Which type of polymer degradation occurs predominantly in aqueous environments?

Bulk degradation is a type of polymer degradation that occurs primarily in aqueous environments. This process involves the uniform breakdown of a polymer throughout its entire volume rather than just on its surface. In bulk degradation, when the polymer is exposed to water, it absorbs moisture, causing the material to swell and ultimately leading to a gradual breakdown of the polymer chains. This form of degradation allows for a more consistent and controlled release of any embedded therapeutic agents and is highly relevant in applications like drug delivery systems and biodegradable implants.

Surface degradation, in contrast, occurs mostly on the exterior layer of the polymer material, which means the integrity of the bulk material can remain intact longer. Thermal degradation typically involves the breakdown of polymers due to heat rather than environmental conditions like moisture. Oxidative degradation involves reactions with oxygen, which can happen in various environments but is not specifically dependent on the presence of water like bulk degradation is. Therefore, the defining characteristics and mechanisms of bulk degradation make it particularly suited to environments that are aqueous, supporting its categorization as the correct answer.