Isopropyl Acrylamide Research Articles

Designing magnetic catalysts based on gold nanoparticles supported by ethylenediamine tetraacetic acid functionalized amino‐modified poly(N‐isopropyl acrylamide) for reduction of nitro compounds in water

AbstractA novel smart catalyst was developed with amino‐modified thermo‐responsive poly(N‐isopropyl acrylamide) (PNIPAM) grafts on silica‐coated magnetic nanoparticles using the conventional free radical polymerization process. By this methodology, the polymer was successfully grafted mainly onto silica‐modified iron oxide nanoparticles (Fe3O4@Si). The PNIPAM‐grafted Fe3O4@Si was then subjected to ethylenediamine treatment to produce the amino‐functionalized support (Fe3O4@Si@PNIPAM‐NH2), which was subsequently modified with carboxyl functional groups by using EDTA (ethylenediaminetetraacetic acid) to create Fe3O4@Si@PNIPAM‐NH2‐EDTA. Au nanoparticles were then decorated on this support through its two amines and four carboxylates. Different methods were used to study this novel catalyst, including inductively coupled plasma, Fourier transport infrared spectroscopy, TGA, dynamic light scattering, SEM, energy‐dispersive X‐ray analysis, vibrating sample magnetometry, XRD and elemental CHN analysis. The reduction of several aryl‐nitro derivatives demonstrated a significant catalytic activity for the as‐synthesized gold catalyst (Fe3O4@Si@PNIPAM‐NH2‐EDTA‐Au). The Au catalyst can be successfully removed from the reaction components using a magnetic field and used again in eight successive reduction reactions without significant gold leaching and loss of catalytic activity. © 2024 Society of Industrial Chemistry.

Poly(N-isopropyl acrylamide)-co-poly(sodium acrylate) hydrogel for the adsorption of cationic dyes from aqueous solution.

In this study, we used radical polymerization to create poly (N-isopropyl acrylamide)-co-poly (sodium acrylate) [PNIPAM-co-PSA] hydrogels and analyzed the resulting products. N, N'-Methylenebisacrylamide was employed as a cross-linker, ammonium persulfate as an initiator, and N,N'-isopropyl acrylamide and sodium acrylamide as monomers. Structural analysis was measured by using FT-IR. Indeed, SEM analysis was used to characterize the morphological structure of the hydrogel. Studies on swelling were also done. The Taguchi approach was used to study and assess the adsorption studies of the hydrogels for the efficient removal of malachite green and methyl orange. For the optimization, a central composite surface methodology was applied. The effect of several parameters, including adsorbent dosage, pH, initial dye concentration, temperature, time, and mixing speed, was examined using the Taguchi technique, and the primary factors were chosen and examined using the central composite surface methodology. It was discovered that MG dye's (cationic) removal efficiency was higher than that of MO dye's (anionic). The results suggest that [PNIPAM-co-PSA] hydrogel can be used as an effective, alternative and promising adsorbent to be applied in the treatment of effluents containing the cationic dyes from wastewater. The synthesis of hydrogels provides a suitable recyclability platform for the adsorption of cationic dyes and allows for their recovery without the use of powerful reagents.

Synthesis of functional polyacrylamide (co)polymers by organocatalyzed post-polymerization modification of non-activated esters.

The broad application of polyacrylamides (PAMs) has greatly promoted the development of new synthetic methods to prepare PAM-based functional (co)polymers regarding their traditional preparation via the direct polymerization of various acrylamide monomers. Herein, we have explored the post-polymerization modification of the poly(2,2,2-trifluoroethyl acrylate) (PTFEA) homopolymer, a typical non-activated ester, and various amines using the organo-catalytic system involving 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,2,4-triazole (TA). The reaction kinetics (e.g., the optimized reaction solvent, temperature, time, initial molar ratio of amines to esters and the molar ratio of DBU to TA) were carefully studied with the modulus substrate of iso-propylamine as the formed poly(iso-propyl acrylamide) (PNIPAM) representing the most investigated PAM. The full and partial amidation of the esters in PTFEA could be precisely regulated just by controlling the kinetic conditions to give (co)polymers with designable compositions and structures. We have demonstrated that the poly(N-acryloyl pyrrolidine) obtained by the post-polymerization modification of non-activated ester and pyrrolidine exhibited a noticeable phase transition, which confirmed the robustness and versatility of the post-polymerization modification. The described method paves the way for the synthesis of various (co)polymers with amide side chains from readily available polymer precursors.

