Template
wetting methods have been widely applied in the preparation
of one-dimensional (1D) polymer nanomaterials. The pattern control
using the template wetting methods, however, still remains a great
challenge, mainly due to the nonselectivity of the polymers toward
the environmental triggering. In this work, we present a facile light-induced
nanowetting (LIN) method to fabricate patterned nanoarrays using anodic
aluminum oxide (AAO) templates. Photoresponsive azobenzene-containing
polymers (azopolymers) that exhibit light-induced reversible solid-to-liquid
transitions are used. Upon exposure to ultraviolet lights, the azopolymer
chains can wet the nanopores of the AAO templates in a liquid state
via capillary force. The azopolymer chains are then solidified by
illuminating them with visible lights, resulting in the formation
of azopolymer nanoarrays. Notably, using designed photomasks, the
patterns of the nanoarrays can be ingeniously controlled with the
characteristic of erasable and rewritable nanostructures.
Regular arrays of anisotropic polymer
nanomaterials have attracted
great attention because of their unique properties and various applications
such as solar cell devices, sensors, and supercapacitors. The control
of the shape manipulation and tailored properties of individual polymer
nanomaterials in arrays, however, remains a great challenging task.
In this work, we demonstrate a versatile approach to fabricate elliptical
and bent polymer nanorod arrays through laser-induced photo-fluidization
of azobenzene-containing polymers (azopolymers). Ordered anodic aluminum
oxide (AAO) membranes are used as templates for generating azopolymer
nanorod arrays via a solvent vapor annealing-induced wetting method.
After being released from the AAO templates and shone by linearly
polarized lights, the nanorod arrays can be transformed into anisotropic
nanostructures, driven by the trans-to-cis and cis-to-trans isomerization
of the azobenzene groups in the azopolymers. Depending on whether
the laser beam is shone at normal or tilt angles of incidence, elliptical
or bent nanorod arrays can be prepared, respectively. The deformation
degrees and water wettabilities of the nanorod arrays can be varied
by changing the illumination times. This study reports a beneficial
route to prepare ordered arrays of anisotropic polymer nanostructures
for advanced applications.
Ordered arrays of polymer nanostructures have been widely investigated because of their promising applications such as solar‐cell devices, sensors, and supercapacitors. It remains a great challenge, however, to manipulate the shapes of individual nanostructures in arrays for tailoring specific properties. In this study, an effective strategy to prepare anisotropic polymer nanopillar arrays via photo‐fluidization is presented. Azobenzene‐containing polymers (azopolymers) are first infiltrated into the nanopores of ordered anodic aluminum oxide (AAO) templates. After the removal of the AAO templates using weak bases, azopolymer nanopillar arrays can be prepared. Upon exposure of linearly polarized lights, azobenzene groups in the azopolymers undergo trans–cis–trans photoisomerization, causing mass migration and elongation of the nanopillar along with the polarization directions. As a result, anisotropic nanopillar arrays can be fabricated, of which the deformation degrees are controlled by the illumination times. Furthermore, patterned nanopillar arrays can also be constructed with designed photomasks. This work presents a practical and versatile strategy to fabricate arrays of anisotropic nanostructures for future technical applications.
The stereocomplexation of poly(methyl methacrylate) (PMMA) is a
unique supramolecular assembling system that has been demonstrated
to be valuable in many applications. The crystallization behaviors
of stereocomplex PMMA (sc-PMMA) under nanoconfinement, however, have
yet to be fully understood. In this work, we fabricate sc-PMMA nanorods
using anodic aluminum oxide (AAO) templates with various pore sizes
to gain a fundamental understanding of sc-PMMA in confined states.
A scanning electron microscope (SEM), a differential scanning calorimeter
(DSC), and an X-ray diffractometer (XRD) are used to examine their
morphologies, crystallization kinetics, and crystal characteristics.
We discover that the crystallization kinetics of sc-PMMA inside the
nanopores is significantly different from the bulk state. Also, the
preferred orientation of sc-PMMA crystallites is mainly governed by
the degree of spatial confinement and the polymer molecular weight.
This work provides a deeper understanding of sc-PMMA under nanoconfinement
and presents opportunities for the applications of supramolecular
nanostructures in miniaturized devices.
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