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Functionalized polymers with carboxylic acid groups were synthesized and used to prepare nanoparticles and nanofibers containing oxazolidine by nanoprecipitation and electrospinning, which were used as pH sensor and oil/water separator, respectively.

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.

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 Fe

Poly(ethylene oxide) (PEO) is one of the most famous polymer electrolytes; however, its low conductivity and capacity have prevented its commercial applications. This study utilizes carboxymethyl starch (CMS) and oxidative carboxymethyl cellulose (OCMC) natural polymers with a high potential to dissolve lithium ions (Li+) in to help PEO ionic conductivity. The semi-interpenetrating polymer networks (semi-IPNs) consist of crosslinked poly(ethylene glycol) methyl ether methacrylate (PEGMA) with poly(ethylene glycol) diallyl (PEGDA) and free CMS/OCMC chains. Effect of increasing the amount of natural polymer on the electrochemical properties of semi-IPNs is investigated. Semi-IPN CMS50% and semi-IPN OCMC50% deliver excellent results such as high conductivity (in order 10-2 Scm-1) at room temperature, electrochemical stability window higher than 4.5 V, high Li+ transfer number, high discharge capacities (191 and 203 mAh g–1 with capacity retention of 85 and 88.5% after 100 cycles at 0.2 C, respectively), and stable cyclic behavior.

Covalent crosslinked stimuli-destructible hydrogels with the ability of irreversible stimuli-controlled bond dissociation have attracted great attentions due to their easy preparation, biocompatibility, biodegradability, stability against hydrolysis, and controlled solubility by applying desired triggers. Stimuli-controlled microstructure, elasticity, and mechanical properties has resulted in their application in selective capturing, proliferation, and detection of human and bacterial cells, drug delivery, wound dressing, and imprint lithography. Polymerization approaches and different functional groups required to prepare these hydrogels with the ability of irreversible bond dissociations, mechanism of stimuli-controlled bond cleavage, degradation products, comparison between the stimulants, and their final applications are highlighted in this review. Photocleavable hydrogels containing nitrobenzyl, coumarin, and perylene drivatives, redox-dissociable hydrogels containing diselenide and succinimide thioether bonds, destructible hydrogels prepared from phenolic ester and aldazine moieties as pH-cleavable bonds, and hydrogels crosslinked by enzyme- and thermo-dissociable moieties are the most important chemically crosslinked stimuli-destructible hydrogels, which show stimuli-controlled covalent bond dissociation with an irreversible mechanism.

Different types of chain extenders in the synthesis of polyurethanes affect its structural, mechanical, and rheological properties. Effects of chain extender length, functionality, and molar ratio of the reactants on different properties of polyurethane elastomers based on poly (oxytetramethylene)glycol as the soft segment and toluene diisocyanate as the hard segment were investigated. Polyurethane samples were synthesized using different chain extenders including glycerol as the trifunctional and 1,2-propanediol, 1,4-butanediol, and 1,6-hexanediol as the bi-functional hydroxyl-containing chemicals. Fourier-transform infrared spectroscopy, X-ray diffraction, rheomechanical analysis, dynamic mechanical thermal analysis, differential scanning calorimetry, and stress–strain analysis were used for characterization of the products. By phase separation of the hard and soft segments, two different glass transition temperatures were observed. Increasing phase separation and degree of hydrogen bonding between the chain extender and diisocynates in the hard segments were resulted in higher mechanical properties. With increasing the amount of hard segment, a higher polymer toughness is determined due to higher degree of hydrogen bonding.

Fluorescent inks based on carbon quantum dots (CQDs) can be used in different applications, such as militaries for anti-counterfeiting messages, banks, money, worthy documents, and cheques. On the other hand, CQDs can be used for biological and imaging purposes like flow cytometry, DNA mutation, drug delivery, drug releasing, and bioimaging. In this study, CQDs were synthesized utilizing a one-step procedure using citric acid, ethylene diamine, and aniline in different ratios using different synthesis methods like hydrothermal, microwave, and simple heating. UV-Visible, Photoluminescence, Energy Dispersive Spectroscopy, Field Emission Scanning Electron Microscopes, Transmission electron microscopy, and water contact angle were carried out to investigate the synthesized carbon quantum dots. The best CQDs were selected as a functional dye to fabricate fluorescent ink and were printed on paper. By analyzing the visual effects of printed papers under UV light and daylight, it was shown that all printings were successfully done, and all samples had noticeable fluorescence emission. Water contact angle measurements were done on both printed area and unprinted paper for further investigations. The results showed that the contact angle decreased after printing on the paper, which was related to the penetration of ink into the substrate’s pores.

