.mat file losing attached texture nodes


After attaching my normal, basecolour, metalness, ao, emissive and roughness textures to my mtl file and saving / exporting my mesh, textures and mtl file and then importing again, only the basecolour, emissive and normal maps remain attached as nodes in the mtl file, the remaining textures, although imported, are no longer nodes in the mtl file. Would appreciate any guidance!

Thank you