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UV-Induced Cationic Ring-Opening Polymerization of 2‑Oxazolines for Hot Lithography
journal contribution
posted on 2020-03-25, 15:03 authored by Nicolas Klikovits, Lisa Sinawehl, Patrick Knaack, Thomas Koch, Jürgen Stampfl, Christian Gorsche, Robert LiskaThe cationic ring-opening
polymerization (CROP) of 2-oxazolines gives polymers with unique characteristics
arising from its polyamide backbones and structural versatility. Up
to now, poly(2-oxazoline)s were obtained by classical thermal polymerization
methods not aiming for application in bulk curing of structural polymers.
We introduce the cationic photopolymerization of 2-oxazolines at elevated
temperatures for the direct UV-induced curing of materials with exclusive
chemical and structural particularities. After efficient photoinitiation
via onium salt photoacid generators (PAGs), the immanent low-rate
propagation is crucially promoted by thermal energy input to the ring-opening
reaction. In simultaneous thermal analysis (STA), photo-DSC, and (thermo)mechanical
analyses we investigated the UV-induced CROP of 2-oxazolines in a
temperature range of 100–140 °C and show the exceptional
potential of the introduced photopolymers. Furthermore, we applied
the photopolymerizable system in Hot Lithography, a stereolithography-based
3D printing technology at elevated temperatures.