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The intramolecular cross-linking of single polymer chains can form single-chain nanoparticles (SCNPs), which have many applications. In this study, styrenic copolymers with pendent triphenylphosphine as the coordination site for platinum ions (Pt(II)) and benzocyclobutene as the latent reactive groups are synthesized. Triphenylphosphine groups in the chains can coordinate Pt(II) and aid slight single-chain folding in dilute solution. The intramolecular cross-linking caused by the ring-open reaction of benzocyclobutene completes the single-chain collapse and forms stable SCNPs in dilute solution. Pt(II) embedded in SCNPs can be further reduced to platinum atoms (Pt(0)). Pt(0) steadily and atomically dispersed in SCNPs exhibits better catalytic properties than normal polymer carried platinum particles do for the reduction of p-nitrophenol to p-aminophenol.

The ring-forming behavior of polymers with an odd number of arms in highly dilute solutions has been studied using tri-arm polystyrene (PSt3) as a model through combining atom transfer radical polymerization (ATRP) and atom transfer radical coupling (ATRC) technologies. The star polymer, PSt3, with three arms and a central core was obtained by ATRP of styrene using a designed initiator with three active Br terminals and ester groups, followed by the Br terminal–Br terminal radical coupling of PSt3, which was implemented via intramolecular ATRC under high dilution conditions. A tadpole-shaped cyclic polymer (tadpole-PSt) was successfully prepared, proving that there no intermolecular side reactions that occur during the intramolecular ATRC of PSt3. Interestingly, the tadpole-PSt not only possesses a cyclic topology, but also contains a living chain, in contrast to other cyclic analogues that have been previously reported. Finally, the tadpole-PSt was used as a building block to construct a type of barbell polymer (barbell-PSt) by removing most of the solvent via vacuum distillation at the end of the intramolecular ATRC of PSt3. Size exclusion chromatography, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, 1H nuclear magnetic resonance spectroscopy and hydrolysis experiments proved that high-purity cyclic polymers (tadpole-PSt and barbell-PSt) were successfully prepared. The thermal properties of the cyclic and star polymers were analyzed using differential scanning calorimetry and thermogravimetric analysis. The results demonstrated that the formation of a cyclic topology makes a huge contribution to the increase in the glass transition temperature (Tg) and thermal stability of the polymer.

A typical multicyclic branched-topology polystyrene (c-BPS) with high molecular weight (30 K ≤ Mw MALLS ≤ 300 K g mol−1) and narrow dispersity (1.2 ≤ Đ ≤ 1.3) was efficiently synthesized by combining atom transfer radical polymerization (ATRP) and atom transfer radical coupling (ATRC) techniques. The topological constraints imposed by the presence of cyclic units and branch points had a marked influence on the entanglement behaviors of the polymer chains in solution. Therefore, c-BPS possesses the lowest loss modulus (G′′) and viscosity (η), the highest diffusion coefficient (D0), the largest mesh size (ξ) and the fastest terminal relaxation (TR), compared with branched and linear precursors.

In this study, novel shape memory composite of polyolefin elastomer (POE)/lauric acid (LA)/carbon black (CB) nanoparticles with triple-stimuli responsive shape memory effect (SME) is investigated. Crystalline small molecule LA, replacing the commonly used semi-crystalline polymers, is utilized to cooperate with POE and acts as the fixing phase. CB nanoparticles are specifically dispersed in the POE phase, resulting in the formation of intensive conductive pathways and an improvement in the recovery force. The composites can be deformed into arbitrary temporary shapes, and exhibit high shape recovery and fast response to thermo-, electro-, and solvent-stimuli. In our hands, 10 V is capable of triggering shape recovery of the POE/LA/CB (50/50/20) composite, which is undoubtedly safe for a wide range of applications. Excitingly, the electroactive SME of the composites can be conveniently regulated by the CB content and the applied voltage.

Poly(ethylene glycol) methyl ether acrylate (PEGMEA) is copolymerized with 2-(ferrocenecarboxylate ethyl) methacrylate (EMA-Fc) and 4-(propoxy urethane ethyl acrylate) azobenzene (EMA-Azob), respectively. The nanoparticles can be obtained via the single-chain folding of these amphiphilic copolymers with hydrophilic poly(ethylene glycol) (PEG) side chains and hydrophobic ferrocene (or azobenzene) pendant groups in dilute aqueous solution via intramolecular hydrophobic interaction. After the addition of cyclodextrin, the inclusion complex can be formed between cyclodextrin and ferrocene (or azobenzene) pendant groups, which makes the amphiphilic copolymers hydrophilic and triggers the chain unfolding of the nanoparticles in aqueous system. Such kind of process has potential application in the fields of drug delivery systems and their controlled release, sensors, controllable catalysis, mimicry of biomacromolecules, as well as other fields.

