Photoresponsive Polymer Research Articles

The recent progress of novel polypeptoid materials and biomedical applications

Polypeptoids are a type of novel biomedicine polymer materials with excellent biocompatibility. Polypeptoids have backbones similar to that of polypeptides, except that their pendant chains are attached to the nitrogen atoms. Thus, polypeptoids lack chiral centers and –NH···O=C– hydrogen bonding along the backbone. Polypeptoids can be synthesized using two typical approaches, the solid-phase submonomer synthesis method and the ring-opening polymerization (ROP). In contrast to the former that offers sequence specificity, near-absolute monodispersity, but with short chain length and low yield, controlled ROP offers polypeptoids with high molecular weights and high yields. Lately, stimuli-responsive polypeptoids have received increasing attention because of their promising applications in biotechnology owing to their biocompatibility, biodegradability, and bioactivity. The properties of polypeptoids are mainly dominated by the sidechain identity, which offers a unique and facile way to tailor the properties of the polymers by structural design of the side chains. A few types of stimuli-responsive polypeptoids, such as thermoresponsive, photoresponsive, and redox-responsive polypeptoid-based polymers, were typically prepared by ROP of functional monomers and post-modification of the well-defined precursors. Thermoresponsive polypeptoids are capable to exhibit a reversible phase transition in a controlled manner to temperature. They have great potential for biomedical applications, such as drug carriers, smart hydrogels and stimuli-responsive surfaces. The thermoresponsive polypeptoid containing oligo(ethylene glycol) (OEG), amino and carboxyl group was synthesized using post-modification. Photoresponsive polypeptoids have received considerable attention as a class of promising smart materials. Due to their high selectivity and efficiency, photoresponsive polypeptoids offer excellent potential in drug delivery, polymer therapeutics, and smart surfaces. The o -nitrobenzyl group has received increasing attention due to its good stability under acidic and basic conditions and highly controllable photochemical properties. The photoresponsive polypeptoid with o -nitrobenzyl group was prepared using ROP of functional monomers. The redox-responsive polypeptoids have drawn considerable attention recently due to their potential applications in drug and gene delivery, especially for cancer therapy. The most extensively investigated redox-responsive groups are based on thiol chemistry, such as the disulfide bond and the thioether group. The nanostructured polypeptoids show great potential for biological and chemical applications. The diblock copolypeptoids can self-assemble to form a variety of nanostructures due to their capacity of microphase separation and crystallization. For example, the poly(ethylene glycol)- block -poly( N -octylglycine) (PEG- b -PNOG) could form a 2D nanosheet structure, which is driven by the crystallization of PNOG block in a selective solvent. In addition, the poly(ethyl glycol)- block -poly(L-glutamic acid)- block -poly( N -octylglycine) (PEG- b -PGA- b -PNOG) triblock copolymers could form the nanodisks and nanosheets at different pH, which is driven by the hydrophobicity of the PNOG blocks. Further, the amphiphilic poly( N -allylglycine)- b -poly( N -octylglycine) (PNAG- b -PNOG) conjugated with thiol-terminated triethylene glycol monomethyl ethers ((PNAG- g -EG3)- b -PNOG) in aqueous solution could assemble different nanostructures. Specifically, the thermoresponsive property of PNAG- g -EG3 initiates the assembly process, promoted by subsequent crystallization of PNOG and physically locks the morphology eventually. The peptoid prepared using the solid-phase submonomer synthesis method results in the formation of giant, free-floating sheets with thickness of only 2.7 nm in aqueous solution. Polypeptoids possess substantial flexibility of the main chain, good solubility, and enzymatic stability, showing great potential in biomedical applications, such as antimicrobial, antifouling, gene transfection, drug delivery and therapeutics. In this article, we will discuss the recent progress of polypeptoids and their biomedical applications. The polypeptoid possess substantial flexibility of the main chain, good solubility, and enzymatic stability, which show great potential for the biomedical applications, such as antimicrobial, antifouling, gene transfection, drug delivery and therapeutics. In this review, we will discuss the recent progress of the polypeptoid and biomedical applications.

Bio-based photo-reversible self-healing polymer designed from lignin

Through structure–activity relationship study and density functional theory, this research designs novel lignin-based photo-responsive crosslinkable polymer with engineerable self-healing properties by utilizing a green photo-polymerization method.

