Tailored Thermoresponsive Polyurethane Hydrogels: Structure-Property Relationships for Injectable Biomedical...

Area of Science:

• Polymer Chemistry
• Biomaterials Science
• Materials Engineering

Background:

• Thermoresponsive hydrogels offer tunable sol-gel transitions near physiological temperatures, ideal for injectable biomedical applications.
• Current materials often require external crosslinkers, complicating in vivo application.

Purpose of the Study:

• To synthesize and characterize a library of polyurethane-based hydrogels with tunable thermoresponsive sol-gel properties.
• To establish a structure-property relationship for designing injectable hydrogels for biomedical applications.

Main Methods:

• Step-growth polymerization of polyethylene glycol (PEG), diisocyanates, and functional diols.
• UV-Vis turbidimetry to determine cloud point temperature (T_CP).
• In vitro degradation assays to assess hydrolytic stability.

Main Results:

• Synthesized polyurethane hydrogels exhibited sol-gel transitions without external crosslinkers, relying on non-covalent interactions.
• T_CP was tunable from 26-49 °C by altering monomer composition, primarily PEG molecular weight and diol structure.
• Diethanolamine (DEA)-based polymers formed stable gels above a lower critical gelation temperature (LCGT) due to amine group interactions.
• Hydrogels showed good hydrolytic stability over four weeks, influenced by PEG length and hydrophobic content.

Conclusions:

• Established a structure-property framework for designing injectable, thermoresponsive polyurethane hydrogels.
• Demonstrated the tunability of sol-gel behavior through monomer selection for tailored biomedical applications.
• Highlighted the role of non-covalent interactions and specific functional groups (amine) in achieving desired hydrogel properties.