Supramolecular Networks from Block Copolymers Based on Styrene and Isoprene Using Hydrogen Bonding Motifs-Part 1:...

The combination of controlled anionic polymerization and subsequent introduction of hydrogen bonding groups was established to form thermo-reversible, supramolecular networks. Several polyisoprene-block-polystyrene-block-polyisoprene (ISI) copolymers-with polystyrene (PS) as the main block, and consequently giving the decisive material characteristics-were synthesized. The novel modification approach to post-functionalize the polyisoprene (PI) end-blocks and to introduce different motifs, which are able to form self-complementary hydrogen bonds, was attained. In the first step, hydroxylation was accomplished using 9-borabicyclo[3.3.1]nonane. Starting from the hydroxylated polymer, esterification with succinic anhydride was implemented to form an ester group with carboxylic end-group (-O-CO-CH₂-CH₂-COOH). In a second approach, 1,1'-carbonyldiimidazole was used as coupling agent to introduce various types of diamines (diethylenetriamine, triethylentetramine, and 2,6-diaminopyridine) to prepare urethane groups with amine end-group (-O-CO-NH-R-NH₂). ¹H NMR spectroscopy was used to confirm the successful synthesis and to calculate the degree of functionalization D. Differential scanning calorimetry (DSC) showed a difference of the glass transition temperature T between unfunctionalized and functionalized block copolymers, but no greater influence between the different types of modification, and thus, on the T of the PS block. In temperature dependent FTIR spectroscopy, reversible processes were observed.