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Fluorescent temperature sensing (FTS) is an important optical property for fluorescent conjugated polymer (FCPs) based composites. Most FCPs-FTS composite films are processed using an organic phase. And the severe aggregation effects of FCPs in the solid state can lead to a significant reduction in fluorescence emission, which results in a substantial decrease in FTS sensitivity. To address the bottleneck issues, a new synergistic molecular mechanism based on hydrogen bonding and aggregation-induced emission luminogens (AIEgen) motion in the polymer dots (Pdots)/water-processable substrates composite system has been implemented to enhance the sensitivity of FTS composite films. The distyreneanthracene (DSA) groups, as a typical AIEgen, have been introduced into the main chain of FCPs. These are co-assembled with polystyrene- b -poly (acrylic acid) (PS- b -PAA) to obtain Pdots in aqueous processing systems. After aqueous processing, waterborne polyurethane (WPU) and polyvinyl alcohol (PVA) can interact with Pdots, resulting in FTS composites with high sensitivity. The new synthetic strategy for preparing FTS composites is promising and deserves to be promoted for applications in optical sensing. [Display omitted] • Novel strategy to fabricate highly-sensitive FTS composites have been implemented. • The strategy is mainly based on the interaction between Pdots and matrixes. • Introduction of AIEgens into CPs chains intensified molecular motion near the T g. • The dual molecular mechanism significantly quenches the fluorescence signal. [ABSTRACT FROM AUTHOR]

Here we utilize the layer-by-layer (LbL) technique to homogenously integrate polyelectrolyte (PE) multilayers with multiple different catalytic functionalities inside an electrospun BPM without forming an electrically and/or ionically non-conductive catalyst layer. BPMs were fabricated by coating an electrospun cation exchange layer alternately with polyethyleneimine (PEI)-poly (acrylic acid) (PAA), followed by hot-pressing between pristine electrospun anion and cation exchange layers. This resulted in a BPM having a thin entangled 3D junction with high surface area and well-integrated catalysts. Optical reflectometry shows that the amount of PE catalysts inside the BPM can be controlled by tuning coating parameters such as the amount of bilayers and the ionic strength of the coating solution, where especially a higher ionic strength resulted in a significantly higher mass adsorption. The BPMs coated at higher ionic strength (500 mM NaCl) showed the lowest water dissociation potential of 0.84 V. Furthermore, it was found that incorporating the PE multilayers diminished the effect of the electric field and that the catalytic activity becomes more dominant in facilitating the water dissociation reaction. The advantage of creating a 3D junction using electrospinning in combination with the versatility of the LbL deposition technique allows for further optimization to create high performance BPMs that can be tailored to specific applications. [Display omitted] • Polyelectrolyte (PE) multilayer water dissociation catalysts in electrospun BPMs. • PE deposition can be controlled by the ionic strength in the coating solution. • Integration of PE multilayers results in a considerable decrease in overpotential. • Properties of especially the final PE layer determines the final BPM performance. • Multilayers with the most available functional groups have the lowest overpotential. [ABSTRACT FROM AUTHOR]

Acrylic acid and vinylamine copolymers represent one of the simplest polyampholyte structures. The acid-base and solution properties of these copolymers are hardly studied, and there are no works devoted to the synthesis of a set of copolymers with different compositions. We have synthesized a set of acrylic acid and vinylamine copolymers containing from 21 to 95 mol% acrylic acid units. The copolymers show the hydrodynamic properties and solubility of typical polyampholytes. Potentiometric titration revealed unusual acid-base properties of the new copolymers. The addition of HCl to the copolymers in the form of sodium/potassium salt results in only partial protonation of carboxyl anions and amine groups, including the acidic range (pH 2.5). This abnormally high acidity of acrylic acid and vinylamine copolymers is probably due to the formation of strong intra- and intermolecular hydrogen or ionic bonds between partially protonated and protonated groups: ∼COO−+H 3 N∼, COOH∙∙∙:NH 2 ∼, ∼H 2 N:∙∙∙ +H 3 N∼. Poly(vinylamine) and copolymers are able to stabilize curcumin in aqueous medium, significantly increasing its concentration in the neutral pH range. Polymers with high content of amine groups prevent curcumin degradation, probably by converting it to a more stable anionic form. New copolymers are promising substances for the creation of nucleic acid carriers for gene therapy and genetic engineering. The copolymer containing 21 % acrylic acid is comparable to poly(vinylamine) in terms of interaction with oligonucleotides, but yields more homogeneous polyplexes without the impurity of positively charged and potentially toxic particles. [Display omitted] • Co(acrylic acid – vinylamine) containing 21–95 mol% acrylic acid units were obtained. • The copolymers showed abnormally high acidity due to intra-/intermolecular bonding. • The copolymers are promising substances as curcumin and nucleic acid carriers. [ABSTRACT FROM AUTHOR]

Polycarboxylate superplasticizers have been synthesized as copolymers of acrylamide with polyethylene glycol metallyl ether (HPEG), acrylic acid, and 2-hydroxyethylacrylate, with a molecular weight of 25–33 kDa. The copolymers were characterized using GPC and NMR, revealing that during copolymerization, the copolymer includes up to 10 mol.% HPEG 3500 Da. Copolymers at a dosage of 0.12 wt% provide significant retention time of the concrete mix. When considering the same mole ratios of HPEG/(other monomers) in the initial mixture, copolymers containing the carboxylate and hydroxyethyl acrylate group are the most effective. In terms of concrete strength, the use of quaternary copolymers (AA/AM/HPEG/2-HEA) results in a slowdown in strength gain at the ages of 1–3 days, while the strength at the age of 28 days exceeds that of double (AM/HPEG) and triple (AA/AM/HPEG) copolymers. [Display omitted] • Copolymers based on methallyl esters were synthesized for use as plasticizers for concrete. • Quadruple acrylamide copolymers containing 2-hydroxyethyl acrylate units and 6.9 mol.% metallyl ether of polyethylene glycol have the best plasticizing ability and ensure longer workability retention of concrete. • Copolymers ensure the workability retention of concrete for 4 h and can be used as individual admixtures or as slump retention agents for concrete. [ABSTRACT FROM AUTHOR]

