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The nanocomposites based on poly(n-butyl acrylate)-grafted magnetic Fe3O4 nanoparticles were synthesized via surface reversible addition-fragmentation chain transfer (RAFT) polymerization approach. To promote the supramolecular hydrogen bonding interactions, 2-ureido-4[1H]-pyrimidinone methyl methacrylate (UPyMA) was used as a copolymerization monomer and introduced into the nanocomposites. Transmission electron microscopy (TEM) showed that the Fe3O4 nanoparticles (NPs) were finely dispersed in the polymer matrix. The magnetic analysis showed that the nanocomposites displayed superparamagnetic properties. After the supramolecular quadruple hydrogen bonding interactions were introduced, the nanocomposites displayed the improved thermomechanical properties as evidenced by the enhanced glass transition temperatures (Tg's), Young's modulus and ultimate tensile mechanical strength compared to the unmodified nanocomposites. Most importantly, the nanocomposites were newly endued with the thermally-induced shape memory properties, which can alternatively triggered by the use of the photothermal effect of Fe3O4 nanoparticles. It was found that the rates of shape recovery were increased with the content of the quadruple hydrogen bonding motif. The introduction of the supramolecular hydrogen bonding motif (viz. 2-ureido-4[1H]-pyrimidinone, UPy) imparted the self-healing properties to the nanocomposites via the intense dynamic exchange of hydrogen bonds. The self-healing process can be accelerated by increasing the content of the hydrogen bonding motif.

In this contribution, we reported the synthesis of linear organic-inorganic polyurethanes with heptaphenyl polyhedral oligomeric silsesquioxane (POSS) as the side groups. First, a novel POSS diol was synthesized; then the POSS diol as well as 1,4-butanediol was used as the chain extender to obtain the organic-inorganic polyurethanes with various content of POSS. Gel permeation chromatography (GPC) showed that the high-molecular-weight products were obtained. Small angel X-ray scattering (SAXS) and transmission electron microscopy (TEM) showed that in the organic-inorganic polyurethanes the spherical POSS microdomains with the size of 10–20 nm were formed via POSS-POSS interactions. Compared to plain polyurethane, the organic-inorganic polyurethanes displayed increased glass transition temperatures. Owing to the formation of POSS-POSS interactions, the mechanical properties of the polyurethanes were significantly improved in terms of Young's modulus and tensile strength. More importantly, the organic-inorganic polyurethanes displayed good shape memory properties, which was in marked contrast to plain polyurethane. The improved shape memory properties are attributable to the formation of the POSS microdomains via POSS-POSS interactions, which promoted the inter-chain interactions.

In this work, a novel organic-inorganic polyurethane thermoset crosslinked with a difunctional polyhedral oligomeric silsesquioxanes (POSS) was synthesized via Diels-Alder (DA) reaction. First, a linear multi-segmented polyurethane with furan rings in the main chain (PU–F) was synthesized via the step-growth polymerization of 4,4′-diphenylmethane diisocyanate (MDI) with poly(tetramethylene ether glycol) (PTMEG) and 2,5-furandimethanol. Second, 3,13-dimaleimido octaphenyl double decker silsesquioxane (3,13-dimaleimido DDSQ) was synthesized and used as the crosslinker of the linear PU-F. By adjusting the feed ratio of the difunctional POSS macromer (i.e., 3,13-dimaleimido DDSQ) to PU-F, the organic-inorganic PU thermosets (denoted DAPU-DDSQs) with variable densities of crosslinking were obtained. It was found that the DAPU-DDSQs were microphase-separated and that POSS cages were aggregated into the spherical microdomains, the sizes of which were 20–40 nm in diameter. It was demonstrated that the crosslinking in the DAPU-DDSQs had two aspects of contribution: i) the chemical crosslinking with D-A adducts between 3,13-dimaleimido DDSQ and PU-F and ii) the physical crosslinking with POSS microdomains via the aggregation of POSS cages. The DAPU-DDSQs displayed the improved thermomechanical properties with increasing 3,13-dimaleimido DDSQ incorporation. Owing to the formation of crosslinked structures, the DAPU-DDSQs displayed excellent shape memory properties. More importantly, the DAPU-DDSQs displayed the reprocessing (or recycling) properties at the temperature of retro DA reaction. The reprocessing properties of the DAPU-DDSQs can be utilized to re-edit the original shapes of shape memory PUs.

A novel poly(ionic liquid) (PIL)-containing diblock copolymer was synthesized via a sequential living/controlled polymerization approach. First, the ring-opening polymerization of e-caprolactone (CL) was carried out to obtain a monohydroxyl-terminated PCL. The terminal hydroxyl group of the PCL chain was then exploited to react with carboxyl group of 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid to obtain a trithiocarbonate-terminated PCL. Thereafter, such trithiocarbonate-terminated PCL was used to mediate the radical polymerization of tri-n-butyl-(4-vinylbenzyl) phosphoniumbis(trifluoromethane)sulfonamide (TBP+-TFSI-) to afford PIL diblock copolymers. Notably, the PIL diblock copolymers are capable of displaying self-assembly behavior in selective solvent (e.g., ethyl acetate). In the suspensions of ethyl acetate, the self-assembly generated the spherical micelles with the aggregates of P(TBP+-TFSI-) as the cores and with PCL blocks as the coronas. Such a self-assembly behavior was further employed to obtain epoxy thermoset with nanostructures. Owing to the introduction of fluorine-containing PIL diblock copolymer, the surface dewettability of the thermosets was significantly improved owing to the enrichment of P(TBP+-TFSI-) at the surface. The introduction of PIL microdomains in epoxy resulted that the dielectric constants of the materials were significantly enhanced. More importantly, the dielectric constants were temperature-dependent and can be further enhanced while the nanostructured thermosets were heated above the glass transition temperature of PIL blocks.

A novel five-membered cyclic carbonate compound was synthesized via the reaction of novolac epoxide with carbon dioxide. The cyclic carbonate was then used as the precursor to prepare polyhydroxyurethane (PHU) thermosets with a trifunctional polyetheramine (i.e., Jeffamine T 403) as the crosslinking agent. To improve the thermomechanical properties as well as hydrophobicity, the PHU thermosets were further nanostructured by the use of a poly(trifluoroethyl acrylate)-block-poly(N-vinylpyrrolidinone) (PTFEA-b-PVPy) diblock copolymer. Compared to plain PHU thermoset, the nanostructured thermosets displayed enhanced glass transition temperatures (Tg's) and mechanical properties. Meanwhile, the surface hydrophobicity was significantly improved; the water surface contact angles of the thermosets have been increased up to 94.6°. With the introduction of PTFEA-b-PVPy, the nanostructured PHU thermosets still preserved the excellent shape memory and reprocessability at elevated temperature.