Hydrogel compositions for direct-write printing applications

A crosslinkable composition, comprising:

• water;
• an ABA type polyether triblock copolymer comprising a central hydrophilic poly(ethylene oxide) block (block B) linked to two peripheral hydrophobic polyether blocks (blocks A), wherein each of the blocks A comprises a random copolymer of i) a first repeat unit of formula (2):
• wherein R′ is a monovalent C1-C10 hydrocarbon group selected from the group consisting of saturated alkyl groups and aromatic groups, and ii) a second repeat unit of formula (3):
• wherein L′ is a monovalent C1-C10 hydrocarbon radical comprising an ene group (*—CH═CH2) capable of undergoing a thiol-ene reaction;
• a water-soluble crosslinking agent comprising two or more methylenethiol groups (*—CH2SH);
• and
• a photoinitiator capable of abstracting hydrogen from a thiol group when exposed to ultraviolet light of wavelength 10 nm to 400 nm;
• wherein
• the triblock copolymer, the crosslinking agent, and the photoinitiator are in contact with the solvent,
• the composition is a liquid at a temperature between 0° C. and about 10° C. and a shear-thinning viscoelastic solid at a temperature of about 15° C. to about 45° C. before crosslinking.