Photoresponsive Polymer Research Articles

Fluoropolymer-Gadolinium(III) Hybrids for Photoactivatable Dual-Mode T1-Weighted 1H MRI and 19F MRI Contrast Agents.

Multimodal imaging probes play a crucial role in overcoming the limitations associated with single-mode imaging for clinical medical diagnosis. This study focuses on the development of a photoresponsive fluorine-containing water-soluble polymer (PF) through RAFT polymerization. Subsequently, a polymer-gadolinium(III) hybrid (PF-Gd) dual-modal probe capable of T1-weighted 1H MRI and 19F MRI was synthesized via postmodification of PF with a Gd-DOTA derivative. Under physiological conditions (pH = 7.4), the hybrids exhibit UV-activated 19F NMR/MRI and enhanced 1H MRI. The inclusion of Gd3+ facilitates the acceleration of water molecule T1 relaxation, leading to high-intensity 1H MRI contrast. Leveraging the paramagnetic relaxation enhancement (PRE) effect between fluorine atoms and Gd3+, the restoration of Gd3+-accelerated 19F T2 relaxation enables precise photoactivation of 19F MRI signals, transitioning from the "OFF" to the "ON" state. This study provides an important reference for the development of hybrid systems that function as real-time diagnostic tools and offers controlled activation for multimodal imaging probes.

Illuminating Biomimetic Nanochannels: Unveiling Macroscopic Anticounterfeiting and Photoswitchable Ion Conductivity via Polymer Tailoring.

Artificial photomodulated channels represent a significant advancement toward practical photogated systems because of their remote noncontact stimulation. Ion transport behaviors in artificial photomodulated channels, however, still require further investigation, especially in multiple nanochannels that closely resemble biological structures. Herein, we present the design and development of photoswitchable ion nanochannels inspired by natural channelrhodopsins (ChRs), utilizing photoresponsive polymers grafted anodic aluminum oxide (AAO) membranes. Our approach integrates spiropyran (SP) as photoresponsive molecules into nanochannels through surface-initiated atom transfer radical polymerization (SI-ATRP), creating a responsive system that modulates ionic conductivity and hydrophilicity in response to light stimuli. A key design feature is the reversible ring-opening photoisomerization of spiropyran groups under UV irradiation. This transformation, observable at the molecular level and macroscopically, allows the surface inside the nanochannels to switch between hydrophobic and hydrophilic states, thus efficiently modulating ion transport via changing water wetting behaviors. The patternable and erasable polySP-grafted AAO, based on a controllable and reversible photochromic effect, also shows potential applications in anticounterfeiting. This study pioneers achieving macroscopic anticounterfeiting and photoinduced photoswitching through reversible surface chemistry and expands the application of polymer-grafted structures in multiple nanochannels.

Lignin-based vitrimer containing dynamic borate ester bonds with intrinsic photoconversion and excellent photothermal remoldability

The development of photoresponsive shape memory materials based on the photothermal conversion properties of lignin and the low activation energy of the dynamic covalent borate bond is of great importance. In this paper, a kind of lignin-based vitrimer polymer (LBP) containing dynamic boronic ester bonds was prepared by a “sulfhydryl-epoxy” click reaction and etherification reaction. The results show that the rigid segment EP-EL (lignin-based epoxy resin) and BDB (2,2′-(1,4-phenylene)-bis-[4-mercapto-1,3,2-dioxaneborane]) with benzene ring structure can impart tensile strength (20.8 MPa) to the LBP, while the flexible segment PEG imparts good elongation at break (15 %). The dynamic binding and dissociation exchange mechanism of the boronic ester bonds enables LBP to exhibit thermal remodelling properties (up to 36.2 %) and water-assisted self-healing properties at room temperature (up to 49.0 %). In addition, LBP exhibits excellent thermal and light-responsive shape memory properties due to its own photothermal conversion performance (photothermal conversion efficiency up to 18.2 %) and the dynamic boronic ester bond thermal activation bond exchange mechanism. The insulating properties of LBP make it suitable for use in high temperature protection circuit devices and light-responsive circuit devices. This study provides new insights into the design and application of Vitrimer and photoresponsive shape memory polymers, and also offers a new avenue for high-value utilization of lignin.

Selective dynamic band gap tuning in metamaterials using graded photoresponsive resonator arrays.

