Thermoplastic PCL-b-PEG-b-PCL and HDI Polyurethanes for Extrusion-Based 3D-Printing of Tough Hydrogels

Abstract

Novel tough hydrogel materials are required for 3D-printing applications. Here, a series of thermoplastic polyurethanes (TPUs) based on poly(ɛ-caprolactone)-b-poly(ethylene glycol)-b-poly(ɛ-caprolactone) (PCL-b-PEG-b-PCL) triblock copolymers and hexamethylene diisocyanate (HDI) were developed with PEG contents varying between 30 and 70 mol%. These showed excellent mechanical properties not only when dry, but also when hydrated: TPUs prepared from PCL-b-PEG-b-PCL with PEG of Mn 6 kg/mol (PCL7-PEG6-PCL7) took up 122 wt.% upon hydration and had an E-modulus of 52 ± 10 MPa, a tensile strength of 17 ± 2 MPa, and a strain at break of 1553 ± 155% in the hydrated state. They had a fracture energy of 17976 ± 3011 N/mm2 and a high tearing energy of 72 kJ/m2. TPUs prepared using PEG with Mn of 10 kg/mol (PCL5-PEG10-PCL5) took up 534% water and were more flexible. When wet, they had an E-modulus of 7 ± 2 MPa, a tensile strength of 4 ± 1 MPa, and a strain at break of 147 ± 41%. These hydrogels had a fracture energy of 513 ± 267 N/mm2 and a tearing energy of 16 kJ/m2. The latter TPU was first extruded into filaments and then processed into designed porous hydrogel structures by 3D-printing. These hydrogels can be used in 3D printing of tissue engineering scaffolds with high fracture toughness.

Novel three‐dimensional printing of poly(ester urethane) scaffolds for biomedical applications

“…Recently, SPU have been explored for FDM processing for biomedical applications. However, most of them were biostable SPU intended for medical devices, 39‐41 and only a few focused in tissue engineering applications 17,20,42‐45 . Among the latter, a segmented poly(ester urethane) (SPEU) with high HS content (77% wt/wt), obtained from the reaction of poly(ε‐caprolactone‐co‐ d,l ‐lactide) diol with a uniform 5‐block chain extender synthesized from butane diisocyanate (BDI) and butanediol (BDO), was filament‐free processed into porous scaffolds with mechanical properties matching those of articular cartilage 42 …”

“…Moreover, the preparation of three new bioresorbable SPEU filaments by hot‐melt extrusion was recently reported, 43‐45 presenting mechanical properties that could fit soft‐tissue engineering applications. Güney et al obtained polyurethane hydrogels from poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) diol and hexamethylene diisocianate (HDI) 45 .…”

“…Moreover, the preparation of three new bioresorbable SPEU filaments by hot‐melt extrusion was recently reported, 43‐45 presenting mechanical properties that could fit soft‐tissue engineering applications. Güney et al obtained polyurethane hydrogels from poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) diol and hexamethylene diisocianate (HDI) 45 . Haryńska et al prepared SPU filaments from α,ω‐dihydroxy(ethylene‐butylene adipate) diol (PEBA diol) and poly(ε‐caprolactone) diol (PCL diol) as SS, and HDI and BDO as HS, with low HS content (28%–29% wt/wt) 43,44 .…”

Medical-Grade PCL Based Polyurethane System for FDM 3D Printing—Characterization and Fabrication

“…In most of the presented works (Table 1), the obtained polyester-urethanes for medical application were processed by electrospining or hydrogels were formed or thin films were produced. Guney et al [24] paper is one of rare examples, in which the synthesis, characterization, and formation of a medical filament for 3D printing in FDM technology are presented. They synthesized thermoplastic tough polyurethane hydrogels from triblock copolymers (PCL-PEG-PCL) and HDI diisocyanate.…”

Solvent‐Cast 3D Printing of Biodegradable Polymer Scaffolds

“…Melt-based 3D printing involves heating polymers above their transition temperatures to induce flow for extrusion. [22][23][24] Most commercially available cartridge-based printer heads have a maximum temperature of 250 °C, [22] which limits the type of polymer that can be printed to those that can be processed below 250 °C. Limited flow due to inadequate processing temperature restricts traditional melt-based extrusion to using needles with diameters larger than 150 μm, which constrains the potential feature sizes, resolution, and complexity that can be achieved.…”