Study of nanoscale structures in hydrated biomaterials using small-angle neutron scattering

Area of Science:

• Polymer science
• Materials science
• Biomaterials

Background:

• Degradable polymers are crucial for biomedical applications.
• Understanding water interaction with these polymers is key to predicting their degradation behavior.
• Previous studies have not fully elucidated water distribution at the nanoscale within various polymer architectures.

Purpose of the Study:

• To investigate the distribution and behavior of water within semicrystalline, amorphous, and copolymeric degradable polymers.
• To correlate water uptake and distribution with polymer structure and degradation.
• To characterize hydration regimes in amorphous copolymers containing hydrophobic and hydrophilic segments.

Main Methods:

• Small-angle neutron scattering (SANS) was employed to probe water distribution.
• Semicrystalline polymers (poly(lactic acid), poly(glycolic acid)) and amorphous polymers (poly(d,l-lactic acid), poly(lactic-co-glycolic acid)) were analyzed.
• Amorphous copolymers with varying poly(ethylene glycol) (PEG) content were incubated and studied.

Main Results:

• In semicrystalline polymers, water preferentially diffused into non-crystalline regions.
• In amorphous polymers, water was observed in microvoids formed during hydrolytic degradation.
• Amorphous copolymers exhibited distinct hydration regimes based on PEG content, ranging from homogeneous distribution to phase inversion, with domain coalescence observed at elevated temperatures.

Conclusions:

• Water distribution is highly dependent on polymer structure (semicrystalline vs. amorphous) and composition (hydrophilic/hydrophobic balance in copolymers).
• Hydrolytic degradation in amorphous polymers leads to microvoid formation, influencing water uptake.
• The observed hydration regimes in PEG-containing copolymers provide insights into their degradation pathways and potential for controlled channel formation.