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The nanocomposites of ferroferric oxide ([Fe.sub.3][O.sub.4]) with polyhydroxyurethane (PHU) were fabricated via a physical mixing approach. This process involved grafting poly(N-vinyl pyrrolidone) (PVPy) chains onto the surfaces of [Fe.sub.3][O.sub.4] nanoparticles via surface-initiated living radical polymerization. The PVPy-grafted [Fe.sub.3][O.sub.4] nanoparticles were directly incorporated into the precursors of PHUs [i.e., bis(cyclic carbonate) and a trifunctional amine] and the mixtures were cured at high temperatures to form organic-inorganic composites. This method ensured that [Fe.sub.3][O.sub.4] nanoparticles were finely dispersed within the PHU matrix through the strong intermolecular hydrogen bonding between PVPy and PHU. Compared to plain PHU network, the nanocomposites had enhanced thermomechanical properties, including higher glass transition temperatures ([T.sub.g]'s) and improved tensile mechanical properties. The inclusion of [Fe.sub.3][O.sub.4] nanoparticles also enhanced the shape memory properties of the PHU networks, improving shape recovery rates, fixity of transient shapes, and recovery of the original shapes. In addition, the nanocomposites demonstrated paramagnetic and photothermal properties and the photothermal behavior enabled a non-contact control of shape recovery. Highlights * Poly(N-vinyl pyrrolidone)-grafted [Fe.sub.3][O.sub.4] nanoparticles were synthesized. * Nanocomposites of PHU with [Fe.sub.3][O.sub.4] were prepared via a physical blending approach. * Incorporation of [Fe.sub.3][O.sub.4] resulted in improved thermomechanical properties. * The nanocomposites had the photothermal properties. KEYWORDS [Fe.sub.3][O.sub.4], nanocomposites, paramagnetic and photothermal properties, polyhydroxyurethane, shape memory properties, 1 | INTRODUCTION Polyurethanes (PUs) were first developed by Otto Bayer in 1939. (1) Over the past decades, PUs have been among the most major synthetic polymers. In general, the [...]

In this work, we investigated the effect of organosilicon modification of an ABA triblock copolymer on the morphologies, thermal properties, and fracture toughness of epoxy thermosets. First, a poly([epsilon]-caprolactone)-block- poly(butadiene) -block-poly([epsilon]-caprolactone) triblock copolymer was synthesized through the ring-opening polymerization of [epsilon]-caprolactone by using an [alpha],[omega]-dihydroxyl-terminated polybutadiene as the macromolecular initiator. Thereafter, the triblock was organosilicon-modified via the hydrosilylation of its midblock (viz. polybutadiene) with pentamethyldisiloxane. It was found that the organosilicon modification resulted in a switch of the nanostructure formation mechanism from reaction-induced microphase separation to self- assembly. As a consequence of the organosilicon modification, the morphological structures of the thermoset were significantly changed, and thus, the materials displayed different improvement in fracture toughness. In addition, the organosilicon modification further enhanced the surface hydrophobicity of the materials. KEYWORDS block copolymer, fracture toughness, nanostructure, reaction-induced microphase separation, self-assembly, thermosets, 1 | INTRODUCTION The use of block copolymers to modify thermosets has been demonstrated to be an effective strategy for improving the properties of materials. The improvement in properties is [...]

In this contribution, we reported the synthesis of the nanocomposites of poly(n-butyl acrylate) with Fe3O4 nanoparticles (NPs) via dynamic crosslinking of poly(n-butyl acrylate)-grafted Fe3O4 NPs with hindered urea bonds (HUBs). Towards this end, the surfaces of Fe3O4 NPs were grafted with poly(n-butyl acrylate-ran-2-(3-tert-butyl-3-ethylureido)ethyl acrylate) chains [denoted as Fe3O4-g-P(BA-r-TBEA)] via living radical polymerization. Thereafter, 1,2-bis(tert-butyl)ethylenediamine was used as a crosslinker to afford the organic–inorganic networks with variable contents of Fe3O4 NPs and crosslinking densities. It was found that the fine dispersion of Fe3O4 NPs in the matrix of poly(n-butyl acrylate) was achieved. The nanocomposites exhibited excellent reprocessing properties, attributed to the introduction of HUBs. Owing to the crosslinking, the nanocomposites displayed excellent shape memory properties. Further, the nanocomposites possessed photo- and magnetic–thermal properties, which were inherited from Fe3O4 NPs. These functional properties allow triggering the shape shifting of the nanocomposites in an uncontacted fashion. [ABSTRACT FROM AUTHOR]