The introduction of metamaterials has provided new possibilities to manipulate the propagation of waves in different fields of physics, ranging from electromagnetism to acoustics. However, despite the variety of configurations proposed so far, most solutions lack dynamic tunability, i.e. their functionality cannot be altered post-fabrication. Our work overcomes this limitation by employing a photo-responsive polymer to fabricate a simple metamaterial structure and enable tuning of its elastic properties using visible light. The structure of the metamaterial consists of graded resonators in the form of an array of pillars, each giving rise to different resonances and transmission band gaps. Selective laser illumination can then tune the resonances and their frequencies individually or collectively, thus yielding many degrees of freedom in the tunability of the filtered or transmitted wave frequencies, similar to playing a keyboard, where illuminating each pillar corresponds to playing a different note. This concept can be used to realize low-power active devices for elastic wave control, including beam splitters, switches and filters.This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 2)'.

Light-responsive Polymers: Developments in Drug Delivery Systems

Abstract: Photoresponsive polymers have emerged as innovative tools in the domain of drug delivery, presenting advanced solutions for controlled and targeted release of therapeutic agents. This review explores recent advances in the design and application of photoresponsive polymers, focusing on their pivotal role in light-triggered drug delivery systems. It also encompasses organic synthesis methodologies, key advancements in polymer design, and the integration of photoresponsive elements into drug carriers. Moreover, this review also focuses on the applications, challenges, and future prospects, providing a comprehensive overview of the evolving landscape of light-responsive drug delivery technologies. The information about the synthesis presented herein aims to contribute to the understanding and advancement of this dynamic field, offering insights for researchers and practitioners engaged in the development of next-generation drug delivery systems.

Design, Synthesis, and Performance of Photo-Responsive Liquid Crystal Polymers with Stepwise Deformation Capability.

Photo-responsive liquid crystal polymers (LCPs) have potential application value in flexible robots, artificial muscles, and microfluidic control. In recent years, significant progress has been made in the development of LCPs. However, the preparation of LCPs with continuous and controllable stepwise deformation capabilities remains a challenge. In this study, visible photo-responsive cyanostilbene monomer, UV photo-responsive azobenzene monomer, and multiple hydrogen bond crosslinker are used to prepare photo-responsive LCPs capable of achieving continuously and controllable stepwise deformation. The comprehensive investigation of the multiple light response ability and photo-induced deformation properties of these copolymers is conducted. The results reveal that in the first stage of photo-induced deformation under 470nm blue light irradiation, the deformation angle decreases with a reduction in cyanostilbene content in the copolymer component, ranging from 40° in AZ0-CS4 to 0° in AZ4-CS0. In the second stage of photo-induced deformation under 365nm UV irradiation, the deformation angle increases with the increase of azobenzene content, ranging from 0° of AZ0-CS4 to 89.4° of AZ4-CS0. Importantly, the deformation between these two stages occurs as a continuous process, allowing for a direct transition from the first-stage to the second-stage deformation by switching the light source from 470 to 365nm.

A multi-element encrypted and decrypted photoresponsive liquid crystal polymer network through the cooperation of cyanostilbene and spiropyran

Photoresponsive polymer materials, in particular, light-driven liquid crystal polymer networks (LCNs) have attracted much attention due to their rapid and significant capacity for photodeformation. However, a single shape change could not meet the growing needs of the information encryption field. Therefore, we aimed to find a photoluminescent and photochromic LCN to enrich the application of photodeformable materials. Here, a light-driven LCN consisting of two distinct kinds of photosensitive moieties, cyanostilbene (CS) and spiropyran (SP), named CS∙SP∙LCN, has been designed and synthesized. The resultant LCN film displayed multiple photo/thermal responsive properties. On the one hand, the trans–cis photoisomerization of CS gave the film capacity for photodeformation. On the other hand, the reversible conversion between ring-closed SP and ring-opened merocyanine (MC) under alternating stimulation of UV irradiation and heating gave the film capacity for tunable photoluminescence and photochromism. The CS∙SP∙LCN film can bend and change color/luminescence under UV irradiation, leading to multi-element writing simultaneously. Then, the written information could be hidden by heating and stretching. Notably, the film resumed bending after the second heating due to the good stability of the cis isomer of CS, realizing the first decryption. Finally, the color/luminescence of the film resumed after the second UV irradiation, completing the second decryption of the information. The CS∙SP∙LCN films synthesized in this study could realize multi-element encryption and step-by-step decryption through the cooperation of CS and SP, achieving more advanced information storage and encryption possibilities.