Sulfonated polybenzimidazole-polyimide block copolymers are synthesized through condensation polymerization at high temperature. The length of the polyimide chain is varied to give a series of block copolymers with various block lengths. The as-synthesized block polymers are used to prepare the corresponding membranes through the solvent evaporation method. The structure of the block copolymers is characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). Their mechanical strength, thermal behavior, water uptake, swelling ratio, and proton conductivity, as well as oxidative stability are also investigated. All the block copolymers exhibit good thermal stability, dimensional stability, mechanical strength, and proton conductivity. Compared to the random sulfonated polyimide-containing benzimidazole membranes with the same degree of sulfonation, the membranes prepared from the block copolymers show higher proton conductivities. The proton conductivities of the block copolymer membranes range from 6.2 × 10−4 to 1.1 × 10−2 S cm−1 at 105 °C. The block copolymer membrane doped with phosphoric acid exhibits proton conductivity higher than 0.2 S cm−1 at 160 °C, indicating its potential applications in proton exchange membrane fuel cells operated under high temperature and low humidity conditions.

Triple-shape memory polymers (triple-SMPs) have one permanent and two temporary shapes, which enable more complex actuation than traditional dual-SMPs. This work reports a novel polyolefin elastomer (POE)/stearic acid (SA) composite with excellent triple-shape memory and dual-responsive properties. SA displays two well-separated thermal transitions when melt-blending with POE, and is capable of memorizing two temporary shapes under different temperatures. It is found that the robust “house of cards” structure formed by the flake-like SA crystals in the composite is the key player behind the unique behavior. In addition, the actuation of the POE/SA composite can also be triggered upon exposing the material to the appropriate chemical vapor at room temperature. The triple-shape memory and dual-responsive ability atop the simple preparation process dramatically widen the applications of this fantastic material.

A simple and efficient technique was developed to generate continuous polymer nanofibers by combining multilayer co-extrusion with a unique exit cutting die. This is an environment-friendly approach and is capable of converting multilayered films to fibers through a simple physical cutting process. Poly(lactic acid) (PLA) fibers with down to 50 nm width were successfully produced using this new technique. Interestingly, the obtained PLA nanofibers had single crystal structure, which previously formed only in dilute solutions. This new approach creates a highly efficient, versatile, and economic pathway for large-scale fabrication of polymer nanofibers. In principle, it is applicable to any melt-processable polymer, and the obtained nanofibers can be used in wide areas such as transparent nanosheets, membranes, filters, tissue scaffolds, etc.

A feasible method to prepare single-chain polymer nanoparticles (SCNPs) loading metal catalysts via intramolecular collapse of the linear polymers is proposed. Styrene sulfonyl azide/acrylonitrile copolymers are synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Acrylonitrile moieties in the copolymers can adsorb cupric ions and form SCNPs via the thermal decomposition of pendant sulfonyl azide and subsequent intramolecular cross-linking. Then L(+)-ascorbic acid sodium salt is used to reduce these cupric ions into cuprous nanoparticles in SCNPs. The mean diameter of composite SCNPs is in the range of 10–30 nm, in which cuprous moieties (diameter 5–10 nm) are implanted. The size of SCNPs has significant influences on the diameter of loaded cuprous moieties. It is indicated that these single-chain polymer nanoparticles carried cuprous exhibit better catalytic properties for the click reaction of alkyne and azide.

Single-chain nanoparticles can be obtained via single-chain folding assisted by intramolecular crosslinking reversibly or irreversibly. Single-chain folding is also an efficient route to simulate biomacromolecules. In present study, poly(N-hydroxyethylacrylamide-co-4'-(propoxy urethane ethyl acrylate)-2,2':6',2''-terpyridine) (P(HEAm-co-EMA-Tpy)) is synthesized via reversible addition fragmentation chain transfer polymerization. Single-chain folding and intramolecular crosslinking of P(HEAm-co-EMA-Tpy) are achieved via metal coordination chemistry. The intramolecular interaction is characterized on ultraviolet/visible spectrophotometer (UV-vis spectroscopy), proton nuclear magnetic resonance ((1)H NMR), and differential scanning calorimetry (DSC). The supramolecular crosslinking mediated by Fe(2+) plays an important role in the intramolecular collapsing of the single-chain and the formation of the nanoparticles. The size and morphology of the nanoparticles can be controlled reversibly via metal coordination chemistry, which can be characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), and atomic force microscope (AFM).

