Supramolecular Networks from Block Copolymers Based on Styrene and Isoprene Using Hydrogen Bonding Motifs - Part 1: Synthesis and Characterization
AbstractThe 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 Df. Differential scanning calorimetry (DSC) showed a difference of the glass transition temperature Tg between unfunctionalized and functionalized block copolymers, but no greater influence between the different types of modification, and thus, on the Tg of the PS block. In temperature dependent FTIR spectroscopy, reversible processes were observed.