Silicone is one of the most widely used polymers in biomedicine because of its versatile use in medical products; it can be modified to improve their properties with potential use in biomedicine. In this research, silicone films were modified by a one-step grafting reaction of N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc) initiated by azobisisobutyronitrile (AIBN) and gamma radiation from a Co-60 source. Variables such as temperature, solvent, reaction time, monomer concentration, dose, and amount of AIBN were studied to determine its influence on the graft. The modified films were characterized by infrared spectroscopy (FTIR-ATR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM-EDS), mechanical tests, and physicochemical studies to determine critical pH and Lower Critical Solution Temperature (LCST). Given the incorporation of the monomers, the synthesis and loading of Ag particles was carried out, through a reaction in water without reducing agents. Finally, the antimicrobial activity of the films synthesized by both methods and loaded with silver was evaluated against S. aureus and E. coli bacteria confirming their in vitro effectiveness. Silicone, acrylic acid, N-isopropylacrylamide, grafting, gamma radiation, silver particles. [Display omitted] • The use of AIBN initiator and gamma radiation were suitable for grafting oh AAc and NIPAAm onto silicone films. • The grafting changed the hydrophobic behavior of silicone films to hydrophilic one. • Grafted silicone films exhibited a dual-response behavior to pH and temperature. • The grafting allowed synthesizing and loading silver particles into silicone films through an eco-friendly method. • Loaded silicone films showed antimicrobial properties against E. coli and S. aureus. [ABSTRACT FROM AUTHOR]

In this work, a simple predictive mathematical model has been presented that quantifies the membrane parameters, e.g., permeability, effective pore diameter and number of charged units in a polymer chain in a pH-varying environment devoid of added salt. This has been validated experimentally for the case of poly(vinylidene fluoride) (PVDF) membranes blended with poly(methyl methacrylate)- co -poly(acrylic acid) (PMMA- co -PAA) additive copolymer. The effect of Donnan potential was incorporated into the model and estimated using electrokinetic characterizations. It varied considerably from 0.25 to −1.93 units (dimensionless) from pH 2 to 11. Variations of surface morphology and the electronic structure of the blend membrane with pH were studied in detail. Molecular simulations were performed to estimate the effective distance between the neighboring units in the charged/uncharged states and for confirming the copolymer chain behavior in different pH environments. Adsorption experiments were conducted to compare the variation of the number of uncharged units with pH with those estimated using the model. A pH-dependent permeability hysteresis behavior was observed which was explained using an intermolecular hydrogen bonding mechanism. About 80 % variation in the permeability of the blend membrane was observed between the pH limits which was in close agreement with the model results. [Display omitted] • PVDF was blended with PMMA- co -PAA copolymer to produce pH-responsive membrane. • Predictive model was proposed to explain the pH-responsiveness of the membrane. • Role of Donnan potential was crucial in quantifying the membrane permeability. • Entropic and electrostatic interactions were investigated using molecular simulations. [ABSTRACT FROM AUTHOR]

The current study examines the effects of important factors (namely, pH, ionic strength and monomer concentration) on the terpolymerization of 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamide (AAm) and acrylic acid (AAc). A good understanding of how these factor levels affect terpolymerization reactivity ratios, and terpolymer composition, microstructure and molecular weight paves the way for the synthesis of custom-made polymers for specific applications. For the range of conditions studied, ionic strength has the greatest influence on reactivity ratios; results indicate that cross-over behavior exists for AMPS-based reactivity ratios. No clear correlation is observed between pH and reactivity ratio estimates (for 5 ≤ pH ≤ 9), but parameter estimation results suggest that the incorporation of acidic comonomers (AMPS and AAc) is affected by pH within this range. Finally, monomer concentration has a dominant impact on molecular weight averages, even when other factors are varied. Image 1 • pH, ionic strength and monomer concentration are all significant factors. • Improved understanding of factor level effects can lead to custom-made materials. • Reactivity ratios can be used to select conditions leading to desirable properties. • Ionic strength has greatest effect over range studied; cross-over behavior observed. [ABSTRACT FROM AUTHOR]

Comparative study of thermo- and pH-sensitive conformational behavior of interpenetrating network (IPN) microgels based on poly(N-isopropylacrylamide) (PNIPA) and poly(acrylic acid) (PAA) with different network structures was conducted. For that purpose, PNIPA microgels were obtained by thermo-induced precipitation polymerization in the presence of the conventional cross-linking agent (N,N′-methylenebis(acrylamide)) and as a result of the self-crosslinking process. Then in situ polymerization of the acrylic acid network within these two types of PNIPA microgel particles was performed resulting in an IPN microgels formation. Dynamic and static light scattering methods were used for in-depth analysis of the system behavior in different conformational states of both networks of the IPN. The studies showed that the self-crosslinking method promoted the increase of pH-response of the system and its swelling ratio. The volume swelling ratio was about 3 times greater for the IPN microgels based on the self-crosslinked PNIPA microgels. Larger swelling coefficient is desirable, as it allows to expand the storage volume of a microgel particle. Image 1 • Thermo- and pH-sensitive IPN microgels were synthesized on the base of BIS-crosslinked and self-crosslinked PNIPA and PAA. • DLS studies showed that self-crosslinking method promotes the increase of pH-response of the system and its swelling ratio. • IPN MGs in a solvent which is poor for PNIPA network and good for PAA network have asymmetry factor of core-corona structure. [ABSTRACT FROM AUTHOR]

Aggregation behavior of an amphiphilic diblock polyelectrolyte poly(n -butylacrylate)- b -poly(acrylic acid) (PnBA- b -PAA) at the air/water interface and its Langmuir−Blodgett (LB) films were respectively characterized by the Langmuir film balance technique and atomic force microscopy. Effects of spreading solution concentration and volume, and subphase temperature and ionic strength on the interfacial aggregation behavior of PnBA- b -PAA under alkaline condition were systematically studied. With the increase of spreading concentration, surface pressure−molecular area isotherms shift to small molecular areas at the corresponding spreading volumes. With the rise in subphase temperature, the isotherms shift to small molecular areas due to the decreased p K a value and increased solubility of PAA blocks. With the increase of subphase ionic strength, the isotherms shift to large molecular areas because of the predominant salting out effect. The LB films transferred from alkaline subphase with different ionic strengths are more likely to exhibit isolated circular micelles. With the increase of spreading concentration, diameters of micelle cores first decrease and then increase, a behavior which is attributed to the gradually increased chain entanglements and surface polymer concentration, respectively. For small spreading volume, core diameters in the LB films first decrease and then increase with the rise in subphase temperature. For large spreading volume, however, core diameters increase with temperature due to the higher mobility and weaker entanglements of PAA blocks underwater. With the increase of subphase ionic strength, furthermore, core diameters first increase and then decrease, which is attributed to the predominant electrostatic shielding and salting out effects, respectively. Image 1 • Spreading condition effect on interfacial behavior of polyelectrolytes is first studied. • Chain entanglement plays an important role on the isotherms and AFM images. • LB films transferred from alkaline subphase usually exhibit circular micelles. • With the rise in temperature, micelle core sizes first decrease and then increase. [ABSTRACT FROM AUTHOR]