Nanoclay attapulgite (ATP) was first activated with hydrochloric acid to enhance the surface reactivity, and was then allowed to react with a synthetic aromatic tertiary amine coupling agent to introduce electron-donor groups. Subsequently, the surface-initiated reversible addition–fragmentation chain transfer (SI-RAFT) polymerization of methyl methacrylate (MMA) was carried out in the presence of a free RAFT agent cyanoisopropyl dithiobenzoate (CPDB) initiated by a redox pair made up of benzoyl peroxide (BPO) and aromatic tertiary amine functionalized ATP (ATP-ATA). The grafting process was verified by 1H nuclear magnetic resonance, UV-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, thermo gravimetric analysis, transmission electron microscopy and gel permeation chromatography. Kinetic behavior indicated that polymerization using this redox initiation system displayed a living/controlled nature. Both the grafted and free polymers were grown in a controlled manner, and the RAFT polymerization proceeded with 37.6% monomer conversion achieved within 10 h at 50 °C, yielding about 47.4% grafting ratio of polymer relative to hybrid particles with high affinity to organic media.

The surface grafting of attapulgite (ATP) with polystyrene (PS) was established via a simultaneous reverse and normal initiation atom transfer radical polymerization (SR&NIATRP). 4-(chloromethyl)phenyltrimethoxysilane (CMPTMS) chemical bounded on the surface of ATP (ATP-Cl, Cl-I) was prepared via one-step self-assembly. SR&NI ATRP of styrene was conducted using CuCl2 complex tris(2-(dimethylamino)ethyl)amine (Me6-TREN) as the catalytic system, initiated by 2,2-azobis(isobutyronitrile) (AIBN) and ATP-Cl. FT-IR, XRD, XPS, TGA and TEM data were consistent with the grafting of benzyl chloride groups and PS chains on ATP surface. The controllability of polymerization was investigated by the kinetics behavior under different molar ratio of AIBN and CuCl2. The obtained polymer possessed a uniform distribution of molecular weights with a lower polydispersity index of 1.2∼1.4. The relationship between polymerization on the surface of ATP and in solution was discussed in detail based on TGA data of hybrid particles and GPC trace of free polymer in solution. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015

Single-chain folding via intramolecular noncovalent interaction is regarded as a facile mimicry of biomacromolecules. Single-chain folding and intramolecular crosslinking is also an effective method to prepare polymer nanoparticles. In this study, poly(methyl methacrylate-co−2-ureido-5-deazapterines functionalized ethylene methacrylate) (P(MMA-co-EMA-DeAP)) is synthesized via free radical polymerization. The single-chain folding of P(MMA-co-EMA-DeAP) and the formation of the nanoparticles in diluted solution (concentration

Researchers have developed many types of nanoscale materials with different properties. Among them, nanofibers have recently attracted increasing interest and attention due to their functional versatility and potential applications in diverse industries, including tapes, filtration, energy generation, and biomedical technologies. Nanolayer coextrusion, a novel polymer melt fiber processing technology, has gradually received attention due to its environmental friendliness, efficiency, simplicity and ability to be mass-produced. Compared with conventional techniques, nanolayer coextruded non-woven nanofibrous mats offer advantages such as a tunable fiber diameter, high porosity, high surface area to volume ratio, and the potential to manufacture composite nanofibers with different components to achieve desired structures and properties. Dozens of thermoplastic polymers have been coextruded for various applications, and the variety of polymers has gradually continued to increase. This review presents an overview of the nanolayer coextrusion technique and its promising advantages and potential applications. We discuss nanolayer coextrusion theory and the parameters (polymer and processing) that significantly affect the fiber morphology and properties. We focus on varied applications of nanolayer coextruded fibers in different fields and conclude by describing the future potential of this novel technology.

