Copolymer Chains Research Articles

Self-doped poly(aniline-co-metanilic acid) copolymer coatings for enhancing the corrosion resistance of 304 stainless steel

Self-doped conducting poly(aniline-co-metanilic acid) (SPANI) copolymer coatings are electropolymerized for corrosion protection of 304 stainless steel (304SS) in a 0.3 M HCl solution. The synthesized SPANI coating is more compact and uniform, which exhibits improved barrier resistance to aggressive ions. The potentiodynamic polarization curve and electrochemical impedance spectroscopy results show that the SPANI copolymer coatings significantly suppress the corrosion current density, increase the charge transfer resistance, and effectively inhibit corrosion of the 304SS substrate. In addition, the SPANI copolymer coating exhibits a nondestructive topography after 120 h of immersion in a corrosive environment, which further confirms its superior protection performance. Owing to their enhanced physical barrier effect (compact coating surface with low porosity) and superior anodic protection, SPANI copolymer coatings are more corrosion resistant. Furthermore, the outcomes of the quantum chemical calculation and molecular dynamic simulation indicate that the SPANI copolymer chains are more stabilized and display favorable compatibility with the Fe (1 1 0) surface via electrostatic force. The better surface coverage and higher adsorption activity ensure an excellent chemical-anchor effect on the Fe (1 1 0) plane and thus achieve higher corrosion inhibition efficiency of the SPANI copolymer coatings.

Structures of the co‐branching reactive products of isotactic polypropylene with high‐density polyethylene and the effect on the in situ compatibilization of mixed recycled materials

AbstractThe recycling of petroleum‐based polymers such as polypropylene (PP) and polyethylene (PE) is an effective means of reducing environmental pollution. However, the incompatible PP and PE blended waste is difficult to separate accurately, which reduces the quality of the recycled material. In this paper, the trifunctional acrylate monomer (trimethylolpropane triacrylate), peroxide (2,5‐dimethyl‐92,5‐di[tert‐butylperoxy] hexane) and free radical activity modifier (zinc dimethyldithiocarbamate) were applied to in situ generate the copolymer of isotactic polypropylene and high‐density polyethylene (iPP‐co‐HDPE) with a long‐chain co‐branched structure via a melt blending method. The co‐crystallization of the branched copolymer chain segments with the chemical identical homopolymers vastly improved the compatibility of iPP and HDPE components. This in situ co‐branching compatibility strategy resulted in a significant improvement in the mechanical properties of PE and PP mixed wastes. The temperature gradient extraction method was used to separate the co‐branching modified iPP/HDPE blends. The results confirm that the separated iPP‐co‐HDPE components have a highly co‐branched structure. The significant improvement in compatibility resulted in a large increase in elongation at break and impact strength of the iPP/HDPE blends, which provides an economic and effective method for the recycling of mixed PE and PP wastes.

Binding of Proteins to Copolymers of Varying Charges and Hydrophobicity: A Molecular Mechanism and Computational Strategies.

Because of their ability to selectively bind to a target protein, copolymer nanoparticles (NPs) containing a selected combination of hydrophobic and charged groups have been frequently reported as potent antibody-like analogues. However, due to the intrinsic disorder of the copolymer NP in terms of its random monomer sequence and the cross-linked copolymer matrix, the copolymer NP is indeed strikingly different from a well-folded protein antibody and the complexation between the copolymer NP and a target protein is likely not due to a lock-key type of interaction but possibly due to a novel and unexplored molecular mechanism. Here, we study a key biomarker protein, vimentin, interacting with a set of random copolymer chains using implicit-water explicit-ion coarse-grained (CG) molecular dynamics (MD) simulations along with biolayer interferometry (BLI) analysis. Due to the charge and hydrophobicity anisotropy on the vimentin dimer (VD) surface, a set of bound copolymers are found inhomogenously adsorbed on the VD, with energetic heterogeneity for different binding sites and cooperative effect in the adsorption. Increasing the charge or hydrophobicity of the copolymer may have different consequences on the adsorption. In this study, we found that with more copolymer charges, the protein coverage increases for copolymers of low hydrophobicity and decreases of high hydrophobicity, which is explained by the distribution and size of various functional patches on the VD in loading those copolymers. Employing a coverage-dependent Langmuir model, we propose a simulation protocol to address the full profile of the copolymer binding free energy through the fit to the simulated binding isotherm. The obtained results correlate well with those from the BLI experiment, indicating the significance of this method for the rational design of the copolymer NP with engineered protein binding affinity.

