Universal water-soluble cyclodextrin polymer–carbon nanomaterials with supramolecular recognition

Functionalization of carbon nanomaterials (including fullerenes, single-walled carbon nanotubes, multi-walled carbon nanotubes (MWCNTs), and graphene sheets) dispersed in water with macromolecules was achieved by a one-step strategy using β-cyclodextrin polymer (CDP). CDP-carbon nanomaterials were characterized by ultraviolet–visible, Raman, and Fourier transform infrared spectroscopies, transmission and scanning electron microscopies, and thermogravimetric analysis. These nanomaterials showed high solubility and stability in water because of the noncovalent interaction between carbon nanomaterials and CDP. The supramolecular recognition abilities of CDP-carbon nanomaterials were studied by cyclic voltammetry (CV). CDP-MWCNTs were also decorated by p-aminothiophenol (PATP) which formed inclusion complexes with the CDP. The conjugates (PATP-CDP-MWCNTs) were ideal templates for the highly efficient assembly of noble metal nanoparticles (Au and Pt) with dramatically different properties. Methanol oxidation of Pt-decorated PATP-CDP-MWCNTs in CV analyses indicated its potential application in direct methanol fuel cells, facilitating the feasibility of metal-decorated CDP-carbon nanomaterials in real technological applications. This universal method of producing carbon nanomaterials functionalized with macromolecules is beneficial for investigating the structure–performance relationship of carbon nanomaterials for designing compounds with specialized functions.     

Synthesis of organic–inorganic polymer hybrids from acrylate polymer having a triphenylimidazole moiety via π–π interactions

Polymer Bulletin - Organic–inorganic polymer hybrids were prepared utilizing π–π interactions. The sol–gel reaction of phenyltrimethoxysilane (PhTMOS) was carried out in...     

Photochemical technology of the formation of polymer materials’ nanomarkers

A new photochemical technology for forming latent markers, i.e., protective identifiers of different polymer products and other materials, is developed. This technique allows one to encode identifiers of both individual products and lots of different kinds of products. Designed markers can be nanostructured and do not violate the appearance of products. The possibility of forming resistant latent identifiers in a variety of materials is shown that can be performed with fine periodic structure, including nanotechnology. The use of these markers realizes the possibility of developing new design elements of the product with multilevel coding. The proposed technology in combination with the development of ways of reading latent and multilevel information can serve as the basis for the development of a new method of identifying and protecting against the falsification of products, documents, data carriers, and valuable objects.     

Platinum–polymer–clay nanocomposite hydrogels via exfoliated clay-mediated in situ reduction

Pt nanoparticles (Pt NPs) are currently used in many areas of nanoscience and technology. Numerous studies have been reported on the design of Pt and Pt-based nanomaterials with different sizes, shapes, and compositions. Here, we report the synthesis, structure, and properties of a novel hydrogel-based nanostructured Pt material, Pt-NC gel, consisting of ultrafine Pt NPs strongly immobilized within a unique polymer−clay network. Pt-NC gels were synthesized through exfoliated clay-mediated in situ reduction of Pt ions in the NC gel at ambient temperature. Pt NPs were trapped on the clay surface, probably at the edges of the clay nanoplatelets. Ultrafine Pt NPs were also obtained as a stable suspension from the NC gel, without any stabilizing agents. The combination of ultrafine Pt NPs and mechanically tough NC gel may open up new possibilities for designing functional Pt-gel materials.     

Preparation of polymer decorated graphene oxide by γ-ray induced graft polymerization

Herein, we report a facile approach to decorate graphene oxide (GO) sheets with poly(vinyl acetate) (PVAc) by γ-ray irradiation-induced graft polymerization. The content of PVAc in the obtained sample, i.e., PVAc grafted GO (GO-g-PVAc) is calculated by the loss weight in thermogravimetric analysis (TGA) curves. A GO-g-PVAc sample with a degree of grafting (DG) of 28.5% was well dispersed in common organic solvents and the dispersions obtained were extremely stable at room temperature without any aggregation, even after standing for 2 months. The excellent dispersibility and stability of GO-g-PVAc in common organic solvents are readily rationalized in terms of the full coverage of PVAc chains and solvated layer formation on graphene oxide sheets surface, which weakens the interlaminar attraction of GO sheets. This approach presents a facile route for the preparation of dispersible GO and shows great potential in the preparation of graphene-based composites by solution-processes.     