Styrenic copolymers with fluorescent anthracene and crosslinkable groups are prepared from styrene (St)/methyl methacrylate (MMA)/1-(azidomethyl)-4-vinylbenzene copolymers (PS-N3), 9-((prop-2-ynyloxy)methyl) anthracene, and 3-(4-ethoxyphenyl)-3,4-dihydro-2H-benzo[e] [1] , [3] oxazine via click chemistry. The fluorescence-labeled nanoparticles are thus prepared via single-chain folding and intramolecular crosslinking in the ultradiluted solution of the polymers with anthracene and benzoxazine functionalities. MMA in the nanoparticles are then hydrolyzed into methacrylic acid, and the nanoparticles become partially hydrophilic. The dimension of the nanoparticles can be controlled in 5–20 nm. Such kind of nanoparticles exhibits excellent fluorescence performance at 412 nm when irradiated under the light of 367 nm.

Fluorine-containing polyimide (FPI) with hydroxyl groups is synthesized from 4,4′-(hexafluoro isopropylidene) diphthalic anhydride (6FDA), 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane (6FAP), and 4,4′-diaminodiphenyl ether (ODA) via high temperature polycondensation. Thereafter, alkynyl groups are introduced into FPI. During the preparation of the composite membrane, alkynyl groups on FPI react with azido methyl of 4,4′-bis(azido methyl) biphenyl via click chemistry and form semi-interpenetrating polymer network (semi-IPN) structure within the composite membranes. The mechanical properties, thermal behavior, water uptake, swelling ratio, proton conductivity, oxidative stability, as well as the performance in single cell operation are investigated. Compared to pure perfluorosulfonic acid (PFSA) polymer membrane, the composite membranes based on semi-IPN of FPI and PFSA exhibit improved mechanical properties, excellent thermal and dimensional stabilities, and suitable proton conductivity. The tensile strength of the composite membranes ranges from 28.0 to 67.0 MPa. With increasing FPI content in the membranes, the dimensional stability of the composite membranes increases. The composite membranes have the proton conductivity from 4.3 × 10 −2 S·cm −1 to 1.0 × 10 −1 S·cm −1 at 100 °C and also have good performances as proton exchange membrane (PEM) in single cell at 80 °C.

O-alkylation of highly polar polyglycerol with alkyl bromides, promoted just by sodium hydroxide in dimethyl sulfoxide (DMSO), is reported. Zimmermann–Dathe type Williamson etherification, which can be carried out by a mild base in DMSO, is very useful in preparing ethers. However, it is always limited to alkyl chlorides or methyl halides due to the elimination reaction. In this contribution, this reaction is promoted to alkyl bromides and iodides just by decreasing the reaction temperature and then it is further applied in preparing a series of O-alkylated hyperbranched polyglycerol (PG). It is found per-alkylation of PG is possible regardless of its dense hydroxyl groups. In addition, the modified method shows selectivity over the halogen species. The resulting core–shell amphiphilic macromolecules (CAMs) can be used for dye encapsulation and they show core-dependent selection over the dye species. For example, the ether-based CAM 1b (PG–O–(C16) 0.61 , 61% of OH groups are O-alkylated by cetyls) is with limited difference from the ester-based CAM 2a ( PG–COO–(C16) 0.60 ), but they show very different guest selection. Controlled release is also available by core design of the CAMs.

A universal method to prepare proton exchange membrane (PEM) with semi-interpenetrating polymer network (semi-IPN) via a versatile crosslinker 1,3-benzenedisulfonyl azide (1,3-BDSA) is proposed. Sulfonyl azide groups can react with any polymer with carbon-hydrogen bonds via hydrogen abstraction. Polyvinylidene fluoride (PVDF) and perfluorosulfonic acid (PFSA) polymer are selected as two precursors for semi-IPN. When 1,3-BDSA is heated to a sufficiently high temperature it can form the nitrene and connect with PVDF via hydrogen abstraction reaction, recombination, or CH-bond insertion. The crosslinking structure of PVDF is formed, and semi-IPN is constructed in the presence of PFSA at the same time. The mechanical properties, degree of crosslinking, water uptake, and proton conductivity of semi-IPN membranes are investigated. Compared with pure PFSA membrane, the mechanical properties and the dimensional stability of the semi-IPN membranes are improved significantly. The tensile strength of the composite membrane (27.2 MPa) is much higher than that of PFSA membrane (10.1 MPa). The maximum power density of the composite membrane can reach 382 mW cm −2 at 940 mA cm −2 . Sulfonyl azide based crosslinkers can be used to prepare semi-IPN or IPN PEMs from any paired polymers with carbon–hydrogen bonds.