Abstract The Reversible Addition Fragmentation chain Transfer (RAFT) polymerizations of acrylic acid were performed in 1,4-Dioxane solution using three different chain transfer agent (CTA), and 4,4′-azobis(4-cyanopentanoic acid) (ACPA) as initiator. The molar ratios of monomer, CTA and initiator were kept similar for each experiment and all polymerization exhibited high conversion (>90%) at 8 h. Well-defined polyacrylic acids (PAAs) were obtained. Their molecular weights increased linearly with monomer conversion and the dispersity of the molecular weight distribution extended between 1.1 and 1.3. Nuclear magnetic resonance (NMR) spectroscopic studies showed that the PAA prepared are actually random copolymers of AA and the dimer of AA (H 2 C=CHCO 2 CH 2 CH 2 CO 2 H), which forms spontaneously from AA, even at room temperature. PAA samples were methylated by addition of trimethylsilyldiazomethane (TMSCHN 2 a methylating agent) using a mixture of water/tetrahydrofuran (THF) or methanol/THF. Samples were submitted to different analyses before and after the methylation process in the order to examine the effect of the methylating agent. PAA were characterized by size exclusion chromatography (SEC) in aqueous phase and also in organic phase following methylation. Methylation is accompanied by variable amounts of chain cleavage in the case of PAA prepared using a symmetrical, trithiocarbonate RAFT chain transfer agent. Less extensive cleavage is seen on treatment of poly(methyl acrylate) (PMA), prepared from the trithiocarbonate RAFT reagent with TMSCHN 2. Fourier transform infrared (FT-IR), UV-Vis, 1D and 2D NMR spectroscopic studies confirmed that TMSCHN 2 reacts with the thiocarbonyl group, though all of the products of this reaction could not be identified. End group analysis using Ellman's reagent demonstrates that some of the polymer chains have a thiol end group, as does a thiol-ene reaction using 9-vinylcarbazole. Graphical abstract Image 1 Highlights • Trimethylsilyldiazomethane (TMSCHN 2) is reactive towards thiocarbonyl groups in PAA or PMA prepared by RAFT polymerization. • The reaction results in partial chain cleavage in the case of PAA or PMA prepared using a symmetrical trithiocarbonate CTA. • Spectroscopic studies prove that thiocarbonyl group reacts with TMSCHN 2 to furnish polymer chains with a thiol end group. • There is considerably less than one thiol end group per chain in the cleaved products. [ABSTRACT FROM AUTHOR]

Abstract This study aims at the effect of electro-osmotic flow on a fibrous membrane comprised of assembled oppositely-charged polyelectrolytes and submerged in aqueous ionic solution. As electric field is applied across an edge-clamped circular membrane, it deforms under the action of a transverse force, the origin of which is in focus. Fibers were electrospun from a blend of poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA). A model is presented, which explains and describes the membrane deformation in terms of the ionic strength and pH level of the solution, the membrane geometry and porosity, the ζ-potential and elastic modulus of the membrane, as well as the applied cross-membrane electric potential difference. The model is corroborated by a set of experiments. The dependence of the membrane deformation on the electric potential was found to be rather weak, while the elastic modulus was found to be strongly dependent on the solution pH. Graphical abstract Image 1 Highlights • Membranes electrospun from poly(allylamine hydrochloride)/poly(acrylic acid) were developed. • Electro-osmotic flow through membrane assembled oppositely-charged polyelectrolytes in aqueous ionic solution was studied. • A model is presented, which explains and describes the membrane deformation. • The effect of the governing parameters on the membrane deformation by the electro-osmotic flow was explained. • The model was corroborated by a set of experiments. [ABSTRACT FROM AUTHOR]

Interest in the development of new materials based on natural polysaccharides has grown exponentially in the last decade. Therefore, polysaccharide hydrogels gain striking attention having unique properties. In this study, karaya gum polysaccharide hydrogels have been synthesized using free radical mechanism. In this mechanism, ammonium persulfate (APS) was used as an initiator to form free radicals of karaya gum and acrylic acid while N, N′-methylenebisacrylamide (MBA) was used to crosslink these radicals. The synthesized hydrogels were characterized in terms of structure and properties. The structural evaluation was performed using different techniques. The vanishing of existing and appearance of new functional groups were analyzed using Fourier transform infrared (FTIR) analysis. The physical state of the hydrogel was evaluated using X-ray diffraction analysis while thermal stability and formation of hydrogels were further confirmed using Differential scanning calorimetry (DSC). The morphology study was conducted using Field emission scanning electron microscope (FESEM). Furthermore, mechanical properties of hydrogels were investigated using rheometer and swelling properties were evaluated in water and buffer solutions of pH 7.4 and pH 1.2. Hydrophobic drug loading and structural stability of drug after drug loading are the major challenges in the drug delivery. Hydrophobic drug quercetin was loaded, and in vitro release studies were conducted. The quercetin release showed complete non-Fickian transport mechanism. All these results revealed the successful synthesis of hydrogels and potential applications of hydrogels in hydrophobic drug delivery. [ABSTRACT FROM AUTHOR]

In this study, we investigate the impact of incorporating poly(acrylic acid) (PAA) as a soft polymer on the long-term stability and flexibility (or stretchability) of a highly conductive composite consisting of hydroquinone (HQ)-modified Poly(3,4-ethylenedioxythiophene): poly(styrene-sulfonate) (HQ-PEDOT:PSS). Our findings demonstrate that PAA can effectively act as a steric hindrance barrier between conductive-PEDOT and insulative-PSS, thus improving the stability of the composite over time. Furthermore, the PAA mixture minimizes the conductivity decrease compared to other representative hydrophilic soft polymers, such as poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP). With the addition of 2 wt% PAA to HQ-PEDOT:PSS, the composite exhibits significantly higher conductivity (290 S/cm) compared to PVA (42 S/cm) and PVP (10−3 S/cm). The HQ-PEDOT:PSS/PAA composite also displays excellent stretchability, with a sharp strain response followed by a drastically enhanced gauge factor over a wide strain range (10%–50%). As a result, the composite shows great potential as a strain sensor, with high sensitivity for detecting diverse body motions. Moreover, due to its high conductivity, the composite exhibits high sensitivity for detecting human electrocardiogram (ECG) signals, with negligible degradation of signal intensity even one month after fabrication. Overall, our results suggest that the HQ-PEDOT:PSS/PAA conductive composite has significant potential for wearable smart textile applications, enabling diverse body motion and vital sign sensing. [Display omitted] • Identified PAA as a dual-functional component to improve both of the stretchability of PEDOT:PSS and its stability. • The conductivity of PEDOT:PSS-based composite was improved from 1.2 to 290 S cm-1 even with insulative soft-polymer, PAA. • The HQ-PEDOT:PSS/PAA composite revealed no plastic deformation even with 50% strain. • The HQ-PEDOT:PSS/PAA composite revealed no plastic deformation even with 50% strain. • Highly enhanced long-term stability of PEDOT:PSS was achieved with HQ and PAA. • Realized (1) high stretchability (2) high conductivity and (3) improved stability of PEDOT:PSS with HQ and PAA at once. [ABSTRACT FROM AUTHOR]