Synthesis of high performance organic–inorganic composite via click coupling of block polymer and polyhedral oligomeric silsesquioxane

Novel hybrid systems based on poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) and a polyhedral oligomeric silsesquioxane (POSS) have been synthesized via click chemistry. Different compositions of SEBS-functionalized POSS were obtained from the reaction of azide-functionalized styrene units of SEBS with alkyne-functionalized POSS molecules. Characterization of SEBS-functionalized POSS by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and nuclear magnetic resonance spectroscopy revealed that the POSS molecules were successfully attached to the phenyl group of the SEBS polymer chain following the click reaction. Homogeneous dispersion of POSS molecules in the polymer matrix was demonstrated by scanning electron microscopy. The POSS molecule showed excellent compatibility with polymer matrix, and as a consequence the remarkable enhancement of mechanical properties (breaking stress = 44%, modulus = 285%) and thermal stability for the resulting composite films was achieved. The reinforcing effect is ascribed to both the compatible homogeneous dispersion of POSS in the matrix and the covalent bond between SEBS and POSS molecules arising from the click coupling.     

Ionic autocrosslinking of water-based polymer latices: A new concept of acid–base interaction occurring upon film formation

Latices of the terpolymer styrene/butyl acrylate/acido-basic monomer, the monomer having either a basic chemical group or an acidic chemical group, were separately prepared by free-radical emulsion polymerization using the nonionic surfactant poly(oxy-1,2-ethanediyl) as steric stabilizer. The basic polymer latices were prepared using 1, 3 or 5% of 2-(dimethylamino)ethyl methacrylate, whereas the acidic polymer latices were prepared using 1, 3 or 5% of acrylic acid (mol% relative to conventional monomers, styrene and butyl acrylate). Blends of the basic and the acidic polymer latices were prepared by simply mixing equal molar quantities of basic and acidic latices. The resulting blends were stable as the steric stabilization prevented unlike particles from colliding. Upon film formation, coalescence of the particles took place, with formation of ionic clusters due to proton exchange from the acidic monomer units to the basic monomer units of neighbouring unlike particles. This constitutes a reversible ionic crosslinking at the periphery of neighbouring particles, which affects the various film properties to different extents.     

Hybrid dual-cure polymer networks via sequential thiol–ene photopolymerization and thermal ring-opening polymerization of benzoxazines

Dual-cure hybrid polymer networks were prepared by sequential thiol–ene photopolymerization followed by thermal ring-opening polymerization of benzoxazines with the aim of increasing the glass transition temperature range of thiol–ene based materials and improving the processibility of polybenzoxazines. The hybrid networks are derived from a multifunctional, dually-polymerizable monomer possessing both bis-“ene” and bis-benzoxazine moieties enabling the formation of two networks through a common constituent monomer when combined with a multifunctional thiol. The photopolymerization kinetics of the thiol–ene reaction were investigated by real-time infrared spectroscopy. Sequential thermal ring-opening polymerization of the benzoxazine moieties incorporated into the thiol–ene network was characterized by FTIR and differential scanning calorimetry. The glass transition of the hybrid material was observed at 150 °C; however, competing thiol–ene (radical-mediated) and thiol–benzoxazine (nucleophilic ring-opening) reactions during the UV cure yield a heterogeneous network structure.     

Dynamic modelling of a bubble column for particle formation via a gas–liquid reaction

This paper presents a dynamic model of a bubble column reactor with particle formation, accomplished by adopting a hybrid CFD-reaction engineering approach. CFD is employed for estimating the hydrodynamics and is based on the two-phase Eulerian–Eulerian viewpoint. The reaction engineering model links the penetration theory to a population balance that includes particle formation and growth with the aim of predicting the average particle size. The model is then applied to the precipitation of CaCO₃ via CO₂ absorption into Ca(OH)₂aq in a draft tube bubble column and draws insight into the phenomena underlying the crystal size evolution.     