The development of stimuli-responsive drug nanocarriers is an increasingly important area in nanomedicine because efficient delivery of toxic drugs to targeted tissues minimizes side effects. The specific objective of this study was to synthesize and characterize a novel pH-responsive drug carrier based on halloysite nanotubes for the controlled release of the anticancer drug doxorubicin. Poly(N,N-dimethylaminoethyl methacrylate) brushes were grafted from the surface of halloysite nanotubes using the combination of mussel-inspired polydopamine surface modification and activators regenerated by electron transfer in atom transfer radical polymerization. The chemical structure and morphology of the modified halloysite nanotubes were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermal gravimetric analysis as well as scanning and transmission electron microscopies. Dynamic light scattering and zeta potential analysis were carried out to evaluate the pH-responsivity of the functionalized halloysite nanotubes. The results of the drug loading and release study of pristine and functionalized halloysite nanotubes showed that grafting of poly(N,N-dimethylaminoethyl methacrylate) brushes on the polydopamine-modified halloysite nanotubes surface leads to a drastic increase in doxorubicin loading capacity and a highly pH-sensitive release behaviour. Less than 10 % of the loaded doxorubicin was released from poly (N,N-dimethylaminoethyl methacrylate)-grafted halloysite nanotubes at pH 7.4 after 24 h; in contrast, at pH 5.5 there was a continuous release of doxorubicin totalling 13 % in the first 30 min, i.e. lower than for the pristine halloysite nanotubes (32 %), but reaching 48 % after 24 h. Poly (N,N-dimethylaminoethyl methacrylate)-grafted halloysite nanotubes can hence be considered as a potential candidate for delivering highly toxic drug molecules to the acidic target sites.

Polyurethane and novolac resins functionalized with epoxide groups were cured by a multifunctional crosslinking agent decorated with amine functional groups. Poly(amidoamine) (PAMAM) was grafted onto (3-aminopropyl) triethoxysilane-functionalized hydroxylated silica nanoparticles by its subsequent reaction with methyl acrylate and then ethylenediamine to prepare PAMAM-modified silica nanoparticles (SD). Successful preparation of SD as the multifunctional crosslinking agent of the epoxide-functionalized resins and also the hybrid composites were studied by Fourier-transform infrared spectroscopy. Thermal characterization and structural investigation of SD and the hybrid composites were carried out by thermogravimetric analysis and X-ray diffraction, respectively. Thermal investigation of the hybrid composites revealed that the sample with 8 mass% of SD and epoxide-functionalized novolac resin matrix presented the highest thermal stability (char residue and degradation peak point of 56.2% and 689.35 K, respectively). Morphological investigation of the bear silica and hybrid composites was also performed using transmission and scanning electron microscopies.

The mechanical behavior of an adhesive, in neat state and reinforced with up to 0.5 wt% of reduced graphene oxide (RGO) was investigated here. Tests were done at temperatures between the ambient temperature and the glass transition temperature ( Tg[Formula: see text] of the adhesive. Using a metal mold, cured plates of the neat and RGO reinforced epoxy adhesive were prepared. The adhesive powder and the bulk dumbbell-shaped specimens, obtained from cured adhesive plates, were subjected to differential scanning calorimetry (DSC) and tensile tests, respectively, to obtain the Tg as well as mechanical properties of the adhesives. The results indicated that adding RGO up to 0.5 wt% increased the glass transition temperature, the modulus of elasticity, and the strength of the adhesive. It was found that the presence of RGO reduced the adhesive’s strain at the break at the ambient temperature. However, at high temperatures, near the Tg, the ultimate strain of RGO-reinforced adhesives decreased slightly when compared to the ultimate strain of the neat specimens. This explains the reduction in toughness at ambient temperature obtained by adding RGO and the increase at high temperatures. Finally, the failure morphology of the neat and RGO-reinforced adhesive specimens was investigated using microscopic imaging of the specimens’ failure cross-sections, which supported and justified the experimental observations.

