The in situ growth of one-dimensional magnetite (Fe 3 O 4 ) nanowire (NW) arrays with deterministic and tunable control over their orientation and morphology on a wide range of flexible and low heat resistance substrates is still a challenge. Herein, a facile method of controlling the orientation of Fe 3 O 4 NW arrays on a polypropylene (PP) nonwoven fabric surface (PP-g-PAO/Fe 3 O 4 ) through simultaneous radiation induced graft polymerization and coprecipitation processes was realized. We demonstrated a control over the orientation and geometric properties of coprecipitated Fe 3 O 4 NWs via complex iron ion using amidoxime groups, which not only endow the material with high durability but also lead to the oriented growth of Fe 3 O 4 NWs. The results showed that Fe 3 O 4 NWs were only grown on the surface of the PP nonwoven fabric (length:diameter ratio ≈ 10), whereas the Fe 3 O 4 produced in the solution exhibited a spherical structure under identical conditions. The PP-g-PAO/ Fe 3 O 4 composite presented a good saturated magnetization, superparamagnetic property, outstanding service life and recyclability, and exhibited two extraordinary sensing capabilities, i.e., UV and magnetic. This strategy can be viewed as the first example of in situ coordination induced growth of Fe 3 O 4 NW arrays on the surface of a flexible substrate under mild conditions, and nanosensors based on PP-g-PAO/Fe 3 O 4 hold tremendous prospects for multiparametric sensing platforms.
High-strength and
high-temperature triple shape memory elastomers
from multiphase polyolefin elastomer (POE)/polypropylene (PP) blends
are prepared via radiation-induced vulcanization. Irradiation generates
cross-linking mainly in the amorphous sequences of POE chains, long
chain branches in the amorphous regions of PP crystals, and grafting
between PP and POE chains at the interface of the POE and PP phases.
The discoid-like PP phase with an average size of 1.6 × 11 μm2, dispersed in the POE matrix, is aligned parallel to the
plane of the recompressed films. The PP lamellar crystals is partially
orientated, and the PP lamellar crystals with (040)α and (110)α planes are arranged parallel and perpendicular
to the surface of the highly cross-linked films, respectively. The
integration of heterogeneous macromolecular structure, partially orientated
crystals, and separated multiphase morphology contributes to excellent
triple shape memory effects and high tensile strength up to 38 MPa.
Consequently, two temporary shapes with fixity ratios of 82 and 97%
are programmed by the reversible aggregation and solidification of
the segregated PP lamellar crystals and POE bundle-like crystals.
Under thermal triggering at the switching temperatures of 90 and 180
°C, the entropy-driven elasticity of the discrete PP and POE
switching segments provides a good shape recovery of 88 and 94% to
the memorized complex permanent shape. These results indicate that
designing and tailoring the unconventional macromolecular architecture
and condensed-state structure provide a novel strategy for developing
low cost, high performance, and flexible intelligent polyolefins.
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