Let's say you have a mixture for which you want to check the composition. Unfortunately, after quite a while, and several TLC analyses using our system, no spots have moved up the plate. What change could you make in the TLC system to try to get at least one compound in the original mixture to move up the plate?
1- try a more polar solvent
2- try a less polar solvent
3- try a more polar adsorbent

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.

thats how its supposed to be