Hydrophilic (AB)_n Segmented Copolymers for Melt Extrusion‐Based Additive Manufacturing

Melt Electrowriting of Amphiphilic Physically Crosslinked Segmented Copolymers

“…Materials: The (AB) n and (ABAC) n segmented copolymers (Figure 1) were synthesized according to the previous work. [16,17,33] Copolymer 1 is a hydrophobic (AB) n segmented copolymer made of bisurea segments Rheology: Oscillatory shear rheology experiments of the copolymers were conducted using a Kinexus lab + rheometer (Malvern Panalytical) at a cooling rate of 2 K min −1 and a frequency of 1 Hz. Samples with a thickness around 1 mm were investigated in a 25 mm plate-plate geometry.…”

“…Bisurea segmented copolymers are also known for excellent bonding between single layers, meaning that physical crosslinks re-assemble after breaking. [17,41] At the MEW processing temperature, the bisurea segments disaggregate and reform during fiber formation upon cooling, acting as physical crosslinks throughout the polymer network. It is therefore expected that layers will strongly bond together at intersection points.…”

“…[10] Beyond PCL, other polymers processed with MEW include poly(vinylidene difluoride), [11] polypropylene, [12] poly(L-lactide-co-Ɛ-CL-co-acryloyl carbonate), [13] poly(L-lactideco-caprolactone), [14] poly(2-ethyl-2-oxazoline), [15] poly(ureasiloxane) [16] and poly(urea-ethylene glycol). [17] The majority of polymers processed to date are hydrophobic, which absorb proteins that influence cell adhesion. [18] Hydrophilic polymers can reduce cell adhesion, [19] recently more and more are available for MEW, which, in turn, aids certain biomedical devices to improve their function.…”

“…There are several ways to achieve this crosslinking, including via UVlight, [13] Diels-Alder chemistry, [15] or using physical crosslinking such as reported with (AB) n segmented copolymers. [17] The (AB) n segmented copolymers belong to the class of physically crosslinked hydrogels. These copolymers are based on reversible, non-covalent crosslinks formed by hydrogen bonding, which allows the processing from the melt.…”

“…Samples with a thickness around 1 mm were investigated in a 25 mm plate-plate geometry. First cooling cycle was recorded, whereas melting the sample in the rheometer was considered as first heating.MEW Device and Printing Parameters: All experiments were performed with a custom-built MEW printer as previously described[17] and syringes pressurized with N 2 and regulated using a pressure gauge (FESTO, Berkheim, Germany). Inside the MEW head, a 26-gauge nozzle with the length of 5.4 or 7 mm (Unimed S.A., Lausanne, Switzerland) and a glass syringe (FORTUNA ® Optima, 3 mL, Poulten & Graf GmbH, Wertheim, Germany) with the copolymer was heated by three ceramic electric heaters (Bach RS, Germany).…”