Stimuli-responsive Polymers Research Articles

Nanomaterials as Next-Gen Corrosion Inhibitors: A Comprehensive Review for Ceramic Wastewater Treatment

This study reviews the use of corrosion inhibitors in industrial wastewater treatment, specifically in ceramic wastewater. It discusses the main problem limits the use of treated wastewater, which is corrosion behavior. To reduce this behavior and enable safe reuse of industrial wastewater, corrosion inhibitors are used. The study aims to provide insights into the selection, use, and effectiveness of corrosion inhibitor types in the media under study. The results can help engineers, researchers, and wastewater treatment professionals to find the best corrosion inhibitors for various municipal wastewater applications, increasing the sustainability and efficiency of wastewater treatment processes. The ceramic industry faces challenges in managing complex aqueous effluents generated from mining, shaping, glazing, and manufacturing processes. Nanomaterial-based alternatives, such as titanium nanotubes, zinc oxide nanoparticles, nanoenhanced filters, and stimuli responsive polymer and silica coatings, have emerged as promising next-generation corrosion inhibitors due to their multilayer passivation and high specific surface area. The analysis focuses on the feasibility of these materials' mechanisms, such as crystal deformation, nucleation hindrance, coating barriers, and passivation improvement, in industrial settings. In conclusion, the use of corrosion inhibitors in industrial wastewater treatment can significantly improve the sustainability and efficiency of wastewater treatment processes. Understanding the mechanisms by which these nanomaterials influence crystal growth modification, deposition kinetics, and passivation performance could lead to more effective and sustainable solutions for industrial wastewater treatment.

PH-Sensitive Polymers with their Important Applications (A Review)

Abstract:: Materials that modify their chemical or physical characteristics in reaction to diverse stimuli, such as moisture, heat, water, or pH, are commonly known as smart materials or stimuli-responsive polymers. Typical applications for these polymers include catalysis, finishing, and coating processes. Tissue engineering, drug delivery, and gene transportation are additional applications that have emerged in the past two decades. As a result, their potential use extends to a wider range of applications, encompassing chemical processes, drug delivery, body-site targeting, separation, membrane activity, sensing and actuation, and agriculture. Recently, pH-responsive polymers have garnered considerable interest for implementation in membrane and 4D printing. The current review work encompasses previously published research through 2022, with a particular focus on the critical application of pH-sensitive polymers.

Tetrazine-based dynamic covalent polymers as degradable extraction materials in sample preparation

BackgroundCurrent trends in Analytical Chemistry are highly focused on the introduction of new extraction materials with a high selectivity towards the target analytes, high extraction capacity as well as sustainable characteristics. In this context, the introduction of smart materials able to respond to an external stimulus constitutes a promising approach in the field. However, investigations regarding the development of such stimuli-responsive polymers have been basically centered on their synthesis and the control of their properties, and hardly on exploiting such properties to generate polymers that, once their extraction function is fulfilled, they can be degraded into fragments with little or negligible toxicity, or even into their constituent monomers for an efficient recycling. ResultsThe applicability of a degradable and recyclable dynamic covalent polymer based on the use of tetrazine as a linker was assessed as sorbent for the extraction of a group of 37 persistent organic pollutants, including 10 polycyclic aromatic hydrocarbons, 11 organochlorine pesticides, 14 polychlorinated biphenyls, and 2 antibacterial agents, from water samples. A microdispersive solid-phase extraction procedure was developed for the selective extraction of the target analytes, while their separation, determination, and quantification were achieved by gas chromatography coupled to mass spectrometry. The optimized procedure was validated for seawater and wastewater obtaining mean relative recovery values between 72 and 112 % for almost all the analytes, with satisfactory relative standard deviation values (<18 %). After extraction, the polymer could be degraded by adding the amino acid L-tyrosine, being possible a quantitative recovery of the initial functional monomer. SignificanceA responsive polymer based on the chemical versatility of the tetrazine ring was used as sorbent in sample preparation providing excellent results, showing good physicochemical properties and the ability to be degraded after use. This polymer constitutes an interesting alternative to reduce chemical waste through the recycling of monomers, contributing to the development of more sustainable analytical methodologies.

Biotinylated Theranostic Amphiphilic Polyurethane for Targeted Drug Delivery.

