A new model for prediction of the effective permeability of gases in mixed matrix membranes (MMMs), considering the effects of particle shape and the interfacial layer, is presented. The proposed model treats core filler particles and interfacial shell layers as complex particles. Moreover, the Bruggman mathematical procedure is used to improve the accuracy of the presented model for high concentrations of fillers in MMMs. Also, an appropriate uniform criterion is established to make efficient use of the new model for various experimental data to avoid the need for curve‐fitting procedures. Finally, the proposed model is examined for several sets of experimental data.
Photoinitiating systems consisting of a highly porous iron(III)‐based metal‐organic framework (MOF), an iodonium salt, and N‐vinylcarbazole are developed to initiate the free radical promoted cationic polymerization of epoxides under air and the free radical polymerization of acrylates in laminate upon exposure to near UV (385 nm) or visible (405 nm) light‐emitting diodes. These systems present a satisfactory initiating ability. Among the five tested iron carboxylate MOFs exhibiting different compositions and topologies, the flexible microporous iron(III) terephthalate MIL53 is particularly interesting, leading to a final conversion of 58% for the ring‐opening polymerization of epoxides. This provides the possibility of designing MOF/polymer composite materials with enhanced mechanical properties through the in situ incorporation of the MOF structure during the photopolymerization process.
Differential scanning calorimetry (DSC) is used to study the kinetics of the coil‐to‐globule transition in aqueous solutions of poly(N‐isopropoylacrylamide) (PNIPAM) prepared in the bulk (3 and 10 wt%) and nanoconfined (10 wt% inside 30 nm silica pores) forms. It is demonstrated that the kinetics can be described in terms of the classical nucleation model. The proposed treatment affords estimating the free‐energy barrier and pre‐exponential factor of the transition. The application of the nucleation model to the DSC data collected for the three systems studied provides physical insights into the effect of increasing the transition temperature due to dilution and nanoconfinement. Dilution appears to raise the free‐energy barrier, whereas nanoconfinement causes a decrease in the pre‐exponential factor.
Four novel well‐defined polyethylene‐bound antioxidants (PE‐bound antioxidants) with distinct secondary structures are synthesized via transesterification reactions between methyl 3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propionate and hydroxyl‐terminated polyethylenes. The results of thermal gravimetric analysis under an air atmosphere demonstrate that the thermal stabilities of PE‐bound antioxidants are higher than that of commercial antioxidant Irganox1076 and are strongly related to their chemical structures. Particularly, the most thermally stable PE‐bound antioxidant is the one bearing both primary and secondary antioxidant moieties. The antioxidant activities of the PE‐bound antioxidants are evaluated in polypropylene by their melt flow index.
Functional nanowires with photochromic spiropyran (SP) species are prepared by reversible addition–fragmentation transfer (RAFT) dispersion polymerization of styrene using poly(4‐vinylpyridine‐co‐spiropyranyl methacrylate) as a macro‐RAFT agent, and then electrospinning technology is used to fabricate fibers from the functional nanowires. The photoisomerization of SP in the nanowires and fibers is studied, and reversible photochromism for both nanowires and fibers is observed. Since the merocyanine (ME form) of the SP emits fluorescence and the SP form is non‐fluorescent, the fluorescence of the nanowires and the fibers can be switched on and off upon alternating UV and visible‐light irradiation.
The self‐organization of colloids into defined structures offers the possibility to develop novel materials with exciting properties. However, this requires the understanding and application of the forces governing interparticle association. A novel approach for a size‐dependent anisotropic assembly between nanoparticles is achieved. Janus‐like iron oxide/polystyrene hybrid nanocolloids are prepared by heterophase polymerization and selectively coated with silica on the iron oxide face to gradually form a cavity. Hence, a shallow surface around the hydrophobic polymer face is created, enabling smaller particles of the same nature to be locked by shape complementarity and colloidal steric stabilization. Further coating with silica fixes these assemblies and allows quantitative analysis of the interaction on a nanoscale.
