Relaxing nonequilibrated polymers in thin films at temperatures slightly above the glass transition

We have studied the dewetting process of thin polystyrene films on nonwettable substrates in the viscoelastic regime slightly above the glass transition temperature. The evolution of the shape of the dewetting rim for varying film thickness, molecular weights and dewetting temperatures allowed us to determine the relaxation rates of residual stresses, which originated from nonequilibrated polymer chain conformations formed during film preparation by spin‐coating. For long chain polymers, we found rates notably faster than the longest bulk relaxation processes, highly independent of molecular weight and temperature. Our study demonstrates that dewetting is a powerful tool for sensitive characterization of nonequilibrium properties of thin polymer films. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 515–523     

TOF-GISANS investigation of polymer infiltration in mesoporous TiO2 films for photovoltaic applications

The structure of porous TiO₂ films and TiO₂:poly(N-vinylcarbazole) (PVK) composite films is investigated with time-of-flight grazing incidence small-angle neutron scattering (TOF-GISANS). The TiO₂ films have been prepared by application of a sol–gel process with a diblock copolymer as structure directing agent, and the conductive polymer PVK is infiltrated in the porous network by spin coating and solution casting. The films show a hierarchical pore structure with mesopores 52 nm in size and additional large macropores with a diameter of about 180 nm. By matching the scattering contrast of the TiO₂ with the polymer information about the penetration of the polymer in the pores is determined. Whereas in the PVK film prepared by solution casting the pores are filled to a high degree; in the spin coated film, PVK wets only the TiO₂ pore walls and forms a solid overlying layer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1628–1635, 2010     

Porphyrin‐based covalent triazine frameworks: Porosity,adsorption performance,and drug delivery

Two porous porphyrin‐based covalent triazine frameworks (PCTFs), in which porphyrin is incorporated as building block, have been synthesized by the Friedel–Crafts reaction. The copolymer PCTFs show large Brunauer–Emmett–Teller specific surface area of up to 1089 m² g^?1, high CO₂ uptake capacity reaching 139.9 mg g^?1 at 273 K/1.0 bar, and good selectivity for CO₂/CH₄ adsorption attaining 6.1 at 273 K/1.0 bar. The resulting porous solids also can be used as matrices for drug delivery of ibuprofen in vitro. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 2594–2600     

Immobilization of AIEgens into metal‐organic frameworks: Ligand design,emission behavior,and applications

Aggregation‐induced emission (AIE), in which the luminophores are highly emissive in aggregate state, is one of the most unique photophysical phenomena and has shown interesting applications in many areas. The immobilization of AIE luminogens (AIEgens) into metal‐organic frameworks (MOFs), which are inorganic‐organic hybrid porous materials with tunable and predictable structures, has been investigated over the past few years. These well‐defined porous frameworks cannot only provide an ideal platform for studying the mechanism of AIE phenomenon in solid state, but also show potential applications from sensing to white light‐emitting diodes. In this highlight, we will summarize the recent progress of AIEgens‐based MOFs, including ligand design, emission behavior, and applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1809–1817     

Controlled co‐solvent vapor annealing and the importance of quenching conditions in thin‐film block copolymer self‐assembly

A controlled co‐solvent vapor annealing system was designed and constructed to investigate the effects of solvent vapor activity during the rapid ambient quenching process on the morphology of a cylinder‐forming poly(styrene)‐b‐poly (ethylene oxide) (PS‐PEO) annealed in toluene and water vapor. A phase transformation from cylinders in the bulk to close‐packed spheres in swollen thin films occurred, which was reversed upon quenching with dry nitrogen. Quenching with humidified nitrogen preserved the spherical morphology but could significantly alter domain spacing and reduce long‐range order in the dried films under some circumstances. Specifically, long‐range order in the quenched films was found to decrease as the quenching humidity decreased from the humidity used during annealing, and the best long‐range order was obtained when the humidity remained consistent throughout both annealing and quenching. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1125–1130     

Induction of Helical Structure by Sesamin,and Production of Oriented Helical Polymer with Liquid Crystal Magneto‐Electrochemical Polymerization

Sesamin was employed as a chiral dopant for preparing cholesteric liquid crystals with right‐handed helical architecture. Helical twisting power of sesamin is to be 13.4 μm^?1. Electrochemical polymerizations were carried out with sesamin‐induced cholesteric liquid crystal electrolyte solution for obtaining conjugated polymer films with helical structure. The film was transcribed the helical order from the liquid crystal electrolyte solution with helical structure produced by sesamin during the polymerization process. The helical axes of the macromolecular superstructure of the polymer films were oriented in a magnetic field of 4.5 T. This results demonstrated liquid crystal magneto‐electrochemical polymerization with helical structure induced by sesamin as a natural chiral compound. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1894–1899     

