Hydrophobically-Modified PEG Hydrogels with Controllable Hydrophilic/Hydrophobic Balance

Area of Science:

• Polymer Chemistry
• Materials Science
• Biomaterials

Background:

• Hydrogels are versatile materials with applications in various fields.
• Developing hydrogels with tunable properties, such as amphiphilicity and mechanical strength, remains a key challenge.
• Existing hydrogel systems often lack the ability to self-heal or adapt to environmental stimuli.

Purpose of the Study:

• To develop a novel method for synthesizing hydrophobically-modified hydrogels.
• To investigate the effect of varying the hydrophilic-lipophilic balance (HLB) on hydrogel properties.
• To explore the potential of these hydrogels in applications requiring enhanced toughness and stimuli-responsiveness.

Main Methods:

• Synthesis of amphiphilic hydrogels via curing epoxy monomers with amines.
• Incorporation of hydrophilic poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) segments with C18 alkyl segments.
• Characterization of hydrogel properties including swelling behavior, thermosensitivity, mechanical strength, and heterogeneity using Low Field Nuclear Magnetic Resonance (LF-NMR).

Main Results:

• The synthesized networks exhibited amphiphilic behavior, swelling in both organic and aqueous media.
• Thermosensitive behavior in aqueous media was observed, influenced by HLB and pH.
• Decreasing HLB led to increased polymer content, enhanced mechanical properties (modulus, elongation, tensile strength), and increased heterogeneity due to physical crosslinking.
• A double network structure, combining chemical and physical crosslinks, was identified in hydrogels with polymer content >10%, significantly improving toughness.

Conclusions:

• The developed method allows for the synthesis of tunable, amphiphilic hydrogels.
• Hydrophobically-modified hydrogels with controlled HLB exhibit significant improvements in mechanical properties and toughness.
• The formation of a dual network structure is key to achieving superior hydrogel performance, opening avenues for advanced material applications.