The nanocomposites of ferroferric oxide (Fe3O4) with polyhydroxyurethane (PHU) were fabricated via a physical mixing approach. This process involved grafting poly(N‐vinyl pyrrolidone) (PVPy) chains onto the surfaces of Fe3O4 nanoparticles via surface‐initiated living radical polymerization. The PVPy‐grafted Fe3O4 nanoparticles were directly incorporated into the precursors of PHUs [i.e., bis(cyclic carbonate) and a trifunctional amine] and the mixtures were cured at high temperatures to form organic–inorganic composites. This method ensured that Fe3O4 nanoparticles were finely dispersed within the PHU matrix through the strong intermolecular hydrogen bonding between PVPy and PHU. Compared to plain PHU network, the nanocomposites had enhanced thermomechanical properties, including higher glass transition temperatures (Tg's) and improved tensile mechanical properties. The inclusion of Fe3O4 nanoparticles also enhanced the shape memory properties of the PHU networks, improving shape recovery rates, fixity of transient shapes, and recovery of the original shapes. In addition, the nanocomposites demonstrated paramagnetic and photothermal properties and the photothermal behavior enabled a non‐contact control of shape recovery. Highlights: Poly(N‐vinyl pyrrolidone)‐grafted Fe3O4 nanoparticles were synthesized.Nanocomposites of PHU with Fe3O4 were prepared via a physical blending approach.Incorporation of Fe3O4 resulted in improved thermomechanical properties.The nanocomposites had the photothermal properties. [ABSTRACT FROM AUTHOR]

In this contribution, the transformation of polydicyclopentadiene (PDCPD) from thermoset into vitrimer is introduced. First, two N‐coordinated diboronic diols are successfully synthesized via the reaction of N,N,N‐tri(2‐hydroxyethyl)amine and/or N,N,N",N"‐tetrakis(2‐hydroxyethyl)ethylene diamine with 4‐(hydroxymethyl) phenylboronic acid and then they are transformed into two N‐coordinated cyclic boronic diacrylates. The latter two dienes carrying electron‐withdrawing substituents are used for the ring opening insertion metathesis copolymerization (ROIMP) of dicyclopentadiene to afford the crosslinked PDCPD. In the crosslinked PDCPD networks, N‐coordinated cyclic boronic ester bonds are integrated. It is found that the as‐obtained PDCPD networks displayed the excellent reprocessing properties. In the meantime, the fracture toughness is significantly improved. Owing to the inclusion of N‐coordinated cyclic boronic ester bonds, the modified PDCPDs have the thermal stability much superior to plain PDCPD. The results reported in this work demonstrate that PDCPD can successfully be transformed into the vitrimers via the introduction of N‐coordinated cyclic boronic ester bonds. [ABSTRACT FROM AUTHOR]

The nanocomposites of polythiourethane (PTU) with Fe3O4 were fabricated via an isocyanate-free approach. The nanocomposites simultaneously had the reprocessing, shape memory and photothermal properties. First, a linear PTU carrying a plethora of thiol groups was synthesized via the ring opening polyaddition between a bicyclic trithiocarbonate and a poly (propylene oxide) diamine. In the meantime, the surfaces of Fe3O4 nanoparticles were functionalized with thiol groups. Second, the co-crosslinking between the linear PTU and the thiol-functionalized Fe3O4 was performed via the coupling of thiol radicals with a radical initiator. Notably, the nanocomposites of PTU with Fe3O4 were successfully obtained with the fine dispersion of Fe3O4 nanoparticle in PTU matrix. Compared to control PTU, the nanocomposites displayed the improved thermomechanical properties. More importantly, the nanocomposites had reprocessing properties. The dynamic exchange of disulfide bonds is responsible for the reprocessing behavior. Owing to the crosslinking with disulfide bonds, PTU had shape memory properties. Notably, the incorporation of Fe3O4 nanoparticles was capable of improving the shape memory properties. In addition, the nanocomposites displayed the photothermal properties with the incorporation of Fe3O4 nanoparticles. The photothermal conversion behavior can be utilized to trigger the shape recovery of the nanocomposites under near-infrared light irradiation and in a non-contact fashion. [ABSTRACT FROM AUTHOR]

In this contribution, we reported to utilize polystyreneo/oc/ c-polybutadiene-o/oc/f-polystyrene(PS-b-PB-6-PS), a commercial triblock copolymer to toughen epoxy thermosets. First, a PS-o-PB-b-PS triblock copolymer was chemically modified with hydroboration-oxidation reaction, with which the midblock was hydroxylated whereas the endblocks remained unaffected. It was found that the degree of hydroxylation was well controlled. One of the hydroxylated PS-Jb-PB-fa-PS samples was then used as the macromolecular initiator to synthesize a poly(e-caprolactone)-grafted PS-fa-PB-o-PS via the ring-opening polymerization. It was found that the PS-b-PB-b-PS with poly (e-caprolactone) grafts can be successfully employed to nanostructure epoxy thermosets; the 'core-shell' microdomains composed of PB and PS were generated in the nanostructured thermosets. The nanostructured thermosets displayed improved fracture toughness., INTRODUCTION Thermosetting polymers such as epoxy, phenolic, unsaturated, and bismaleimide resins have wide-spread application in the fields such as aerospace and electronics owing to their high modulus, chemical resistance, and [...]