Coumarin-Modified Starch Fluorescent Nanoparticles as Sensor of Fe3+ and Zn2+ ions Utilizing Dynamic Quenching and Chelation Mechanisms.

Zinc and iron are two essential trace minerals that play a pivotal role in maintaining optimal health and well-being in the human body. Despite being required in relatively small quantities, their significance can be understated as they participate in a wide array of critical physiological processes such as oxygen transport, DNA synthesis, controlling nutrient availability, etc. Understanding the distribution and behavior of these ions in natural water bodies is essential for assessing water quality, studying ecological processes, and managing environmental impacts. In this study, we have developed a dual fluorescence probe using starch which was functionalized with coumarin derivatives, for efficient detection of Fe3+ and Zn2+ ions. This structure led a self-assembled starch/coumarin (SC) fluorescent nanoparticles with strong fluorescence intensity under ultraviolet light (365 nm). The quenching effect of Fe3+ on the SC fluorescent probe enabled efficient specific detection of Fe3+. Furthermore, Zn2+ ions increased fluorescence intensity of coumarin compounds (λemission = 459). This phenomenon occurs when the coumarin compound forms a complex or interacts with the zinc ion, resulting in enhanced fluorescence emission. In summary, the developed fluorescent probe offered a promising approach for sensitive and specific detection of iron and zinc ions in aqueous solutions.

Synthesis and evaluation of cellulose/polypyrrole composites as polymer electrolytes for lithium-ion battery application.

Natural polymers as battery components have a number of advantages, including availability, biodegradability, unleakage, stable form, superior process, electrochemical stability, and low cost. In other sides, conductive polymers can improve the electrochemical properties of the battery, such as charge/discharge rates, cycling stability, and overall energy storage capacity. Therefore, the combination of these two materials can provide acceptable features. In this study, polymer electrolytes based on cellulose have been synthesized by solution casting method to prepare a thin polymer film. Then, polypyrrole (PPy) was blended with cellulose in different weight ratios. To prevent electrical conductivity of blends, PPy was used <10 wt%. The electrochemical properties of prepared electrolytes have been investigated by different methods. The results showed that ionic conductivity was increased by addition of PPy to cellulose due to the creation of pores and also due to the high dielectric constant of conductive polymers. All synthesized electrolytes had suitable ionic conductivity (in the range of 10-3 S cm-1), significant charge capacity, stable cyclic performance, excellent electrochemical stability (above 4.8 V), and high cation transfer number (between 0.38 and 0.66 for pure cellulose and the sample containing 10 wt% PPy).

Adsorption kinetics of methylene blue from wastewater using pH-sensitive starch-based hydrogels.

In this work, starch/poly(acylic acid) hydrogels were synthesized through a free radical polymerization technique. The molar ratios of acrylic acid to N,N'-methylenebisacrylamide were 95:5, 94:6, and 93:7. The samples exhibited an amorphous porous structure, indicating that the size of the pores was contingent upon the amount of cross-linking agent. The quantity of acrylic acid in structure rose with a little increase in the amount of the cross-linking agent, which improved the hydrogels' heat stability. The swelling characteristics of the hydrogels were influenced by both the pH level and the amount of cross-linking agent. The hydrogel with a ratio of 94:6 exhibited the highest degree of swelling (201.90%) at a pH of 7.4. The dominance of the Fickian effect in regulating water absorption in the synthesized hydrogels was demonstrated, and the kinetics of swelling exhibited agreement with Schott's pseudo-second order model. The absorption of methylene blue by the hydrogels that were developed was found to be influenced by various factors, including the concentration of the dye, the quantity of the cross-linking agent, the pH level, and the duration of exposure. The hydrogel 95:5 exhibited the highest adsorption effectiveness (66.7%) for the dye solution with a concentration of 20 mg/L at pH 10.0. The examination of the kinetics and isotherms of adsorption has provided evidence that the process of physisorption takes place on heterogeneous adsorbent surfaces and can be explained by an exothermic nature.

Photoluminescent Polymer Nanoparticles Based on Oxazolidine Derivatives for Authentication and Security Marking of Confidential Notes.

