Photopatternable Epoxy-Based Thermosets

Area of Science:

• Polymer Chemistry
• Materials Science
• Photochemistry

Background:

• Epoxy-based thermosets are versatile materials with tunable properties.
• Photopatterning offers precise control over material modification.
• o-nitrobenzyl ester (o-NBE) chemistry enables light-induced property changes.

Purpose of the Study:

• To comparatively study the photopatterning of epoxy thermosets.
• To investigate the influence of network structure and mobility on photopatterning.
• To achieve local solubility switching via photolysis of o-NBE groups.

Main Methods:

• Synthesis of o-NBE derivatives with terminal epoxy groups.
• Thermal curing with various cycloaliphatic anhydrides to control network properties (Tg, hardness).
• Photolysis of o-NBE groups to induce network degradation and solubility changes.
• Fourier transform infrared (FT-IR) spectroscopy and sol-gel analysis to study degradation.
• Photolithography to create micropatterns and evaluate resist performance.

Main Results:

• Network structure and mobility significantly affect photolysis rate and yield.
• Higher network mobility (lower Tg or elevated temperature) enhances photolysis.
• Low-Tg networks exhibit secondary photoreactions (re-crosslinking) at higher doses.
• Rigid networks demonstrate superior resist performance (contrast 1.17, resolution 8 µm) compared to flexible ones.

Conclusions:

• Photopatterning of epoxy thermosets is effectively controlled by network structure and mobility.
• o-NBE chemistry provides a versatile route for light-induced solubility switching.
• Rigid epoxy networks are advantageous for high-resolution photolithographic applications.