Lipid diffusion and swelling in a phase separated biocompatible thermoplastic elastomer.

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Materials Engineering

Background:

• Biocompatible polymers like poly(styrene-block-isobutylene-block-styrene) (SIBS) are crucial for in vivo applications.
• Understanding lipid interactions is vital for predicting the long-term performance and degradation of medical implants.

Purpose of the Study:

• To analyze lipid uptake and swelling behavior in SIBS copolymers.
• To investigate the influence of molecular weight and polystyrene content on SIBS properties.
• To develop a predictive model for lipid susceptibility in SIBS.

Main Methods:

• Gravimetric measurements were used to quantify lipid uptake.
• Fickian diffusion models were applied to analyze absorption kinetics.
• Physical stability and swelling were monitored during lipid immersion.

Main Results:

• Lipid uptake followed Fickian diffusion, with saturation levels ranging from 45% to 63% by weight.
• Lower polystyrene content and molecular weight led to increased swelling (32%-58%) and surface cracking.
• Lipid plasticization primarily occurred in the soft polyisobutylene phase, affecting polymer network flexibility.

Conclusions:

• SIBS copolymer properties, including lipid uptake and swelling, are tunable via polystyrene content.
• While biocompatible, the lipophilic nature and degradation of SIBS require careful consideration for specific in vivo uses.
• A predictive model for lipid uptake aids in designing robust SIBS-based medical devices.