Tethering inorganic luminous upconverting nanoparticles with macromolecular chppendixains using silica functionalized with RAFT agent

Upconversion nanoparticles (UCNPs) are superior next-generation nanomaterials due to their exclusive features, such as tunable emission, high quantum yield, and excellent stability against photo-blinking/bleaching/degradation. One can compel these UCNPs to target selective applications by surface functionalization of these nanocrystals with functional groups or polymers to make them chemically active, possessing colloidal stability, better biocompatibility as well as tunable emission region. Herein, we report the preparation of rare earth (Er 3+ , 0.5% mmol) doped upconversion nanoparticles (UCNPs) and their surface functionalization using RAFT agent primed silica followed by polymer functionalization. The polymer functionalization was performed using photo-induced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization in the presence of Eosin Y (EY) which act as a photocatalyst when exposed to blue light at room temperature. The polymer functionalization of UCNPs was performed with different types of polymers, for example, poly( N -isopropyl acrylamide), poly(acrylic acid), poly(ethylene glycol)methacrylate, and poly(methyl methacrylate) via “grafting-from” approach. Numerous characterizations were performed which confirm the successful grafting of polymers via PET-RAFT polymerization. The enhancement of photoluminescent efficiency towards the red region/window was observed after the grafting of polymers. The emission in the red region is marked as suitable for biological applications. Thus, indicating the potential use of the as-synthesized core@shell@shell system for various biological platforms. Interestingly, the cytocompatibility studies render the polymer functionalized UCNPs’ potential to be used in a variety of biological applications.

Preparation of Isopropyl Acrylamide Grafted Chitosan and Carbon Bionanocomposites for Adsorption of Lead Ion and Methylene Blue.

Wastewater, which is rich with heavy elements, dyes, and pesticides, represents one of the most important environmental pollutants. Thus, it has been significant to fabricate environmentally friendly polymers with high adsorption ability for those pollutants. Herein, crosslinked chitosan (C-Cs) was prepared using isopropyl acrylamide and methylene bisacrylamide. Carbon nanoparticles (C-NPs) were also obtained by the treatment of the agricultural wastes, which was used with C-Cs to prepare C-Cs/C-NPs nanocomposite (C-Cs/C-NC). Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscope (TEM) were used to investigate the prepared adsorbent. C-Cs, C-NPs, and C-Cs/C-NC were used in water treatment for the adsorption of lead ions (Pb+2) and methylene blue (MB). The adsorption process occurred by the prepared samples was investigated under different conditions, including contact time, as well as different doses and concentrations of adsorbents. The findings exhibited that the adsorption of Pb+2 and MB by C-Cs/C-NC was higher than C-Cs and C-NPs. In addition, the kinetic and isotherm models were studied, where the results showed that the adsorption of Pb+2 and MB by various adsorbents obeys pseudo-second-order and Langmuir isotherms, respectively.

AS1411 conjugated magnetic‐based poly N‐isopropyl acrylamide nanoparticles for delivery of erlotinib to prostate cancer cells

AbstractThe present study expanded the magnetic pH‐dependent, and nucleolin receptor‐targeted nano‐drug delivery system consists of synthesized superparamagnetic iron oxide nanoparticles (SPIONs) and poly N‐isopropyl acrylamide (PNIPAM) with aptamer AS1411 to deliver the erlotinib (ERL) to prostate cancer (PC) cells. Their properties were characterized using different techniques. The encapsulation efficiency (EE) and drug loading (DL) were found to be about 34% and 85%, respectively. The characterization studies disclosed that formulated SPION‐PNIPAM/ERL@AS1411 nanoparticles (NPs) were spherical with an average particle size of 97.8 nm, polydispersity index (PDI) of 0.03, and the zeta potential of −2 mV. The flow cytometry and cell viability assay results disclosed that SPION‐PNIPAM/ERL@AS1411 NPs operated cancer cell death via the pH‐sensitive release of ERL. The conjugation of the AS1411 modified the cellular uptake of ERL as proved by cellular sensing fluorescence. Therefore, the present study revealed that the SPION‐PNIPAM/ERL@AS1411 NPs improved the treatment effect of ERL in PC via the nucleolin‐targeted drug release.

Aggregation induced emission (AIE) active cross-linked poly(N-isopropyl acrylamide-co-tetra(phenyl)ethene di-acrylates): sensors for effective nitroaromatics detection in an aqueous environment

The fluorescence of AIE active polymer CP1-4 in water could be quenched by many nitroaromatics. The detection sensitivity of CP1-4 could be greatly improved to the levels as 0.25 ppm by a collapsing-swelling process.