Role of polythiophenes as electroactive materials

Semiconducting polythiophenes display electroactive properties which make them excellent candidates for applications as electroactive materials. Ability to undergo doping and to switch between different oxidation states allow tuning the chemical and physical properties of polythiophenes. Furthermore, the ability to integrate polythiophenes into copolymers, hybrid composites with metals and inorganic materials make them useful in electronic and biomedical applications. The capability to vary the properties of the final material with low production cost and high processability into thin films makes polythiophenes desirable materials for many applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3327–3346     

Effect of the crosslinking level on the properties of temperature‐sensitive poly(N‐isopropylacrylamide) hydrogels

In this study, the effect of the level of crosslinking on the properties of poly(N‐isopropylacrylamide) (PNIPAAm) hydrogels was investigated in terms of their lower critical solution temperature (LCST), interior morphology, equilibrium swelling, and deswelling and swelling kinetics. The thermal analysis showed that PNIPAAm hydrogels, having a wide range of crosslinking levels, exhibited almost the same LCSTs, and this was different from what the conventional theory would have predicted. Scanning electron micrographs revealed that the interior network structure of the PNIPAAm matrix became more porous with an increase in the level of crosslinking. This more porous matrix provided numerous water channels for water diffusion in or out of the matrix and, therefore, an improved response rate to the external temperature changes during the deswelling process and the swelling process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 582–593, 2003     

Superhydrophobic polymer multilayers for the filtration- and absorption-based separation of oil/water mixtures

We report layer-by-layer approaches to the design of superhydrophobic and superoleophilic substrates for the filtration- or absorption-based separation of bulk oil from oil/water mixtures. Fabrication of covalently cross-linked, nanoporous polymer multilayers on mesh substrates yielded superhydrophobic and superoleophilic porous media that allow oil to pass, but completely prevent the passage of bulk water. This approach can be used to promote the filtration of oil/water mixtures, and these film-coated substrates can be bent and physically manipulated without affecting oil- and water-wetting properties. Fabrication on three-dimensional macroporous polymer pads yielded flexible objects that float on water and absorb oil at contaminated air/water interfaces. This approach permits oil to be recovered by squeezing or rinsing with solvent and the reuse of these materials without decreases in performance. These pads can also absorb oil from simulated seawater, brine, and other media representative of marine or industrial contexts where oil contamination can occur. Our results address issues associated with the design of polymer-based coatings for the separation, removal, and collection of oil from oil-contaminated water. With further development, this approach could provide low-energy alternatives to conventional remediation methods or yield new strategies that can be implemented in ways that are impractical using current technologies. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3127–3136     

A convection–diffusion porous media model for moisture transport in polymer composites: Model development and validation

Moisture may cause many detrimental effects to polymers and their composites, thus inhibiting the applications of polymeric materials in hot and humid environments. In this article, a convection–diffusion porous media model is derived to better characterize rapid moisture transport in polymer composites at high temperatures. The model considers both continuum diffusion in solid and high‐pressure convection taking place in the pore network. Coupling of convection and diffusion is achieved by combining the law of conservation of mass, Darcy's law, the liquid–vapor chemical equilibrium, and the ideal gas law. The presented model is validated by conducting experimental tests on an epoxy compound. It is found that the proposed convection–diffusion model is more effective than diffusion‐only and convection‐only models for interpreting rapid desorption tests at high temperatures. A numerical study is also performed to predict maximum vapor pressure during a rapid heating process. Vapor pressure is found to be as high as 6.5 MPa at a heating rate of 10 K/s. It is concluded that the convection–diffusion model is able to capture both vapor dynamics and diffusion mechanism in porous polymeric materials, and can be potentially used to further investigate polymer‐moisture interactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1440–1449     

Isosorbide telechelic bio‐based oligomers

This article deals with the preparation of novel co‐oligoethers constituted with 1,3‐propanediol (PDO) and isosorbide units and, prepared according to two different melt processes, without any solvent in the presence of acid catalyst: co‐etherification of PDO and isosorbide (process A) and, trans‐etherification between polytrimethylene ether glycol (PTEG) and isosorbide (process B). Complementary analytical methods: D and 2D ¹H NMR and gas chromatography analysis, coupled with FID and MS‐MALDI‐TOF mass spectrometry, were performed to precisely define the microstructure of the final products. In particular, one can observe that two mechanisms involve during the reaction: etherification and trans‐etherification where isosorbide reacts decreasing the molar mass of polymers chains. This led to oligomers having isosorbide units at each extremity and little inner isosorbide units. Computational calculations have been performed in parallel, and the data well duplicate the experimental results. Finally, it was shown that these new telechelic oligoethers have higher compatibility to water and higher T_g level and thermal stability than PTEG homopolymer. Therefore, such oligomers can be considered as new intermediates for designing new surfactants and/or new copolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2178–2189     