Random copolymer adsorption onto a periodic heterogeneous surface: A partially directed walk model.

The adsorption of a single AB random copolymer (RC) chain onto an inhomogeneous ab surface with a regular periodic pattern is studied theoretically. The problem is considered within the simplest model of a partially directed random walk in two dimensions by using the method of generating functions and the annealed approximation for the averaging over disorder in the RC sequence. The existence of the "optimal" RC composition and the degree of correlation in the monomer sequence, at which the inverse transition temperature has a local minimum, is shown. This is characteristic for symmetric and weakly asymmetric surfaces, whereas for surfaces with pronounced asymmetry there is no such local minimum. The best adsorbate for a strongly asymmetric surface is the homopolymer composed of monomer units that are complimentary to the majority sites on the surface. The results for the adsorption transition point obtained in the annealed approximation are compared with the numerical results for random-periodic AB-copolymers with a long period being a quenched random sequence of A and B units. The comparison shows that the annealed approximation provides a very good quantitative estimate of the adsorption transition point.

Preparation of amphiphilic cationic polyacrylamide (CPAM) with cationic microblock structure to enhance printing and dyeing sludge dewatering and condition performance.

Flocculation is an important pretreatment technology for sludge dewatering, and the flocculant's performance is the key factor to determine the flocculation effect. Cationic polyacrylamide (CPAM) is commonly used in dewatering and conditioning of printing and dyeing sludge (PD sludge), and the research of high-efficiency flocculant is a hot spot in the field of PD sludge dewatering. Hydrophobic butylacrylate (BA) and (2-(Methacryloyloxy)ethyl) trimethylammonium chloride (DMC) were introduced into the copolymer, and amphiphilic (hydrophilic/lipophilic) CPAM, namely TP-ADB, with microblock structure was synthesized by ultrasonic initiated template copolymerization in this study. The functional group composition of TP-ADB was determined by FTIR and 1H NMR. Thermogravimetric analysis (TGA) showed that TP-ADB had good thermal stability. The amphiphilic rheological properties of the copolymer were measured according to the apparent viscosity. In addition, 1H NMR and TGA results confirmed the existence of microblock structure in the copolymer chain. The polymerization mechanism was discussed by association coefficient (KM) measurement. The results showed that the template copolymerization initiated by ultrasonic followed the law of free radical copolymerization. The pre-adsorption of DMC with sodium polyacrylate template (NaPAA) before the reaction confirmed that the template polymerization accorded with ZIP I mechanism. The cationic microblock structure and hydrophobic association of TP-ADB promoted the dewatering performance of PD sludge (FCMC = 72.9%, turbidity removal rate = 98.9%, SRF = 4.2 × 1012m·kg-1). Hydrophobic association enhanced the bridging, sweeping, and net catching effect, and promoted the growth of floc size and fractal dimension. Cationic microblock structure can produce compact floc with higher mechanical strength by enhancing electrical neutralization and electrical patching. As a skeleton, the compressibility of filter cake was reduced and the permeability was enhanced, and the PD sludge dewatering effect was significantly improved.

Modifying Frank–Kasper Mesophases by Modulating Chain Configuration in PDMS-b-PTFEA Copolymers

The common spherical mesophases observed from chemically distinct compounds have promoted extensive studies of packing structures in soft-matter self-assemblies. Here, we present a new approach for controlling sphere-packing phases by modulating homologous copolymer chain configurations. To this end, three sets of sample pairs, compositionally asymmetric polydimethylsiloxane-b-poly(2,2,2-trifluoroethyl acrylate) (PDMS-b-PTFEA) diblock copolymers (diBCPs) and their homologues containing the corresponding triblock copolymer (triBCP), are synthesized via atom transfer radical polymerization and designed with the consistent volume fractions of the core-forming PTFEA block, fPTFEA = 0.20, 0.18, and 0.15. We identify the formation of C15 and hexagonally close-packed (HCP) phases in the triBCP-containing PDMS-b-PTFEAs, whereas the σ and C14 phases are formed in their diBCP analogues, respectively. These phase shifts into C15 and HCP, due to molecular configuration differences, reveal a significant yet unrealized role of chain configurations and the associated chain size effects in determining the stable sphere-packing phases in BCP systems.

