What is the chemical structure of HPMA? How is it prepared?

The chemical structure of HPMA (Hydrolyzed Polymaleic Anhydride) is a water-soluble polymer derived from maleic anhydride. Its structure consists of repeating units of maleic acid and its derivatives. Here is the simplified chemical structure of HPMA:

HOOC-(CH₂-CO)ₙ-OH

In this structure, (CH₂-CO)ₙ represents the repeating units of maleic acid or its derivatives.

HPMA is prepared through the hydrolysis of maleic anhydride. The hydrolysis reaction involves the addition of water to the maleic anhydride molecule, resulting in the formation of maleic acid. This hydrolysis process can be catalyzed by various agents such as alkalis or acids. The reaction typically occurs under controlled conditions, including specific temperature, pressure, and reaction time, to achieve the desired degree of hydrolysis.

During the hydrolysis process, the maleic anhydride molecule undergoes ring-opening, breaking the cyclic structure and forming a linear polymer chain composed of maleic acid and its derivatives. The resulting polymer is then neutralized and transformed into its sodium salt form, known as HPMA.

The exact preparation method and conditions may vary depending on the desired product specifications and applications.