Amphoteric polymers have been studied for various applications such as separation of low molecular weight organic molecules from inorganic salt mixtures, selective ion transport, drug delivery through membranes of biological interest, separation of ionic drugs and proteins, and separation of alcohol and water. Typical amphoteric polymers consist of weak base and weak acid groups. In present study, the copolymerization of 5-vinyltetrazole (VT) and diisopropyl-p-vinylbenzyl phosphate (DIPVBP) via free radical polymerization is studied. The reactivity ratio of VT and DIPVBP, which is calculated from Kelen-Tudos plot, is 0.251 and 0.345, respectively. The amphoteric copolymer of VT and diisopropyl-p-vinylbenzyl phosphonic acid (poly(VT-co-VBPA)) is obtained from hydrolysis of the copolymer of VT and DIPVBP (poly(VT-co-DIPVBP)). Poly(VT-co-VBPA) is thermally stable under 190 °C. The anhydrous proton conductivity of amphoteric poly(VT-co-VBPA) can reach 1.54 × 10-4 S cm−1 at 170 °C with an activation energy of 114.7 kJ mol−1. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3486–3493

The reinforced composite membranes based on Nafion ® membranes attract a lot of attention as proton exchange membrane (PEM) for polymer electrolyte membrane fuel cells (PEMFCs). Fluorine-containing polyimide (FPI), end-capped with alkynyl, is synthesized from 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 2,2′-bis(trifluoromethyl)- 4,4′-diaminobiphenyl (TFMB), and 3-aminophenylacetylene (APA). The chemical structure of FPI is characterized by 1 H-NMR. The reinforced composite membrane based-on semi-interpenetrating polymer network (semi-IPN) is prepared via solution casting of FPI and Nafion ® 212, and crosslinking thereafter. During the membrane preparation, alkynyl in FPI reacts with azide and itself via click chemistry and addition polymerization. The water uptake, swelling ratio, mechanical properties, thermal behavior, proton conductivity, and oxidative stability of the composite membranes are investigated. Compared to Nafion ® 212, the composite membrane shows improved thermal stability, mechanical properties, and dimensional stability. The tensile strength of the composite membranes is in the range of 35.0–55.6 MPa, which is much higher than that of Nafion ® 212 membrane. The composite membranes show considerable proton conductivity from 2.0 × 10 −2 S cm −1 to 9.9 × 10 −2 S cm −1 at a temperature range from 30 °C to 100 °C, depending on FPI content.

Poly(N-(2-hydroxyethyl)acrylamide) with pendant β-cyclodextrin is synthesized and intramolecularly crosslinked with bridged bis(ferrocene). This supramolecular nanoparticle can be changed reversibly between a coil and a nanoparticle upon external voltage stimuli.

A new method to prepare reinforced proton exchange membranes (PEMs) for polymer electrolyte membrane fuel cells (PEMFCs), which can work either in humidified environment or at anhydrous state, is proposed via constructing semi-interpenetrating polymer network (semi-IPN) of polybenzimidazole (PBI) and perfluorosulfonic acid polymer, with poly(vinylbenzyl phosphonic acid) functionalized hollow silica spheres (HPSS) as the additive. Vinyl functionalized PBI, which is synthesized from poly[2,2′-(m-phenylene)-5,5′-bibenzimidazole] and p-vinylbenzyl chloride, is thermally crosslinked in the presence of Nafion ® as well as HPSS during the membrane preparation. Thus semi-IPN structure is formed in the composite membranes. Compared with Nafion ® , the composite membranes show higher thermal stability and water uptake, wider range of working temperature, improved mechanical properties, as well as better dimensional stability. Under humidified condition, the proton conductivity of the composite membranes is mainly provided by hydrated Nafion ® , whereas PBI and the acidic moieties in the membranes contribute to the proton conductivity at higher temperature and anhydrous state. HPSS in the composite membranes behave like the micro-reservoir and help provide proton conductivity at the state between hydrated and anhydrous states.

