Model-based visualization and understanding of monomer sequence formation in the synthesis of gradient copoly(2-oxazoline)s

For the first time, the formation of monomer sequences of individual macromolecules during cationic ring-opening copolymerization (CROcoP) of 2-methyl-2-oxazoline (MeOx) and 2-phenyl-2-oxazoline (PhOx) in acetonitrile (3 mol L-1; 100-140 degrees C; target degree of polymerization (DP): 50-400) is visualized via kinetic Monte Carlo simulations with model parameters optimized based on experimental data. It is shown that chain transfer via beta-elimination and branching reactions are required to describe the experimental data. At complete monomer conversion for target DPs below 200, at most 5% of the chains are macromonomers and the average number of branches per chain remains below 15%. A higher amount of chains with a defined, steeper MeOx to PhOx gradient is obtained by lowering the polymerization temperature albeit at the expense of polymerization time. The simulations results highlight the great potential of CROcoP of 2-oxazolines for the direct synthesis of well-defined steep gradient copolymers.

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