Toward flexible and antibacterial piezoresistive porous devices for wound dressing and motion detectors

Wearable and antibacterial porous devices are promising new multifunctional materials with a wide range of applications in wound dressing and human motion monitoring systems. The deposition of carbon nanotubes and polypyrrole coating on conventional elastomers (polyurethane) is a single‐step procedure that results in a low‐cost, highly conductive, and flexible piezoresistive material with pressure sensitivity of 0.09 kPa⁻¹, Gauge Factor of −10.3, high stability in response to different mechanical efforts and reversible netlike microcracks formation under moderate stretching deformation. The resulting porous material provides direct detection of simple movements from human joints (knee, finger, and elbow) and intrinsic antibacterial activity against Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1063–1072     

Coarse‐grained molecular dynamics simulation study on spherical and tube‐like vesicles formed by amphiphilic copolymers

Molecular‐level understanding of the vesicular structure and formation process is beneficial for potential vesicle applications, especially in drug delivery. In this article, coarse‐grained molecular dynamics simulation was used to study the self‐assembly behavior of amphiphilic poly(acrylic acid)‐b‐polystyrene copolymers in water at different concentrations and PS/PAA block ratios. It was found that various spherical and tube‐like vesicles formed at PS/PAA 3:3 and 4:2. For spherical vesicles, analysis of vesicular structure indicated that the cavity size was influenced by copolymer concentration and wall thickness by the block ratio. Tube‐like vesicle was formed via the fusion of two spherical vesicles, and a key factor for this morphology is polymer movements between inner and outer layer. This simulation study identifies the key factors governing vesicle formation and structure, and provides a guidance to design and prepare various vesicles for wide applications in drug delivery. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1220–1226     

Temperature effects on spreading of water nano‐droplet on poly(methyl methacrylate): A molecular dynamics simulation study

In this article, the effect of temperature on the spreading behavior of a water nano‐droplet on poly(methyl methacrylate) substrate is investigated. The contact angle analysis illustrates that the spreading process occurs in a stage‐like manner and the increase in temperature causes a regime change from partial to total wetting. The interaction energy distributions show that there exist sites on the surface which could trap water molecules and provide a better path for other molecules to overcome the asperities. Estimations of the coefficients of self‐diffusivity suggest that temperature has a major effect in the reorientation stage, which results in the formation of the interfacial layer. In the second stage of spreading, temperature affects the process by providing sufficient energy for water molecules to overcome the interactions with the substrate. Therefore, this stage is controlled by the movement of water molecules on the surface and is highly influenced by their interaction with the surface asperities, strong interaction sites, and the carbonyl groups. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1532–1541     

Continuous flow synthesis of poly(methyl methacrylate) via a light‐mediated controlled radical polymerization

Controlled radical polymerizations have significantly impacted the field of polymer science by facilitating the synthesis of polymers with greater control over molecular weight, structure, and dispersity (Ð). As these synthetic techniques continue to evolve, more degrees of control can be realized via external regulation. Recent work has demonstrated external regulation of a controlled radical polymerization process with light using a photoredox Ir‐catalyst. While light offers many advantages as a stimulus for polymerization, scaling up presents unique challenges such as shallow and uneven penetration of light through the reaction medium, which negatively impacts the rate of polymerization. This work addresses some of the challenges associated with scaling up light‐mediated controlled radical polymerizations by employing a continuous flow microreactor and selecting appropriate reactor materials for oxygen sensitive reactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2693–2698     

Stimuli‐responsive antifouling polyisobutylene‐based biomaterials via modular surface functionalization

