Macromolecules with branched architecture via radical polymerization: Insight from computer simulations

Area of Science:

• Polymer Chemistry
• Materials Science
• Computational Chemistry

Background:

• Branched polymers offer tunable properties but are difficult to synthesize with desired characteristics via conventional radical polymerization (RP).
• A systematic investigation into controlling macromolecular architecture during RP is lacking.

Purpose of the Study:

• To develop a computational model for simulating branched polymer formation using RP.
• To investigate the influence of crosslinker (CL) and chain-transfer agent (CTA) concentrations on polymer architecture and solubility.

Main Methods:

• A three-dimensional coarse-grained molecular-dynamics model based on the Kremer-Grest framework was employed.
• Simulations incorporated stochastic reactions including initiation, propagation, crosslinking, chain transfer, and termination.
• Macromolecular architecture was analyzed using graph-based decomposition and fractal dimension calculations.

Main Results:

• Two distinct polymerization regimes were identified based on CTA content.
• Low CTA content led to early gelation and a network-dominated system.
• Increased CTA content shifted gelation to higher conversions, promoting a soluble fraction of high-molecular-weight branched polymers.
• An optimal condition [CL] = 2[CTA] was found for achieving high conversion gelation, yielding soluble branched macromolecules.

Conclusions:

• The study provides quantitative guidance for synthesizing soluble branched polymers using standard RP.
• Control over reagent ratios (CL and CTA) is crucial for tailoring polymer architecture and achieving desired properties.