We propose a new strategy to enhance mechanical properties of ABA triblock copolymer-based elastomers by incorporating transient cross-links into the soft middle block. An ABA triblock-type copolymer, poly(4vinylpyridine)-b-[(poly(butyl acrylate)-co-polyacrylamide]-bpoly(4-vinylpyridine) (P−Ba−P), was synthesized via RAFT polymerization. In the molecular design, the poly(4-vinylpyridine) (P) end blocks with a high T g formed pseudo-crosslink domains due to segregation against the soft Ba middle block, while acrylamide units on the middle block formed selfcomplementary hydrogen bonding, serving as transient crosslinks. According to tensile tests, the Young's modulus, elongation at break, maximum stress, and material toughness were 1.9 MPa, 200%, 2.6 MPa, and 2.8 MJ/m 3 , respectively. Comparison between mechanical properties of P−Ba−P and those of another triblock copolymer, poly(4-vinylpyridine)-bpoly(butyl acrylate)-b-poly(4-vinylpyridine) (P−B−P), revealed that P−Ba−P showed larger Young's modulus, longer elongation at break, and larger maximum tensile stress than P−B−P. Particularly, the material toughness of P−Ba−P (2.8 MJ/ m 3 ) was more than 100 times larger than that of P−B−P (0.02 MJ/m 3 ). Rheological analysis on the basis of sticky Rouse relaxation of Ba middle block of P−Ba−P suggested that the hydrogen bonds on the middle block serve as dynamic stickers in elastic strands of elastomers under stress. Such dynamic behavior of the hydrogen bonds could prevent local concentration of applied stress for activating break/failure of the materials during elongation, leading to mechanical property enhancement of the materials. In addition, zinc chloride was blended with P−Ba−P to form metal−ligand coordination in the P end block domains, which also affected the mechanical properties of the elastomers.

Thermoreversible supramolecular polymer gels were prepared via metal−ligand coordination by mixing a poly(4-vinylpyridine)-b-poly(ethyl acrylate)-b-poly(4-vinylpyridine) (P4VP−PEA− P4VP) triblock copolymer and zinc chloride (ZnCl 2 ) in a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imidide. FT-IR spectroscopy revealed metal−ligand coordination between zinc in ZnCl 2 and pyridine groups as ligands on P4VP blocks, even in an ionic liquid. Thermoreversible viscoelastic properties between a semisolid (gel-like) state and a liquid-like state were confirmed by temperature-ramp oscillatory shear measurements. It was also revealed that thermoreversibility of supramolecular polymer gels depended strongly on stoichiometry between ligands and metals, where the maximum of storage modulus-loss modulus crossover temperature (T gel ) as an indicator of gelation was achieved when a molar amount of available coordination sites was a certain excessive amount (coordination site/ ligand ratio ∼1.6). The molar ratio at the maximum T gel is nearly independent of the number of ligands per triblock copolymer. On the other hand, the number of ligands per triblock copolymer affected the T gel , where a larger number of ligands per triblock copolymer gave a higher T gel , regardless of almost the same molecular weight of triblock copolymers.

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We describe the preparation and catalytic reactions of new CCN pincer Rh and Ru complexes containing NCH-oxazoline hybrid ligands. Oxazolinyl-phenyl-imidazolium derivatives (3) were suitable ligand precursors for the CCN pincer scaffold. C−H bond activation of 3 with RhCl 3 • 3H 2 O in the presence of NEt 3 yielded the desired CCN pincer Rh complexes 5 in 13−27% yields. The related CCN pincer Ru complexes 8−10 were synthesized in good yields by C−H bond activation of p-cymene Ru complexes 7 in the presence of NaOAc in DMF. The chiral complexes 8 and 9 had two diastereomers according to the coordination of CO and OAc ligands.The CCN Rh complexes showed catalytic activity for conjugate reduction of ethyl β-methylcinnamate with hydrosilane, with moderate enantioselectivity. The CCN Ru complexes were found to be active in the hydrogenation of aromatic ketones. In particular, hydrogenation of 9-acetylanthracene took place at not only the CO bond but also the anthracene ring. The Ru complexes were also used as catalysts in the transfer hydrogenation of 9-acetylanthracene with 2-propanol; again, both the CO bond and the anthracene ring were hydrogenated.