In the area of drug delivery aided by stimuli-responsive polymers, the biodegradability of nanocarriers is one of the major challenges that needs to be addressed with the utmost sincerity. Herein, a hydrogen sulfide (H2S) responsive hydrophobic dansyl-based trigger molecule is custom designed and successfully incorporated into the water-soluble polyurethane backbone, which is made of esterase enzyme susceptible urethane bonds. The amphiphilic polyurethanes, PUx (x = 2 and 3) with a biotin chain end, formed self-assembled nanoaggregates. A hemolysis and cytotoxicity profile of doxorubicin (DOX)-loaded biotinylated PU3 nanocarriers revealed that it is nonhemolytic and has excellent selectivity toward HeLa cells (biotin receptor-positive cell lines) causing ∼60% cell death while maintaining almost 100% cell viability for HEK 293T cells (biotin receptor-negative cell lines). Furthermore, better cellular internalization of DOX-loaded fluorescent nanocarriers in HeLa cells than in HEK 293T cells confirmed receptor-mediated endocytosis. Thus, this work ensures that the synthesized polymers serve as biodegradable nanocarriers for anticancer therapeutics.

Understanding the Phase Behavior of a Multistimuli-Responsive Elastin-like Polymer: Insights from Dynamic Light Scattering Analysis.

Elastin-like polymers are a class of stimuli-responsive protein polymers that hold immense promise in applications such as drug delivery, hydrogels, and biosensors. Yet, understanding the intricate interplay of factors influencing their stimuli-responsive behavior remains a challenging frontier. Using temperature-controlled dynamic light scattering and zeta potential measurements, we investigate the interactions between buffer, pH, salt, water, and protein using an elastin-like polymer containing ionizable lysine residues. We observed the elevation of transition temperature in the presence of the common buffering agent HEPES at low concentrations, suggesting a "salting-in" effect of HEPES as a cosolute through weak association with the protein. Our findings motivate a more comprehensive investigation of the influence of buffer and other cosolute molecules on elastin-like polymer behavior.

Effect of isothermal aging on Poly(N-isopropylacrylamide): Correlation between chemical structure and phase transition temperature property

Poly(N-isopropylacrylamide) (PNIPAm) is a stimuli-responsive polymer with wide applications as a scaffold in biomedical applications. This study presents the PNIPAm's thermoresponsive behavior during storage and its stability in potential pharmaceutical formulations as a drug delivery excipient. Therefore, the turbidity curves of linear PNIPAm aqueous solutions are investigated before and after its thermal oxidation under air at 120°C and 130°C. First, PNIPAm aqueous phase separation diagram is determined for unaged polymer and then compared to thermally aged samples at two distinct points (1 and 10%(w/w)). After isothermal aging, the transition temperature has increased with a shift up to 4°C. The correlation between PNIPAm's chemical structure and phase transition temperature properties is illustrated in terms of chemical modifications, macromolecular changes as well as the polar/non-polar groups balance. It is observed that the water affinity and glass transition temperature (Tg) have increased at the macromolecular level. In addition, chains scissions are highlighted and seem to explain the shift of transition temperature. Chemical changes have revealed the presence of supplementary polar groups induced by aging. This multiscale study suggests a possible mechanism for the partial thermal oxidation based on all the observations.

Stimuli-responsive Biomaterials for Tissue Engineering Applications.

The use of ''smart materials,'' or ''stimulus responsive'' materials, has proven useful in a variety of fields, including tissue engineering and medication delivery. Many factors, including temperature, pH, redox state, light, and magnetic fields, are being studied for their potential to affect a material's properties, interactions, structure, and/or dimensions. New tissue engineering and drug delivery methods are made possible by the ability of living systems to respond to both external stimuli and their own internal signals) for example, materials composed of stimuliresponsive polymers that self assemble or undergo phase transitions or morphology transformation. The researcher examines the potential of smart materials as controlled drug release vehicles in tissue engineering, aiming to enable the localized regeneration of injured tissue by delivering precisely dosed drugs at precisely timed intervals.

Synthesis and Characterization of Multiple Stimuli-Responsive Fluorescent Polymer Hydrogels Based on Terpyridine and N-Isopropylacrylamide.