Colloidal materials have widely been used to develop innovative anticounterfeiting nanoinks for information encryption. Latex nanoparticles based on methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) bearing hydroxyl functional groups were synthesized via semicontinuous miniemulsion polymerization. The size determination of the nanoparticles and microscopic results showed mostly spherical nanoparticles with a narrow size distribution and a mean size of about 80 nm. Two oxazolidine derivatives were physically doped at the surface of the nanoparticles to prepare photoluminescent polymer nanoparticles. Hydroxyl functional groups at the surface of the nanoparticles led to their hydrogen bonding interactions with the doped luminescent compounds. Optical analysis of the photoluminescent nanoparticles displayed different fluorescence emission and UV-vis absorbance intensities based on the amount of polar groups located at the surface of colloidal nanoparticles. Reducing the particle size to below 100 nm along with increasing the surface area can assist the decrease of the light reflectance and improvement of the latex nanoparticles' efficiency in the anticounterfeiting industry. This preparation methodology can efficiently provide remarkable photoreversible anticounterfeiting nanoinks used in different applications, such as print marking, security encoded tags, labeling, probing, and handwriting.

Stimuli-Responsive Dendritic Macromolecules for Optical Detection of Metal Ions and Acidic Vapors by the Photoinduced Electron Transfer Mechanism: Paper-Based Indicator for Food Spoilage Sensing.

Visual detection of analytes has been a significant challenge in the design and development of optical chemosensors. Sensing of analytes in aqueous solution by organic molecules has encountered some issues, such as poor water solubility and quenching of optical properties. In this study, a new category of smart dendritic macromolecules was designed and synthesized by functionalization of the poly(amidoamine) (PAMAM) dendrimer with spiropyran molecules to afford a photoluminescent dendritic structure (SP-PAMAM). Smart optical sensors were prepared by physical incorporation of four different oxazolidine derivatives containing hydroxyl and nitro substituted groups into the SP-PAMAM structure. Investigation of optical properties demonstrated photoinduced electron transfer (PET) between the spiropyran end group of SP-PAMAM and oxazolidine derivatives (in a concentration of about 0.0002 M), which can result in quenching of fluorescence emission of spiropyran photoswitch in the form of merocyanine (MC). Treatment of the oxazolidine-doped SP-PAMAM samples with metal ions resulted in changes in the PET mechanism (switching on or off), as observed in the case of Fe3+, Pb2+, Cu2+, Zn2+, Cd2+, Co2+, and Ni2+ by different oxazolidine derivatives through various mechanisms (increase or decrease of fluorescence emission). These smart photoluminescent dendritic macromolecules have potential applications for photodetection of metal ions in aqueous media as optical chemosensors. In addition, the smart macromolecules displayed disconnection of PET between MC and oxazolidine and also showed red fluorescence emission under acidic conditions (pH 1-5). It is due to the protonation of the MC to MCH form and demonstrates a remarkable red shift in fluorescence spectra. The pH-responsivity of smart macromolecules was used for designing a paper-based pH indicator for visual detection of spoilage in the food industry, especially in the case of milk. The prepared papers applied on cap of the milk bottles did not show any fluorescence emission in the case of fresh milk; however, a red fluorescence emission was observed after milk spoilage as a result of adsorption of acidic volatile components generated by bacterial degradation and oxidation process on the paper surface. The reported smart papers can serve as optical portable pH indicators for timely detection of spoilage in food materials, which are usable in food packaging as smart indicator tags.

Synthesis and characterization of fluorescence poly(amidoamine) dendrimer-based pigments.

In this work, we looked at how to make fluorescence hybrid poly(amidoamine) dendrimer (PAMAM) dendrimers using calcozine red 6G and coumarin end groups. After synthesis of ethylenediamine (EDA)-cored 4th generation PAMAM dendrimer (G4.0), surface functional groups is reacted with calcozine red 6G (Rh6G) and 7-methacryloyloxy-4-methylcoumarin. Fourier transform infrared spectroscopy, proton nuclear magnetic resonance (1H NMR), and X-ray diffraction are used to characterize the structure of synthesized fluorescent hybrid dendrimers. Optical properties are demonstrated using a fluorescence spectrophotometer, and UV-Vis-NIR reflectance spectra. According to UV-Vis-NIR reflectance spectra, hybrid dendrimers were transparent in the NIR range. Moreover, quantum yield (Φs) of hybrid dendrimers was calculated in dimethylformamide (DMF), ethanol, dimethyl sulfoxide (DMSO), and distilled water (H2O). Dendrimers in which Rh6G was utilized to modification showed the maximum quantum yield in ethanol due to great interaction of structure with ethanol and the arrangement of ring-opened amide shape of calcozine red 6G.