Construction of double dynamic covalent bond crosslinked hydrogel based on water-soluble block polymers

Functional phenylboronic-and hydrazide-containing N -isopropyl acrylamide based diblock polymer, and ketone-and glucose group-containing acrylamide based diblock polymer, were prepared by the reversible addition-fragmentation chain transfer (RAFT) polymerization. The structure and properties of the copolymers were studied, and doubly dynamic hydrogel was prepared under different conditions. The main driving force of gel formation is the acylhydrazone bond formed by the hydrazine and ketone group, and the boronate ester bond formed by the boronic acid and glucose group. Under acidic conditions, the acylhydrazone bond ensures the rapid formation kinetics and good self-healable ability of the hydrogel. Under neutral or weak alkaline conditions, the active boronate ester bond endows the hydrogel with fast gelation kinetics and maintains the gel state, while the stable acylhydrazone bond can enhance the mechanical strength of the hydrogel gradually. Under alkaline conditions, the two dynamic covalent bonds are synergistic, giving the hydrogel multiple responsiveness and macroscopically self-healable ability.

Semi-interpenetrating Polyurethane Network Foams Containing Highly Branched Poly(N-isopropyl acrylamide) with Vancomycin Functionality.

Highly branched poly(N-isopropylacrylamide) (HB-PNIPAM), functionalized with vancomycin at the chain ends, acted as a bacterial adhesive and was incorporated into polyurethane foams to form semi-interpenetrating networks. PNIPAM was labeled with a solvatochromic dye, Nile red. It was found that the thermal response of the polymer was dependent on the architecture, and temperature-dependent color changes were observed within the foam. The foams had open pore structures, and the presence of HB-PNIPAM substantially reduced the shrinkage of the foam as the temperature was increased up to 20 °C. The foams were selectively adhesive for Staphylococcus aureus (Gram-positive bacteria) compared to Pseudomonas aeruginosa (Gram-negative bacteria), and the presence of S. aureus was indicated by increased fluorescence intensity (590-800 nm).

Mechanism of polymer particles formation during the soap-free emulsion terpolymerization of styrene - acrylic acid – N -(isopropyl acrylamide) for photonic crystals fabrication

This study presents the synthesis and characterization of a styrene (ST), acrylic acid (AA), and N-(isopropyl acrylamide) (NiPAM) terpolymer obtained by a soap-free emulsion process. The influence of AA/NiPAM ratio on the reaction mechanism and the reaction kinetics was investigated. Thus, the polymerization rate increases with the concentration of NiPAM in the substrate. The obtained polymer colloids permitted the fabrication of photonic crystals (PCs) in all four cases, regardless of the substrate composition. The structures were investigated by UV–vis, SEM, and optical microscopy. A micellar polymerization mechanism in the case of AA rich substrates and a heterogeneous mechanism for NiPAM rich substrates were ascertained using the UV–vis, DLS, TEM, and XPS analyses. As the NiPAM concentration increased in detriment to AA, the particle formation mechanism leads to the formation of two distinct types of polymer particles. The zeta (ζ) potential values confirmed the latexes stability in all cases. The LCST values situated in the range of 37−44 °C were determined by DSC analysis. The humidity responsive characteristics were evaluated as an application for the obtained PCs.

Synthesis of thermo-sensitive polymers with super narrow molecular weight distributions: PET-RAFT polymerization of N-isopropyl acrylamide mediated by cross-linked zinc porphyrins with high active site loadings

To overcome the aggregation of porphyrins and realize heterogeneous photo-catalysis with high active site loadings, twisted ZnTHP–Me2Si and layered ZnTHP–Ph2Si are prepared through cross-linking zinc porphyrins by different chlorosilanes.

Effect of Cross‐Linker in Poly(N‐Isopropyl Acrylamide)‐Grafted‐Gelatin Gels Prepared by Microwave‐Assisted Synthesis

AbstractThe combination of thermoresponsive polymers with natural biomaterials can extend the properties portfolio, especially in the field of biomedicine, where a great cell adhesiveness and biodegradation is necessary for bone regeneration. The poly(N‐isopropylacrylamide)‐grafted‐gelatin gels were already reported where several synthetic parameters, such as polymer or gelatin were varied and final properties were studied. Nevertheless, the ratio of the cross‐linker was always the same, and consequently, their properties were not analyzed yet. There are various preparation methods of these systems but microwave synthesis was not deeply studied, and consequently, important benefits can be obtained due to its efficiency and time saving. In this work, we modified the ratio of cross‐linker and important changes are observed in the thermoresponsive and mechanical properties tested by calorimetry, thermogravimetry, rheology, and atomic force microscopy. The amount of cross‐linker modulates the homogeneity of the resulting gels, and consequently, the lower critical solution temperature, the absorption of water into surfaces and the mechanical behavior of the new materials.