Hydrogels have received increasing interest as a flexible material. However, the integration of multiple functions into one hydrogel remains a great challenge. For the application of hydrogels in the field of biosensors, both rigidity and toughness of hydrogels are usually necessary. Herein, a kind of multifunctional hydrogel with a combination of ideal properties, including transparency, fatigue resistance, flexibility, conductivity, self-adhesive and low contact impedance is designed. The hydrogel is prepared via a one-pot method by polymerizing the monomers acrylic acid (AA), acrylamide (AM) and [2-(Methacryloyloxy) ethyl] dimethyl-(3-sulfo-propyl) ammonium hydroxide (SBMA) under UV light to form a copolymer. The chemical cross-linking and hydrogen bonding jointly impart the hydrogel with good fatigue resistance and flexibility. Furthermore, the hydrogel can adhere to a wide range of substrate surfaces through intermolecular forces and give precise, stable and clear ECG signals when detecting small physical movements. It is believed that the designed hydrogel will show great prospects in wearable devices and biosensors. [Display omitted] • Multifunctional chemically cross-linked hydrogels prepared by UV cross-linking. • AAS hydrogel demonstrates excellent fatigue resistance. • The hydrogel can be used to detect minor physical movements and collect precise ECG signals. [ABSTRACT FROM AUTHOR]

A lignosulfonate-derived material was prepared by complexing polyethylene glycol (PEG)-grafted lignosulfonate (LS- g -PEG) with a cationic polyelectrolyte (PDADMACl). The mechanical property of this LS- g -PEG/PDADMACl complex was similar to those of the conventional unmodified-LS/PDADMACl complex, however, the addition of poly(acrylic acid) (PAAc) improved the toughness of the LS- g -PEG complex more than seven-fold at the optimal composition (from 0.7 to 5.2 MJ/m3). This increase in toughness upon PAAc addition was not observed in the conventional unmodified-LS/PDADMACl complex and it was attributed to the synergistic effect of plasticization by the amorphous PEG component, as well as the formation of a rigid polyelectrolyte complex. In addition to better strain and toughness than other reported lignosulfonate-derived materials, the LS- g -PEG/PDADMACl/PAAc complex displayed a humidity-induced self-healing property; complete healing of mechanical properties was observed under optimal conditions. These good toughness and excellent self-healing properties may broaden the applications of lignin-derived materials as highly durable and damage-resistant materials. [Display omitted] • Polyethylene-glycol-grafted-lignosulfonate/cationic-polyelectrolyte complexes were prepared. • Addition of poly(acrylic acid) to the complex improved its tensile strain and toughness. • The melting of the polyethylene-glycol crystal resulted in the improved strain and toughness. • The optimized complex archived complete self-healing by control of ambient humidity. [ABSTRACT FROM AUTHOR]

The present study focuses on the swelling behavior of copolymer microgels of N -isopropylacrylamide (NIPAM) and acrylic acid (AAc) containing different concentrations of acrylic acid. The incorporation of the comonomer is investigated by Fourier transform infrared (FT-IR) spectroscopy and an incorporation threshold value for the comonomer is found, if the “classical” Pelton synthesis approach is used. The swelling of these microgels is analyzed by photon correlation spectroscopy (PCS) and fluorescence spectroscopy, using pyrene as a fluorescent probe. The deswelling of copolymer microgels with 10mol% and 15mol% nominal acrylic acid content can not be detected by PCS. However, in fluorescence measurements the PNIPAM phase transition is still observable. The reason for this difference is a non-uniform distribution of acrylic acid in the copolymer microgels, which makes them promising candidates for drug-delivery and -targeting applications. [ABSTRACT FROM AUTHOR]

Two new near-UV and visible-light-sensitive photobase generators (PBGs) are synthesized and investigated. They are built on a near-UV and visible light sensitive ( E )-3-(2,2′-bithiophen-5-yl)-2-cyanoacrylic acid chromophore and a latent strong base such as 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) and 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD). Upon irradiation, decarboxylation occurs and the base is released. The anionic curing of epoxy/thiol as well as thiol/divinylsulfone formulations in the presence of these PBGs under LEDs at 385 and 405 nm is studied. More than 60% of conversion of the thiol and epoxy functions is achieved upon LED@385 nm without any post baking. [ABSTRACT FROM AUTHOR]

Interpolymer complexes of homopolymer macromolecules are often described as ‘laddered’ or ‘ribbon’ type structures. The proposition of the existence of these ladder structures seems to us not reasonable and here we examine this hypothesis. To address this we have used polymers enabled for Förster Energy Transfer (FRET). Chromophores bound to a macromolecular backbone can transfer energy across short distances via FRET. The close binding of poly(acrylamide) and poly(acrylic acid) interpolymer complex formation at low pH forms a structure compact enough for significant energy transfer to occur between different chains containing naphthalene and anthracene labels. In the context of the proposition that ladder polymers can form it was surprising that the distance between labels on the same polymer back-bone was equivalent regardless of whether the polymer was complexed or not. The data indicated that the bicomponent structure may be more compact than previously supposed: I.e. the complexes are not ladders composed of extended chains. This evidence suggests formation not of ordered ‘ladder’ systems but colloidal ‘co-globules’. [ABSTRACT FROM AUTHOR]

Branching has been investigated in poly(acrylic acid) synthesized by conventional radical polymerization with and without chain transfer agent (CTA) at different temperatures and initial monomer concentrations. The average number of branches per monomer unit (i.e. degree of branching) was quantified by solution-state 13 C NMR spectroscopy. The heterogeneity of branching (dispersity of the electrophoretic mobility distributions) was measured by capillary electrophoresis in the critical conditions (CE-CC). The degree of branching ( DB ) increases with the reaction temperature due to a rise in the frequency of reactions leading to branches, while the heterogeneity of branching remains steady. DB is lower in polymer synthesized with CTA. This decrease is due to either the CTA quenching the mid-chain radicals or a reduction of the rate of chain transfer to polymer relative to (chain-end) propagation. No influence of initial monomer concentration on DB and on the heterogeneity of branching was observed. [ABSTRACT FROM AUTHOR]

Two-scale multicomposite (meth)acrylate latexes containing nano-sized liquid crystalline domains were synthesized in a two step (mini)emulsion polymerization using a series of methacrylate side chain liquid crystalline monomers and mixture of short chain (meth)acrylates. Detailed characterization of the composite films obtained from the latexes using a combination of DSC, TEM, polarized light microscopy, SAXS and WAXS showed that the liquid crystalline polymers had a layered structure with a 2D-organization that was not perturbed by the amorphous polymer, which on the other hand was partially intercalated between layers. This leads to a two-scale composite with enhanced mechanical properties and higher number of degrees of freedom to fine tune the mechanical properties. The effect of liquid crystalline domains on barrier properties as well as on the water resistance of the films formed from these latexes was also investigated. The persistence of crystalline order of the liquid crystalline polymer phase up to very high temperatures leads to materials with a very broad temperature range of application, improving significantly the performance with respect to other routes based on incorporation of crystalline domains via copolymerization with comb-like monomers. [ABSTRACT FROM AUTHOR]

