Structure, preparation and properties of liquid fluoroelastomers with different end groups

Area of Science:

• Polymer Chemistry
• Materials Science
• Organic Synthesis

Background:

• Liquid fluoroelastomers are advanced materials with tunable properties.
• Controlling end-group functionality is crucial for tailoring elastomer performance.
• Existing synthesis methods may have limitations in efficiency or scope.

Purpose of the Study:

• To synthesize carboxyl-terminated and hydroxyl-terminated liquid fluoroelastomers.
• To investigate the relationship between molecular structure and material properties.
• To develop and characterize a suitable curing system for these novel fluoroelastomers.

Main Methods:

• Oxidation degradation and functional group conversion for end-group synthesis.
• Spectroscopic techniques (ATR-FTIR, 1H-NMR, 19F-NMR) and chemical titration for characterization.
• Gel permeation chromatography (GPC), DSC, TGA, viscometry, universal testing machine, and contact angle measurements for property analysis.

Main Results:

• Successfully prepared carboxyl-terminated liquid fluoroelastomers (2.71 wt% carboxyl groups) via oxidation degradation.
• Achieved >95% conversion of carboxyl to hydroxyl groups using lithium aluminum hydride.
• Observed temperature-dependent viscosity (approx. 10 Pa·s at 70 °C) for both types.
• Hydroxyl-terminated fluoroelastomers demonstrated enhanced curing reactivity, higher Tg and Td, and improved mechanical properties.
• Distinct hydrophilicity was observed between the two end-group types.

Conclusions:

• Established efficient synthesis routes for distinct end-group functionalized liquid fluoroelastomers.
• Demonstrated that hydroxyl-terminated fluoroelastomers offer superior performance characteristics.
• Highlighted the significant impact of end-group functionality on fluoroelastomer properties and applications.