Hybrid silica micro-particles with light-responsive surface properties and Janus-like character

The present work highlights the synthesis and post-modification of silica-based micro-particles containing photo-responsive polymer brushes with photolabile o-nitrobenzyl ester (o-NBE) chromophores.

Selected Applications of Stimuli-Responsive Polymers: 4D Printing by the Fused Filament Fabrication Technology

In the past few years four-dimensional (4D) printing technologies have attained worldwide interest and they are now considered the "next big thing". The aim of this research is to provide three selected examples of stimuli-responsive polymer (SRP) applications additively manufactured (AM) by the fused filament fabrication (FFF) technique. To that end, a CCT BLUE filament of thermo-responsive polymer was chosen to produce a water temperature indicator, which changes colour from blue to white when temperature increases; a CCU RED filament of photo-responsive polymer was used to produce a sunlight / UV indicator bracelet; a transparent PLA CLEAR polymer, a CCU RED photo-responsive polymer, and an electrical conductive PLA polymer were selected to produce a smart business card stand. The temperature indicator capability was analysed based on examining colour changes as a function of temperature changes. The sunlight/UV indicator capability was analysed based on the inspection of colour change as a function of absorbed sun/ultraviolet light. The electrical conductivity of the conductive PLA polymer was examined by performing resistance measurements. All three objects were successfully produced and their functionality was demonstrated. We hope that these examples will catalyse the expansion of FFF 4D printed SRP applications, as much work remains to be done in designing the parts and developing FFF printing parameters that take advantage of the stimuli-responsive materials currently being developed for FFF technology.

Structures and Applications of Photo-Responsive Shape-Changing Liquid Crystal Polymers

Structures and Applications of Photo-Responsive Shape-Changing Liquid Crystal Polymers

Semi-convertible Hydrogel Enabled Photoresponsive Lubrication

Summary A semi-convertible hydrogel with reversible photoresponsive supramolecular lubricating ability is demonstrated by integrating a responsive supramolecular system of α-cyclodextrins/polyethylene glycol (α-CD/PEG) and competitive guest 1-[p-(phenylazo)benzyl]pyridinium bromide (AzoPB) within a poly(vinyl alcohol) (PVA) and polyacrylamide (PAAm) framework. The competitive host-guest interaction between α-CD/PEG supramolecular network and AzoPB after UV and visible-light irradiation enables the appearance and disappearance of the sol-state layer on the hydrogel surface while the PVA and PAAm consistently keeps the framework. This semi-convertible process realizes the reversible photoresponsive lubricating ability and variable toughness. We envision that this finding will offer a possible way for fabricating novel smart devices far beyond lubrication, leading to an emerging branch of interdisciplinary materials science that integrates supramolecular chemistry, hydrogel, and surface science.

Improved photothermal therapy of brain cancer cells and photogeneration of reactive oxygen species by biotin conjugated gold photoactive nanoparticles

Herein, we report on the design and development of functionalized acrylic polymeric nanoparticles with Spiropyrans (SPs) and imidazole moieties via superficial polymerizations. Then, Au3+ ions were immobilized and reduced on their surface to obtain photoresponsive gold-decorated polymer nanoparticles(Au-NPs). The synthesized Au-NPs were surface adapted with biotin as specific targeting tumor penetration cells and enhance the intercellular uptake through the endocytosis. FT-IR (Fourier-transform Infrared Spectroscopy), UV–Vis (Ultra Violet-Visible Spectrophotometer), EDS (Energy Dispersive X-Ray Spectroscopy), SEM (Scanning Electron Microscope) and HR-TEM (High-resolution transmission electron microscopy) descriptions were engaged to illustrate their spectral analysis and morphological examinations of Bt@Au-NPs. Fluorescence microscopy images of cellular uptake descriptions and ICP-MS (Inductively coupled plasma mass spectrometry) investigation established the cell lines labeling ability and enhanced targetting efficacy of biotin-conjugated Au-NPs (Bt@Au-NPs) toward C6 glioma cells (brain cancer cells) with 72.5% cellular uptake relative to 30.2% for non-conjugated lone. These were further established through intracellular ROS examinations and in vitro cytotoxicity investigation on the C6 glioma cell line. The solid surface plasmon absorptions of the Au-NPs and Bt@Au-NPs providing raised photothermal therapy under UV irradiation. The synthesized multifunctional Bt@Au-NPs with an inclusive combination of potential resources presented encouraging nanoprobe with targeting capability, improved photodynamic and photothermal cancer therapy.