Polyhedral oligomeric silsesquioxane copolymerized with butyl acrylate (BA), methyl methacrylate (MMA), and acrylic acid (AA) induced ca. twofold increase of fracture energy Γ and of Young's modulus E of cast films at only 1 wt% content. The copolymer of composition BA:MMA:AA:POSS 56:41:2:1 mol% was synthesized in situ by seeded semi-batch emulsion polymerization. Films cast from the corresponding emulsions were optically transparent and transmission electron microscopy (TEM) showed that POSS was predominantly dispersed at nearly single unit in the acrylic matrix. Shear rheology and time-temperature superposition (TTS) analysis demonstrated an entangled state with the absence of terminal regime, and POSS increased the segmental relaxation time τ e and the rubbery modulus G e , hence the free volume and packing length p decreased, relative to the neat copolymer. The efficient dispersion of POSS and its size smaller than the virtual tube diameter suggests that POSS is intercalating the molecular mesh. Therefore, the entanglement density increased and induced an increase of tensile mechanical modulus. The mesh intercalation by POSS means that it did not act as stress concentrator and consequently the critical fracture strain ε* and the fracture energy Γ also increased. These results evidenced the topological constraints imposed by the bulky POSS to hinder chains past each other thus inducing an increase of entanglement density and this manifested in simultaneous mechanical reinforcement and resistance to fracture. [Display omitted] • POSS simultaneously increased mechanical modulus and toughness of acrylic nanocomposite. • Well-dispersed POSS intercalated the macromolecular mesh. • The intercalation increased the entanglement density and hence induced mechanical reinforcement. • The intercalated POSS did not act as stress concentrator. [ABSTRACT FROM AUTHOR]

In the present work, the in situ incorporation of curcumin was carried out in a polymer matrix through bulk polymerization to improve its photostability. It was found that extraction of curcumin from turmeric extract by the precursor monomer methyl methacrylate (MMA) can be performed immediately before the polymerization in order to reduce the degradation of the fluorescent species by the initiator system, although the obtained results also showed that incorporation of the turmeric extract into monomer can retard the polymerization kinetics. Despite that, the fluorescence properties of curcumin were preserved after incorporation in a solid polymeric matrix, which also enhanced the fluorophore photostability, avoiding the rapid degradation of the fluorophore observed when it is dispersed in solvents. Furthermore, it was also observed that addition of acrylic acid (AA) as a comonomer enhanced the photochemical stability of the turmeric extract incorporated into the polymer matrix and promoted the bathochromic effect, when compared to the spectroscopic behavior of the extract obtained from MMA, both in solution and solid state. It was possible to optimize the synthesis condition with help of a standard factorial experimental design, allowing the simultaneous attainment of high monomer conversion and fluorescence properties of the obtained material. [Display omitted] • Fluorescent polymers are versatile materials due to their accumulating properties. • The photochemical stability of curcumin is higher when incorporated into a polymer matrix. • Fluorescent polymers can be used as biomarkers in biomedical applications. [ABSTRACT FROM AUTHOR]

This study examines the feasibility of using colloidal silica nanoparticles as active agents in high concentration waterborne polymer latex formulations. We showed that distributing the silica throughout the waterborne emulsion formed a composite coating material with a hydrophilic surface that consequently reduced exterior dirt pickup. Two grades of silica nanoparticles were studied, one using sodium stabilisation and another using epoxysilane modification to introduce glycidoxypropyltrimethoxysilane surface functionality. Rheological study of the waterborne latex on mixing showed that there was an immediate pH responsive interaction between the silica sols and the polymer latex. Once loading of sodium charge stabilised silica NPs exceeded the volume required for heteroflocculation to occur the mixture demonstrated the potential to gel on standing – a process which took weeks, or months, to occur depending on the pH and relative concentrations used. At least fifty percent silane modification to the NP surface was found to be necessary to maintain a stable colloidal dispersion for long term storage of the waterborne latex. Despite this both grades of silica were found to imbue reductions in dirt pickup when applied to exterior masonry concrete studies over a 3-month weathering test. [Display omitted] • Silica nanoparticles can be mixed with high concentration polymer latex solutions to decorate latex surface nut give pH responsive viscosity increase. • Storage of non-modified silica NP – latex mixtures showed predisposition to gel with latex over 3–6 month timescale. • Epoxysilane modification improves stability of Silica NPs on storage with waterborne latex at all pH values. • Incorporation of Silica NPs into commercial latex formulation changes surface properties of coating and reduced dirt pickup of exterior masonry by over 50%. [ABSTRACT FROM AUTHOR]

Calcium bentonites (CaB), rich in European and Asian countries, are potential barrier materials for landfill leachate containment. However, CaB has to be converted into sodium bentonite (NaB) by Na-activation so as to facilitate intercalation modification. In this study, salt-resistant poly(acrylic acid-N, N-diethyl acrylamide) [P(AA-DEA)] was designed to intercalate and graft CaB by in situ polymerization without prior Na-activation. By this design, acrylic acid monomers were first adsorbed into interlayers of Ca-montmorillonite (Ca-MT) through the electrostatic complexation with Ca2+, dislodging Ca2+ from montmorillonite surfaces. Then, ammonium ions of N, N-diethyl acrylamide were adsorbed into Ca-MT interlayers. Swelling index of the obtained CaB/P(AA-DEA) nanocomposite in aggressive coal combustion product (CCP) leachate is 15.8 mL/2g, which is as high as 3.4 times that of CaB. CaB/P(AA-DEA)-based geosynthetic clay liners (GCLs) exhibit very low hydraulic conductivity (1.6✕10−12 m/s) to CCP leachate, which is as low as 3.3% that of the U.S. standard requirement and ∼4 orders of magnitude lower than that of CaB-based GCL. Polymer elution of CaB/P(AA-DEA)-8% in CCP leachate is as low as 1.9% that of the dry mixed samples. A calcium-bentonite/P(acrylic acid-N, N′-diethyl acrylamide) [P(AA-DEA)] nanocomposite was prepared by in-situ intercalative polymerization, exhibiting excellent barrier property in geosynthetic clay liner application (hydraulic conductivity = 1.6✕10−12 m/s) that is 3.3% of the US standard. [Display omitted] • Straightforward preparation of Ca-bentonite nanocomposite. • Barrier performance of the nanocomposites is 30 times as high as the U.S. standard requirement for GCLs. • Polymer elution of the nanocomposites is 1.9% of the traditional dry mixtures. [ABSTRACT FROM AUTHOR]