Effects of glutaric anhydride functionalization on filler-free benzoxazine/epoxy copolymers with shape memory and self-healing properties under near-infrared light actuation

We have developed new types of thermosets from bio-based benzoxazine/epoxy copolymers with shape memory and self-healing properties that could be triggered by using near-infrared (NIR) light, without using any filler. The copolymers were prepared from bio-based raw materials, including vanillin, furfurylamine, and epoxidized castor oil, along with functionalized with glutaric anhydride (GA), due to which self-healing properties of the copolymers were enabled through dynamic covalent bonds. Effects of GA content (0.00, 0.02, 0.04, 0.06, 0.08, and 0.10 mol) on molecular structure, mechanical properties, dynamic mechanical properties, and thermal stability of the copolymers were investigated. The results from infrared spectroscopy showed the formation of ester linkages and free carboxylic acids upon functionalization of copolymers with GA. The increased crosslinking density by GA was observed from increased tensile strength (from 11 to 16 MPa), glass transition temperature (72–150 °C), and degradation temperature at 5% weight loss (382–405 °C) of the copolymers. However, excess contents (0.08 and 0.10 mol) of GA might result in the existence of free components, hindering the formation of the copolymer network and diminishing the mechanical properties of the copolymers. Shape memory properties of GA-functionalized V-fa/ECO copolymers were investigated under NIR actuation; the results showed a 100% of shape recovery ratio within 20 s of actuation. Self-healing properties of GA-functionalized V-fa/ECO copolymers were investigated under NIR actuation; the results showed 94% of restored storage modulus after 20 min of actuation. Lastly, the self-healing mechanism under NIR actuation was proposed that NIR photothermal effects of the copolymers induced the crack closing due to their shape memory effects. Consequently, the copolymer chains could diffuse across the crack interface along with transesterification through GA functionalities, leading to crack healing. The findings of this study suggested a new way to produce NIR light-responsive self-healing polymer without using NIR photothermal filler. • Filler-free benzoxazine/epoxy copolymers with shape memory and self-healing effects triggered by NIR light were developed. • Copolymers were synthesized from bio-based raw materials and functionalized with glutaric anhydride (GA). • Copolymers showed 100% shape recovery within 20 s and 94% restored storage modulus after 20 min of NIR light actuation. • Self-healing mechanism involved shape memory effects and transesterification induced by NIR photothermal effects.

Investigation of self-assembled poly(ethylene glycol)-poly(L-lactic acid) micelle as potential drug delivery system for poorly water soluble anticancer drug abemaciclib

Polymer-based drug delivery systems have the ability to organize stable self-assembled nanocarriers containing hydrophobic cores allow to delivery of poorly water-soluble anticancer drugs by drug encapsulation process. Computational investigations can assist in designing of efficient drug-delivery systems. However, the high computational cost of simulation of nanocarrier self-assembly processes due to long-timescale required for equilibration are challenging. In this study we investigated the assembly mechanism of the abemaciclib anticancer drug encapsulated by the PEG-PLA copolymer micelle; molecular dynamics simulations were carried out for analyzing the aggregation of the PEG-PLA copolymer chains. The process of drug encapsulation is mostly operated by the hydrophobic and hydrophilic interactions. The hydrogen bonding and electrostatic interactions also play an important role in aggregation of the PEG-PLA copolymer chains. Analyses of radial distribution function and solvent accessible surface area show that the PEG-PLA copolymer micelles can increase the hydrophobic drugs solubility. The study presents insights into the mechanism of the structure of drug-loaded PEG-PLA copolymer micelles to design the drug delivery systems with helpful properties.

Impact of Polydopamine Nanoparticle Surface Pattern and Roughness on Interactions with Poly(ethylene glycol) in Aqueous Solution: A Multiscale Modeling and Simulation Study.