Accounting for effective interactions among charged microgels

We introduce a theoretical approach to describe structural correlations among charged permeable spheres at finite particle concentrations. This theory explicitly accounts for correlations among microions and between microions and macroions and allows for the proposal of an effective interaction among macroions that successfully captures structural correlations observed in poly-N-isopropyl acrylamide microgel systems. In our description the bare charge is fixed and independent of the microgel size, the microgel concentration, and the ionic strength, which contrasts with results obtained using linear response approximations, where the bare charge needs to be adapted to properly account for microgel correlations obtained at different conditions.

Rheological Aspects and Extension‐Induced Phase Separation in Electrospinning of Poly(N‐isopropyl acrylamide) Solutions in Dimethylformamide

AbstractSolutions of poly(N‐isopropyl acrylamide) in dimethylformamide are used to study the relation between the rheological properties and electrospinning behavior. Light scattering of electrospinning jet is conducted to obtain the jet diameter at the straight jet end, from which the average extension rate of the jet is derived based on a simple approach. The extension rate is found to be higher than the terminal relaxation rate of polymer chains determined from the dynamic rheological properties. Based on this finding, the original single‐phase polymer solutions may undergo extensional flow‐induced phase separation in the straight jet section during electrospinning. String‐like structures in the liquid jet as well as in the solid fiber are observed by OM, SEM, TEM, and AFM to validate the hypothesis. The inhomogeneity in the jet, due to the presence of dissipative string structures, may serve as the potential precursor to produce lateral perturbations of jet motion to initiate the macroscopic bending instability at the straight jet end for the jet whipping. Moreover, the formation of the beaded fiber, that is, beads‐on‐a‐string structures, is likely relevant with the dissipative structures developed in the jet, besides the Rayleigh instability of the jet arising from surface tension.

Influence of Hydrophilic Co-Monomer on the Drug Release from Hydrogels with Thermosensitive N-(isopropyl)acrylamide Derivatives.

Polymers sensitive to external stimuli are intensively studied. They are used for preparation of controlled drug delivery systems for variety of active pharmaceutical ingredients. Poly-N-isopropyl acrylamide is a temperature sensitive polymer, and its properties have been used to obtain a series of thermally sensitive polymeric structures. The present study evaluates the effect of hydrophilic co-monomer, N-(2-hydroxyethyl)acrylamide on the properties of thermosensitive hydrogels with hydroxypropyl methylcellulose and assesses the release rate of the model drug naproxen sodium embedded into the hydrogel. N-isopropyl acrylamide derivatives were synthesized by surfactant free precipitation polymerization. The chemical structure of the particles was evaluated via nuclear magnetic resonance spectroscopy, whereas the hydrodynamic diameter DH was measured by dynamic light scattering method. The molecular weight was determined using the static light scattering. Hydrogel formulations with naproxen sodium were assessed in the terms of model drug release rate at two temperatures: 22 °C and 42 °C, using the pharmacopoeial method. The assessed formulations released lower amounts of drug, as compared to the control formulation, containing only hydroxypropyl methylcellulose as the main hydrophilic component.

Biocatalytically active microgels by precipitation polymerization of N-isopropyl acrylamide in the presence of an enzyme.

We present a novel protocol for the synthesis of enzymatically active microgels. The protocol is based on the precipitation polymerization of N-isopropylacrylamide (NIPAm) in the presence of an enzyme and a protein binding comonomer. A basic investigation on the influence of different reaction parameters such as monomer concentration and reaction temperature on the microgel size and size distribution is performed and immobilization yields are determined. Microgels exhibiting hydrodynamic diameters between 100 nm and 1 μm and narrow size distribution could be synthesized while about 31–44% of the enzyme present in the initial reaction mixture can be immobilized. Successful immobilization including a verification of enzymatic activity of the microgels is achieved for glucose oxidase (GOx) and 2-deoxy-d-ribose-5-phosphate aldolase (DERA). The thermoresponsive properties of the microgels are assessed and discussed in the light of activity evolution with temperature. The positive correlation of enzymatic activity with temperature for the GOx containing microgel originates from a direct interaction of the enzyme with the PNIPAm based polymer matrix whose magnitude is highly influenced by temperature.