Fluorescent cellulosic composites based on carbon dots: Recent advances, developments, and applications.

Cellulose and its derivatives are highly applicable in advanced applications on the basis of fluorescence phenomena. Carbon dots (CDs) have also appealing properties, such as high photoluminescence, easy synthesis pathway, cheap source materials, chemical stability, and easy functionalization. In this regard, combination of luminescent CDs with natural cellulosic materials could adjust or expand its desirable properties and have advanced applications. This review summarizes chemical and physical incorporation of CDs and graphene quantum dots into different types of cellulosic materials to yield smart fluorescent materials with applications in films, catalysts, bioimaging, drug delivery, anticounterfeiting, and fluorescence chemosensors for sensing pH, temperature, cations, anions, glucose, and aromatic amines. The challenges and future directions in fluorescent materials based on CDs are also briefly discussed. We hope that these studies will provide more consideration and curiosity for chemists, biologists, and materials scientists working in the field of fluorescent and CDs-containing cellulosic materials.

Optical Chemosensors based on Spiropyran-Doped Polymer Nanoparticles for Sensing pH of Aqueous Media.

Photochromic polymers, which are prepared by the incorporation of photochromic compounds into polymer matrices, show fluorescence emission along with color change under UV light irradiation. Polymer nanoparticles yield high chromic properties at low chromophore loadings, as they have a large surface area to absorb a high level of light irradiation. Particle size is a significant parameter to control optical properties, where the decrease of particle size results in a high light absorption and efficiency of photochromism and fluorescence emission. Reverse atom transfer radical polymerization was used to synthesize methyl methacrylate homopolymer and its copolymers with different comonomers to yield polymers with a narrow molecular weight distribution. Spiropyran was doped to the polymeric nanoparticles during nanoprecipitation to yield photochromic polymer nanoparticles. Particle size below 100 nm for the photochromic nanoparticles was shown by dynamic light scattering. Morphology investigation with microscopic analysis showed spherical morphology for nanoparticles. The photochromic properties of the polymer nanocarriers were studied in both acidic and alkaline media. The results indicated that the pH of the media as well as the copolymer composition significantly affect the optical properties. Therefore, the photochromic polymer nanoparticles could have potential applications as optical pH chemosensors by colorimetric and fluorometric detection mechanisms. The nanoparticles with hydroxyl- or amine-functional groups were shown to be highly efficient for pH chemosensor applications. Finally, photochromic cellulosic papers prepared from the photochromic polymer nanoparticles were highly applicable in the detection of acid vapors.

Rewritable acidochromic papers based on oxazolidine for anticounterfeiting and photosensing of polarity and pH of aqueous media.

Oxazolidine is a new category of stimuli-chromic organic compounds with unique characteristics in response to polarity, pH changes, water, light, and metal ions that were well-known as solvatochromism, acidochromism, hydrochromism, photochromism, and ionochromism, respectively. Therefore, oxazolidine derivatives have been developed for their potential applications in chemosensors, anticounterfeiting, and rewritable hydrochromic papers. In this study, various oxazolidine derivatives containing hydroxyl and naphthalene substituted groups were synthesized by using two different indolenine compounds. The synthesized oxazolidine derivatives were used for investigation of solvatochromism in different solvents, and also acidochromism in various pHs by using UV-Vis and fluorescence spectroscopies. In addition, the oxazolidine derivatives were coated on cellulosic papers using a layer-by-layer strategy to develop rewritable acidochromic papers for printing of security tags on cellulosic papers by using acidic and alkaline solutions as water-based inks. Therefore, the developed rewritable acidochromic papers could be used as security papers.

Reflectance and photophysical properties of rhodamine 6G/2-(4-methyl-2-oxo-2H-chromen-7-yloxy) acetic acid as cold hybrid colorant.

