At the core of HPMC’s appeal are its unique chemical and physical properties. HPMC is water-soluble, which allows it to easily dissolve in both hot and cold water, forming a gel-like solution. This solubility is vital for its application in pharmaceuticals, where it serves as a thickener, film-former, and controlled-release agent. The degree of substitution (DS) of the hydroxyl groups by methoxy and hydroxypropyl groups influences its solubility and viscosity, making it a customizable polymer. A higher DS often results in lower solubility in water, which can be advantageous in certain formulations.