Hydrogen-bonded liquid crystalline polymers have emerged as promising “smart” supramolecular functional materials with stimuli-responsive, self-healing, and recyclable properties. The hydrogen bonds can either be used as chemically responsive (i.e., pH-responsive) or as dynamic structural (i.e., temperature-responsive) moieties. Responsiveness can be manifested as changes in shape, color, or porosity and as selective binding. The liquid crystalline self-organization gives the materials their unique responsive nanostructures. Typically, the materials used for actuators or optical materials are constructed using linear calamitic (rod-shaped) hydrogen-bonded complexes, while nanoporous materials are constructed from either calamitic or discotic (disk-shaped) complexes. The dynamic structural character of the hydrogen bond moieties can be used to construct self-healing and recyclable supramolecular materials. In this review, recent findings are summarized, and potential future applications are discussed.

Bottom-up methods for the fabrication of nanoporous polymer membranes have numerous advantages. However, it remains challenging to fabricate nanoporous membranes that are mechanically robust and have aligned pores, that is, with a low tortuosity. Here, a mechanically robust thin-film composite membrane was fabricated consisting of a two-dimensional (2D) porous smectic liquid crystalline polymer network inside an anisotropic, microporous polymer scaffold. The polymer scaffold allows for relatively straightforward planar alignment of the smectic liquid crystalline mixture, which consisted of a diacrylate cross-linker and a dimer forming benzoic acid-based monoacrylate. Polymerized samples displayed a smectic A (SmA) phase, which formed the eventual 2D porous channels after base treatment. The aligned 2D nanoporous membranes showed a high rejection of anionic solutes bigger than 322 g/mol. Cleaning and reusability of the system were demonstrated by intentionally fouling the porous channels with a cationic dye and subsequently cleaning the membrane with an acidic solution. After cleaning, the membrane properties were unaffected; this, combined with numerous pressurizing cycles, demonstrated reusability of the system.

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Liquid-releasing artificial skins are made from films made of a smectic liquid-crystal polymer network (LCN) photopolymerized in the presence of a photoactive azobenzene chromophore and a liquid-crystal porogen. The nonreactive porogen phase separates during the polymerization process, and the polymer forms a spongy polymer network filled with liquid. The liquid is excreted from the film when exposed to UV light upon conversion of trans-azobenzene to its cis isomer. Here, localized liquid secretion at preset positions at the polymer film is described. The design principle is based on creating a hybrid molecular architecture with both smectic and nonordered isotropic alignments in a continuous LCN coating. This coating is fabricated by a maskwise photopolymerization of the monomer mixture in the smectic phase, followed by a flood exposure at an elevated temperature above the isotropic state of the unpolymerized region. The smectic regions that polymerized during the maskwise exposure are not affected by the heating needed for the second polymerization step of the isotropic area. Upon activation under light illumination, the embedded liquid is exclusively released from the area with the smectic alignment. This approach reveals films of which the excretion process is reversible. The secreted liquid is reabsorbed spontaneously when azobenzene takes its initial trans-form. This process occurs thermally in time or can be accelerated by light irradiation with visible light.

mostly involving a multitude of elaborate and laborious processing steps, from high energy irradiation to chemical treatment, including plasma treatment, [14][15][16][17][18] gamma irradiation, [19] electron beam irradiation, [20][21][22] ion irradiation, [23,24] and chemical treatment [25,26] have been thoroughly investigated. Near infra-red lasers have been used extensively to write and mark on PE blended with additives, fillers, pigments, or dyes which enhance the absorption of the laser energy. Three main surface reactions are employed to mark the surface. [27] The first one consists of increasing the local temperature high enough to cause thermal degradation of the polymer. The charring of the polymer forms a dark marking contrast. The second surface reaction consists of using foaming agents. During the degradation of this additive, gas is released resulting in the foaming of the polymer. The third writing method is heating and/or degrading one colorant in a colorant mixture blended in the polymer, resulting in the presence of only one colorant in the irradiated regions, thus a change of color. [28] Most of these methods produce black marking/writing, require a tight control of the laser operating parameters, and also depend on mixed colorant systems stability. Other patterning techniques such as inkjet printing are not suitable because of the poor adhesion properties of PE or require preliminary treatment such as Corona treatment. Therefore, it is still challenging to write/mark non-colored patterns on PE using simple and reliable methods. Moreover, the abovedescribed methods are predominantly performed with close to isotropic polyolefines and very little literature exists on the patterning of drawn HDPE. This paper reports a new marking route to produce optical patterns on drawn HDPE by direct laser writing with a pulsed UV laser.Optical images were written on solid state drawn blends of high density polyethylene (HDPE) with UV absorber 2-(2H-benzotriazol-2-yl)-4,6-ditertpentylphenol (BZT) at 2 and 5 wt% loading, called respectively PE-2 wt% and PE-5 wt%. The drawn HDPE films are irradiated by direct laser writing with a pulsed UV laser (355 nm, 10 Hz, 2 ns) at various laser doses. Lines are written on the drawn HDPE films by the overlapping of the laser pulses when moving the sample at a constant speed during irradiation. In Figure 1, a schematic representation of the writing process, a photograph and polarized optical microscopy (POM) images of line patterns at Laser Writing Optical patterns are produced on the surface of drawn linear polyethylene containing 2-(2H-benzotriazol-2-yl)-4,6-ditertpentylphenol (BZT), a photothermal dye, by direct laser writing. The photothermal dye absorbs the UV light and dissipates heat in the polyethylene film. This heat locally results in the melting, shrinking, and recrystallization of PE and the loss of the fibrillar crystalline morphology which is typical for these materials. By using this writing method, an optical image can be obtained by controlling the local UV irr...