Rhodamine 6G (Rh6G) is modified by ethylenediamine to obtain rhodamine with amine functional groups (Rh6G-NH2). Rh6G-NH2 as an initial core is used to bond coumarin derivatives. Synthesized fluorescent colorants are specified using Fourier transform infrared spectroscopy (FT-IR), proton and carbon nuclear magnetic resonance (1H NMR and 13C NMR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM) to analyze the structure of the fluorescent pigments. Fluorescence microscopy, fluorescence spectrophotometer, and UV-visible-NIR reflectance spectra are used to demonstrate the optical properties. UV-Vis-NIR reflectance spectra showed that synthesized colorants were transparent in NIR region. Also, photophysical properties of 2-(4-methyl-2-oxo-2H-chromen-7-yloxy) acetic acid (MOHCYAA), Rh6G-NH2, and hybrid 2-(4-methyl-2-oxo-2H-chromen-7-yloxy) acetic acid/rhodamine 6G (HMR) were investigated. Type of solvent had a strong effect on quantum yield. Rh6G-NH2 (ϕs = 0.66) and HMR (ϕs = 0.72) displayed the maximum quantum yield in ethanol due to good interaction with ethanol and the formation of ring-opened amide form of rhodamine group. Finally, Rh6G-NH2 and HMR displayed the maximum quantum yield in ethanol due to good interaction of structure with ethanol and the formation of ring-opened amide form of rhodamine group in compound.

Development of highly sensitive metal-ion chemosensor and key-lock anticounterfeiting technology based on oxazolidine.

Optical chemosensors and ionochromic cellulosic papers based on oxazolidine chromophores were developed for selective photosensing of metal ions and information encryption as security tags, respectively. The oxazolidine molecules have been displayed highly intense fluorescent emission and coloration characteristics that are usable in sensing and anticounterfeiting applications. Obtained results indicated that oxazolidine molecules can be used for selective detection of pb2+ (0.01 M), and photosensing of Fe3+, Co2+ and Ag+ metal ion solutions by colorimetric and fluorometric mechanisms with higher intensity and sensitivity. Also, oxazolidine derivatives were coated on cellulosic papers via layer-by-layer method to prepare ionochromic papers. Prepared ionochromic papers were used for printing and handwriting of optical security tags by using of metal ion solutions as a new class of anticounterfeiting inks with dual-mode fluorometric and colorimetric securities. The ionochromic cellulosic papers can be used for photodetection of metal ions in a fast and facile manner that presence of metal ions is detectable by naked eyes. Also, key-lock anticounterfeiting technology based on ionochromic papers and metal ion solution as ink is the most significant strategy for encryption of information to optical tags with higher security.

Polymer-functionalization of carbon nanotube by in situ conventional and controlled radical polymerizations.

Functionalization of carbon nanotube (CNT) with polymers has drawn much attention due to its wide range of applications. Polymer-functionalized CNT could exhibit variety of properties, such as responsivity to environmental stimuli, ability of complexation with metal ions, increased dispersibility in different solvents, higher compatibility with polymer matrix, etc. Chemical and physical methods have been developed for the preparation of polymer-functionalized CNT. Polymer chains are chemically bonded to the CNT edge or surface in the chemical methods, which results in highly stable CNT/polymer composites. "Grafting to", "grafting from", and "grafting through" methods are the most common chemical methods for polymer-functionalization of CNT. In "grafting to" method, pre-fabricated polymer chains are coupled with the either functionalized or non-functionalized CNT. In "grafting from" and "grafting through" methods, CNT is functionalized by polymers simultaneously synthesized by in situ polymerization methods. Conventional free radical polymerization (FRP) and also controlled radical polymerization (CRP) are the most promising methods for in situ tethering of polymer brushes onto the surface of CNT due to their control over the grafting density, thickness, and functionality of the polymer brushes. The main focus of this review is on the synthesis of polymer-functionalized CNT via both the "grafting from" and "grafting through" methods on the basis of FRP and CRP routs, which is commonly known as in situ polymerizations. Finally, the most important challenges and applications of the in situ polymer grafting methods are discussed, which could be interesting for the future works.

Photoswitchable surface wettability of ultrahydrophobic nanofibrous coatings composed of spiropyran-acrylic copolymers.