A significant research effort in the past few years has been devoted to engineering synthetic mimics of naturally occurring eumelanin. One such effort has involved the assembly of oligomers of 5,6-dihydroxyindole (DHI), a synthetic precursor of polydopamine (PDA), into melanin-mimicking nanoparticles for use in a variety of applications with desired optical, photonic, thermal, and electrical properties. In many of these applications, the PDA nanoparticles are mixed with other polymers or oligomers, thus motivating this specific study to understand how the surface characteristics of the assembled PDA-nanoparticles affect their interaction with poly(ethylene glycol) (PEG) chains in aqueous solution. We use molecular dynamics (MD) simulations to study the interaction of linear 20-mer PEG chains with different PDA-nanoparticles assembled using four types of oligomers of 5,6-DHI: two isomers of 5,6-DHI 2-mers with the monomers bonding either at the 2-2' position (A-type isomer) or 7-7' position (B-type isomer), denoted as A:2-mer and B:2-mer, respectively, and a 4-mer and an 8-mer of B-type chemistry denoted as B:4-mer and B:8-mer, respectively. Using explicit-solvent atomistic MD simulations, we find that PDA-nanoparticle surfaces assembled from B:8-mer exhibit smaller density fluctuations of water molecules and, as a result, are relatively more hydrophilic than the PDA-nanoparticle surfaces assembled from A:2-mer, B:2-mer, and B:4-mer. The surface composition of PDA-nanoparticles assembled from A:2-mer contains relatively fewer hydroxyl (-OH) groups compared to PDA-nanoparticles assembled from a B:2-mer, B:4-mer, or B:8-mer, yet the sample of PEG chains show more collapsed and adsorbed conformations on A:2-mer nanoparticles' surface. To explain the atomistically observed behavior of PEG chains on the nanoparticles' surfaces, we use coarse-grained (CG) MD simulations and explain the roles of the pattern formed by the attractive sites (e.g.,-OH groups) exposed on the surface and the roughness of the surface on interactions with a genric PEG-like copolymer chain. By comparing atomistic and CG MD simulation results, we confirm that the -OH groups' pattern on the surface of the PDA-nanoparticle assembled from A:2-mer is patchier than the random or string-like patterns on the PDA-nanoparticle assembled from B:2-mer, B:4-mer, or B:8-mer, and it is this -OH groups' surface pattern that dictates the PEG chain conformations and adsorption on the PDA-nanoparticle surface. Overall, these results guide the design of chemically and physically heterogeneous nanoparticle surfaces for the desired polymer interaction and conformations.

Structure, properties, and in vitro degradation behavior of biodegradable poly(L‐lactic acid)‐trimethylene carbonate‐glycolide terpolymer

AbstractFor biodegradable medical implants, it is critical to match the degradation rate of the material with the lesion healing rate of the tissue defect. Here, we report the synthesis of poly(L‐lactic acid) (PLLA)‐trimethylene carbonate (TMC)‐glycolide (GA) terpolymers with various monomer feeding ratios of L‐lactide, TMC, and GA. The terpolymers were prepared through ring‐opening polymerization with the purpose to improve degradation and mechanical properties of the terpolymers for biomedical applications. The influence of various GA contents in PLLA‐TMC‐GA terpolymers on the chain structure and their in vitro degradation performances were evaluated by using gel permeation chromatography, differential scanning calorimetry, X‐ray diffraction, 1H nuclear magnetic resonance, and tensile tests. Compared with pure PLLA, the degradation rate of terpolymers increased with the increase of GA content, because GA segments, which have a faster hydrolysis rate, not only effectively disrupt the regularity of LLA segment, but also increase the probability of chains scission during the degradation process. In a 28‐week long degradation study, the mass loss of PLLA‐TMC‐GA terpolymers was about 36%, which is a faster rate than reported for pure PLLA. Therefore, it is possible to tailor the copolymer chain structures by varying the ratio of GA in the terpolymer to balance its degradation rate with body's lesion healing rate.

Effects of concentration and chain length of the sequence copolymer on interfacial properties of homopolymers/sequence copolymers ternary blends: A DPD simulation study.

The effect of the concentration and chain length of the copolymer AB with sequence length τ = 8 on the interfacial properties of the ternary mixtures A10/AB/B10 are investigated by the dissipative particle dynamics (DPD) simulations. It is found that: i) As the copolymer concentration varies from 0.05 to 0.15, increasing the copolymer enrichment at the center of the interface enlarges the interface width ω and reduces the interfacial tension. However, as the concentration of the sequence copolymers further increases to 0.2, because the interface has formed micelles and the micellization could lower the efficiency of copolymers as a compatibilizer, the interfacial tension exhibits a slightly increase; ii) elevating the copolymer chain length, the copolymer volumes vary from a cylinder shape to a pancake shape. The blends of the copolymer with chain length Ncp = 24 exhibit a wider interfacial width w and a lower interfacial tension γ, which indicates that the sequenced copolymer Ncp = 24 exhibits a better performance as the compatibilizers. This study illustrates the correlations between the reduction in interfacial tension produced by the sequence copolymers and their molecular parameters, which guide a rational design of an efficient compatibilizer.

