Abstract
This paper presents the first attempt to texturize a fully crosslinked thermoset shape memory polymer using a hot embossing technique. UV-cured thiol-ene films were successfully embossed with anisotropically-etched Si (100) stamps at a temperature of 100 °C, which is about 50 °C above the glass transition temperature of the polymer. The low storage modulus of the polymer in a rubbery state allowed us to permanently emboss random micro-pyramidal patterns onto the surface of the film with high fidelity by applying 30 MPa pressure for 1 h. Atomic force microscopy (AFM) investigation showed perfect replication of the stamp micropattern with typical height of the largest inverted pyramids close to 0.7 µm and lateral dimensions in the range of 1–2 µm. Changes in surface roughness parameters of the embossed thiol-ene films after annealing them at 100 °C for 1 h or storing for 2 months in air at standard room conditions were negligible. The achieved results open new perspectives for the simple and inexpensive hot embossing technique to be applied for the micropatterning of prepolymerized thermoset shape memory films as an alternative to micropatterning using UV casting.
Highlights
Hot embossing has become a conventional method for micro- and nanostructuring of thermoplastic polymers with up to 5–10 nm resolution
This paper presents the first attempt to texturize a fully crosslinked thermoset shape memory polymer using a hot embossing technique
We tried to fabricate the stamps for hot embossing using
Summary
Hot embossing has become a conventional method for micro- and nanostructuring of thermoplastic polymers with up to 5–10 nm resolution. A few studies on this topic related to heat polymerization on the mold or hot embossing of the partially crosslinked SMP and subsequent crosslinking at elevated temperature can be found in the scientific literature, including preparation of superhydrophobic surfaces by curing epoxy-based material on a micro/nanostructured substrate [25,26], tuning wettability by using surface patterned crosslinked polycyclooctene [27], formation of photonic structures in polydiolcitrates (PDCs) [28] and thermal embossing of micropillars and subsequent thermal crosslinking of poly(e-caprolactone) with allyl alcohol and Fe3 O4 nanoparticles [29]. Thermosets capable of forming covalently crosslinked networks are usually tougher than thermoplastic polymers and demonstrate high shape fixity and shape recovery rates and thermal stability They are of great interest for the control of topography-dependent material properties, switchable carriers of information and deployable aerospace structures [30]. Annealing and aging effects on the embossed texture were studied as well
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