This study investigated the macrophase and microphase transitions of blends comprising polystyrene- block -poly(ethylene oxide) (PS- b -PEO) and polystyrene- block -poly(acrylic acid) (PS- b -PAA). PEO and PAA molecules formed hydrogen bonds that enabled the two block copolymers to organize into a single microphase-separated morphology composed of two PS block chains in a common PS microdomain and PEO and PAA block chains in a coexisting PEO/PAA microdomain. Increasing temperature weakened the hydrogen-bonding interaction through the formation of PAA monomers and anhydride, causing the blends to macrophase separate into PS- b -PEO-rich and PS- b -PAA-rich phases. Further increasing the temperature weakened the repulsive interactions between both the PS and PEO segments and the PS and PAA segments, inducing order-to-disorder transitions in the PS- b -PEO-rich and PS- b -PAA-rich phases. However, the increasing repulsive interaction between the PEO and PAA segments with increasing temperature prevented the blends from forming an isotropic phase. The unique phase transformation of each block copolymer in the blend with an upper critical ordering transition (UCOT)-type interaction parameter, which caused the formation of a lower-critical-solution-temperature-type phase diagram, was attributed to the hydrogen-bonding interaction between PEO and PAA, which outweighed the UCOT behaviors of PS- b -PEO and PS- b -PAA and reversed the phase behaviors of their blends. [Display omitted] • Hydrogen-bonding interaction reverses the phase behaviors of copolymer blends. • Hydrogen bonds enable copolymer blends to co-organize in a microdomain morphology. • High temperatures cause hydrogen-bonded PEO/PAA to form PAA monomers and anhydride. • Increasing temperature debonds hydrogen bonds, forming macrophase-separated phases. [ABSTRACT FROM AUTHOR]

Hydrogen (H)-bonding interaction was introduced into a poly(ethylene oxide)- b -poly( tert -butyl acrylate) (PEO- b -P t BA) block copolymer (BCP) by partial hydrolysis of t BA units into acrylic acid (AA) ones, in order to compete with the segregation force between the PEO and P t BA blocks. It was found that, as the hydrolysis degree ( D hyd ) of the P t BA block increased, the structure of the PEO- b -P( t BA- co -AA) BCPs underwent the change from hexagonally packed cylindrical (HEX) into body-centered cubic spherical (BCC), then into HEX. The first HEX-to-BCC transition at lower D hyd arose from the enhanced compatibility between the PEO and P( t BA- co -AA) blocks induced by the H-bonding interaction. When a PEO- b -P( t BA- co -AA) BCP with a HEX structure was heated, the BCC-to-HEX order-order transition (OOT), which was opposed to that in the common BCPs with an upper critical ordering temperature (UCOT) phase diagram, could be achieved because the H-bonding interaction was weakened at higher temperature. The second BCC-to-HEX at higher D hyd was interpreted in terms of the enhanced chain rigidity and the chain arrangement approximately parallel to the microdomain interface induced by H-bonding interaction. The variation of the H-bonding interaction with temperature and the conformational change of the PEO block induced by H-bonding interaction were verified with FT-IR. [ABSTRACT FROM AUTHOR]

Natural rubber (NR)-based hollow latex (HL) particles have been prepared by seeded emulsion polymerization of methyl methacrylate/divinyl benzene/acrylic acid (MMA/DVB/AA) monomers on NR seed. By using tert -butyl hydroperoxide/tetraethylene pentamine ( t -BuHP/TEPA) as a redox initiator, the locus of polymerization was localized at the surface of the NR particle. After swelling with monomers, DVB in NR particle gradually moved outward to compensate the co-polymerization. Phase separation between the NR seed and the polymeric shell occurred and a void was subsequently formed at a MMA/DVB molar ratio of 2.7/1. The void cavity was enlarged when the monomer to seed (M/S) weight ratio was increased to 4/1. Without the necessity of any residual core removal, polydisperse NR-based hollow nanocomposites (298 ± 58 nm) possessing NR-P(MMA/DVB/AA) double-layered shell and a single void (155 ± 37 nm) were obtained. SEM images revealed an increase in surface roughness of the HL particle with increasing M/S weight ratios. The large specific surface area of these NR-based hollow nanocomposites (114.6 m 2 /g) with a 3.5 nm pore diameter indicates that the polymeric shell is mesoporous. The presence of carboxyl groups, as indicated by negative zeta potentials, can further facilitate surface functionalization. The large void cavity of these NR-based HL particles makes them particularly suited as delivery vehicle systems. [ABSTRACT FROM AUTHOR]

The reversible addition-fragmentation chain transfer (RAFT) copolymerization of non-ionized acrylic acid with acrylamide in dimethyl sulfoxide is investigated and compared with the conventional free radical process carried out at the same conditions. The effect of the living nature of the RAFT process on overall polymerization rate and on copolymer composition is studied by in situ 1 H NMR. The same values of reactivity ratios (r AA = 1.55 ± 0.02 and r Am = 0.75 ± 0.02) are estimated for both the processes, living and non-living. The copolymers prepared by RAFT polymerization exhibit well-controlled composition, with narrow distribution. This approach can be applied to the synthesis of copolymer standards at specific composition for direct calibration of size-exclusion chromatography. [ABSTRACT FROM AUTHOR]

An effect of surface segregation of polyhedral oligomeric silsesquioxanes (POSS) on surface physical properties was investigated. Hard coating layer with various MA 8 POSS loadings was prepared on a bilayer of soft layer and PMMA substrate via a UV curing process. The scratch resistance of the coating layer showed specific properties. When MA 8 POSS loadings in the coating layers were less than 10 wt %, the coating layers showed a great performance in scratch resistance. While MA 8 POSS loadings were higher than 10 wt %, the surface performance was deteriorated. This is because the outermost surface of the coating layer was covered by MA 8 POSS molecules when the MA 8 POSS loadings were higher than 10 wt %, resulting in uncompleted curing reaction caused by large steric hindrance of MA 8 POSS. [ABSTRACT FROM AUTHOR]

Processing-induced residual stresses in polymer films can cause microscopic defects and macroscopic dimensional changes. Although stress relaxation behavior of polymer films has been studied for several decades, little work has addressed random copolymers. We probed the residual stress relaxation in non-equilibrated random copolymer films of styrene (S) and n -butyl acrylate (nBA) using two optical techniques, ellipsometry and fluorescence. Both techniques show that incorporation of very low levels of nBA (2 mol% to 5 mol%) in S/nBA random copolymers can lead to dramatic increases in stress relaxation time of copolymer films relative to neat polystyrene films. For example, relative to polystyrene, the bulk-film stress relaxation time at 130 °C of 95/5 mol% S/nBA copolymer increases by factors of at least six as determined by ellipsometry and three as determined by fluorescence. Nanoconfined, 25-nm-thick films exhibit similar differences. This work provides implications for how low comonomer levels may deleteriously affect stress relaxation in polymer films, and we highlight that these findings are important for applications in which thin polymer films are required. [Display omitted] • Stress relaxation was characterized in thin and ultrathin spin-coated films. • Ellipsometry and fluorescence provide sensitive measures of stress relaxation. • Studies employed polystyrene and styrene (S)/ n -butyl acrylate (nBA) copolymers. • 95/5 mol% S/ n BA copolymers relaxed by factor of 3–6 more slowly than polystyrene. • Similar effects were observed in bulk and nanoconfined (25 nm thick) films. [ABSTRACT FROM AUTHOR]