Electrochemical oxidative polymerization of rigid, multifunctional monomers allows for the synthesis of microporous thin films with high surface areas. Multifunctional, carbazole‐ and thiophene‐based rigid monomers have been utilized as rigid 3D building blocks (tectons) toward microporous polymer films with relatively smooth surface morphology. Within the last four years, several studies following this approach have been published that report interesting results on the application of these electrogenerated films in organic electronics, photoluminescence‐based or electrochemical chemodetectors, electrochemical supercapacitors, and light‐harvesting antennae for exciton pumping. In this work, the synthetic approaches for the electrochemical polymerization of multifunctional carbazole‐ and thiophene‐based tectons as well as resulting properties and application possibilities of the electrogenerated microporous polymer films are reviewed.
Nitroxide‐mediated polymerization (NMP) affords the synthesis of well‐defined ABA triblock copolymers with polystyrene external blocks and a charged poly(1‐methyl‐3‐(4‐vinylbenzyl)imidazolium bis(trifluoromethane sulfonyl)imide central block. Aqueous size‐exclusion chromatography (SEC) and 1H NMR spectroscopy studies confirm the control of the composition and block lengths for both the central and external blocks. Dynamic mechanical analysis (DMA) reveals a room temperature modulus suitable for fabricating these triblock copolymers into electroactive devices in the presence of an added ionic liquid. Dielectric relaxation spectroscopy (DRS) elucidates the ion‐transport properties of the ABA triblock copolymers with varied compositions. The ionic conductivity in these single‐ion conductors exhibits Vogel–Fulcher–Tammann (VFT) and Arrhenius temperature dependences, and electrode polarization (EP) analysis determines the number density of simultaneously conducting ions and their mobility. The actuators derived from these triblock copolymer membranes experience similar actuation speeds at an applied voltage of 4 V DC, as compared with benchmark Nafion membranes. These tailorable ABA block copolymers are promising candidates for ionic‐polymer device applications.
The study reports the fabrication of a free‐standing reactive macroinitiator thin film via simple layer‐by‐layer assembly and dissolution of the sacrificial layer. The resulting macroinitiator thin film can be postfunctionalized by grafting polymer brush from it. Since the thin film is free from any substrate, bifacial functionalization can be done on the free‐standing film. This approach is expected to significantly increase the functionality of free‐standing polymer brush for most applications like catalysis and sensor because of the increase in functional group density per area.
The inner walls of thin glass capillaries are coated with a reactive precursor coating that can be converted into different temperature‐ and light‐responsive coatings. The switching range of wettability can be determined by measuring the meniscus height of water inside these capillaries at different temperatures and upon UV‐light irradiation. In comparison with the sessile drop measurement, very accurate equilibrium contact angles are obtained by this method.
Renewable alternating aliphatic–aromatic copolyesters are obtained through the polycondensation of biobased diacyl chlorides and bisphenols derived from ferulic acid and biosourced diols. The Tg of these thermoplastics can be tailored to closely match those of petroleum‐based poly(ethylene terephthalate) (PET) and also give access to applications requiring polyesters with lower glass‐transition temperatures.
The synthesis of high‐aspect‐ratio (AR) CdSe (NRs) nanorods and their ordered assembly over large areas are reported. Long‐range ordering of hexagonal arrays of high‐AR NRs is achieved by a combination of controlled solvent evaporation and the use of an applied electric field. Vertically oriented assemblies of CdSe NRs functionalized with oligo‐ and polythiophene are also obtained. Aligned and oriented polythiophene CdSe NRs have potential applications in organic–inorganic hybrid bulk‐heterojunction photovoltaic devices.
Core–corona inversion of micelles of diblock copolymer poly(acrylic acid)‐block‐poly(N‐isopropylacrylamide) (PAA‐b‐PNIPAM), has been successfully realized by switching either pH or temperature. The strong interaction of doxorubicin with the PAA block and the pH‐sensitive drug release from the polymer make the system very useful as a controlled drug delivery system. The encapsulation of hydrophobic Nile Red molecules above the lower critical solution temperature of PNIPAM suggests that this polymer may be useful for removing hydrophobic pollutants.
