Reaction-Induced Phase Separation (RIPS) in Amine-Cured Epoxy/Epoxy Thermosets.2. Visualization of Heterogeneity using Fluorescence Lifetime Imaging Microscopy (FLIM)

Published

February 25, 2023

Author(s)

Jeremiah Woodcock, Stephan J. Stranick, Anthony Kotula, Gale A. Holmes

Abstract

The strategic integration of a rhodamine-spirolactam (RS) mechanophore into a transparent bis-epoxide/bis-epoxide/amine and corresponding bis-epoxide/amine networks has revealed, for the first time using fluorescence lifetime imaging microscopy (FLIM), multiple phases in the cured epoxies despite observing only a single glass transition temperatures (T_g) in the solid rheology data. For the bis-epoxide/bis-epoxide blend composed of the diglycidyl ether of bisphenol-A (DGEBA) and the diglycidyl ether of 1,4-butanediol (DGEBD) cured with meta-phenylenediamine (m-PDA), the heterogeneous morphology is caused by differences in the reaction kinetics of the two miscible bis-epoxides with m-PDA. Heterogeneity in the DGEBA/m-PDA network is partially associated with network under-curing. In the fully cured DGEBD/m-PDA network, heterogeneity appears to be caused by the high-molecular mass oligomers in the 60 wt. % DGEBD that likely self-associate in the predominately DGEBD monomer medium, thereby creating discrete regions of low crosslink density.

Citation

Macromolecules

Pub Type

Journals

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Keywords

epoxy, thermoset, mechanophore, fluorescence lifetime imaging microscopy, reaction-induced phase separation, rhodamine-spirolactam

Citation

Woodcock, J. , Stranick, S. , Kotula, A. and Holmes, G. (2023), Reaction-Induced Phase Separation (RIPS) in Amine-Cured Epoxy/Epoxy Thermosets.2. Visualization of Heterogeneity using Fluorescence Lifetime Imaging Microscopy (FLIM), Macromolecules, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=933080 (Accessed October 27, 2025)