Photoinduced Strain-Assisted Synthesis of a Stiff-Stilbene Polymer by Ring-Opening Metathesis Polymerization.

Developing a novel strategy to synthesize photoresponsive polymers is of significance owing to their potential applications. We report a photoinduced strain‐assisted synthesis of main‐chain stiff‐stilbene polymers by using ring‐opening metathesis polymerization (ROMP), activating a macrocyclic π‐bond connected to a stiff‐stilbene photoswitch through a linker. Since the linker acts as an external constraint, the photoisomerization to the E‐form leads to the stiff‐stilbene being strained and thus reactive to ROMP. The photoisomerization of Z‐form to E‐form was investigated using time‐dependent NMR studies and UV/Vis spectroscopy. The DFT calculation showed that the E‐form was less stable due to a lack of planarity. By the internal strain developed due to the linker constraint through photoisomerization, the E‐form underwent ROMP by a second generation Grubbs catalyst. In contrast, Z‐form did not undergo polymerization under similar conditions. The MALDI‐TOF spectrum of E‐form after polymerization showed the presence of oligomers of >5.2 kDa.

Photoresponsive Surface Molecularly Imprinted Polymers for the Detection of Profenofos in Tomato and Mangosteen.

As a moderately toxic organophosphorus pesticide, profenofos (PFF) is widely used in agricultural practice, resulting in the accumulation of a high amount of PFF in agricultural products and the environment. This will inevitably damage our health. Therefore, it is important to establish a convenient and sensitive method for the detection of PFF. This paper reports a photoresponsive surface-imprinted polymer based on poly(styrene-co-methyl acrylic acid) (PS-co-PMAA@PSMIPs) for the detection of PFF by using carboxyl-capped polystyrene microspheres (PS-co-PMAA), PFF, 4-((4-(methacryloyloxy)phenyl)diazenyl) benzoic acid, and triethanolamine trimethacrylate as the substrate, template, functional monomer, and cross-linker, respectively. PS-co-PMAA@PSMIP shows good photoresponsive properties in DMSO/H2O (3:1, v/v). Its photoisomerization rate constant exhibits a good linear relationship with PFF concentration in the range of 0~15 μmol/L. PS-co-PMAA@PSMIP was applied for the determination of PFF in spiked tomato and mangosteen with good recoveries ranging in 94.4–102.4%.

Four-Dimensional Printed Liquid Crystalline Elastomer Actuators with Fast Photoinduced Mechanical Response toward Light-Driven Robotic Functions.

Remote light exposure of photoresponsive liquid crystalline polymers has drawn great attention over the last years as an attractive strategy to generate mechanical work with high spatial resolution. To tailor these materials into practical engineering devices, it is of key importance to gain control over their morphology and thus precisely program their mechanical response, which must also be fast and relevant in magnitude. In this communication, we report the four-dimensional (4D) printing of azobenzene-containing liquid crystalline elastomers (LCEs) that respond to light. During extrusion of the LCE precursor, mesogen orientation is defined by the needle's moving direction enabling a precise definition of the director, which is later fixed by photopolymerization. Fast mechanical responses have been observed in these 4D printed LCE elements when excited with ultraviolet (UV) light. These 4D printed elements lift objects many times heavier than their own weight, demonstrating a capacity to produce effective work. Photochemical and photothermal contributions to the deformation and force have been identified. Advantageously, the use of blue and UV light excitation enables adjustment of generated forces that can be maintained even in the dark and can be released by light excitation or temperature. The demonstrated ability to generate light-responsive elements quickly delivering sufficient work paves the way for implementing remotely addressed mechanical functions to future soft robotics and engineering.