A facile surface modification procedure for electrospun poly(butylene terephthalate) (PBT) fibers by surface‐initiated atom transfer radical polymerization (SI‐ATRP) is reported. Initiators are introduced through aminolysis and chemical vapor adsorption. SI‐ATRP is subsequently carried out to prepare a polymer‐grafted layer at the PBT fiber surface without altering the fiber geometry. After modification with a zwitterionic poly(sulfobetaine), poly(3‐(N‐2‐methacryloyloxyethyl‐N,N‐dimethyl) ammonatopropanesulfonate), the surface is superhydrophilic. The surface properties are thermally stable due to the high melting temperature of the PBT crystallites and are maintained for a prolonged period.
Polysulfone‐based membranes with excellent chemical resistance and a wet thickness up to 200 μm are obtained via UV curing of unmodified polymers after careful tuning of the photoinitiating system and the crosslinker structure. Combinations of photoinitiator and crosslinker are studied in depth, followed by a characterization of the formed macromolecular structure. The performance of the resulting membranes is then evaluated through long‐term immersion in solvents. Classical depth‐curing acyl phosphine oxide‐based photoinitiators in combination with a pentaacrylate crosslinker are found to be the optimal system.
A synthesis route to siloxane‐based thermoplastic elastomers (TPE) with functional hard blocks is described. The photophysical functionality is provided by oligothiophenes, namely terthiophene and bithiophene. Polyaddition of isocyanate‐bearing thiophenes and amine‐terminated siloxanes yields polymers incorporating a bisurea structure motive. Phase separation and strong hydrogen bonds provide ordering of the thiophenes, which is shown by wide‐angle X‐ray scattering (WAXS) and X‐ray powder diffraction (XRD). Fluorescence measurements reveal a strong red shift of emission of polymer films compared with polymer solutions, thus confirming the existence of hard block segments with an enhanced π system and higher charge–carrier mobility. Tuning of the optical band gap by different polymer compositions and various post polymerization treatments is demonstrated.
A porous polymeric substrate covered with a thin polydimethylsiloxane (PDMS) coating is used for the surface‐initiated polymerization of polyethylene glycol (PEG)‐based polymer brushes. Successful synthesis of the brushes is evidenced by several methods and their impact on the characteristics of the polymeric multilayer substrate is studied. Investigation into the behavior of PEG‐based brushes using atomic force microscopy and multiple transmission‐reflection infrared (MTR‐FTIR) spectroscopy reveals conformational changes of the brush chains upon exposure to carbon dioxide. The results presented here highlight an elegant way to covalently modify porous, PDMS‐coated substrates with polymer brushes to alter their characteristics.
Nonionic aliphatic polymers containing ester and sulfonyl moieties, [poly(ester‐sulfones)s] were found to undergo anode‐selective electrophoresis under electrophoretic deposition conditions. Herein are reported the syntheses of unsaturated nonionic polyesters containing sulfide linkages and double bonds on the polymer backbone via acyclic diene metathesis polymerization using a Grubbs' catalyst. Subsequent oxone oxidation was carried out, affording the corresponding poly(ester‐sulfone), followed by electrophoretic deposition of the unsaturated poly(ester‐sulfone) onto stainless steel. Subsequent UV‐irradiation cured the deposited film, improving the peeling strength of the coating.
In this paper, “star anise”‐like anisotropic micelle (AM) from direct aqueous self‐assembly of poly(ethylene oxide)‐block‐poly(p‐dioxanone) amphiphilic diblock copolymer is presented. By adding poly(ethylene imine) (PEI), the AM shows morphological change from “star anise” to swollen sphere. The mechanism of PEI‐triggered morphological transition involving complexation and weakening of crystallizability is revealed.
The synthesis of three different electron‐deficient internal alkynes for the metal‐free 1,3‐dipolar azide–alkyne cycloaddition is shown. The alkynes are polymerized with several multifunctional azides and the reaction enthalpy (ΔH) is investigated by differential scanning calorimetry (DSC). The mechanical properties of the resulting polymers are analyzed using nanoindentation. The polymerization results in hard materials with an E‐modulus of maximum 2.5 GPa, which make them interesting in particular for biomedical applications.
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