ICAR ATRP-induced surface self-assembly in the fabrication of the surface nanostructures

Polymerization induced surface self-assembly (PISSA) technology is a state-of-the-art method in the fabrication of the hierarchical surface nanostructures. Previously, we demonstrated that reversible addition−fragmentation chain transfer (RAFT) polymerization-based PISSA could be used to construct hierarchical surface nanostructures on the silica particles. Atom transfer radical polymerization (ATRP) has many advantages, especially in the synthesis of the macroinitiator. In this research initiators for continuous activator regeneration (ICAR) ATRP-induced PISSA approach is used to fabricate surface nanostructures. Poly(ethylene glycol) (PEG) macroinitiator and poly(oligo(ethylene glycol) monomethyl ether methacrylate-co-2-(2-bromoisobutyrnyloxy) ethyl methacrylate) (P(OEGMA-co-BIEM)) polymer brush macroinitiator on silica particles are used to initiate ATRP of styrene in methanol/water mixture. With the chain extensions, POEGMA-g-PS graft copolymer brushes and “free” PEG-b-PS block copolymer chains make surface coassembly into surface nanostructures. With an increase in monomer feeding ratio, the surface morphology gradually changes from small-sized spherical surface micelles (s-micelles), to big-sized s-micelles, and to asymmetric layered structures. Kinetics studies indicate that with an increase in monomer conversion there is a transition from homogeneous to heterogeneous polymerization.

Molecular simulation of poly(ethylene-ran-propylene) nanoparticles with different comonomer composition

Poly(ethylene-ran-propylene), PErP, nanoparticles at various comonomer compositions were studied by Monte Carlo simulation of coarse-grained copolymer models for their structural and surface properties. At higher ethylene fraction (fE) in PErP chains, the relative bulk densities in the interior portion of nanoparticles were increased and the nanoparticles became more condensed structures with sharper surfaces. In addition, chain ends were more preferably segregated at the surface while the co-monomers at the middle position were homogeneously distributed in the interior of nanoparticles. Chain dimensions and chain shape were changed mostly in the surface region and significantly decreased with fE. Bond orientation was mostly random arrangement irrespective of fE. For orientation at the molecular level, the longest principal axis of copolymer chains tended to align parallel to the surface but preferably changed toward isotropic random arrangement for copolymers with smaller fE.

Preparation of Photoswitchable Polyacrylic Nanocomposite Fibers Containing Au Nanorods and Spiropyran: Optical and Plasmonic Properties

Photoswitchable nanofibers and nanocomposite fibers containing plasmonic nanoparticles have attracted a great deal of interest in optical and plasmonic devices. Herein, photoswitchable poly(methyl methacrylate-co-vinylimidazole-co-spiropyran ethyl acrylate) (MVSP) and its copolymer with butyl acrylate (MBVSP) were prepared via emulsion polymerization, and the corresponding nanofibers (MVSP@NF and MBVSP@NF) and nanocomposite fibers (MVSP/Au@NF and MBVSP/Au@NF) containing AuNRs were fabricated through electrospinning. FTIR and 1H NMR analyses confirmed the progress of the copolymerization reaction. The morphology of the prepared nanofibers containing AuNRs with an aspect ratio of 2.5 was identified by SEM and TEM techniques. The inclusion of vinylimidazole into the copolymer chains resulted in well-dispersed AuNRs. Photoisomerization studies revealed a higher photochromic efficiency for MBVSP@F (reflective intensity of 37.4%) with respect to MVSP@NF (reflective intensity of 62.5%) because of the greater flexibility of the chains. In addition, the presence of AuNRs in the nanocomposite fibers with high absorptivity intensified the photochromic properties for both samples. The polarization-dependent plasmonic band of AuNRs was switched between 650 and 634 nm through the photoisomerization of nonpolar SP to polar MC reversibly for MVSP/Au@NF. This displacement was just 4 nm for MBVSP/Au@NF, owing to the limited coupling between AuNRs and MC isomers. Besides, the capability of both nanocomposite fibers for reversible optical patterning was investigated by fast write-erase cycles. Enhanced photofatigue resistance in those fibers and the photomodulation of the plasmonic band of AuNRs using SP to MC isomerization revealed their promising potential for optical patterning and on-demand real-time plasmonic devices.

Azide Photochemistry in Acrylic Copolymers for Ultraviolet Cross-Linkable Pressure-Sensitive Adhesives: Optimization, Debonding-on-Demand, and Chemical Modification.

