3D printable aliphatic polycarbonate networks from cationic ring-opening photopolymerization of spiro-orthocarbonates

We demonstrate light-based 3D printing of pure poly(ether carbonate) networks free of shrinkage stress. Expanding the recently pioneered concept of pure cationic double ring-opening photopolymerization of spiroorthoesters at elevated temperatures, we herein investigate spiro-orthocarbonates. Thereof resulting poly (ether carbonate) networks could find manyfold applications in biological and medical settings as well as in applications searching for more sustainable material solutions. We have determined the dependence of single and double ring-opening and the presence of backbiting side reactions for three synthesized spiro-orthocarbonate monomers in combination with an oxetane crosslinker on the ring size and photopolymerization temperature to optimize the photogenerated network and thus material properties. The absence of residual stresses in the polymer network was confirmed by tracking the decrease of sample birefringence with increasing spirocarbonate monomer content of the sample. Based on this fundamental study, the best-performing monomer was printed in combination with an oxetane crosslinker.