*2.2.4 Polymer MW*

The MW of a polymer is the molecular mass of its polymeric chains and affects the delivery system properties. High MW polymers have a large amount of chain entanglement and low chain mobility. Compared with low MW polymers, high MW polymers show the benefits of lower mass transfer rates, a lower swelling rate, a lower elastic modulus, and reduced solubility. Low MW polymers have a reduced number of polymeric chain entanglements, leading to greater molecular mobility. Water molecules can be comfortably absorbed in the polymeric matrix of these low MW polymers, resulting in faster hydrolytic degradation and a faster drug release rate.
