Anionically polymerized supramolecular thermoplastic elastomers

Oligomers of Nylon 3 (Oligo(beta-alanine)) were used as monodisperse hard blocks in poly(butadiene) and poly(isoprene) based thermoplastic elastomers. All polymers were of linear ABA tri-block architecture. The dicarboxy or dihydroxy terminated diene midblocks were synthesized via anionic polymerization and served as the B block while oligo(beta-alanine) served as the A block.;A series of low-vinyl content (Mn ~60K, 12% vinyl) poly(butadiene)s were functionalized with oligo(beta-alanine)n (n = 2, 3, 4) and hydrogenated, forming low-butyl content poly(ethylene-butylene) (PEB) polymers. To reduce the crystallinity of the hydrogenated mid-block, two other diene mid-blocks were synthesized. The first was a set of high-vinyl content, dicarboxy terminated poly(butadiene)s (A. Mn ~44K, 30% vinyl B. Mn ~116K, 46% vinyl). High-butyl content PEB polymers resulted after hydrogenation. The second was a set of dicarboxy terminated poly(isoprene)s (Mn ~15K, 44K, 98K), forming poly(ethylene-propylene) (PEP) polymers after hydrogenation. Another dihydroxy terminated poly(isoprene) (Mn ~18K) was synthesized. Each polymer was oligo(beta-alanine)4 functionalized.;FT-IR spectroscopy showed beta-sheet formation for all of the synthesized polymers. The low-butyl set behaved as a physically cross-linked network and acted as an elastomeric solid at 105 °C by rheological measurements at ≤1.2 wt% of beta-alanine peptide. These materials were classified as 'solids'. The high-butyl content PEBs formed physically cross-linked networks but did not act as stable, elastomeric solids at 105 °C. The dihydroxy terminated PEP acted in similar fashion to the high-butyl PEB after oligo(beta-alanine) functionalization. These were classified as 'solid-liquid' materials. The remaining PEP samples did not form physically cross-linked networks and acted as higher molecular weight, chain-extended structures. They were classified as liquid materials.;The sterics of the mid-block end-group immediately adjacent to the oligo(beta-alanine) end-group likely led to disruption in the beta-sheet stacking, thus not allowing complete crystallization of the oligo(beta-alanine) units to take place. The varying degree of disruption led to three types of materials, indicating that the mid-block end-group was a key factor in determining the formation of a physically cross-linked network. When beta-sheet stacking was completely disrupted as in the 'lquid' classified polymer, the addition of a supramolecular filler resulted in the formation of a physically cross-linked network.