Photo-responsive supramolecular polymer bottle-brushes: The key role of the solvent on self-assembly and responsiveness

HypothesisSupramolecular polymer bottlebrushes (SPBs) consist in the 1D self-assembly of building blocks composed of a self-assembling core with pendant polymer arms. Kinetic hurdles often hinder their stimuli-responsiveness in solution. Changing the nature of the solvent should alleviate these hurdles by modulating the self-association strength, leading to stimuli-responsive SPBs. ExperimentsThe SPBs were formed, in various solvents, by hydrogen bond-driven self-assembly of an azobenzene-bisurea decorated with poly(ethylene oxide) polymer arms. The photo-isomerization of the azobenzene unit was studied by UV/visible spectroscopy and proton NMR spectroscopy, whereas the consequences on supramolecular self-assembly were studied by small angle neutron and X-ray scattering. FindingsIn water, the assembly was previously shown to be driven by both hydrogen-bonds and strong hydrophobic effects, the latter rendering the system kinetically frozen and the disassembly irreversible. Here we show that in organic solvents such as toluene or chloroform, reversible light-responsive dissociation is achieved. Solvophobic effects in these solvents are expected to be much weaker than in water, which probably allows reversibility of the light-response in the former solvents. The key role of the solvent on the reversibility of the process opens up new perspectives for the design of stimuli-responsive SPBs and their applications in various fields.

Group Control of Photo-Responsive Colloidal Motors with a Structured Light Field

Using structured light to drive colloidal motors, due to its advantages of remote manipulation, energy tunability, programmability, and the controllability of spatiotemporal distribution, has been attracting much attention in the fields of targeted drug delivery, environmental control, chemical agent detection, and smart device design. Here, we focus on studying the group control of colloidal motors made from a photo-responsive organic polymer molecule NO-COP (N,O-Covalent organic polymer). These colloidal motors mainly respond to light intensity patterns. Considering its merits of fast refreshing speed, good programmability, and high-power threshold, we chose a digital micromirror device (DMD) to modulate the structured light field shining on the sample. It was found that under ultraviolet or green light modulation, such colloidal motors exhibit various group behaviors including group spreading, group patterning, and group migration. A qualitative interpretation is also provided for these observations.

Developing biobased and degradable polyazomethines from hemin

The development of biobased polymers is emerging as a critical issue for researchers in this era, especially for conjugated or semiconducting polymers, due to the lack of natural conjugated building blocks. In addition, it is of urgent importance to develop degradable polymers to diminish the increasing amount of plastic waste. Therefore, we aim to utilize hemin-based materials as a building block to develop semi-conjugated, degradable, and biobased polymers in this study. Accordingly, hemin derived from bovine is modified to remove the ferric ion and functionalize with amine or aldehyde groups. The aldehyde-functionalized protoporphyrin is copolymerized with p-phenylenediamine, 2,7-fluorenediamine, and amine-functionalized protoporphyrin to form a series of polyazomethines of PDA, FDA, and PPIX. The semi-conjugated polyazomethines exhibit varied electrostatic potential distributions and frontier energy levels based on their compositions; in addition, all the polyazomethines present high biobased contents spanning the range of 60–80%. Notably, PPIX can be rapidly depolymerized by acid hydrolysis with 0.01 mol L−1 of HCl within several hours, guaranteed by the evolutions of optical absorption and size-exclusion chromatography, which show that the polyazomethines degrade to monomers to short-chain oligomers. In the aspect of the optoelectronic device application, the semi-conjugated characteristics of the hemin-based polyazomethines give rise to their high performance as a photoresponsive polymer electret in photonic transistor memory. By fine-tuning the molecular structure and energy levels, the developed polyazomethine of FDA achieves decent data discernibility and long-termed cyclic operation as a component of memory electronics, thereby rendering green electronics exceptionally economical and environmentally feasible.

Skin-Friendly Flexible Ultraviolet Detectors Based on Reversibly Deformable Worm-Like Polymer Nanoparticles.

Flexible ultraviolet (UV) light detection technology has important applications in wearable devices, smart sensors, and other fields and attracts much attention in recent years. However, for most semiconductor-based UV detectors, the elastic modulus between rigid semiconductors and flexible substrates is mismatched, which makes it difficult to fabricate UV detectors that meet the needs of wearable devices. Herein, a fully flexible, large-scale, skin-friendly UV photodetector component centered on photo-responsive worm-like polymer nanoparticles (NPs) is developed, and the resulting device can quantitatively detect UV illumination. Skin-friendly poly(vinyl alcohol) (PVA), amphiphilic azobenzene-containing polymer NPs (AzNPs), and water-soluble ionic liquids (IL) are formed into (AzNPs-IL)/PVA fabrics by electrospinning. There are interactions such as hydrogen bonding among PVA, AzNPs, and IL, which make the material system stable. The UV detector made of the fabric realizes UV sensing through the illuminance-mechanical stress-electrical signal conversion mechanism. It is capable of achieving a response time of 9 s, a detection range of 10-150mW cm-2 , and stability for 1000 cycle tests upon 365nm UV irradiation. Moreover, it has good skin affinity, and the water contact angle of the fabric is only 23.57°, which holds great promise for wearable smart devices.

