Stiffening of poly(dicyclopentadiene) based polyHIPEs using a norbonene-ester based crosslinker

High internal phase emulsion templating of dicyclopentadiene (DCPD) and subsequent curing via Ring-opening Metathesis Polymerization (ROMP) is a straight forward way to prepare throughout open macroporous polymer foams characterized by outstanding mechanical properties [1] and a high degree of unsaturation facilitating further functionalization.[2] The polymer foams show high uptake of nonpolar solvents (up to about 1500 w%). However, upon deswelling the original porous structure is corrupted or even lost, narrowing the possible selection of solvents for post-polymerization functionalization.[3]
Herein we wish to report foams of nominal porosity of 80% made from a formulation containing DCPD and a second difunctional monomer bearing two polymerizable norbornene moieties (1) which overcome the said limitation. It will be shown that swelling and subsequent deswelling of monolithic foam specimens in solvents like toluene results in the same macroscopic as well as microscopic structure of the monoliths as the untreated samples, facilitating post-polymerization functionalization.A series of foams with 80% nominal porosity was prepared by varying the content of 1 (10–40 wt% in respect to DCPD). The resulting foams were characterized and most importantly, the mechanical properties were studied by tensile testing. The foams are stiff (E-moduli from 106–117 MPa) and exhibit offset yield points at 0.2 % strain in the range of 1.10-1.78 MPa. Maximal elongations between 24 % and 8% were found.

Literature: [1] S. Kovačič, N. B. Matsko, K. Jeřabek, P. Krajnc, C. Slugovc, J. Mater. Chem. A 2013, 1, 487; [2] A.-C. Knall, S. Kovačič, M. Hollauf, D. P Reishofer, R. Saf, C. Slugovc, Chem. Commun. 2013, 49, 7325; [3] S. Kovačič, F. Preishuber-Pflügl, C. Slugovc, Macromol. Mater. Eng. 2014, 299, 843.