Functionalized acrylic polyhydroxy urethanes as molecular tool box for photocurable thermosets and 3D printing

Abstract

Liquid urethane (meth)acrylates represent attractive components of photocurable thermosets for applications ranging from coatings and adhesives to 3D printing. Herein we tailor liquid polyfunctional urethane methacrylates (UMA) derived from acrylic polyhydroxy urethanes. Cyclic carbonate methacrylates react with diamines to form dihydroxy-functional urethane dimethacrylates. In an "onepot" process the hydroxy groups are functionalized either by reaction with 2-isocyanatoethyl methacrylate (IEMA) or by esterification with methacrylic anhydride (MAA) and acetic anhydride (AA). The hydroxy group esterification substantially lowers the resin viscosity (26-156 Pa•s). Hydroxy functionalization with IEMA and MAA affords tetrafunctional methacrylates. The corresponding photo-cured thermosets exhibit higher crosslinking density and improved stiffness as reflected by increasing the Young's modulus from 2900 to 3700 MPa combined with increasing the glass temperature from 135 to 204 C. Hence, this facile molecular UMA design enables to control functionality and thermoset properties over a wide range and meets the demands of 3D printing applications.

Bio‐based and hydrolytically degradable hydroxyurethane acrylates as photocurable thermosets

“…Despite HU-CL 5 -A being an acrylate, it could not be cured as the sole monomer because of its relatively high viscosity and restricted chain mobility. Hence, mixing it with ACMO as a reactive diluent at a proportion of 40/60 (wt/wt) was successful in getting a cured film, similar to previous studies, 10,11 whose swelling index (SI) and gel content (GC) in THF were found to be 79.7% ± 1.3 and 87.4% ± 1.2, respectively. Since ACMO and HU-CL 5 -A dissolve in THF, the high GC F I G U R E 1 Conversion of CL tracked from 1 H-NMR using signals of two different proton sets (the disappearance and appearance of protons at 4.23 and 3.65/4.07 ppm (method 1), respectively, and those of 2.64 and 2.33 ppm (method 2), respectively).…”

“…The resulting HU-CL 5 is acrylated with acryloyl chloride (ACl) to finally obtain the photocurable macromonomer diacrylate, HU-CL 5 -A. However, the photocuring was achieved by diluting the diacrylates with ACMO, similar to Mülhaupt et al's studies, 10,11 to prepare the final degradable films which can be used not only as coatings and materials for 3Dprinting, like previously reported, but also as patches and films for biomedical applications. The following study is divided into two main parts: a synthesis section focusing mainly on the ring-opening polymerization (ROP) of CL followed by the examination of the final film after degradation and identifying the degradation products.…”

“…The curing of HU-CL 5 -A was done by diluting the diacrylate with ACMO, a photosensitive monomer. 10,11 The UV curing was conducted at λ = 254 nm, as the wavelength, which activated the photoinitiator, Irgacure 819, to statistically copolymerize the ACMO/HU-CL 5 -A mixture via free radical polymerization. The crosslinking occurred because HU-CL 5 -A has two vinyl groups, thus permitting branching.…”

“…The resulting HUMAs were mixed with 4-aryloylmorpholine (ACMO), which is a photosensitive monomer, to obtain photocurable thermosets used in 3D-printing. 10,11 They even functionalized the OH in their HUMAs with methacrylic and acetic anhydrides as well as 2-isocyanatoethyl methacrylate to replace them with vinyl groups. 11 These different methods targeted the synthesis of nontoxic photocurable thermosets, and the final HUMA or hydroxyurethane acrylate (HUA) materials proved to be capable of replacing conventional UVcurable PU (meth)acrylate coatings.…”

“…Unlike the previous studies on photocurable HUMAs and HUAs, 10,11 the objective of this work is to synthesize photocurable films that are hydrolytically degradable and prepared from largely bio-based HUA. This is achieved by, first, reacting Priamine 1074, a bio-derived diamine from dimer fatty acids, with ethylene carbonate (EC) to prepare the HU which is, then, used as a macroinitiator to grow short degradable PCL chains of five ε-caprolactone (CL) units on average.…”