A multifunctional hybrid curing component (GSD) for epichlorohydrin-modified novolac resin (ENR) was synthesized via grafting poly(amidoamine) (PAMAM)-modified silica nanoparticles (SD) on graphene...

Thermal characteristics of epoxy-modified polyurethane and novolac resins composites were investigated by using graphene oxide (GO) functionalized with hyperbranched poly(amidoamine) (PAMAM) as the curing component (GOD). The dendritic hybrid curing agent of GOD was synthesized via a divergent method and used to cure epoxy-terminated polyurethane (EPU) and epoxidized novolac resin (ENR). After preparation of the first generation of PAMAM dendrimer by using amino-functionalized GO as the core, Fourier transform infrared spectra, X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were used to prove the successful preparation method of GOD. TGA also showed that thermal characteristics of the hybrid EPU and ENR composites were determined by the amount of GOD and portion of the resins in the composites matrix. The hybrid composites with higher amounts of GOD and ENR matrix showed higher thermal stability and char residue. As example, the ENR-based hybrid composites with 3 wt% of GOD showed char residue of 57.2% at 600 °C and Tmax of 401.2 °C. In addition, morphological and structural study of the graphitic and hybrid samples was investigated by XRD and electron microscopies.

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.

Carbon nanotube (CNT) grafted with hyperbranched poly(amidoamine) (PAMAM) dendrimer (CNTD) were used as a multifunctional curing and composite agent of polyurethane (PU) terminated with epoxy units. Amino-functionalized CNT was used as the core for grafting the first generation of PAMAM dendrimer by sequential addition of methyl acrylate and ethylenediamine. Two different epoxy-terminated PUs (PUB and PU-PMDA) were prepared from the reaction of poly(ethylene glycol), excess amounts of hexamethylene diisocyanate, and different chain extenders (1,4-butanediol for PUB and pyromellitic dianhydride (PMDA) for PU-PMDA), and subsequent end group transformation of the isocyanate groups to epoxy functionalities using glycidol. Fourier transform infrared spectra and thermogravimetric analysis (TGA) results showed that CNTD was successfully prepared. TGA thermograms revealed that thermal decomposition of composites were carried out in two main steps related to the soft and hard segments. In addition, char content and thermal stability of the composites were increased with increasing the CNTD content. Most importantly, the PMDA chain extender resulted in high thermal stability of the epoxy-terminated PU composites. X-ray diffraction and scanning and transmission electron microscopies presented morphological and structural properties of nanotubes and hybrid composites.

A hyperbranched hybrid curing agent (CSD) for epoxidized novolac resin (ENR) was prepared by grafting silica nanoparticles modified with poly(amidoamine) (PAMAM) dendritic structure (SD) to carbon ...

Polyurethane/crystalline nanocellulose (PU/CNC) nanocomposites were fabricated through in-situ polymerization by using polydimethylsiloxane (PDMS), methylene diphenyl diisocyanate (MDI), and 1,4-butanediol (BDO) as polyol, aromatic diisocyanate, and chain extender, respectively. CNC content affected the microstructure and thermophysical properties of the nanocomposites. Incorporation of CNCs into PU affected the interactions between soft and hard segments. Although CNCs had slight effect on thermal degradation of nanocomposites, they significantly affected thermophysical properties. For example, CNCs decreased the crystallization of hard segment and glass transition temperatures of hard and soft segments were shifted to higher temperatures. PU showed a relatively high toxicity against human fibroblast cells because of presence of aromatic segments in its structure. Although cytocompatibility was improved by addition of CNCs, PU/CNC nanocomposites showed relatively cytotoxic behavior at higher concentrations.