A series of stimuli-responsive fluorescent hydrogels were successfully synthesized via micelle radical copolymerization of hydrophilic acrylamide (AM), hydrophobic chromophore terpyridine-based monomer (TPY), and N-isopropylacrylamide (NIPAM). These hydrogels presented blue emissions (423-440 nm) under room temperature, which is caused by the π-π* transition of the conjugated structures. Once the ambient temperature was increased to 55 °C, the fluorescence color changed from blue (430 nm) to pink (575 nm) within 10 min, subsequently to yellow (535 nm), and eventually back to pink. The thermal-responsive properties are attributed to the transition of the TPY units from unimer to dimer aggregation via the intermolecular charge transfer complex at high temperatures. The hydrogels showed pH-responsive properties. The emission peak of the hydrogel exhibited a blue shift of ~54 nm from neuter conditions to acidic conditions, while a 6 nm red shift to an alkaline environment was observed. The hydrogels demonstrated an obvious change in fluorescence intensity and wavelength upon adding different metal ions, which is caused by the coordination between the terpyridine units incorporated on the backbones and the metal ions. As a consequence, the hydrogels presented a sharp quenching fluorescence interaction with Fe2+, Fe3+, Cu2+, Hg2+, Ni2+, and Co2+, while it exhibited an enhanced fluorescence intensity interaction with Sn2+, Cd2+, and Zn2+. The microstructural, mechanical, and rheological properties of these luminescent hydrogels have been systematically investigated.

Access to Main-Chain Photoswitching Polymers via Hydroxyl-yne Click Polymerization.

Main-chain stimuli-responsive polymers synthesized via polymerization techniques that do not rely on metal-based catalysis are highly desirable for economic reasons and to avoid metal-polymer interactions. Herein, we introduce a metal-free head-to-tail organobase-catalyzed hydroxyl-yne click polymerization of an AB-type monomer to realize photoswitchable polymers featuring α-bismines as main-chain repeating units. The prepared main-chain α-bisimine-based polymers show excellent photoswitching in solution. We further post-functionalize the obtained polymers with various thiol compounds via thiol-Michael reactions to significantly lower the glass transition temperature (Tg), likely to be beneficial for the photoswitching process in the solid state. Thus, the herein introduced polymerization technique not only provides metal-free access to main-chain stimuli-responsive polymers, but also allows for the flexible post-modification of the obtained polymers to generate advanced macromolecular architectures with tunable properties.

Electrochemical detection of glutamate and histamine using redox-labeled stimuli-responsive polymer as a synthetic target receptor.

Glutamate (Glu) and histamine (His) are two major neurotransmitters that play many critical roles in brain physiological functions and neurological disorders. Therefore, specific and sensitive monitoring of Glu and His is essential in the diagnosis and treatment of various mental health and neurodegenerative disorders. Both being non-electroactive species, direct electrochemical detection of Glu and His has been challenging. Herein, we report a stimuli-responsive polymer-based biosensor for the electrochemical detection of Glu and His. The polymer-based target receptors consist of a linear chain stimuli-responsive templated polymer hybrid that is labeled with an osmium-based redox-active reporter molecules to elicit conformation-dependent electrochemical responses. The polymers are then attached to a gold electrode to implement an electrochemical sensor. The cyclic voltammetry (CV) and square-wave voltammetry (SWV) results confirmed the polymers' conformational changes due to the specific target (i.e., Glu and His) recognition and the corresponding electrochemical detection capabilities. The voltammetry results indicate that this biosensor can be used as a 'signal-on' and 'signal-off' sensors for the detection of Glu and His concentrations, respectively. The developed biosensor also showed excellent regeneration capability by fully recovering the initial current signal after rinsing with deionized water. To further validate the polymer's utility as a target bioreceptor, the surface plasmon resonance (SPR) technique was used to characterize the binding affinity between the designed polymers and the target chemical. The SPR results exhibited the equilibrium dissociation constants (KD) of 2.40 μM and 1.54 μM for the polymer-Glu and polymer-His interactions, respectively. The results obtained this work strongly suggest that the proposed sensing technology could potentially be used as a platform for monitoring non-electroactive neurochemicals from animal models.

Programmable Colloids with Analogous Hypercoordination Complex Architectures.

Colloidal molecule clusters (CMCs) are promising building blocks with molecule-like symmetry, offering exceptional synergistic properties for applications in plasmonics and catalysis. Traditional CMC fabrication has been limited to simple molecule-like structures utilizing isotropic particles. Here, we employ molecular dynamics simulation to investigate the co-assembly of anisotropic nanorods (NRs) and the stimulus-responsive polymer (SRP) via reversible adsorption. The results of the simulation show that it is possible to fabricate hypercoordination complex structures with high symmetry from the co-assembly of NRs and the SRP, even in analogy to the Th(BH4)4 structure. The coordination number of these CMCs can be precisely programmed by adjusting the shape and size of the ends of the NRs and the SRP cohesion energy. Furthermore, a finite-difference time-domain simulation indicates these hypercoordination structures exhibit significantly enhanced optical activity and plasmonic coupling effects. These findings introduce a new design approach for complex molecule-like structures utilizing anisotropic nanoparticles and may expand the applications of CMCs in photonics.