Thermally and mechanically superior hybrid epoxy–silica polymer films via sol–gel method

Hybrid organic–inorganic polymer films composed of an epoxy resin crosslinked with a flexible diamine hardener, and a silica reinforcing phase were produced and their thermo-mechanical properties were determined. Two types of hybrid epoxy–silica polymer films, named EAS-1 and EAS-2, were obtained by hydrolysis and condensation of various amounts of tetraethoxysilane within epoxy network matrix. In EAS-2 hybrids, minor amounts of an amine silane coupling agent were added to enhance interfacial compatibility. FTIR spectroscopy confirmed the formation of organic and inorganic networks. The grafting of amine silane on to the epoxy resin influenced the size and distribution of hyper-branched clusters of silica as indicated by transmission electron microscopy (TEM). The dynamic mechanical and thermal analysis (DMTA) and thermo-gravimetric analysis (TGA) results showed an increase in the storage modulus, the glass-transition temperature, and the thermal stability of hybrid polymer films as compared to the neat matrix. The integration of amine silane coupling agent produced smaller, effectively dispersed silica nanoparticles and consequently improved the ultimate properties of polymer films.     

Resistivity–temperature characteristics of filler-dispersed polymer composites

Composites containing carbon nano tube (CNT) or carbon black (CB) conductive particle filler have the special characteristics of positive-temperature-coefficient (PTC) effects of resistivity. We quantitatively studied the relationship between poly(vinylidene fluoride) (PVDF) polymer's thermal volume expansion and the PTC effects of PVDF/CNT and PVDF/CB. The equation to revise filler content at each temperature due to the considerable thermal volume expansion rate of PVDF polymer indicates that filler content decreased with rising temperature. The graphs of filler content at room temperature plotted against apparent filler content with PTC effect were linear and their slopes were constant. From these graphs, we can determine the filler content necessary to occurring PTC effects. For example, the CNT content was 89% at room temperature, and the CB content was 93%. To our knowledge, this study is the first to report such phenomena.     

Study of autocorrelation function of polymer and polymer–nanocomposite solutions using dynamic light scattering method

Dynamic light scattering (DLS) of polymer and polymer–nanocomposite solutions has been performed to examine the effect in the morphology of polymer solution in presence of nanoparticles analyzing their correlation functions. The size of the nanoparticle was determined using UV–Vis absorption spectroscopy measurements. Analysis of the correlation functions of polymer solution shows existence of two modes, namely, fast and slow modes, along with the distinct values in their corresponding amplitudes and relaxation times. Interestingly, the fast mode of the solution was found to smear out, enhancing the slow mode when we grow nanoparticles into the polymer solution. Apart from the above study, the temperature variation study of both the solutions show that above and below room temperature, the polymer solution becomes more heterogeneous compared to the solution when nanoparticles are grown into it.     

Toughening of semi-IPN structured epoxy using a new PEEK-type polymer via in situ azide–alkyne click polymerization

A new poly(ether ether ketone)-type polymer prepared from 1,4-bis(azidomethyl)benzene (p-BAB), 4,4′-bis(2-propynyloxy)benzophenone (PBP) or 4,4′-sulfonylbis(propynyloxy)-benzene (SBP) via azide–alkyne click polymerization was used as a toughening agent to improve the fracture toughness, thermal stability of the toughened epoxy and reduce its viscosity during processing. The epoxy was toughened by the polymer [poly(p-BAB/PBP)] via in situ polymerization during the curing process, which largely decreased viscosity during the epoxy mixing process compared to that of a neat epoxy. The fracture toughness of 5 wt % poly(p-BAB/PBP) toughened epoxy is two times higher than that of the neat epoxy, and even higher than that of the polyethersulfone-type [poly(p-BAB/SBP)] toughened epoxy using the same amount of toughening agents. In addition, the T _g of this toughened epoxy is higher than that of engineering plastic, which could be regarded as the evidence for the excellent thermal resistance. These phenomena might be attributed to the formation of semi-interpenetrating polymer networks composed by the epoxy network and the linear poly(p-BAB/PBP). In situ poly(p-BAB/PBP) has unique advantages such as decreased viscosity and improved thermal stability in comparison with in situ poly(p-BAB/SBP). These features are significant for the development of carbon-fiber-reinforced plastics as alternate materials to metals. Therefore, in situ poly(p-BAB/PBP) is a promising toughener for epoxy systems. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48178.     