Light-Triggered Disassembly of Molecular Motor-based Supramolecular Polymers Revealed by High-Speed AFM.

Photoresponsive supramolecular polymers have a major potential for applications in responsive materials that are externally triggered by light with spatio-temporal control of their polymerisation state. While changes in macroscopic properties revealed the adaptive nature of these materials, it remains challenging to capture the dynamic depolymerisation process at the molecular level, which requires fast observation techniques combined with in situ irradiation. By implementing in situ UV illumination into a High-Speed Atomic Force Microscope (HS-AFM) setup, we have been able to capture the disassembly of a light-driven molecular motor-based supramolecular polymer. The real-time visualisation of the light-triggered disassembly process not only reveals cooperative depolymerisation, it also shows that this process continues after illumination is halted. Combining the data with cryo-electron microscopy and spectroscopy approaches, we obtain a molecular-level description of the motor-based polymer dynamics reminiscent of actin chain-end depolymerisation. Our detailed understanding of supramolecular depolymerisation will drive the development of future responsive polymer systems.

A Solar and Seawater Co‐Involved Durable Rechargeable Battery Enabled by Crown Ether‐Rich Polymer‐Mediated Photoelectrodes

AbstractThe first flow‐type solar and seawater co‐mediated sodium‐air rechargeable battery (SSRB) for efficient solar‐to‐electrochemical energy conversion/storage is established. Such SSRB is enabled by a robust self‐regulated CEP/ZnWO4/WO3 heterojunction photoelectrochemical electrodes (PE) by passivating predesigned crown ether‐rich photoresponsive covalent organic polymer (CEP) layers onto ZnWO4‐modified WO3 nanosheet arrays. The PE design utilizes the previously‐unexplored self‐mediated effect of CEP to endow PE with superior stability, facilitated electrode reaction kinetics, and high efficiency of spatial charge separation simultaneously. This leads to remarkable light‐enhanced oxygen evolution catalysis with impressive photocurrent density up to 6.1 mA cm−2 at 1.23 V versus RHE in seawater – surpassing metal‐oxide‐based PEs ever reported for seawater splitting. Thus, the SSRB breaks the limit of the equilibrium voltage (3.47 V) of conventional seawater sodium‐air cells to deliver a low charge voltage of 2.71 V along with stable photo‐charge over 100 h and good photo‐charge/normal discharge cycling stability over 240 h – superior to almost all existing light‐involved air batteries. Combined experimental and modeling studies for the first time unveil the multi‐regulation effects of CEP passivation which prevents detrimental Cl‐corrosion, and promote oxygen evolution kinetics.

Manipulation of photoresponsive liquid-crystalline polymers and their applications: from nanoscale and to macroscale

As one kind of smart material, photoresponsive liquid-crystalline polymers exhibit interestingly tunable properties from nanoscale to macroscale, which is attributed to their combination of liquid crystal ordering and photo-switchable features....

Photo-responsive nanoporous liquid crystal polymer films for selective dye adsorption.

Photo-responsive nanoporous polymer films (AZOF-R(NC6)) have been developed by a template method based on a hydrogen-bonding supramolecular liquid crystal (LC) and a light-sensitive azobenzene LC crosslinker in this work. Anionic nanopores were obtained after the removal of template NC6 using KOH solution. The AZOF-R(NC6) demonstrates charge-selective dye adsorption and the maximum adsorption capacity for Rh6G is 504.6 mg g-1. The AZOF-R(NC6) film without UV light treatment shows a 32% higher adsorption capacity for Rh6G than the AZOF-R(NC6) film treated with UV light within the initial 10 min. In addition, UV light can trigger the release of the adsorbed dye from the polymer film due to the pore size change arising from the trans-cis isomerization. Besides, the used polymer film can be effectively regenerated using a HCl solution. Such functional polymer films with highly ordered nanopores and photo-responsive properties hold great promise in selective adsorption and mass separations.

