Cyclic swelling as a phenomenon inherent to biodegradable polyesters.

Area of Science:

• Polymer Science
• Materials Science
• Biomaterials Engineering

Background:

• Biodegradable and bioerodible materials are crucial in various applications.
• The dynamic volume changes of these materials in aqueous environments are not well-documented.
• Understanding these phenomena is key to controlling material behavior.

Purpose of the Study:

• To investigate and elucidate the mechanism of spontaneous cyclic swelling and deswelling in aliphatic polyesters.
• To describe the volume fluctuations of linear and branched polyesters in aqueous media.
• To identify factors influencing the observed cyclic behavior.

Main Methods:

• Observation of spontaneous cyclic swelling and deswelling in linear and branched aliphatic polyesters.
• Analysis of polyester samples of varying sizes (25-1000 mg).
• Controlled variation of environmental conditions including temperature (7°C-42°C), ionic strength, and pH.

Main Results:

• Polyester samples demonstrated cyclic volume changes over periods of hours to days.
• Swelling correlated with ester bond hydrolysis, forming water-soluble, osmotically active molecules.
• Deswelling occurred due to decreased osmotic pressure and reduced matrix hydrophilicity, likely driven by hydrophobic chain interactions.

Conclusions:

• Spontaneous cyclic swelling and deswelling is an inherent property of these aliphatic polyesters.
• The observed phenomenon is driven by a interplay of hydrolysis, osmotic pressure, and polymer chain characteristics.
• This behavior has significant implications for the application and degradation of biodegradable polyesters.