Double-decker silsesquioxane (DDSQ) cages were introduced into the main chains of polycyclooctadiene via a ring-opening metathesis polymerization (ROMP) approach. Toward this end, a macromolecular chain transfer agent for the ROMP was synthesized via acyclic diene metathesis polymerization of 3,13-diallyl DDSQ with the Grubbs second catalyst. To regulate the intermolecular specific interactions, 4-(2-hydroxyethyl)-10-oxa-4-azatricyclo-[5.2.1.02,6]dec-8-ene-3,5-dione-2-ureido-4[1H]-pyrimidinone was synthesized and used as a monomer of copolymerization. It was found that the organic−inorganic copolymers were heterogeneous at the nanometer scale. The POSS (viz., DDSQ) cages were aggregated into the POSS nanophases with the size of 20−30 nm. The POSS microdomains behaved as the netpoints of physically cross-linked networks and thus the organic−inorganic copolymers can display the behavior of cross-linked elastomers. As a result of the physical crosslinking, the organic−inorganic copolymers possessed shape memory properties. Meanwhile, the materials possessed excellent self-healing properties and plasticity in solids with the quadruple hydrogen bonds with 2-ureido-4[1H]-pyrimidinone groups. While the organic−inorganic copolymers were used as shape memory materials, their original shapes can be reprogrammed by the use of the plasticity in solids of the materials.

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In this contribution, we reported the synthesis of a novel trifunctional POSS cyclic carbonate [POSS-3(5CC)]. With a difunctional five-member cyclic carbonate and a trifunctional polyetheramine as the precursor, the nanocomposites of polyhydroxyurethane (PHU) with POSS were synthesized. Transmission electron microscopy (TEM) showed that the nanocomposites of PHUs with POSS were microphase-separated; the spherical POSS microdomains via POSS-POSS interactions were generated with the size of 20~40 nm in diameter. After the introduction of POSS microdomains, the nanocomposites displayed improved thermal and mechanical properties. More importantly, the nanocomposites still displayed the reprocessing properties of vitrimers.

Linear organic–inorganic polyureas (PUreas) with polyhedral oligomeric silsesquioxane (POSS) cages in the main chains were synthesized via polycondensation of diamines with carbon dioxide (CO2). First, 3,13-dianilino double decker silsesquioxane (denoted 3,13-dianilino DDSQ) was synthesized. An α,ω-diamino-terminated poly­(propylene oxide) as well as the POSS diamine was exploited for polycondensation with CO2; PUrea and PUrea-DDSQ with sufficiently high molecular weights were obtained with various contents of POSS. The morphological investigation shows that the linear PUreas with POSS cages in the main chains were microphase-separated; the POSS cages were aggregated into spherical microdomains with the size of 50–120 nm in diameter. Owing to the introduction of POSS cages, PUrea was transformed from a viscous liquid into elastic solids in the ranges of composition investigated. At room temperature, linear organic–inorganic PUreas behaved as cross-linked elastomers. This behavior is ascribed to the generation of physical cross-linking with POSS microdomains as the cross-linking sites. In addition, the organic–inorganic PUreas displayed self-healing properties via the dynamic exchange of multiple hydrogen bonds. It was found that the self-healing properties were significantly affected by the content of 3,13-dianilino DDSQ.