Polarization-driven reversible actuation in a photo-responsive polymer composite

Light-responsive polymers and especially amorphous azopolymers with intrinsic anisotropic and polarization-dependent deformation photo-response hold great promises for remotely controlled, tunable devices. However, dynamic control requires reversibility characteristics far beyond what is currently obtainable via plastic deformation of such polymers. Here, we embed azopolymer microparticles in a rubbery elastic matrix at high density. In the resulting composite, cumulative deformations are replaced by reversible shape switching – with two reversible degrees of freedom defined uniquely by the writing beam polarization. We quantify the locally induced strains, including small creeping losses, directly by means of a deformation tracking algorithm acting on microscope images of planar substrates. Further, we introduce free-standing 3D actuators able to smoothly undergo multiple configurational changes, including twisting, roll-in, grabbing-like actuation, and even continuous, pivot-less shape rotation, all dictated by a single wavelength laser beam with controlled polarization.

A styrylpyrene‐containing liquid crystal polymer for photoinduced crosslinking

AbstractPhotoresponsive polymers have attracted increasing attention. Herein, we designed and synthesized a photoresponsive liquid crystal polymer (LCP). The LCP was prepared through the copolymerization of a styrylpyrene‐containing photoresponsive monomer and a monomer containing mesogen 4‐cyanophenyl benzoate. Gel permeation chromatography (GPC) curve and 1H nuclear magnetic resonance (1H NMR) spectrum confirmed that the LCP was successfully synthesized. Thermogravimetric analysis and differential scanning calorimetry curves showed that the LCP had high thermal stability, with a decomposition temperature at 5% weight loss of 305°C, and Tg and Ti of 46 and 128°C, respectively. Polarized optical microscopy studies suggested that thermal annealing promoted the orientation of the LCP films. Model compounds containing styrylpyrene units showed photo‐controlled dimerization. Furthermore, the dimerization of the styrylpyrene units could control the crosslinking densities in the LCP, thereby regulating the network structures and properties. These properties demonstrate that the LCP is a promising photoresponsive material.

A Photopatternable Conjugated Polymer with Thermal-Annealing-Promoted Interchain Stacking for Highly Stable Anti-Counterfeiting Materials.

Photoresponsive polymers can be conveniently used to fabricate anti-counterfeiting materials through photopatterning. However, an unsolved problem is that ambient light and heat can damage anti-counterfeiting patterns on photoresponsive polymers. Herein, we develop photo- and thermostable anti-counterfeiting materials by photopatterning and thermal annealing of a photoresponsive conjugated polymer (MC-Azo). MC-Azo contains alternating azobenzene and fluorene units in the polymer backbone. To prepare an anti-counterfeiting material, an MC-Azo film is irradiated with polarized blue light through a photomask, and then thermally annealed under the pressure of a photonic stamp. This strategy generates a highly secure anti-counterfeting material with dual patterns, which is stable to sunlight and heat over 200 °C. A key for the stability is that thermal annealing promotes interchain stacking, which converts photoresponsive MC-Azo to a photostable material. Another key for the stability is that the conjugated structure endows MC-Azo with desirable thermal properties. This study shows that the design of photopatternable conjugated polymers with thermal-annealing-promoted interchain stacking provides a new strategy for the development of highly stable and secure anti-counterfeiting materials. This article is protected by copyright. All rights reserved.

Synthesis of photoresponsive biobased adhesive polymers via the Passerini three-component reaction

Synthesis of photoresponsive biobased adhesive polymers via the Passerini three-component reaction

Quadri-Dimensional Anti-counterfeiting Flexible Label Programmed by a Photoresponsive Liquid Crystal Polymer Film

Creating flexible materials with multi-dimensional security holds great promise for anti-counterfeiting labels in food, currency, and pharmaceuticals, but it is proven extremely challenging. Herein, we propose a photoresponsive liquid crystal polymer (LCP) film by incorporating polymerizable photoswitch into commercial LCP with ultraviolet (UV) light exposure. Reversible photochromism can be observed between light- and dark-red under UV and visible light irradiation alternatively, accompanying by variation of fluorescence intensity. In addition, a series of photonic microstructures are written on the flexible LCP film by taking advantage of the predefined patterned light. A quadri-dimensional anti-counterfeiting flexible label, featuring photochromism, fluorescence, embedded microstructures, and optical diffraction is constructed with the assistance of photoresponsive LCP film. This strategy represents a beneficial step toward flexible anti-counterfeiting materials, which enhances the secure level for practical product engineering applications.