A uranyl based coordination polymer showing response to low-dosage ionizing radiations down to 10−5 Gy

Radiation detection material is a central component of nuclear technology finding applications in many critical fields. Developing a highly radiation-sensitive material that shows a facilely detectable response to ultra-low dosage of radiation is a long-term research target and remains to be a challenge. Previously reported most optimal chemical radiation dosimeter can detect low-dosage X- and γ-ray radiations down to 10−4 Gy. We document here a new photoresponsive coordination polymer showing upgraded radiation detection capabilities with the detection limit on the radiation dose one order of magnitude lower than the previous record. The radiation induced photoluminescence quenching process was elucidated by multiple spectroscopic characterizations.

Controlling the curvature

Liquid Crystals Molecular chirality is often required to make chiral liquid crystalline phases, but liquid crystallinity has also been obtained using curved elongated rods known as bent-core or banana-shaped molecules. Fernandez-Rico et al. developed a method to controllably alter the curvature of the rods using ultraviolet light and a photoresponsive polymer (see the Perspective by Godinho). From a single starting batch can come a family of rods with different curvatures but similar overall rod thickness, length, and length distribution. The researchers explored a range of liquid crystalline phases, including the splay-bend nematic phase that was predicted more than 40 years ago. Science , this issue p. [950][1]; see also p. [918][2] [1]: /lookup/doi/10.1126/science.abb4536 [2]: /lookup/doi/10.1126/science.abd3548

Photo-responsive polymer micelles from o-nitrobenzyl ester-based amphiphilic block copolymers synthesized by mechanochemical solid-state copolymerization

Polymer micelles with a tunable drug release would be suitable for the concept of drug delivery system. We constructed photo-responsive polymer micelles from amphiphilic block copolymers. The polymer micelles were synthesized by mechanochemical solid-state copolymerization of poly[N-(2-hydroxypropyl)methacrylamide] (PHPMA) and 4,5-dimethoxy-2-nitrobenzyl methacrylate as a photosensitive moiety. The above mechanochemical solid-state copolymerization was performed by vibratory-ball milling at 30 Hz in a nitrogen atmosphere with the use of an agate vessel and an agate ball to yield amphiphilic block copolymers (PHPMA-b-PDNMA). Spherical polymer micelles were formed by the self-assembly of PHPMA-b-PDNMA. The diameter of the PHPMA-b-PDNMA micelles was in the range of 130-200 nm. The PHPMA-b-PDNMA micelles loaded with the antitumor drug 5-fluorouracil (5-FU) showed photo irradiation induced time-dependent release of 5-FU with an associated decrease of micellar size. The drug release profile of the PHPMA-b-PDNMA micelles followed a clear sigmoid curve. Our approach provides a controlled drug release system through the use of photo-responsive polymer micelles, accompanied by the gradual decrease of micellar size. Polymer micelles with a tunable drug release are promising carriers for drug delivery system. It is very important to clarify the correlation between micellar dissociation kinetics and drug release profile on a stimuli-induced deformation of polymer micelles. In this study, photo-cleavable o-nitrobenzyl ester-based amphiphilic block copolymer was successfully designed and prepared by mechanochemical solid-state copolymerization without any solvents and initiators. The self-assembled block copolymer micelles containing anticancer drugs showed sigmoidal decrease of micellar size and released the corresponding drugs depending on the photo-irradiation time.

Photo-triggered large mass transport driven only by a photoresponsive surface skin layer

Since the discovery 25 years ago, many investigations have reported light-induced macroscopic mass migration of azobenzene-containing polymer films. Various mechanisms have been proposed to account for these motions. This study explores light-inert side chain liquid crystalline polymer (SCLCP) films with a photoresponsive polymer only at the free surface and reports the key effects of the topmost surface to generate surface relief gratings (SRGs) for SCLCP films. The top-coating with an azobenzene-containing SCLCP is achieved by the Langmuir–Schaefer (LS) method or surface segregation. A negligible amount of the photoresponsive skin layer can induce large SRGs upon patterned UV light irradiation. Conversely, the motion of the SRG-forming azobenzene SCLCP is impeded by the existence of a LS monolayer of the octadecyl side chain polymer on the top. These results are well understood by considering the Marangoni flow driven by the surface tension instability. This approach should pave the way toward in-situ inscription of the surface topography for light-inert materials and eliminate the strong light absorption of azobenzene, which is a drawback in optical device applications.

