Degradation kinetics of methacrylated dextrans in aqueous solution

Area of Science:

• Polymer Chemistry
• Materials Science
• Biomaterials Degradation

Background:

• Dextran derivatives with methacrylate esters are used in various biomedical applications.
• Understanding their hydrolysis kinetics is crucial for predicting material stability and performance.
• Methacrylate ester linkages can be susceptible to degradation in aqueous environments.

Purpose of the Study:

• To systematically investigate the hydrolysis kinetics of glycidyl methacrylate derivatized dextran (dex-MA), hydroxyethyl methacrylate derivatized dextran (dex-HEMA), and hydroxyethyl methacrylate (HEMA).
• To determine the influence of pH and acid/base catalysis on the degradation rates.
• To compare the stability of these methacrylate-containing compounds under different pH conditions.

Main Methods:

• Hydrolysis kinetics were studied in aqueous solutions across a wide pH range (-1.8 to 10.4) at 37°C.
• Degradation products were quantified using reversed-phase High-Performance Liquid Chromatography (HPLC).
• Rate constants were calculated to assess the stability and degradation pathways.

Main Results:

• Degradation followed first-order kinetics, influenced by specific acid and base catalysis.
• Reaction rate constants were independent of concentration and degree of substitution for dextran derivatives.
• Stability varied with pH: dex-MA was most stable at high acidity, while HEMA was most stable at alkaline pH.

Conclusions:

• The hydrolysis of dex-MA, dex-HEMA, and HEMA is governed by proton, solvent, and hydroxyl catalysis.
• At alkaline pH, dex-HEMA degradation is primarily via carbonate ester hydrolysis, while methacrylate ester hydrolysis dominates at low pH.
• The distinct degradation profiles highlight the importance of environmental pH in controlling the stability of these methacrylate-functionalized dextran polymers.