A facile crosslinking method of polybenzimidazole (PBI) with sulfonyl azide groups (sPBI-SA) for proton conducting membranes is proposed. Thermally crosslinkable sPBI-SA is synthesized from sulfonated PBI (sPBI) and sodium azide. The structures of sPBI, sPBI-SA, and crosslinked sPBI are confirmed by FTIR and 1H NMR. Upon heating, sPBI-SA loses nitrogen and form nitrene, which reacts with CH-bond of the backbone of another chain of PBI via the reactions of hydrogen abstraction, recombination, or CH-bond insertion. The crosslinking structure of PBI membranes is thus formed. Compared with the uncrosslinked membranes, the crosslinked sPBI membranes exhibit improved tensile strength, migration stability of phosphoric acid (PA), dimensional stability, and chemical oxidative stability. Whereas, the doping ability of PA and the proton conductivity of the crosslinked membranes decrease a little.

Poly(2,2′-imidazole-5,5′-bibenzimidazole) (PBI-imi) was synthesized via the polycondensation between 3,3′,4,4′-tetraaminobiphenyl and 4,5-imidazole-dicarboxylic acid. Effects of the reaction conditions on the intrinsic viscosity of the synthesized polymers were studied. The results show that the molecular weight of the polymers increases with increasing monomer concentration and reaction time, and then levels off. With higher reaction temperature, the molecular weight of the polymer is higher. With the additional imidazole group in the backbone, PBI-imi shows improved phosphoric acid doping ability, as well as a little higher proton conductivity when compared with widely used poly[2,2′-(m-phenylene)-5,5′-bibenzimidazole] (PBI-ph).Whereas, PBI-imi and PBI-ph have the similar chemical oxidation stability. PBI-imi/3.0 H3PO4 composite membranes exhibit a proton conductivity as high as 10–4 S cm–1 at 150 °C under anhydrous condition. The temperature dependence of proton conductivity of acid doped PBI-imi can be modeled by an Arrhenius equation.

A new approach to prepare polymeric nanoparticles via intramolecular collapse of single chain of sulfonyl azide functionalized polymers is proposed. Upon heating, the sulfonyl azide functionalized linear copolymers lose nitrogen and form nitrene. This nitrene reacts with C H bond of the backbone in dilute solution and leads to the efficient intramolecular crosslinking and formation of nanoparticles where the diameter of nanoparticles can be controlled by both the molecular weight and the content of sulfonyl azide groups. A significant reduction in the hydrodynamic volume is observed on going from the starting random coil of linear chains to the corresponding nanoparticles. The morphology and the dimension of nanoparticles are characterized by using transmission electron microscope (TEM), atomic force microscopy (AFM), as well as dynamic laser scattering (DLS).

A new method to prepare proton exchange membranes based on semi-interpenetrating polymer networks (semi-IPN) of Nafion® and poly(vinylidene fluoride) (PVDF) via radiation crosslinking was proposed. The tensile strength, degree of crosslinking, water uptake, and swelling ratio of the composite membranes were studied. Compared to the recast Nafion®212 membrane, the composite membranes show much better mechanical properties and improved dimensional stability. The tensile strength of the composite membranes ranges from 34.3 MPa to 53.4 MPa, which is higher than that of the recast Nafion®212 membrane (23.9 MPa). The dimensional stability of the composite membranes also increases with increasing PVDF content in the membranes. The composite membranes show considerable proton conductivity even at 100–120 °C. The membrane containing 40% PVDF shows the highest proton conductivity of 3.37 × 10−2 S/cm at 115 °C. These properties make them a great potential in polymer electrolyte membrane fuel cells (PEMFC).

The chemical oxidative stabilities of poly(2,2-(m-phenylene)-5,5-bibenzimidazole) (PBI-ph), poly(2,5-benzimidazole) (ABPBI), poly(2,2′-hexyl-5,5′-bibenzimidazole) (PBI-hex), and poly(2,2′-imidazole-5,5′-bibenzimidazole) (PBI-imi) are studied. By means of FTIR and 1HNMR analysis, more information about the degradation process of PBI-ph is found as: CH2 groups are left in the residual polymers; after the N–H bond and the trisubstituted benzene ring are oxidized by oxidative free radicals, the meta-phenylene is relatively stable. Through Fenton tests, the chemical oxidative stabilities of these PBIs are compared and results show that PBI-ph is the stablest material while PBI-imi is the unstablest one. Through FTIR analysis, the structure changes to those degraded PBIs are compared. The conjugated structure formed between meta-phenyl and benzimidazole can protect the main chain of PBI-ph from the attack of oxidative free radicals. Additionally, effects of acid on PBI-ph degradation rate are evaluated and the results show that phosphoric acid can slow down the chemical oxidative degradation.

