TLC of amino acids

[Mendelejev]

Could someone explain me the following :

 

I made a TLC of three amino acids : glycine, leucine and aspartic acid. I used a ethanol-water-ammonia (25%) solution (8 parts ethanol, 1 part water and 1 part ammonia). My calculated Rf values were quite similar with those found on internet :

 

aspartic acid : 0,24

glycine : 0,26

leucine : 0,73

 

But why does leucine go so high ??? Aspartic acid is the most polar, so i would think it would have the highest Rf value becouse my solution is also polar. Glycine with R = H is less polar, but leucine is quite apolar becouse R = (CH3)2-CH-CH2- ! So it would be logical that leucine would have the smalles Rf-value.

 

Could someone explain me why it's just the opposite of what I've just said ???