In this article the spectroscopic studies basing on 1H, 13C, 27Al NMR combined with FT-IR and Raman investigations are applied to the methylalumoxane (MAO)–oligoethhyleneglycol (PEG-ME) reaction leading to the formation of the inorganic–organic heterocomposite polymeric electrolyte. This process is analyzed in terms of the stoichiometry, chemical reaction observed and Al coordination properties changes. As the studied system is extremely complicated some model reaction systems basing on MAO and CH3OH, AlMe3 and PEG-ME, AlMe3 and CH3OH and finally Al(i-Pr)3 and PEG-ME were also tested for comparison. A coordination change is observed for all alkiloaluminum compounds upon reaction progress starting from n =4 to n =6. Contrary, the reaction basing on the alcoxyaluminum compound does not reveal this phenomenon as the initial coordination number for aluminum is equal to six. Additionally, the optimal MAO to PEG-ME ratio was proved to be equal to six.