A series of reinforced composite membranes were prepared from Nafion ® 212 and crosslinkable fluorine-containing polyimide (FPI) with various crosslinkers. The crosslinkable FPI reacts with the crosslinkers and forms semi-interpenetrating polymer networks (semi-IPN) structure with Nafion ® 212. The water uptake, swelling ratio, mechanical properties, thermal behavior, proton conductivity, and chemical oxidation stability of the composite membranes are studied. The degree of crosslinking is characterized by gel fraction of the composite membranes. Compared to pure Nafion ® 212, the composite membranes exhibit excellent thermal stability, improved mechanical properties and dimensional stability. The tensile strength of the composite membranes is in the range of 37.3–51.2 MPa. All the composite membranes exhibit high proton conductivity which ranges from 1.9 × 10 −2 to 9.9 × 10 −2 S cm −1 . The proton conductivity of the composite membrane with 2-propene-1-sulfonic acid sodium salt (SAS) as the crosslinker is 9.9 × 10 −2 S cm −1 at 100 °C which is similar to that of Nafion ® 212 under the same condition.

The proton conductivity of perfluorosulfonic polymers, such as Nafion ® , increases with increasing relative humidity and decreases enormously after 80 °C at the standard atmosphere due to the dehydration of the membranes. In present study, a new strategy to prepare the proton conducting membrane with higher water retaining capacity via the composite of perfluorosulfonic polymer and the hollow nanosphere of sulfonated polystyrene (sPS) is proposed. The hydrophilic and hollow nanospheres of sPS were prepared via the template polymerization. Thermogravimetric analysis (TGA) results show that the hollow sPS nanospheres exhibit an additional weight loss peak of dehydration at 136 °C besides that at 80 °C. Compared to 85–90 °C of the normal hydrated Nafion ® membranes without nanospheres, the maximum temperature for dehydration in proton exchange membranes (PEMs) based on the composite of perfluorosulfonic polymer and hydrophilic hollow nanospheres is 30 °C higher. The hollow nanosphere with a nano-hole on the shell, in which the nano-hole may be formed during the etching of the template, behaves like a reservoir and provides necessary water above 100 °C as the boiling point of the water through the nano-hole is higher than 100 °C. The dehydration of the hollow nanosphere is significantly more difficult than that of the hollow sphere with micron-scale.

Two new kinds of fluorine-containing polybenzimidazoles (PBI), poly(2,2′-(tetrafluoro-p-phenylene)-5,5′-bibenzimidazole) and poly(2,2′-tetradecafluoroheptylene-5,5′-bibenzimidazole), were synthesized by condensation polymerization of 3,3′-diaminobenzidine and perfluoroterephthalic acid (or perfluoroazelaic acid), with polyphosphoric acid as solvent. Thermogravimetric analysis results show that the fluorine-containing polymers synthesized exhibit promising thermal stability. The film-forming properties of the fluorine-containing polymers are improved over nonfluorinated PBI. The introduction of fluorine into the backbone of the polymers has significant positive affection on their chemical oxidation stability demonstrated by Fenton test. Compared with poly(2,2′-(m-phenylene)-5,5′-bibenzimidazole)/phosphoric acid (PA) composite membrane, the resulting fluorinated membranes with a same PA doping level exhibit better flexibility and higher proton conductivity. The maximum proton conductivity gained is 3.05 × 10−2 S/cm at 150 °C with a PA doping level of 7. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2115–2122, 2010

A series of reinforced composite membranes as proton exchange membranes were prepared from Nafion®212 and crosslinkable fluorine-containing polyimides (FPI). FPI was prepared from the polymerization of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFMB), and 3,5-diaminobenzoic acid (DABA). Then FPI was thermally crosslinked during the membrane preparation and formed the semi-interpenetrating polymer networks (semi-IPN) structure in the composite membranes. The thermal properties of the composite membranes were characterized by thermogravimetric analysis. The crosslinking density of FPI in the composite membranes was evaluated by the gel fraction. These membranes showed excellent thermal stabilities and good oxidative stabilities. Compared with Nafion®212, the obtained composite membranes displayed much improved mechanical properties and dimensional stabilities. The tensile strength of the composite membranes was more than twice that of Nafion®212. The composite membranes exhibited high proton conductivity, which ranged from 2.3 × 10−2 S cm−1 to 9.1 × 10−2 S cm−1. All membranes showed an increase in proton conductivity with temperature elevation.