HYPOTHESIS: Light-controlling of surface characteristics in polymeric coatings has been a significant research area because of its potential application in development of smart surfaces. Wettability of light-responsive polymeric coatings based on spiropyran photochromic compound could be tuned by light irradiation. This is mainly because of spiropyran isomerization between the hydrophobic and hydrophilic states. EXPERIMENTS: Light-responsive latex nanoparticles containing spiropyran moieties were synthesized by semi-continuous emulsion copolymerization of acrylate monomers, which have different chain flexibility depending on the copolymer composition. Photochromic properties of spiropyran in stimuli-responsive latex nanoparticles displayed dependence of photochromism intensity and its kinetics to flexibility of the polymer chains in addition to the polarity of media. Photoswitchable surface wettability of the spiropyran-containing acrylic copolymer coatings was investigated, where the photo-responsive coatings were prepared by solution casting and electrospinning methods. FINDINGS: The photoswitchable coatings prepared by solution casting and electrospinning methods showed significant differences in their physical characteristics and especially surface wettability. The polymeric coatings displayed water droplet contact angles in the range of 60-93°, which could reversibly be switched to 55-86° upon UV light (365 nm) illumination as a result of isomerization of the hydrophobic spiro form to the zwitterionic merocyanine form. The nanofibrous coatings prepared by electrospinning method displayed higher contact angles in the range of 120-136°, which was switched to 78-105° upon UV light irradiation. The developed photo-responsive coatings displayed highly-efficient photoswitching between the two hydrophobic and hydrophilic states as a response to UV and visible light irradiation. The photoswitchable nanofibrous coatings displayed ultrahydrophobic characteristics, where the colored water droplets were stable on their surface and could easily be adsorbed by a cellulosic tissue. In summary, the photoswitchable nanofibrous coatings could be applied for design and development of ultrahydrophobic materials with the ability of photo-controlling of surface wettability by light irradiation with tunable intensity.

Photoluminescent and Chromic Nanomaterials for Anticounterfeiting Technologies: Recent Advances and Future Challenges.

Counterfeiting and inverse engineering of security and confidential documents, such as banknotes, passports, national cards, certificates, and valuable products, has significantly been increased, which is a major challenge for governments, companies, and customers. From recent global reports published in 2017, the counterfeiting market was evaluated to be $107.26 billion in 2016 and forecasted to reach $206.57 billion by 2021 at a compound annual growth rate of 14.0%. Development of anticounterfeiting and authentication technologies with multilevel securities is a powerful solution to overcome this challenge. Stimuli-chromic (photochromic, hydrochromic, and thermochromic) and photoluminescent (fluorescent and phosphorescent) compounds are the most significant and applicable materials for development of complex anticounterfeiting inks with a high-security level and fast authentication. Highly efficient anticounterfeiting and authentication technologies have been developed to reach high security and efficiency. Applicable materials for anticounterfeiting applications are generally based on photochromic and photoluminescent compounds, for which hydrochromic and thermochromic materials have extensively been used in recent decades. A wide range of materials, such as organic and inorganic metal complexes, polymer nanoparticles, quantum dots, polymer dots, carbon dots, upconverting nanoparticles, and supramolecular structures, could display all of these phenomena depending on their physical and chemical characteristics. The polymeric anticounterfeiting inks have recently received significant attention because of their high stability for printing on confidential documents. In addition, the printing technologies including hand-writing, stamping, inkjet printing, screen printing, and anticounterfeiting labels are discussed for introduction of the most efficient methods for application of different anticounterfeiting inks. This review would help scientists to design and develop the most applicable encryption, authentication, and anticounterfeiting technologies with high security, fast detection, and potential applications in security marking and information encryption on various substrates.

Encryption and authentication of security patterns by ecofriendly multi-color photoluminescent inks containing oxazolidine-functionalized nanoparticles.