Studies on PA6–PP–wollastonite composite compatibilised by PP–graft–maleic anhydride prepared via pan milling

Abstract

A composite of PA6–PP–wollastonite compatibilised by PP-g-maleic anhydride has been prepared using pan type milling equipment, and its structure and properties investigated by IR, DSC, melt index measurements, SEM, and mechanical testing. The experimental results show that during pan milling, PP, PA6, and wollastonite are effectively pulverised, reaching better mixing owing to the very strong shear forces and pressure exerted by the pan type milling equipment. In particular, some PA6 polymer chains are grafted onto the wollastonite surface and the pan milling affects the crystallinity of PA6 and PP to some degree. The compatibiliser prepared via solid phase grafting of maleic anhydride onto PP via pan milling shows a reasonably good compatibilising effect on the composite, improving the morphology and therefore the mechanical properties of the composite. If combined with suitable coupling agent, the PA6–PP–wollastonite compatibilised by PP-g-maleic anhydride prepared via pan milling (wollastonite content 30 wt-%) possesses much better mechanical properties, its tensile strength increases from 54·6 to 58·6 MPa, and its notched Izod impact strength increases from 29·4 to 48·7 J m^-1, compared with the uncompatibilised system. Pan milling is a novel way to achieve desired structure and hence improved properties of polymer based materials via the polymer processing procedure.     

Synthesis of water dispersible reduced graphene oxide via supramolecular complexation with modified β-cyclodextrin

A noncovalent functionalization of the edges of reduced graphene oxide (RGO) with β-cyclodextrin-graft-hyperbranched polyglycerol (β-CD-g-HPG) was successfully performed via a host-guest interaction. The results showed that β-CD-g-HPG disperses the graphene sheets better than pure β-CD or HPG. The resulted supramolecular structure is stable in neutral water medium more than one week. However, in acidic medium the host-guest interaction is collapsed and graphene nanosheets precipitate.     

A supramolecular gene carrier composed of multiple cationic α-cyclodextrins threaded on a PPO-PEO-PPO triblock polymer

Cationic polymers have been studied as promising nonviral gene delivery vectors. In contrast to the conventional polycations with long sequences of covalently bonded repeating units, this work reports a supramolecular gene carrier where many cationic cyclic units are threaded over a polymer chain to form a chain-interlock structured gene carrier. A series of novel supramolecular cationic polyrotaxanes consisting of multiple α-cyclodextrin (α-CD) rings grafted with various linear or nonlinear oligoethylenimine (OEI) chains, which are threaded and capped over a reverse Pluronic poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEO-PPO) amphiphilic triblock copolymer chain, were synthesized and characterized in term of their molecular and supramolecular structures, DNA binding and condensation ability, cytotoxicity, and in vitro gene transfection efficiency in cultured cells. The supramolecular cationic polyrotaxanes were found to contain 8 cationic α-CD rings that are threaded on a PPO-PEO-PPO triblock copolymer chain. They demonstrated strong ability to bind and condense plasmid DNA into nano-sized particles which are suitable for gene delivery. In both HEK293 and COS7 cells, these polyrotaxanes show low cytotoxicity and high transfection efficiency. In particular, the cationic polyrotaxanes displayed sustained gene delivery capability in HEK293 cells in both serum and serum free condition with the increasing expression duration.     

