Terpene Coordinative Chain Transfer Polymerization: Understanding the Process through Kinetic Modeling.

Area of Science:

• Polymer Chemistry
• Materials Science
• Catalysis

Background:

• Increasing interest in using naturally occurring terpenes for high-performance rubber production.
• Coordinative Chain Transfer Polymerization (CCTP) offers a pathway for controlled synthesis of terpene-based polymers.
• Understanding polymerization kinetics and chain transfer mechanisms is crucial for material property control.

Purpose of the Study:

• To synthesize poly(β-myrcene) using CCTP with a neodymium versatate (NdV3) and diisobutylaluminum hydride (DIBAH) catalytic system.
• To investigate the polymerization kinetics and chain dynamics through GPC analysis and mathematical modeling.
• To optimize catalyst ratios and determine kinetic parameters for controlled poly(β-myrcene) synthesis.

Main Methods:

• Synthesis of poly(β-myrcene) via CCTP using NdV3/DIBAH catalytic system and dimethyldichlorosilane activator.
• Gel Permeation Chromatography (GPC) to analyze molecular weight distribution and identify chain populations (dormant vs. dead).
• Development of a mathematical kinetic model using the Method of Moments to fit experimental data and estimate rate constants.

Main Results:

• Bimodal GPC distributions at low conversions indicated distinct dormant and dead polymer chains, shifting to unimodal at higher conversions.
• The kinetic model accurately predicted experimental results, with an excellent fit achieved through SSE minimization.
• Arrhenius parameters were estimated, and optimal ratios of [β-myrcene]0:[NdV]0:[DIBAH]0:[Me2SiCl2]0 were identified for catalytic activity and end-group functionality preservation.

Conclusions:

• CCTP is a viable method for synthesizing poly(β-myrcene) with controllable chain characteristics.
• The developed kinetic model provides valuable insights into the polymerization mechanism, including reversible chain transfer.
• Optimizing monomer-to-catalyst ratios is key to balancing catalytic activity and maintaining desired end-group functionality for high-performance rubber applications.