Self-Healing Supramolecular Materials Constructed by Copolymerization via Molecular Recognition of Cavitand-Based Coordination Capsules.

The repeating guest units of poly-(R)-2 were selectively encapsulated by the self-assembled capsule poly-1 possessing eight polymer side chains to form the supramolecular graft polymer (poly-1)n ⋅poly-(R)-2. The encapsulation of the guest units was confirmed by 1 H NMR spectroscopy and the DOSY technique. The hydrodynamic radius of the graft polymer structure was greatly increased upon the complexation of poly-1. The supramolecular graft polymer (poly-1)n ⋅poly-(R)-2 was stably formed in the 1:1 host-guest ratio, which increased the glass transition temperature by more than 10 °C compared to that of poly-1. AFM visualized that (poly-1)n ⋅poly-(R)-2 formed the networked structure on mica. The (poly-1)n ⋅poly-(R)-2 gelled in 1,1,2,2-tetrachloroethane, which led to fabrication of distinct viscoelastic materials that demonstrated self-healing behavior in a tensile test.

Facile Synthesis of an Eight-Armed Star-Shaped Polymer via Coordination-Driven Self-Assembly of a Four-Armed Cavitand.

The polystyrene chains were installed at the lower rim of a resorcinarene-based cavitand via reversible addition-fragmentation (RAFT) polymerization to form a four-armed star-shaped polymer. A star-shaped polystyrene-functionalized supramolecular capsule was prepared through the coordination-driven self-assembly of the four-armed start-shaped polymer with silver ions. The eight-armed start-shaped supramolecular capsule encapsulated 4,4'-diacetoxybiphenyl as did a cavitand-based self-assembled capsule. A DOSY measurement indicated that the eight-armed star-shaped polymer was twice as large as the four-armed star-shaped polymer. The solution behaviors of these compounds resulted in a difference in their zero-shear viscosities.

Supramolecular Graft Copolymerization of a Polyester by Guest-Selective Encapsulation of a Self-Assembled Capsule.

Repeating guest units of polyesters poly-(R)-2 were selectively encapsulated by capsule 1(BF4 )4 to produce supramolecular graft polymers. The encapsulation of the guest units was confirmed by 1 H NMR spectroscopy. The graft polymer structures were confirmed by the increase in the hydrodynamic radii and the solution viscosities of the polyesters upon complexation of the capsule. After the capsule was formed, atomic force microscopy showed extension of the polyester chains. The introduction of the graft chains onto poly-(R)-2 resulted in the main chain of the polymer having an M-helical morphology. The complexation of copolymers poly-[(R)-2-co-(S)-2] by the capsule gave rise to the unique chiral amplification known as the majority-rules effect.

Molecular recognition of upper rim functionalized cavitand and its unique dimeric capsule in the solid state.

Cavitand 1 possesses four 2,2'-bipyridyl pillars on its upper rim that encapsulates small guests, such as nitromethane, acetonitrile, methyl acetate, ethyl acetate, and N-methylacetamide, into a deep cavity to form host-guest complexes in a 1:1 ratio. Nitroethane, N,N-dimethylformamide, and N,N-dimethylacetamide were not bound in this manner. A guest-binding study and molecular mechanics calculations revealed that the four 2,2'-bipyridyl pillars of cavitand 1 created a steric boundary that is responsible for selective guest recognition. In the solid state, cavitand 2 formed a unique chiral capsule 2(2) by π-π stacking interactions between the 2,2'-bipyridyl pillars. A nitromethane molecule was unusually placed deep inside the cavity, as directed by the multiple hydrogen bonding interactions between the nitromethane oxygen atoms, the C-H bonds of the bridge methylenes and the pillar phenyl groups.