Copolymer consisting of acrylonitrile (AN) and acrylic acid (AA) segments with different molar ratios were synthesized via a mixed-solvent precipitation polymerization method. The prepared polymer was then applied to fabricate nanofiber membrane via electrospinning technique. It was found that when the molar ratio of AN/AA was 80/20, the resultant membrane presented outstanding hydrophilicity with a water contact angle of 0° and water adsorption ratio of 17.10. In addition, the breaking force of optimized membrane was increased by more than 60% when comparing with those of pure PAN homopolymer counterpart due to the hydrogen bonding interaction resulting from the carboxyl groups in AA chain segments. The developed membrane possessed fascinating underwater oleophobicity with oil contact angle over 150° and could effectively separate oil/water mixture and oil-in-water emulsion with excellent separation efficiency beyond 95%, ascribing to the hydration layer on the membrane surface and size-sieving effect arising from the multi-scale pore size in the material. The current study provides a novel insight into the fabrication of hydrophilic membrane for oily wastewater treatment for practical applications. [Display omitted] • An optimum poly(acrylonitrile-acrylic acid) copolymer was synthesized. • Membrane with superhydrophilicity was achieved by using the copolymer. • Membrane possessed fascinating underwater superoleophobicity. • The membrane showed excellent separation efficiency for oily wastewater. [ABSTRACT FROM AUTHOR]

Dispersion polymerization stabilized with poly(acrylic acid) has been performed for decades to produce polymer particles whose surfaces are modified with pH-responsive poly(acrylic acid) moieties. To improve stabilizer efficiency, poly(acrylic acid) block copolymers, in which a poly(acrylic acid) chain is attached to the terminus of a polystyrene or PMMA chain, were used as stabilizers for the dispersion polymerization of styrene or MMA. Compared with the poly(acrylic acid) homopolymer, polystyrene- block -poly(acrylic acid) was found to improve the controllable ranges of particle size and the carboxylic-acid-group surface density of the resulting polystyrene particles. Furthermore, we also investigated the effect of heterogeneity between the polymer species of the particle core and the attached polystyrene or PMMA chains in the poly(acrylic acid) block copolymers. Finally, we also examined the applicability of polystyrene- block -poly(acrylic acid) as a stabilizer and surface modifier for the dispersion polymerization of various monomers. [Display omitted] • Polymer particles surface-modified with poly(acrylic acid) were prepared. • Block copolymerization improves the stabilizing effect of poly(acrylic acid). • Segments attached to the poly(acrylic acid) affect stabilization. • Polystyrene- block -poly(acrylic acid) is a versatile functional stabilizer. [ABSTRACT FROM AUTHOR]

We describe the fabrication of polymer foams from aqueous solutions of 2-hydroxyethyl cellulose (HEC), using freezing-induced phase-separation and solvent removal methods. Freezing aqueous solutions of HEC produced 3D polymer networks by a mechanism involving polymer exclusion from ice crystals and concentration at grain boundaries. This phase-separation is viewed as a kinetically controlled process, with properties of the resultant foams reliant on the processing temperatures and other conditions employed. Specifically, HEC foams were obtained by removal of the ice phase either by lyophilization or solvent exchange techniques. The morphology and pore characteristics of the resultant foams were visualized by scanning electron microscopy (SEM), which showed fibrillar and flake-like polymer material embedded in an open-cell porous structure. Foam density and stiffness increased as a function of the initial HEC concentration employed, while the mechanical integrity of the resultant foams was improved by crosslinking with poly(acrylic acid) (PAA) or maleic anhydride (MA). Such crosslinking successfully enabled liquid water sorption into the foams without loss of structural integrity, thus providing opportunities for further incorporation of chemical moieties. Dynamic vapor sorption (DVS) was employed to assess water uptake into the HEC foams, which was generally greater for foams produced by lyophilization, and in all cases exceeded that achieved by conventional, commercially available cellulose foams. [Display omitted] • Demonstrated a facile method to fabricate hydrophilic foams from hydroxyethyl cellulose solutions by freezing-induced phase separation. • Demonstrated that freezing rate and temperature affect the pore size of the resultant foams, while processing conditions impact the kinetics of phase-separation. • Successfully crosslinked hydroxyethyl cellulose foams by esterification to afford robust structures with stability in water. • Utilized biopolymer foams as platforms for functionalization by grafting of zwitterionic groups. [ABSTRACT FROM AUTHOR]

In this work we present a dielectric relaxation study of Acrylic/Polyurethane polymers synthesized via miniemulsion photo-polymerization. Three different samples, both parts of the synthesized hybrid latex (SOL and GEL fractions) and a full acrylic sample as reference have been considered. Besides dielectric experiments using Broadband Dielectric Spectroscopy (BDS) technique, complementary Differential Scanning Calorimetry measurements have been performed. The thermodynamic characterization outcomes evidence very similar characteristics of the glass transition phenomena among the investigated samples without any signature of melting/crystallization. However BDS experiments show three well resolved dielectric relaxation processes above Tg, two of them evidence marked differences among the samples. A detail study allows us to provide a molecular origin for these three dielectric relaxation processes in connection with the sample characteristics. In particular, our results show that the characterization of these hybrid Acrylic/PU by BDS can provide access to some of the structural features that would ultimately influence the adhesives properties. [ABSTRACT FROM AUTHOR]

This article describes the preparation of hybrid gradient porous surfaces by using the breath figures approach. In a first step gradient porous surfaces were created from polymeric blends consisting of a linear polystyrene as major component and amphiphilic copolymers of poly(styrene- co -acrylic acid) as minor component. THF was used as solvent conducting to porous surfaces with a gradual variation of the pore size in a radial manner due to the long evaporation time. A detailed investigation of the influence of chemical composition of the copolymer (i.e. ratio styrene/acrylic acid) on the porous films was carried out. These films were successfully employed to prepare hybrid gradient surfaces by incorporating of magnetic nanoparticles inside the cavities. For this purpose two different strategies were explored. On one hand a magnetic nanoparticles aqueous suspension was placed on the porous surface with a magnet below the film, and subsequently the colloidal suspension was removed. Alternatively, the magnetic suspension was placed onto the surface and left until complete evaporation. A further step of peeling off the top layer also conducts to the decoration of the nanoparticles exclusively in the interior of the holes. Both strategies allow the preparation of hybrid surfaces with a variation of the content of magnetic nanoparticles magnetic inside the holes as a function of the radial position. [ABSTRACT FROM AUTHOR]

