Green polymer chemistry: living dithiol polymerization via cyclic intermediates

Area of Science:

• Polymer Chemistry
• Materials Science
• Organic Synthesis

Background:

• Disulfide polymers offer unique redox-responsive properties.
• Efficient and environmentally friendly polymerization methods are crucial for advanced materials.

Purpose of the Study:

• To synthesize and characterize novel disulfide polymers from 2-[2-(2-sulfanylethoxy)ethoxy]ethanethiol (DODT).
• To investigate the polymerization mechanism and properties, including molecular weight, thermal behavior, and reversibility.
• To demonstrate the living/controlled nature of the polymerization for potential applications.

Main Methods:

• Oxidative polymerization of DODT using air, hydrogen peroxide, and a recyclable triethylamine catalyst.
• Determination of absolute molecular weight using dn/dc in THF.
• Thermal analysis via Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA).
• Reductive cleavage using dithiothreitol and chain extension with 1,2-ethanedithiol.
• Analysis of polymerization intermediates using MALDI-ToF mass spectrometry.

Main Results:

• High molecular weight disulfide polymers (M(n) up to 250,000 g/mol) with low polydispersity (M(w)/M(n) = 1.15) were achieved.
• Polymers exhibited a glass transition temperature (T(g)) of -50 °C and degradation onset at 250 °C.
• Complete polymer reduction to monomeric units was observed in 33 hours.
• Evidence of oligodisulfide ring involvement and successful chain extension indicated living polymerization characteristics.

Conclusions:

• A benign and efficient method for synthesizing high molecular weight disulfide polymers was developed.
• The synthesized poly(DODT) demonstrates excellent thermal stability and redox-responsive behavior.
• The polymerization exhibits living characteristics, enabling controlled chain extension and potential for complex polymer architectures.