Amphiphilic model gels composed of complementary tetra-functionalized star polymers*

In this work, we compare the synthesis and structure of model networks built from tetra-PEG and tetra-PCL star polymer solutions with computer simulations. Covalent networks at stoichiometric conditions result from selective coupling of amine end groups on PEG branches with benzoxazinone end groups on PCL, for varying polymer volume fractions and molecular weights of the stars.

We analyze the extent of reaction, the weight fraction of sol, and the equilibrium degree of swelling of the networks and compare them with computer simulations at similar parameters for molecular weight and concentration. These studies demonstrate that our coupling procedure provides excellent networks, similar to the quality level reached in Sakai's group. We further explore the impact of an imperfect mixing of both types of stars on the network structure due to a possible weak association of the end groups prior to cross-linking, or due to solvent conditions that might be of slightly different quality for both types of polymer.