This review paper summarizes the categories, sensing mechanisms, and affecting factors of flexible conductive polymer composite-based stretchable strain sensors.
Confined self-assembly of block copolymers
(BCPs) is effective
to manipulate various shapes of particles. In emulsion confined self-assembly,
reversibly light-trigged switchable BCP particles are extremely expected,
yet rarely reported. Herein, a novel strategy is developed to realize
reversibly light-responsive shape-transformation of BCP particles
by constructing functional surfactants with light-active azobenzene
(azo) groups in the confined self-assembly of BCPs within emulsion
droplet. Ultraviolet and visible lights can reversibly modulate the
amphiphilicity and interfacial affinity of the surfactants to different
blocks, triggering the reversible microphase structure transformation
of BCP particles with high temporal-spatial resolution. We can realize
shape and morphological transitions of BCP particles from onion-shaped
spherical particles to striped ellipsoids and, ultimately, to inverse
onion-like particles by ultraviolet irradiation. More importantly,
this shape transformation is reversible by the irradiation of visible
light, attributed to the reversible trans–cis isomerization of azo groups. We also demonstrate that
the light-triggered shape transformation of BCP particles can be employed
in a controllable drug release through a noncontacted and programmed
manner, showing promising potential in clinic and biomedicine.
The miscibility and physical and rheological properties
of binary
poly(vinylidene fluoride)/maleic anhydride (PVDF/MAH) blends have
been systematically investigated. MAH was found to be miscible with
PVDF by scanning electron microscopy (SEM), differential scanning
calorimetry (DSC), and dynamic mechanical analysis (DMA). Fourier
transform infrared (FTIR) investigations provided positive evidence
for the specific interaction between the carbonyl groups of MAH and
the methylene groups of PVDF. Rheological measurements showed that
both the storage modulus and the melt viscosity of PVDF increase with
the addition of MAH, followed by a decrease with excess MAH. In addition,
the elongation of the PVDF/MAH blend with 10 wt % MAH is 589.7%, which
is almost 5 times that of neat PVDF. It is concluded that MAH small
molecules act as physical “crosslinking” points for
the neighboring PVDF molecule chains due to this specific interaction
between PVDF and MAH. Such a physical crosslinking function enhances
the storage modulus, viscosity, and mechanical properties of PVDF.
Inside Front Cover: In article number 1900316, Jichun You and co‐workers provide an efficient strategy to prepare poly(L‐lactic acid) (PLLA) with high ductility and transparency, in which tiny amount of polyvinylidene fluoride (PVDF) and compatibilizers are added to the PLLA matrix. The left part is the PVDF/PLLA blend without compatibilizers while the right part is the PVDF/PLLA blend with compatibilizers. The PVDF/PLLA blends containing compatibilizers exhibit better mechanical and optical properties.
In this work, we proposed an effective route, i.e., three-dimensional (3D) confined co-assembly of block copolymers (BCPs) and inorganic nanoparticles (NPs) within the organic emulsion droplet, to efficiently encapsulate high-density...
Reactive
compatibilization is a cost-effective and efficient way
to fabricate high-performance multicomponent polymeric materials.
The reactive compatibilization of low-density polyethylene (LDPE)
and poly(l-lactide) (PLLA) blends has seldom been reported
because LDPE is inert to the chemical reaction during melt compounding.
In this work, we first grafted carboxylic acid groups onto the PE
molecular chains (m-LDPE), followed by a facile binary grafting strategy
to compatibilize PLLA/LDPE blends. Poly(styrene-co-glycidyl methacrylate) (SG) has been used as the main chains for
the binary grafting. The carboxylic acid groups of both PLLA and m-LDPE
can react with the epoxide groups on SG main chains during the melt
blending, leading to the in situ formation of both LDPE and PLLA grafted
copolymers. Such binary grafted copolymers act as effective compatibilizers
for the highly immiscible PLLA/LDPE (80/20) blends. The compatibilized
blends exhibit excellent mechanical performance. The tensile strength
of the compatibilized PLLA/LDPE blends increases from 26.4 to 36.7
MPa, and the elongation remarkably enhances from 9 to 367%, as compared
with the same blends without compatibilization. At the same time,
the Charpy impact strength of the compatibilized blend is 100.1 kJ/m2, which is 6.2 times that of the LDPE/PLLA binary blend. The
fabricated PLLA/LDPE blends show potential engineering applications
as environment-friendly materials. In addition, the in situ binary
grafting strategy paves a new possibility for the reactive compatibilization
of immiscible polymer blends with no reactive groups.
Poly(L‐lactic acid) (PLLA) with high ductility and transparence is fabricated by a blending tiny amount of polyvinylidene fluoride (PVDF) and reactive comb compatibilizers (RCC). Upon blending, the reaction between terminal carboxyl groups in PLLA and expoxy groups in RCC produces graft copolymer (PLLA‐g‐poly(methyl methacrylate) (PMMA)), which locates at the PVDF/PLLA interface due to the balanced stress on two sides. On the one hand, the PVDF domain size decreases remarkably with the help of compatibilization, accounting for the excellent transparence. On the other hand, the interface is enhanced significantly, resulting in an activated PLLA layer surrounding PVDF domains. The thickness exhibits higher magnitude because of the high molecular weight of grafted PLLA (relative to premade compatibilizers). During uniaxial tension, the activated PLLA layers (in addition to PVDF) can cause effective energy absorption and dissipation in the case of percolation of them, which is the reason for the better ductility. These results provide an efficient strategy to improve the ductility and transparence simultaneously.
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