Liquid to Thermo-responsive Gel Using Liquid-Liquid Printing: Properties and Applications*

Poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) with tertiary amine functional groups, exhibits lower critical solution temperature (LCST) behavior and is both thermoresponsive and pH-sensitive. These attributes make it a promising candidate for liquid-to-gel printing processes. PDMAEMA typically forms a soft, brittle gel for T<100^oC.  We exploited physical and electrostatic interactions to generate hollow-tubular-like hydrogels by liquid-liquid printing, taking advantage of a polyelectrolyte complex (PEC) formed between PDMAEMA and sodium poly (styrene sulfonate) (NaPSS). We investigated a range of compositions of PDMAEMA and the PEC system, correlating their behaviors with temperature. The liquid-gel transition was corroborated rheologically, showing that the introduction of PEC, in combination with alginate, substantially elevated the modulus, and transitioned the LCST to an upper critical solution temperature (UCST) response. Following the formation of the liquid membrane and hydrogel membrane, we quantified the diffusion of self-interaction.