Split Material Library is one of my recent max scripts.
* (You can get the script more quickly from my web archive)
Split your Material Library (.mat files) on parts using chosen amount of materials per file into new file sequence with enumerated file names and save them into the same (source .mat) folder.
Early of January I help a friend of main to split his material libraries into files holding 24 or less materials per .mat file, to can easy batch loading them to Max Material Editor for processing, so, there is, this mini tool goes out. And to be more customizeble (not constant 24), I added a spinner to enter desired amount of materials per file you like.