A novel and ultrasensitive yellow to taupe brown colorimetric sensing and removal method for Hg(ii) based on the thermosensitive poly(N-isopropyl acrylamide) stabilized silver nanoparticles

AgNP/PNIPAm was developed as a dual-functional colorimetric probe and removal system for Hg2+.

Coordinate bond breaking induced by collapse of poly(N-isopropyl acrylamide) as ligands of a rare Earth complex

A novel water-soluble luminescent complex consisting of Eu(ally-dbm)3-2Tppo and poly(N-isopropyl acrylamide) (PNIPAM) is synthesized through a series of chemical reactions. The structure of the complex is characterized by TGA, GPC, HNMR, and the thermal-responsive fluorescence of the complex in aqueous solution is investigated. It is found that PNIPAM collapse above the lower critical solution temperature causes the coordination bond breaking, leading to weakening of the fluorescence from Eu3+ and enhancing of the fluorescence from the ligands. When temperature decreases, the fluorescence from Eu3+ is found to boost up and the fluorescence from ligands weakens accordingly. It is deduced from this phenomenon that the ligands re-coordinate with europium ions again along with the temperature decreasing, which is further confirmed by IR measurements. This thermal-responsive fluorescence is of reversibility, which can be used as molecular probes for biological imaging and collapse studying of PNIPAM.A novel water-soluble luminescent complex consisting of Eu(ally-dbm)3-2Tppo and poly(N-isopropyl acrylamide) (PNIPAM) is synthesized through a series of chemical reactions. The structure of the complex is characterized by TGA, GPC, HNMR, and the thermal-responsive fluorescence of the complex in aqueous solution is investigated. It is found that PNIPAM collapse above the lower critical solution temperature causes the coordination bond breaking, leading to weakening of the fluorescence from Eu3+ and enhancing of the fluorescence from the ligands. When temperature decreases, the fluorescence from Eu3+ is found to boost up and the fluorescence from ligands weakens accordingly. It is deduced from this phenomenon that the ligands re-coordinate with europium ions again along with the temperature decreasing, which is further confirmed by IR measurements. This thermal-responsive fluorescence is of reversibility, which can be used as molecular probes for biological imaging and collapse studying of PNIPAM.

Segmental Mobility Studies of Poly(N-isopropyl acrylamide) Interactions with Gold Nanoparticles and Its Use as a Thermally Driven Trapping System.

Thermal desolvation of poly(N-isopropylacrylamide) (PNIPAM) in the presence of a low concentration of gold nanoparticles incorporates the nanoparticles resulting in suspended aggregates. By covalently incorporating <1% acenaphthylene into the polymerization feed this copolymer is enabled to be used as a model to study the segmental mobility of the PNIPAM backbone in response to gold nanoparticles both below and above the desolvation temperature, showing that there is a physical conformational rearrangement of the soluble polymer at ultralow nanoparticle loadings, indicating low affinity interactions with the nanoparticles. Thermal desolvation is capable of extracting >99.9% of the nanoparticles from their solutions and hence demonstrates that poly(N-isopropylacrylamide) can act as an excellent scrubbing system to remove metallic nanomaterial pollutants from solution.

Synthesis and biocompatibility of dual-responsive thermosonic injectable organogels based on crosslinked N-(isopropyl acrylamide) for tumour microenvironment targeting

A series of three dual-responsive ‘thermosonic’ (thermo- and ultrasound-responsive) injectable organogels (TIOs) based on crosslinked N-(isopropyl acrylamide) (NIPAM) bearing biocompatible polymeric constituents were investigated for strong gelation in response to tumour temperature, and sol-like fluid gel formation upon the application of an ultrasonic stimulus. A time-efficient free radical polymerisation reaction of ˂15 min resulted in TIO formation. Moreover, the formulation of the TIOs integrated green chemistry principles to ensure enhanced biocompatibility. Fourier Transform Infrared (FTIR) spectral analysis revealed the presence of new molecular vibrations at 847 and 771 cm−1 (CH deformation), which were indicative of the functionalisation of the NIPAM backbone with hydrophobic and ultrasound-responsive aromatic moieties. Thermo- and ultrasound-response analysis and rheological analysis demonstrated that the TIOs displayed a temperature-induced transition to a strong highly-structured gel, and an ultrasound-triggered increase in gel flowability dependant on the composition of the formulation. Cell proliferation studies were undertaken for the TIOs, which verified that the designed TIOs were all non-cytotoxic and promoted cell proliferation over 1, 3, and 5 day intervals. The rational design and formulation of a biocompatible injectable in-situ depot drug delivery system for ultimate application in tumour targeting was successfully achieved and warrant further investigation.