMA, which was attributed to its weak binding to the polymer functional groups. With quartz crystalline microbalance (QCM) gravimetry, we have determined that this only occurs at elevated temperatures above PMMA’s glass transition temperature, and that below this temperature, the DEZ does not form a hybrid material with PMMA because it cannot dissolve into the polymer matrix.

Finally, the last part of this thesis explores a very unusual result discovered during the creation of the polymer survey. Though VPI is used to create hybrid materials from precursors and polymers, we observed that exposing polylactic acid (PLA) to diethylzinc results in the polymer disappearing, rather than forming a hybrid. The infiltration of trimethylaluminum (TMA) into PLA also shows a similar phenomenon, and we have proposed two competing chemical mechanisms to describe this process. The results of this experiment opens a new application space for VPI, beyond just hybrid formation and into selective etching and material replacement.