Sustainable Design of High-Performance Polyurethanes Using Medium-Chain-Length Polyhydroxyalkanoates.

Area of Science:

• Polymer Science and Engineering
• Sustainable Materials Development
• Biomaterials

Background:

• The circular economy drives demand for high-performance, sustainable polymers from renewable resources.
• Medium-chain-length polyhydroxyalkanoates (mcl-PHAs) are biodegradable polyesters with tunable properties, suitable for advanced applications.
• Polyurethanes (PUs) synthesis traditionally relies on petrochemical feedstocks, prompting research into greener alternatives.

Purpose of the Study:

• To develop novel bio-based polyurethanes (PUs) by incorporating mcl-PHAs as flexible soft segments.
• To investigate the structure-property relationships of PUs synthesized with varying ratios of mcl-PHAs and castor oil (CO).
• To evaluate the biocompatibility and eco-toxicological profile of the novel bio-based PUs.

Main Methods:

• Polyurethane networks synthesized using castor oil (CO) and mcl-PHAs as polyols, and hexamethylene diisocyanate (HMDI) as the hard segment.
• Systematic variation of the mcl-PHA/CO ratio from 100/0 to 0/100 to tune material properties.
• Comprehensive characterization including thermal analysis, mechanical testing, swelling behavior, and morphology assessment.
• In vitro biocompatibility testing with MRC-5 fibroblasts and eco-toxicological evaluation using *Caenorhabditis elegans*.

Main Results:

• Successful synthesis of bio-based PUs confirmed by urethane bond formation.
• Materials exhibited tunable thermal and mechanical properties, with increased mcl-PHA content enhancing elasticity.
• Predominantly amorphous structures were observed, with phase organization influenced by mcl-PHA content.
• Adjustable swelling behavior and morphology were achieved.
• In vitro biocompatibility and eco-toxicological assessments confirmed the absence of toxicity.

Conclusions:

• Medium-chain-length polyhydroxyalkanoates (mcl-PHAs) are effectively utilized as sustainable, flexible soft segments in polyurethane synthesis.
• The developed bio-based PUs demonstrate tunable properties and competitive mechanical performance.
• These novel materials present a promising, non-toxic alternative for advanced polymer applications within a circular economy framework.