Interfacial Photopolymerization: A Method for Light-Based Printing of Thermoplastics

Abstract

Ultraviolet (UV) printing of photopolymers is a widely adopted manufacturing method because of its high resolution and throughput. However, available printable photopolymers are typically thermosets, resulting in challenges in postprocessing and recycling of printed structures. Here, we present a new process called interfacial photopolymerization (IPP) which enables photopolymerization printing of linear chain polymers. In IPP, a polymer film is formed at the interface between two immiscible liquids, one containing a chain-growth monomer and the other containing a photoinitiator. We demonstrate the integration of IPP in a proof-of-concept projection system for printing of polyacrylonitrile (PAN) films and rudimentary multi-layer shapes . IPP shows in-plane and out-of-plane resolutions comparable to conventional photoprinting methods. Cohesive PAN films with number-average molecular weights greater than 15 kg mol–1 are obtained, and to our knowledge this is the first report of photopolymerization printing of PAN. A macrokinetics model of IPP is developed to elucidate the transport and reaction rates involved and evaluate how reaction parameters affect film thickness and print speed. Last, demonstration of IPP in a multilayer scheme suggests its suitabiliy for three-dimensional printing of linear-chain polymers.

Structural Color Out of the Blue: A Quantitative Framework for the Self-Assembly Kinetics of Cholesteric Cellulosic Mesophases

“…All EC varieties had degrees of substitution between 2.35 and 2.5, as determined through proton nuclear magnetic resonance (NMR) and similar Fourier-transform infrared (FTIR) spectroscopy results (400 MHz Bruker Avance III HD Nanobay NMR and Bruker Alpha II FTIR Spectrometer) (Figures S1–S7). AA was also sourced from Sigma (anhydrous, contains 200 ppm MEHQ as the inhibitor, 99%), but the inhibitor was removed prior to use by running AA through columns containing Al 2 O 3 (Sigma, activated, neutral, Brockmann I) . Specifically, each column was assembled by packing cotton fibers into a Pasteur pipet to a height of approximately 2 cm and placing 1–2 cm of Al 2 O 3 on top of the dense fiber conglomerate.…”