This article demonstrates a new, modular approach to surface functionalization that harnesses chain entanglement. A layer of functionalized polyisobutylene, (PIB)‐ω, where ω = ‐OH, ‐thymine (T), ‐hexaethylene glycol (HEG), poly(ethylene glycol) (‐PEG‐OH), methoxy‐functionalized poly(ethylene glycol) (‐PEG‐OCH₃), and ‐tetraethylene glycol‐α‐lipoate (TEG‐αL) was adhered to PIB‐based thermoplastic elastomer (TPE) surfaces. X‐ray photoelectron spectroscopy (XPS) at angles ranging from 20° to 75° showed decreasing polar group concentration with increasing penetration depth, confirming segregation of polar groups toward the surface. Water contact angle (WCA) of the PIB‐based TPE dropped from 95° to 79°?83° upon coating, and soaking in water for 24 h further decreased the WCA. Dynamic WCA measurements showed 40–30° receding angles, showing that stimulus from an aqueous environment elicits enrichment of polar groups on the surface. Fibrinogen (Fg) adsorption on the various surfaces was quantified using surface plasmon resonance (SPR). Static and dynamic WCA did not vary significantly among TPE + PIB‐ω surfaces, but there were dramatic differences in Fg adsorption: 256 ng/cm² was measured on the native TPE, which dropped to 40 and 22 ng/cm² on PIB‐PEG‐OCH₃ and PIB‐PEG‐OH‐coated surfaces. PIB‐TEG‐αL‐coated surfaces presented the lowest Fg adsorption with 14 ng/cm². © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1742–1749     

Effect of the structure of titanium–magnesium catalysts on the morphology of polyethylene produced

The structure and formation of polyethylene (PE) particles on supported titanium–magnesium catalysts having different structural characteristics (sizes of microcrystallites, mesopores, and subparticles) were studied for the first time. Scanning electron microscopy was used to identify structural elements of the polymer particles formed over such catalysts and to reveal morphological changes in the growing polymer particles when the yield was increased from approximately 0.2 g PE/g catalyst to approximately 13 kg PE/g catalyst. A relationship was found between structural characteristics of the porous catalyst particles, morphology of the nascent polymer particles, and bulk density of the polymer powder. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2298–2308     

Preparation and characterization of mesoporous silica thin films from polyethoxysiloxanes

Tetraethoxysilane (TEOS) and polyethoxysiloxanes (PEOSs; prepared by the acid‐catalyzed hydrolytic polycondensation of TEOS) were subjected to the sol–gel process in the presence of cetyltrimethylammonium bromide (CTAB), respectively. The PEOSs with M_w 700–26,000, as prepared by sol–gel coating of TEOS and PEOS under various conditions, were used. Uniform and crack‐free thin films of thickness 276–613 nm were prepared by spin‐coating of a PEOS solution containing CTAB. When the coating films were sintered at 400 °C, the combustion of ethoxy groups and CTAB took place to provide porous silica thin films. The structure of the thin films was found to be dependent on the molecular weight of PEOS and the molar ratio of CTAB/Si: lamellar or hexagonal phase was observed for M_w less than 15,000 and for CTAB/Si molar ratios greater than 0.10. Honeycomb structures were observed for M_w less than 5000 and for CTAB/Si molar ratios of 0.15. The honeycomb structure was also observed by atomic force microscopy and transmission electron microscope. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2542–2550, 2006     

Nanofibers prepared by electrospinning from solutions of biobased polyamide 4

A successful preparation of polyamide 4 nanofibers via electrostatic spinning with diameters close to 100 nm is described. Polyamide 4 was prepared by the anionic ring‐opening polymerization of 2‐pyrrolidone and characterized. The effect of the system parameters (i.e., molar mass of the polymer, the solvent system) and the process parameters (i.e., the electrode‐to‐collector distance) during the electrostatic spinning have been studied. The morphology of the polyamide 4 fiber layers is given except molar mass of the polymer and the concentration of its solution primarily by the conformation of polyamide chains due to polyelectrolyte effect which was confirmed by viscosity measurements. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2203–2210     

On-Water Polymerization of Phenylacetylene Catalyzed by Rh Complexes Bearing Strong π-Acidic Dibenzo[a,e]cyclooctatetraene Ligand

A series of new mononuclear neutral and water-soluble cationic rhodium (Rh) complexes bearing strong π-acidic dibenzo[a,e]cyclooctatetraene (dbcot) diene ligand have been synthesized and structurally characterized. In the polymerization of phenylacetylene, the dbcot Rh complex exhibits higher catalytic activity than the corresponding cod-based Rh complex in both of organic solvent and aqueous media, affording the high cis-transoidal PPAs with up to 99% of cis-contents, moderate molecular weights, and moderate to broad molecular weight distributions. Moreover, on-water polymerization of substituted phenylacetylenes is achieved by these complexes under air atmosphere, in which 3- to 163-fold acceleration of the polymerization rate is observed in aqueous polymerization compared to that in organic solvents. The nature of the Rh complex, solvent, polymerization temperature, and substituted group on the phenylacetylene impact on the polymer's yield, stereoselectivity, molecular weight, and molecular weight distribution. In addition, the water-soluble cationic Rh complexes can be reused for three times. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 716–725