Stimuli-Responsive Polymer Networks: Application, Design, and Computational Exploration

Stimuli-Responsive Polymer Networks: Application, Design, and Computational Exploration

Nanotechnology Integrated Innovative Drug Delivery and Therapy for Cancer.

Cancer remains a significant global health challenge, necessitating innovative approaches to enhance the efficacy and specificity of therapeutic interventions while minimizing adverse effects on healthy tissues. Nanotechnology has emerged as a promising avenue in cancer treatment, offering novel strategies for targeted drug delivery. Nanoparticles, liposomes, and polymer-based systems have played pivotal roles in revolutionizing cancer therapy. Nanotechnology possesses unique physicochemical properties, enabling efficient encapsulation of therapeutic agents and controlled and prolonged release at tumour sites. Advancement in formulations using nanotechnology has made it possible to make multifunctional systems that respond to the microenvironment of a tumour by releasing payloads in response to changes in pH, temperature, or enzymes. Stimuli-responsive polymers can release drugs in response to external cues, enabling site-specific drug release and minimizing systemic exposure. This review explores recent studies and preclinical trials that show how nanoparticles, liposomes, and polymerbased systems could be used to treat cancer, discussing challenges such as scalability, regulatory approval, and potential toxicity concerns along with patents published recently.

Real-time swelling-collapse kinetics of nanogels driven by XFEL pulses.

Stimuli-responsive polymers are an important class of materials with many applications in nanotechnology and drug delivery. The most prominent one is poly-N-isopropylacrylamide (PNIPAm). The characterization of the kinetics of its change after a temperature jump is still a lively research topic, especially at nanometer-length scales where it is not possible to rely on conventional microscopic techniques. Here, we measured in real time the collapse of a PNIPAm shell on silica nanoparticles with megahertz x-ray photon correlation spectroscopy at the European XFEL. We characterize the changes of the particles diffusion constant as a function of time and consequently local temperature on sub-microsecond timescales. We developed a phenomenological model to describe the observed data and extract the characteristic times associated to the swelling and collapse processes. Different from previous studies tracking the turbidity of PNIPAm dispersions and using laser heating, we find collapse times below microsecond timescales and two to three orders of magnitude slower swelling times.

Recent Advances in Stimuli-Responsive Self-Immolative Polymers for Drug Delivery and Molecular Imaging

Recent Advances in Stimuli-Responsive Self-Immolative Polymers for Drug Delivery and Molecular Imaging

Responsive Supramolecular Polymers for Diagnosis and Treatment.

Stimuli-responsive supramolecular polymers are ordered nanosized materials that are held together by non-covalent interactions (hydrogen-bonding, metal-ligand coordination, π-stacking and, host-guest interactions) and can reversibly undergo self-assembly. Their non-covalent nature endows supramolecular polymers with the ability to respond to external stimuli (temperature, light, ultrasound, electric/magnetic field) or environmental changes (temperature, pH, redox potential, enzyme activity), making them attractive candidates for a variety of biomedical applications. To date, supramolecular research has largely evolved in the development of smart water-soluble self-assemblies with the aim of mimicking the biological function of natural supramolecular systems. Indeed, there is a wide variety of synthetic biomaterials formulated with responsiveness to control and trigger, or not to trigger, aqueous self-assembly. The design of responsive supramolecular polymers ranges from the use of hydrophobic cores (i.e., benzene-1,3,5-tricarboxamide) to the introduction of macrocyclic hosts (i.e., cyclodextrins). In this review, we summarize the most relevant advances achieved in the design of stimuli-responsive supramolecular systems used to control transport and release of both diagnosis agents and therapeutic drugs in order to prevent, diagnose, and treat human diseases.

Polymerization-induced emission of borinic acid towards stimuli-responsive luminescent polymers

Stimuli-responsive luminescent polymer is generally prepared by incorporation of both stimuli-responsive and luminescent moieties into polymer chain, which cause difficulties in molecular design and synthesis. The preparation of stimuli-responsive luminescent polymer from one moiety represents a time-saving approach and is highly desirable. Here, we demonstrate a simple approach to achieve stimuli-responsive luminescent polymers through polymerization-induced emission of nonemissive borinic acid moiety. Attributed to versatile borinic acid moiety, the prepared borinic acid polymer (PBA) exhibits upper critical solution temperature (UCST) type thermo-responsive behavior and chemical sensitivities. Interestingly, PBA is not only stimuli-responsive but also luminescent, while the repeating borinic acid moiety is nonemissive, indicating borinic acid is a novel PIE luminogen (PIEgen). This work therefore opens a new avenue to molecularly design stimuli-responsive luminescent polymer from nonemissive borinic acid moiety, which might cause inspirations to the fields of boron chemistry, stimuli-responsive polymer and luminescent polymer.

