Pore structure of the polyethyleneimine/SBA-15 nanocomposites studied by positron annihilation lifetime spectroscopy

Pore structure of Polyethyleneimine (PEI)/SBA-15 nanocomposites was investigated by Positron Annihilation Lifetime Spectroscopy (PALS) in conjunction with other conventional means like TEM, XRD and N(2 )adsorption and desorption techniques. In this study, PALS could help us obtain the information of micropores and mesopores in the SBA-15 matrix at same time via analyzing the change of long lifetime components tau(3 )and tau(4). The size of micropores and mesopores could be obtained based on theoretical models, which is slightly smaller than the mesopore size obtained by N-2 adsorption and desorption techniques due to the existence of open micropores in the channel. This provides unique tool for understanding the evolution of the nanometer-sized pores in SBA-15 and PEI/SBA-15 composites and quantitative description of the relationship between the materials structure and its CO2 adsorption capacity in the future.