 Solution

Relevant interactions include van der Waals attraction, electrostatic attraction or screened repulsion, hydrogen bonding, and hydrophobic/solvophobic association. Coordination bonding, magnetic dipole interactions and capillary forces can also organize suitable building blocks. Entropic effects, including depletion attraction and packing entropy, can drive ordering even without a new chemical bond. Which contribution favours assembly depends on solvent, temperature, concentration and surface chemistry; the complete balance is a free-energy change, not a requirement that every interaction be attractive.