Synthesis of phosphate hydrogels with excellent swelling behavior prepared by ascorbic acid -mediated ARGET ATRP

This manuscript explores the synthesis of hydrogels through reversible deactivation radical polymerization (RDRP) methods, specifically, activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and Cu0-mediated ATRP. These techniques are known to offer improved control over polymer network structures due to their slow polymerization kinetics. However, these methods have historically been challenging to apply to stimuli-responsive polymers, such as those with acidic or basic moieties. In this study, the direct synthesis of poly(2-(methacryloyloxy) ethyl phosphate) (PMOEP), a phosphate-pendant hydrogel, was investigated in aqueous media by both ascorbic acid (AsA)-mediated ARGET ATRP and Cu0-mediated ATRP. 2-(methacryloyloxy) ethyl phosphate (MOEP) was utilized as the active monomer with tris(2-pyridylmethyl) amine (TPMA) as the ligand. A unique feature of this work is that the diene moiety inherently present in the commercial monomer, bis[2-(methacryloyloxy) ethyl] phosphate (BMOEP), served as the crosslinking agent to obtain the novel PMOEP hydrogel. Formulations were tuned to optimize the swelling characteristics of the hydrogels, with the restriction that the hydrogels should swell homogeneously without fracture. Importantly, using AsA as the reducing agent in the ARGET ATRP reaction resulted in improved homogeneity and enhanced swelling properties of the hydrogel. Furthermore, tuning the target degree of polymerization (Dp) ([monomer]:[initiator]) had a significant impact on swelling characteristics. Specifically, PMOEP hydrogels synthesized via ARGET ATRP with a target Dp of 300 and 1 mM CuII catalyst demonstrated outstanding water absorption capacity of more than 2500% (relative to the dry mass) in phosphate buffer solution (PBS) at pH 7.4 and over 6000% in pure water. The morphology of these hydrogels was imaged using field emission environmental scanning electron microscopy (FE-ESEM) and the chemical composition was examined using Fourier transform infrared (FTIR) spectroscopy. Furthermore, nuclear magnetic resonance (NMR) analysis was performed to investigate the conversion rate of monomer during Cu0-mediated ATRP. To the authors’ knowledge, the synthesis of a 100% phosphate-pendant hydrogel using AsA-mediated ARGET ATRP and an internal phosphodiester crosslinking moiety without dilution or comonomer, has not been reported previously. This facile method for synthesizing and controlling phosphate-based hydrogel properties also provides an opportunity to include additional functional groups and holds significant promise for applications in biomedical engineering, agriculture, and membrane separations.

PH/GSH-responsive diselenide-containing micelle via backbone ketoxime cross-links for efficient drug delivery and controlled release

Stimulus-responsive polymers are promising drug delivery systems for cancer therapy. However, low drug loading and drug leakage of polymeric carriers remain challenges. Here, a crosslinked diselenide-containing micelle was developed with pH/GSH dual responsiveness. Polyesters with multiple diselenide bonds and pendant ketone groups were synthesized by the ring-opening copolymerization of three cyclic monomers (diselenide-containing macrocyclic carbonate, 2-oxepane-1,5-dione, and 1,3-dioxan-2-one). The crosslinked polyester was obtained by the oxime click reaction of pendant ketone groups with hydroxylamine and then self-assembled into crosslinked micelle. This crosslinked micelle remained stable for 14 days, and responded to disassembly under the condition of pH = 5.0 and 10 mM glutathione (GSH). When the crosslinked micelle was loaded with the chemotherapeutic drug DOX, which possessed an active ketone group, the encapsulation efficiency of the crosslinked micelle increased to 91.36 %. The cumulative DOX release reached approximately 45 % under pH = 5.0 and 10 mM GSH. Importantly, the crosslinked diselenide-containing micelle could be taken up in MCF-7 breast cancer cells, responding to the tumor microenvironment and releasing encapsulated DOX. This crosslinked diselenide-containing micelle with pH/GSH dual responsiveness was proven to be a stable and efficient carrier with a promising application.

Flavylium-Containing Stimuli-Responsive RAFT Polymers: Synthesis and Enhanced Stability

Flavylium-Containing Stimuli-Responsive RAFT Polymers: Synthesis and Enhanced Stability