Light-Induced Nanowetting: Erasable and Rewritable Polymer Nanoarrays via Solid-to-Liquid Transitions.

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.

Photoresponsive wood composite for photoluminescence and ultraviolet absorption

Transparent wood has received much attention for construction applications due to its good mechanical properties, optical properties, and ideal thermal insulation. Since ultraviolet light is one of the most significant environmental stress agents for human skin, ultraviolet absorbing transparent wood composite will be highly desirable. Herein, ultraviolet absorbing photoluminescence wood composite was obtained by immersing wood templates into photoresponsive polymer. The injected substances were well polymerized in wood cell lumen, resulting in good dimensional stability, mechanical properties, and thermal stability. In addition, the sample displayed a good photoluminescence process, during which it could intercept and absorb high-intensity ultraviolet light. The unique properties of the ultraviolet absorbing photoluminescence wood composite could potentially be applied in building, furniture, windows, sensor, and security materials.

Recent Trends in Applying Rrtho-Nitrobenzyl Esters for the Design of Photo-Responsive Polymer Networks.

Polymers with light-responsive groups have gained increased attention in the design of functional materials, as they allow changes in polymers properties, on demand, and simply by light exposure. For the synthesis of polymers and polymer networks with photolabile properties, the introduction o-nitrobenzyl alcohol (o-NB) derivatives as light-responsive chromophores has become a convenient and powerful route. Although o-NB groups were successfully exploited in numerous applications, this review pays particular attention to the studies in which they were included as photo-responsive moieties in thin polymer films and functional polymer coatings. The review is divided into four different sections according to the chemical structure of the polymer networks: (i) acrylate and methacrylate; (ii) thiol-click; (iii) epoxy; and (iv) polydimethylsiloxane. We conclude with an outlook of the present challenges and future perspectives of the versatile and unique features of o-NB chemistry.

Photo-responsive Self-Reducible Polymers: Overcoming the Spatiotemporal Barriers for Hypersensitivity

To overcome the spatiotemporal barriers to conventional stimuli-responsive polymeric materials, we report a photo-responsive self-reducible polymer with a built-in photo-locked stimulus precursor d...

Structural design of soft robotics using a joint structure of photoresponsive polymers

Photoresponsive polymers (PRPs) have a non-contact bending behavior based on their position when they are irradiated by a specific wavelength of light. In this paper, the behavior of self-deforming PRPs is discussed through multiscale simulations and structural designs. In repeated bending, it is difficult to return to the initial state through different paths because the PRP moves periodically in the same path. We designed an anti-obstructing motion of a PRP operator based on a nonlinear co-rotational finite element model, which could not be designed for the existing bending behavior. The PRP operator can move independently in specified directions by attaching an opaque part to the PRP operator as a joint structure. The device can be divided into two separate regions. One region can be bent to move the desired object, and then the PRP operator can move away, avoiding the object by bending in the other region. The PRP operators can take actions whether to move an object or to avoid an obstacle and adjust the friction force of robot feet based on bio-inspiration. In our experiments, the production process of PRPs is presented, and operations implemented in soft robot applications of gear rotation and walking.

Morphological Transitions of Photoresponsive Vesicles from Amphiphilic Polypeptoid Copolymers for Controlled Release.

Photoresponsive polymers have attracted increasing interest for a variety of applications. Here, we report a family of photoresponsive polypeptoid-based copolymer poly(ethylene glycol)-b-poly(N-(S-(o-nitrobenzyl)-thioethyl) glycine)-co-poly(N-(2-phenylethyl) glycine) (PEG-b-PNSN-co-PNPE) synthesized by the controlled ring-opening polymerization (ROP) technique. The key feature of the design is to incorporate both o-nitrobenzyl group moiety to offer the photoresponsive property and phenethyl residues to tune the structural and amphiphilic property of the system. We demonstrate that the cleavage degree of the o-nitrobenzyl group can reach to 100% upon UV-irradiation. With delicate design, a photoresponsive vesicle-to-sphere transition has been observed that facilitates the release of the encapsulants. This work provides a facile approach to prepare a type of photoresponsive polymers with tunable properties for drug delivery.