Pressure-sensitive adhesives (PSAs) are usually made from viscoelastic, high-molecular-weight copolymers, which are fine-tuned by adjusting the comonomer ratios, molecular weights, and cross-link densities to optimize the adhesion properties for the desired end-use. To create a lightly cross-linked network, an ultraviolet (UV) photoinitiator can be incorporated. Here, we present the first use of perfluorophenylazide chemistry to control precisely a polyacrylate network for application as a PSA. Upon UV irradiation, the highly reactive nitrene from the azide moiety reacts with nearby molecules through a C–H insertion reaction, resulting in cross-linking via covalent bonding. This approach offers three benefits: (1) a means to optimize adhesive properties without the addition of an external photoinitiator; (2) the ability to switch off the tack adhesion on demand via a high cross-linking density; and (3) a platform for additional chemical modification. A series of poly(n-butyl acrylate-co-2,3,4,5,6-pentafluorobenzyl acrylate) or poly(PFBA-co-BA) copolymers were synthesized and modified post-polymerization into the photo-reactive poly(n-butyl acrylate-co-4-azido-2,3,5,6-tetrafluorobenzyl acrylate) [azide-modified poly(PFBA-co-BA)] with various molar contents. When cast into films, the azide-modified copolymers with a high azide content achieved a very high shear resistance after UV irradiation, whereas the tack and peel adhesion decreased strongly with the increase in azide content, indicating that excessive cross-linking occurred. These materials are thus photo-switchable. However, in the low range of azide content, an optimum probe tack adhesion energy was obtained in films with a 0.3 mol % azide content, where a long stress plateau (indicating good fibrillation) with a high plateau stress was observed. An optimum peel adhesion strength was achieved with 0.5 mol % azide. Thus, the adhesion was finely controlled by the degree of cross-linking of the PSA, as determined by the azide content of the copolymer chain. Finally, as a demonstration of the versatility and advantages of the material platform, we show an azide–aldehyde–amine multicomponent modification of the azide copolymer to make a dye-functionalized film that retains its adhesive properties. This first demonstration of using azide functionality has enormous potential for functional PSA design.

Long-Term Stability of Pickering Nanoemulsions Prepared Using Diblock Copolymer Nanoparticles: Effect of Nanoparticle Core Crosslinking, Oil Type, and the Role Played by Excess Copolymers.

A poly(N,N′-dimethylacrylamide) (PDMAC) precursor is chain-extended via reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization of diacetone acrylamide (PDAAM) to produce PDMAC77-PDAAM40 spherical nanoparticles. Post-polymerization core-crosslinking of such nanoparticles was performed at 20 °C, and the resulting covalently stabilized nanoparticles survive exposure to methanol. The linear and core-crosslinked nanoparticles were subjected to high-shear homogenization in turn in the presence of n-dodecane to form macroemulsions. Subsequent processing of these macroemulsions via high-pressure microfluidization produced nanoemulsions. When using the core crosslinked nanoparticles, the droplet diameter was strongly dependent on the copolymer concentration. This indicates that such nanoparticles remain intact under the processing conditions, leading to formation of genuine Pickering nanoemulsions with a z-average diameter of 244 ± 60 nm. In contrast, the linear nanoparticles undergo disassembly to afford molecularly dissolved diblock copolymer chains, which stabilize oil droplets of 170 ± 59 nm diameter. The long-term stability of these two types of n-dodecane-in-water nanoemulsions with respect to Ostwald ripening was examined using analytical centrifugation. When prepared at the same copolymer concentration, Pickering nanoemulsions stabilized by core-crosslinked nanoparticles proved to be significantly more stable than the nanoemulsion stabilized by the amphiphilic PDMAC77-PDAAM40 chains. Moreover, higher copolymer concentrations led to a significantly faster rate of droplet growth. This is attributed to excess copolymer facilitating the diffusion of n-dodecane through the aqueous phase. Finally, analytical centrifugation is used to assess the long-term stability of the analogous squalane-in-water nanoemulsions. These systems are much more stable than the corresponding n-dodecane-in-water nanoemulsions, regardless of whether the copolymer is adsorbed as sterically stabilized nanoparticles or surface-active chains.

