The hydrogen bond is an attractive interaction between a hydrogen atom from a molecule or a molecular fragment X-H in which X is more electronegative than H, and an atom or a group of atoms in the same or a different molecule, in which there is evidence ofbond formation. Strengthof hydrogen bonds depends on local environment.Hydrogen bonds have a significant impactonthe properties of many substances. The most famoussystem with hydrogen bonds is water. Anomalies occur in the water due to occurrenceof hydrogen bonds. Water is an excellent solvent for ionic and polar compounds. The presence of ions in the aqueous solution also affects the strength of the hydrogen bond between the water molecules.Hydrogen bonding is also an important interaction in biological systems. In addition to hydrophobic interactions, it plays a key role in protein folding and maintaining native structure. In DNA molecule, the nitrogenous bases are linked
to each other with hydrogen bonds, which causes the moleculeto twist into double helix.Recently, the hydrogels have been the subject of many researches, where the hydrogen bond is one of the most important interactions. Some strong hydrogels were developed, where the key interactions are hydrogen bonds.