The application of photochromic materials in the development of anticounterfeiting technologies has shown a significant growth in recent years because of their advantages in displaying dual-mode security as simultaneous photochromic coloration and fluorescence emission. Photochromic copolymers based on styrene and spiropyran (5, 10, and 20 wt% with respect to styrene) with carboxylic acid chain end groups were synthesized by solution polymerization. The chemical structure, thermal behavior, and optical characteristics of the copolymers were studied using proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and UV-vis spectroscopy. The copolymer solutions in toluene and DMF were electrospun to yield photochromic nanofibers. The electrospun nanofibers from the copolymer solutions in toluene showed a well-defined morphology, a smooth surface, and a narrow size distribution in their diameter. These nanofibers were applied on cellulosic papers and banknotes for the induction of dual-mode security with a fast and facile authentication strategy. The induced security marks are virtually invisible under visible light and become visible by photochromic coloration from colorless to purple after UV irradiation. They also displayed red fluorescence emission under UV irradiation. Both the photochromic coloration and fluorescence emission showed high intensities, the security marks were rapidly authenticated upon UV irradiation, and this process was fully reversible for several cycles of UV/visible light irradiation because of the higher photofatigue resistance of the spiropyran-containing copolymers. These advantages originated from the high surface area of the photochromic nanofibers leading to higher light absorption and subsequent intense optical responses as coloration and fluorescence emission. Finally, a fast and facile anticounterfeiting strategy based on electrospun security marking was developed for the induction of dual-mode security marks on cellulosic documents and banknotes.

Among molecular structures, colloidal molecules have attracted the attention of the scientific community because of their distinct geometry (topology, size on a nanometer scale). In this field, dendrimers are an example of colloidal polymeric molecules which have a specific size and are identified and regulated by repeating units as generations. The dendrimers are very similar to the colloidal particles in geometric form and size, which is more evident in the higher generations of the colloidal dendrimers. On the other hand, the unique structural features of these macromolecules resemble them as macromolecular colloids. These properties including the high degree of freedom, the controllable molecular size and weight, the need for no initiator, the presence of end groups, the high drug transfer capacity, etc., have made dendrimers applicable to a variety of fields such as medicine, biomedical, pharmaceutical, catalyst, and so on.

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.

Smart polymers with extraordinary characteristics are studied in drug-delivery applications. In the current study, temperature-responsive hybrid core-shell nanoparticles were synthesized by precipitation polymerization of N-isopropylacrylamide and vinyl-modified silica nanoparticles. These temperature-responsive hybrid core-shells were prepared with different cross-linking densities by using 2, 4, and 8 mol % of N,N-methylene bisacrylamide (MBA). Hydrolysis of the silica cores of the hybrid core-shells resulted in hollow poly(N-isopropylacrylamide) (PNIPAM) nanogels. Functionalization of silica nanoparticles with vinyl-containing silane modifier of 3-(trimethoxysilyl) propyl methacrylate (MPS) in two different contents was proven by Fourier transform infrared spectroscopy. Preparation of the hybrid PNIPAM nanogels and etching of the silica cores were studied using thermogravimetric analysis and also electron microscopy imaging. Sensitivity of the PNIPAM nanogel samples to temperature was studied using ultraviolet-visible (UV-vis) spectroscopy. In addition, dynamic light scattering was used for investigation of the squeezing and expansion of the hybrid and hollow samples against variation of temperature. The UV-vis spectroscopy results display higher absorption intensities in higher contents of MPS modifier and MBA cross-linker. The swelling content of the nanogels with hollow cavities was higher than that of the hybrid samples. The hybrid nanogels with 2 and 8 wt % silica content and different cross-linking densities and also their hollow nanoparticles were used for loading and release of doxorubicin (DOX). The release characteristics of the DOX-loaded nanogels were studied at different temperatures using UV-vis spectroscopy. The DOX release was higher at temperatures lower than the gel collapse temperature of the PNIPAM network. Although the nanogels with hollow cavities displayed higher loading capacities, the release percentage was higher for the hybrid PNIPAM nanogels, which was confirmed by the experimental release profiles and mathematical models. The most appropriate fitting of the DOX release data from the PNIPAM nanogel samples was observed for the Korsmeyer-Peppas model. Cytotoxicity studies on HeLa cell line showed that drug-loaded hollow samples showed higher toxicity due to loading of a higher amount of DOX.