Cellulose-based hydrogel coated porous membranes as "water removing" materials have received considerable attention in the field of oil/water separation. However, the majority of them are vulnerable to external mechanical destruction and inevitably suffer from organic and biological fouling. In this work, a novel Ag/AgCl nanoparticles (NPs) hybrid cellulose-based hydrogel (AHCH) derived from hydroxyethyl cellulose (HEC) and poly(acrylic acid) (PAA) was successfully prepared that exhibited good mechanical properties, followed by anti-swelling, self-healing, and self-cleaning properties. To apply this AHCH for oil/water separation, it was coated on a piece of cotton fabric (AHCH@CF) through the facile sol-gel coating method. The as-prepared AHCH@CF presented superhydrophilic and underwater superoleophobic features, resulting in its satisfactory anti-oil-fouling ability. Meanwhile, it exhibited excellent oil/water separation properties for various water/oil mixtures, accompanied by separation efficiency of around 99.5% and high water flux up to approximately 15,246 L−1 m−2 h−1. Moreover, the separation efficiency could still maintain at greater than 99.0% after 50 cycles. Notably, the as-obtained AHCH@CF showed excellent stability even in highly acidic, basic, saline solutions, and ultrasonic treatment. Most importantly, due to the existence of numerous spherical Ag/AgCl NPs on the surface, AHCH@CF exhibited good photo-induced self-cleaning property and antibacterial activity. Hence, this AHCH@CF with high performance provides a new candidate material for the application in efficient and durable oil/water separation. [Display omitted] • Novel AHCH@CF is fabricated by sol-gel method with superhydrophilicity. • AHCH@CF can separate oil/water mixtures with high flux, efficiency, stability. • AHCH@CF presents self-healing and photo-induced self-cleaning features. • AHCH@CF exhibits excellent anti-oil-fouling property and antibacterial activity. [ABSTRACT FROM AUTHOR]

Hydrogel is an ideal choice as wearable sensors for human motion detection. However, low electrical sensitivity, narrow strain detection range and lack of self-healing performance still limit the further application and service life of hydrogel sensors. Herein, we report a self-healing ionic hydrogel based on copolymers of acrylic acid (AA) and acrylamide (AM), in which Fe3+ and tetramethylammonium chloride (TMAC) can bind with carboxylate through complex crosslinking and electrostatic interaction, respectively. Attribute to its supramolecular forces (including electrostatic interactions, hydrogen bonds) and complex cross-linking structure, the stretchable hydrogel has electrical-mechanical dual self-healing properties, that possess excellent mechanical properties (tensile strength at ∼320 kPa and strain at break ∼1600%), dual self-healing ability (∼87.5% self-healing efficiency in mechanical and instantaneous self-healing in electrical), ultra-high electrical sensitivity (GF = 18.26), and an extensive monitoring range (0.1–300% in strain and 8.15–31.56 kPa in pressure). This hydrogel shows great potential in wearable sensors for human motion detection. [Display omitted] • Physical cross-linking hydrogel prepared by one-pot method. • Electrical-mechanical dual self-healing. • Ultra-high electrical sensitivity (GF = 18.26). • Strain and pressure dual sensing ability. • Ionic self-healing hydrogels as wearable sensors for human motion detection. [ABSTRACT FROM AUTHOR]

Hydrogels with remarkable hydrophilicity and tunable toughness are appealing materials to serve as superabsorbent polymers. However, chemically cross-linked hydrogels often suffer from low toughness regardless of their considerable swelling, restricting their widespread applications. In comparison, the network of physically cross-linked hydrogels can be regulated to meet both a high swelling ratio and considerable toughness. Here, we develop superabsorbent and tough hydrophobic associated hydrogels using terpolymerization of poly acrylic acid (PAA), polyacrylamide (PAM), and lauryl methacrylate (LMA) within the micelles formed by sodium dodecyl sulfate (SDS) surfactant. To this end, various parameters such as AA/AM molar ratio, the concentration of hydrophobic and hydrophilic monomers in the hydrogel network were optimized by morphological, mechanical, rheological, and swelling studies. The multiple physical interactions inside the hydrogel endow it with suitable mechanical properties (stretchability 1500–3000%, tensile strength 50–150kPa, and toughness up to 2.4 MJ/m3). On the other hand, the macroporous network of the hydrogels caused by the hydrophobic association is responsible for their outstanding swelling ratio. On this basis, the hydrogels can absorb water up to 1000 g/g while keeping their 3D network noticeably, exceeding the swelling degree of hydrophobic associated hydrogels reported till now. Such a fascinating feature can widen the hydrogels' applications in various areas. [Display omitted] • Terpolymer hydrogels with high swelling ratio and superior toughness were synthesized. • AA/AM ratio, hydrophobic and hydrophilic monomer contents were adjusted to obtain mechanical and swelling properties. • Hydrophobic cross-linked centers render remarkable toughening to the hydrogels. • Hydrogels with a 3-D network and microporous structure revealed outstanding swelling. • Structural stability of the hydrogels and their reusability are beneficial for their practical applications. [ABSTRACT FROM AUTHOR]

A detailed kinetic Monte Carlo simulation was used to predict the characteristics of the batch miniemulsion polymerization of an isocyanate and an acrylic monomer mixture that contains a hydroxyl functional monomer (HEMA). The simulation takes into account the simultaneous polyaddition of the polyurethane prepolymer with the hydroxyl group of HEMA and the free radical polymerization of the acrylic monomers and all reactions in aqueous and polymer particle phases. The model has been assessed by batch miniemulsion polymerizations carried out using an aliphatic isocyanate prepolymer, n-butyl acrylate, 2-hydroxyethyl methacrylate monomers and potassium persulfate as an initiator. It was found that partitioning of water had a significant effect on both kinetics and microstructure of the resulting polymer. Evolution of different species of PU prepolymer produced in the reaction and the sol and gel fractions revealed that the terminal pendent double bond of the HEMA in polymer chains has significantly lower reactivity than that of the HEMA free monomer. Detailed information on gel microstructure has been derived in the model by both distribution of molecular weight between crosslinking points in acrylic chains and distribution of chain extension of PU prepolymers. These crosslinking density distributions can be related to mechanical and adhesive properties of the polymer. [ABSTRACT FROM AUTHOR]

Abstract: Janus poly (N-isopropylacrylamide)-co-acrylic acid/Au microgels that resemble a “snowman”, “dumbbell”, and an “abalone” were prepared by thermally evaporating a layer of Au on half of the microgel surface, followed by exposure to thiolated single-stranded DNA with complementary sequences. We hypothesize that when the complementary single-stranded DNA attached to the Au forms the more stable double strand, the Au reorganizes on the microgel surface, yielding the observed unique Janus particle structures. [Copyright &y& Elsevier]