Structural analysis of poly(amidoamine) dendrimer immobilized in crosslinked poly(ethylene glycol)

Polymeric membranes comprised of poly(amidoamine) (PAMAM) dendrimer immobilized in a poly(ethylene glycol) (PEG) network exhibit an excellent CO ₂ separation selectivity over H ₂. The CO ₂ permeability increases with PAMAM dendrimer concentration in the polymeric membrane and becomes 500 times greater than H ₂ permeability when the dendrimer content was 50 wt % at ambient conditions (5 kPa of CO ₂ partial pressure). However, the detailed morphology of the membrane has not been discussed. The immiscibility of PAMAM dendrimer and PEG matrix results in phase separation, which takes place in a couple of microns scale. Especially, laser scanning confocal microscope captures a 3D morphology of the polymeric blend. The obtained 3D reconstructions demonstrate a bicontinuous structure of PAMAM dendrimer-rich and PEG-rich phases, which indicates the presence of PAMAM dendrimer channel penetrating the polymeric membrane, and CO ₂ will preferentially pass through the dendrimer channel. In addition, Fourier transform of the 3D reconstructions indicates the presence of a periodic structure. An average size of the dendrimer domain calculated is 2-4 μm in proportion to PAMAM dendrimer concentration.