Effect of synthetic polymers on polymer–protein interaction

Synthetic polymers are often used for delivery of therapeutic drugs and proteins. We report the binding of milk β-lactoglobulin (β-LG) with poly(ethylene glycol) (PEG), methoxypoly(ethylene glycol) polyamidoamine (mPEG-PAMAM-G-3) and polyamidoamine (PAMAM-G4) nanoparticles in aqueous solution at pH 7.4, using Fourier Transform infrared (FTIR), circular dichroism (CD), fluorescence spectroscopic methods, transmission electron microscopy (TEM) and molecular modeling. Structural analysis showed that polymers bind β-LG via both hydrophilic and hydrophobic contacts with overall binding constants K_{PEG-8000-β-LG} = 4.8 (±0.4) × 10⁴ M⁻¹ and K_{mPEG-PAMAM-G3-β-LG} = 5.8 (±0.6) × 10⁵ M⁻¹ and K_{PAMAM-G4-β-LG} = 6.7 (±0.9) × 10⁴ M⁻¹. The number of binding sites were occupied by polymers on protein (n) was 0.3 for PEG-8000, 0.4 for mPEG–PAMAM-G3 and 0.4 for PAMAM-G4. The order of binding is mPEG-PAMAM-G3 > PAMAM-G4 > PEG-8000. Transmission electron microscopy showed significant changes in protein morphology as polymer–protein complexation progressed with major increase in the diameter of the protein aggregate (180%). Furthermore, modeling showed several H-bonding systems between PEG and different amino acids stabilize polymer–β-LG complexes. mPEG-PAMAM-G3 is a stronger protein binder than PAMAM-G4 and PEG-8000.     

Electromagnetic absorbing properties of graphene–polymer composite shields

A graphene-based composite, consisting of a thermosetting polymeric matrix filled with multilayer graphene microsheets (MLGs), is developed for application in thin radar absorbing materials. An innovative simulation model is proposed for the calculation of the effective permittivity and electrical conductivity of the composite, and used for the electromagnetic design of thin radar absorbing screens. The model takes into account the effects of the MLG morphology and of the fabrication process on the effective electromagnetic properties of the composite. Experimental tests demonstrate the validity of the proposed approach and the accuracy of the developed simulation models, which allow to understand the interaction mechanism between the incident electromagnetic field radiation and the MLG-based composite. Two dielectric Salisbury screen prototypes with resonant frequency at 12 GHz or 12.5 GHz and total thickness of 1.8 mm and 1.7 mm, respectively, are fabricated and tested. The results and technique proposed represent a simple and effective approach to produce thin absorbing screens for application in stealth technology or electromagnetic interference suppression.     

Novel dispersion analysis and selective quantification of particulate components in graphene nanoplatelets–polymer–polymer hybrid composites

Up until now, no standard procedure to analyze and quantify the dispersion of particles in the polymer matrix exists. From the conductive hybrid polymer–polymer–graphene nanoplatelets composites we developed, this article attempts to showcase methodologies to analyze and quantify particle with the use of scanning electron microscopy images and collection of the elemental maps of carbon, oxygen, and nitrogen by energy dispersive spectroscopy (EDS) analysis. Image analysis was performed on the resulting map to extract the area and location data of graphene particles by subtracting elemental maps. Shadowing or charging problem in the images acquired from EDS was overcome by the polished surface and analyzing a sample twice using a novel approach of 180° opposed. Merging the data from the two elemental maps, taken 180° opposed, can be an alternative to the use of polished samples. From these different dispersion analysis approaches, it was possible to quantify different particles and their effects on the properties of the composites.     

Optimization and simplification of polymer–fullerene solar cells through polymer and active layer design

Polymer–fullerene bulk heterojunction (BHJ) solar cells have consistently been at the forefront of the growing field of organic photovoltaics (OPV). The enduring vision of OPV is the promise of combining a simple, low-cost approach with an efficient, flexible, lightweight platform. While efficiencies have improved remarkably over the last decade through advances in device design, mechanistic understanding, and evolving chemical structural motifs, steps forward have often been tied to a loss of simplicity and a deviation from the central vision of OPV. Within the context of active layer optimization, our focus is to target high efficiency while maintaining simplicity in polymer design and active layer processing. To highlight this strategy, this feature article focuses on our work on random poly(3-hexylthiophene) (P3HT) analogs and their application in binary and ternary blend polymer–fullerene solar cells. These random conjugated polymers are conceptually based on combining simple monomers strategically to influence polymer properties as opposed to the synthesis of highly tailored and synthetically complex monomers. The ternary blend approach further exemplifies the focus on device simplicity by targeting efficiencies that are competitive with complex tandem solar cells, but within the confines of a single active-layer processing step. These research directions are described within the broader context of recent progress in the field of polymer–fullerene BHJ solar cells.