Upcycling Polytetrahydrofuran to Polyester

Upcycling Polytetrahydrofuran to Polyester

Molecular and structural design of polyacrylonitrile-based membrane for oil-water separation

Herein, a durable superhydrophobic/superoleophilic membrane with micro-/nano-hierarchical structure was achieved through molecular and structural design of fluorinated polyacrylonitrile-based membrane. In which, the introduction of perfluorooctanol acrylate into copolymer chain and usage of electrospinning/electrospraying technology followed by heat post-treatment provided low surface energy and durable hierarchical structure, respectively. The resultant membrane demonstrated superhydrophobicity and superoleophilicity with water contact angle of 160° and oil contact angle of 0° in air, which endowed the membrane with excellent separation ability for oil/water mixture with separation efficiency above 99% and ultrahigh flux beyond 8000 L/m 2 /h. Furthermore, the obtained membrane maintained its superhydrophobicity after exposure to broad pH, organic solvents, high temperature and ultrasonic treatment, ascribed to the chemical reaction of cyano groups on the surface of fibers and particles during the heat post-treatment. This work provides a promising strategy to fabricate superwetting membrane to remove trace amount of water in oil. A durable and robust membrane with micro-/nano-hierarchical structure was achieved through molecular and structural design of polyacrylonitrile-based membrane for efficient separation of various oil/water mixtures. • A novel fluorinated polyacrylonitrile copolymer was synthesized. • Membrane with micro-/nano-scale structures was constructed by using the copolymer. • The fibers and particles in membrane were integrated by chemical interactions. • Durable superhydrophobicity of membrane was achieved. • The membrane showed excellent separation efficiency for oily wastewater.

Compatibilization of Immiscible Polymer Blends Using Block Copolymer: Influence of the Dry Brush Model Modifications on Model Results

AbstractThe compatibilization of polymer blends using a copolymer can be estimated, among other, using simple theoretical models based on Leibler's mean field theory and its modification by Noolandi. The case when copolymer chain is shorter than homopolymer chains can be described in the “dry brush” approximation for high concentration of the copolymer in the interfacial layer and in the approximation for the low copolymer concentration in the interfacial layer. Since, there is a discontinuity between results provided by them, the effect of several modifications of the dry brush approximation has been studied. None of the tried modifications shifts results closer to the approximation of the low copolymer concentration.

Tuning the Glass Transition Temperature of a Core-Forming Block during Polymerization-Induced Self-Assembly: Statistical Copolymerization of Lauryl Methacrylate with Methyl Methacrylate Provides Access to Spheres, Worms, and Vesicles.

A series of poly(lauryl methacrylate)–poly(methyl methacrylate-stat-lauryl methacrylate) (PLMAx–P(MMA-stat-LMA)y) diblock copolymer nanoparticles were synthesized via RAFT dispersion copolymerization of 90 mol % methyl methacrylate (MMA) with 10 mol % lauryl methacrylate (LMA) in mineral oil by using a poly(lauryl methacrylate) (PLMA) precursor with a mean degree of polymerization (DP) of either 22 or 41. In situ1H NMR studies of the copolymerization kinetics suggested an overall comonomer conversion of 94% within 2.5 h. GPC analysis confirmed a relatively narrow molecular weight distribution (Mw/Mn ≤ 1.35) for each diblock copolymer. Recently, we reported an unexpected morphology constraint when targeting PLMA22–PMMAy nano-objects in mineral oil, with the formation of kinetically trapped spheres being attributed to the relatively high glass transition temperature (Tg) of the PMMA block. Herein we demonstrate that this limitation can be overcome by (i) incorporating 10 mol % LMA into the core-forming block and (ii) performing such syntheses at 115 °C. This new strategy produced well-defined spheres, worms, or vesicles when using the same PLMA22 precursor. Introducing the LMA comonomer not only enhances the mobility of the core-forming copolymer chains by increasing their solvent plasticization but also reduces their effective glass transition temperature to well below the reaction temperature. Copolymer morphologies were initially assigned via transmission electron microscopy (TEM) studies and subsequently confirmed via small-angle X-ray scattering analysis. The thermoresponsive behavior of PLMA22–P(0.9MMA-stat-0.1LMA)113 worms and PLMA22–P(0.9MMA-stat-0.1LMA)228 vesicles was also studied by using dynamic light scattering (DLS) and TEM. The former copolymer underwent a worm-to-sphere transition on heating from 20 to 170 °C while a vesicle-to-worm transition was observed for the latter. Such thermal transitions were irreversible at 0.1% w/w solids but proved to be reversible at 20% w/w solids.