Fabrication of polymer monoliths within the confines of non-transparent 3D-printed polymer housings

In the last decade, 3D-printing has emerged as a promising enabling technology in the field of analytical chemistry. Fused-deposition modelling (FDM) is a popular, low-cost and widely accessible technique. In this study, RPLC separations are achieved by in-situ fabrication of porous polymer monoliths, directly within the 3D-printed channels. Thermal polymerization was employed for the fabrication of monolithic columns in optically non-transparent column housings, 3D-printed using two different polypropylene materials. Both acrylate-based and polystyrene-based monoliths were created. Two approaches were used for monolith fabrication, viz. (i) in standard polypropylene (PP) a two-step process was developed, with a radical initiated wall-modification step 2,2′-azobis(2-methylpropionitrile) (AIBN) as the initiator, followed by a polymerization step to generate the monolith; (ii) for glass-reinforced PP (GPP) a silanization step or wall modification preceded the polymerization reaction. The success of wall attachment and the morphology of the monoliths were studied using scanning electron microscopy (SEM), and the permeability of the columns was studied in flow experiments. In both types of housings polystyrene-divinylbenzene (PS-DVB) monoliths were successfully fabricated with good wall attachment. Within the glass-reinforced polypropylene (GPP) printed housing, SEM pictures showed a radially homogenous monolithic structure. The feasibility of performing liquid-chromatographic separations in 3D-printed channels was demonstrated.