Counterfeiting of confidential documents has been a costly challenge for banks, companies, and customers. Encryption of invisible security marks, such as barcodes, quick response codes, and logos, in national or international confidential documents by high-security anticounterfeiting inks is the most significant solution for counterfeiting problems. Ecofriendly multi-color photoluminescent anticounterfeiting inks based on highly-fluorescent polymer nanoparticles functionalized with new oxazolidine derivatives were developed for the fast and facile encryption of security labels on cellulosic documents, such as paper currency, passport, and certificate. Depending on the polarity of functionalized polymer nanoparticles, a wide range of colors and fluorescence emissions were observed as a result of polar-polar interactions between the oxazolidine molecules and surface functional groups of the nanoparticles. The fluorescent polymer nanoparticles showed spherical, vesicular, and cauliflower-like morphologies resulted from different surface functional groups. Functional polymer nanoparticles displayed high stability and printability on cellulosic substrates due to hydrogen bonding interactions. The highly-fluorescent polymer nanoparticles were also used to prepare anticounterfeiting inks with different colors and fluorescence emissions. All the ecofriendly polymeric anticounterfeiting inks were loaded to stamps with specific marks, and then applied to different confidential documents. Printed labels displayed highly intense fluorescence emission in different colors (green, orange, pink, and purple depending on the matrix polarity) under UV irradiation (365 nm). These water-based multi-color fluorescent anticounterfeiting inks with highly intense, bright, and sensitive fluorescence emission have potential applications in encryption and authentication of security patterns.

Encryption and optical authentication of confidential cellulosic papers by ecofriendly multi-color photoluminescent inks.

Photodetection of originality and authentication of security documents such as money, passport, bank note, and national card have been a significant challenge in recent decade. Using of advanced optical systems could remarkably reduce copy and counterfeiting of such national and international documents. Novel ecofriendly multi-color photoluminescent inks were developed for information encryption on cellulosic papers and optical authentication of confidential/original documents by synthesis of water-based latex nanoparticles modified with photoluminescent coumarin (blue emission) and two photochromic spiropyran derivatives (red and orange emissions). Some of the latexes with higher fluorescence emission were formulated to water-based inks, and then loaded to stamps with different marks for printing of quick response code, barcode, finger print, and other marks on cellulosic documents. All of the printed marks display ultra-bright blue, red, and orange fluorescence emissions upon UV irradiation, which have potential applications in encryption, security marking and optical authentication of confidential cellulose substrates.

Adsorption kinetics of methyl orange from water by pH-sensitive poly(2-(dimethylamino)ethyl methacrylate)/nanocrystalline cellulose hydrogels.

A series of hydrogel nanocomposites was fabricated by in situ polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) in presence of different amounts of (amine- and alkyl-modified) nanocrystalline cellulose (NCC). Modification and nanocomposites properties were proved by different analysis methods such as Fourier-transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), and field emission scanning electron microscopy (FE-SEM). The new hydrogel nanocomposites were applied for removing methyl orange (MO) used as anionic dye and presented in process water at different pH values. The effects of the fabrication process such as modification and content of NCC, contact time, and pH value on swelling ratio (SR), and equilibrium adsorption kinetics were studied. Results showed that the swelling ratio of PDMAEMA-based nanocomposites varied with the different types of nanoparticles showing the significant effect of the modification process. The MO adsorption into the hydrogel nanocomposites was affected by intermolecular and electrostatic interactions between functional groups of hydrogel and dye. The adsorption capacity decreased at high pH value, and it was significantly affected type of nanoparticles introduced into the hydrogel network. The addition of unmodified NCC did not affect adsorption kinetics significantly. Finally, adsorption kinetics was investigated by pseudo-first-order, pseudo-second-order and intraparticle diffusion models where pseudo-first-order model showed the best correlation with experimental results.

Seed's morphology-induced core-shell composite particles by seeded emulsion polymerization for drug delivery.

Cross-liked poly(2-hydroxyethyl methacrylate-co-methacrylic acid) seeds with different morphologies such as cauliflower-like, lobed spherical, and spherical were used in seeded emulsion polymerization (SEP) of 2-(dimethylamino)ethyl methacrylate (DMAEMA), 2-hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA). The morphological structure of produced composite particles was observed using field emission scanning electron microscopy (FE-SEM). The origin of the formation of different morphologies was discussed using various thermodynamic parameters such as solubility parameters and intermolecular forces between polymeric components involved. Also, the effect of the morphology of seed particles on the resultant structures was investigated. Results showed that morphology of fabricated composite particles is induced from morphology of seed particles with larger sizes. Finally, the fabricated composite particles were utilized in the controlled release of DOX. The effect of morphological changes of synthesized composite particles on the cumulative release behavior at acidic environment indicated the pH-sensitive nature of drug release through carriers. The particles with PDMAEMA shell showed the highest release of DOX at pH = 7.4 whereas PMAA shells displayed the least cumulative release. Inversely, the lowest cumulative release at pH = 1.2 was shown by PDMAEMA-coated carriers. Moreover, particles with spherical morphology had better drug release than cauliflower-like ones originated from smart nature of carriers.

