Figure 6.

Reaction scheme illustrating worm core cross-linking chemistry by (i) epoxy ring-opening via nucleophilic attack with APTES and (ii) intermolecular cross-linking via hydrolysis-condensation. The latter step involves either reaction of the APTES with hydroxyl groups on HPMA residues on another copolymer chain (denoted as 1) and/or condensation with other APTES groups (denoted as 2). In reality, ¹H NMR studies indicate that these two steps occur more or less simultaneously, rather than consecutively as shown (see main text for details). Moreover, the chemistry is likely to be more complex than that shown as the secondary amine species may react further.