Light-, temperature-, and pH-responsive micellar assemblies of spiropyran-initiated amphiphilic block copolymers: Kinetics of photochromism, responsiveness, and smart drug delivery.

Multi-responsive polymer assemblies are a significant class of smart polymers with potential applications in drug-delivery and gen-delivery systems. Poly(dimethylaminoethyl methacrylate) (PDMAEMA) is among the most applicable multi-responsive polymers that changes its physical and chemical properties in response to temperature, pH, and CO2. Herein, different types of light-, temperature-, pH-, and CO2-responsive polymer assemblies were developed based on multi-responsive PDMAEMA and hydrophobic poly(methyl methacrylate) blocks. In addition, spiropyran was incorporated at the chain ends by using spiropyran-initiated atom transfer radical polymerization method. Novel smart drug-delivery systems were developed by self-assembly of these amphiphilic block copolymers to micellar morphologies in aqueous media. Dynamic light scattering results showed that size of the polymer assemblies changed in response to pH variations (from 5 to 9), temperature changes (above the lower critical solution temperature (LCST) of PDMAEMA), and also UV light irradiation (wavelength of 365 nm). The LCST of PPDMAEMA showed a shift from 53 to 60 °C after isomerization of the SP to MC form, as a result of increase of polarity and water-solubility. The PDMAEMA block results in responsivity of the prepared copolymer assemblies to CO2, which display pH variation from 8-8.6 to 5-6 after 2 min of CO2 gas bubbling. All the multi-responsive micellar polymer assemblies showed various loading capacities and release profiles, and the DOX release can be controlled by pH, temperature, and light. The release efficiency is reached to 60-85% at pH 5.3, 80-90% at temperatures higher than the LCST of PDMAEMA (60 °C), and also 90-100% under UV light irradiation after 48 h. In summary, the multi-responsive polymer assemblies based on amphiphilic block copolymers containing spiropyran chain end groups in the current study have potential applications in smart drug-delivery systems, and offer controlling over the drug-release by different triggers, such as light irradiation, pH variation, and temperature change. A very low concentration of spiropyran molecules (one per polymer chain) showed light-controlling of drug-release from the assemblies with high efficiencies.

Functionalization of carbon nanotubes by combination of controlled radical polymerization and "grafting to" method.

This paper reviews the recent advances in non-covalent and covalent tethering of small molecules and polymer chains onto carbon nanotube (CNT) and its derivatives. The functionalized CNT has recently attracted great attention because of an increasing number of its potential applications. In non-covalent functionalization of CNT, the sp2-hybridized network plays a crucial role. The non-covalent grafting of small molecules and polymers can mainly be carried out through hydrogen bonding and π-stacking interactions. In covalent functionalization of CNT, condensation, cycloaddition, and addition reactions play a key role. Polymer modification has been reported by using three main methods of "grafting from", "grafting through", and also "grafting to". The "grafting from" and "grafting through" rely on propagation of polymer chains in the presence of CNT modified with initiator and double bond moieties, respectively. In "grafting to" method, which is the main aim of this review, the pre-fabricated polymer chains are mainly grafted onto the surface using coupling reactions. The coupling reactions are used for grafting pre-fabricated polymer chains and also small molecules onto CNT. Recent studies on grafting polymer chains onto CNT via "grafting to" method have focused on the pre-fabricated polymer chains by conventional and controlled radical polymerization (CRP) methods. CRP includes reversible activation, atom transfer, degenerative (exchange) chain transfer, and reversible chain transfer mechanisms, and could result in polymer-grafted CNT with narrow polydispersity index of the grafted polymer chains. Based on the mentioned mechanisms, nitroxide-mediated polymerization, atom transfer radical polymerization, and reversible addition-fragmentation chain transfer are known as the three commonly used CRP methods. Such polymer-modified CNT has lots of applications in batteries, biomedical fields, sensors, filtration, solar cells, etc.