Fluorine-containing polyimide with crosslinkable vinyl group (FPI) was synthesized from 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (PFMB), and 4-amino styrene (AS). The reinforced composite membranes based on semi-interpenetrating polymer networks (semi-IPN) were prepared via solution casting of FPI and Nafion ® 212, and crosslinking thereafter. The water uptake, swelling ratio, mechanical properties, thermal behavior, proton conductivity, and oxidative stability of the composite membranes were investigated. Compared with the recast Nafion ® 212, the composite membrane shows better mechanical properties and improved dimensional stability. The tensile strength of the composite membranes ranges from 39.0 MPa to 80.0 MPa, which is higher than that of the recast Nafion ® 212 membrane (26.6 MPa). The dimensional stability of the composite membranes increases with increasing FPI content in the membranes, whereas the proton conductivity decreases. The composite membranes show considerable proton conductivity from 2.0 × 10 −2 S cm −1 to 8.9 × 10 −2 S cm −1 at a temperature from 30 °C to 100 °C, depending on the FPI contents. The composite membranes with semi-IPN from FPI and Nafion ® 212 have considerable high proton conductivity, excellent mechanical properties, thermal and dimensional stabilities.

Soft magnetic composite particles of reduced iron coated with ultrathin films of poly(p-xylylene) (PPX) were prepared via chemical vapor deposition (CVD) polymerization. The structure, morphology, magnetic properties, and chemical stability of PPX encapsulated reduced iron particles were studied. It can be confirmed from FTIR spectrum that the polymer covered outside the reduced iron particles is PPX. The thickness of PPX film is averagely 100 nm according to the results of transmission electron microscopy (TEM). The mean diameter of the composite particles is about 6.0 μm. The resistance to thermooxidation of the composite particles is much higher than that of the reduced iron particles due to the protection of PPX ultrathin film outside the iron powder. After being encapsulated with PPX ultrathin film, the resistance to acidic corrosion of the reduced iron particles is obviously improved. Although the saturation magnetization (Bs) of the composite particles is reduced from 1.42 T to 1.33 T after the coating process, their coercive force (Hc) decreases from 10.6 kA/m to 6.02 kA/m, which is advantageous for the application of soft magnetic particles in MR fluid.

A novel approach toward the preparation of newly UV-curable polyurethane coatings composed of multifunctional thiol- and ene-terminated polyurethane aqueous dispersions is presented. By a synergistic combination of polyurethane dispersions synthesis and thiol-ene chemistry, strategies for the preparation of newly UV-curable polyurethane coatings are developed. Photo-DSC, real-time FTIR, DMA and tensile tests measurements are used to investigate the photopolymerization and mechanical behaviors of newly UV-curable polyurethane coatings. The newly polyurethane coatings have 1.5 times higher polymerization rate and final 99% functional groups conversion in air conditions compared to current urethane-acrylate based UV-curable polyurethane dispersions coatings. UV-cured polyurethane films prepared by this method are also found to exhibit increase in Young's modulus and tensile strength at break by 25% and 10%, respectively. These experiment facts suggest that the incorporation of thiol-ene chemistry to the polyurethane dispersion coatings increase their polymerization rate, producing a high degree of cross-linking. This confirms the preparation of the targeted novel UV-curable polyurethane coatings and reveals the dramatic effect that changes in incorporation of thiol-ene chemistry can have on the photopolymerization behaviors of UV-curable polyurethane dispersions coatings systems.

The chemical oxidative degradation process of poly [2,2′-(m-phenylene)-5,5′-bibenzimidazole] (PBI) in simulated environment of fuel cells was evaluated. From the mechanical properties and the intrinsic viscosity of PBI, it was observed that the stress at break of PBI membranes decreased and the macromolecular chains of PBI were broken after the treatment in Fenton reagent for 24 h. From the photos of Scanning Electron Microscope, it was identified that there were lots of corroded holes in PBI membranes. By means of FTIR and 1 H NMR analysis, it was shown that during the treatment of PBI in the presence of HO or HOO free radicals the hydrogen atom of N–H bond in imidazole ring was liable to be oxidized, and the phenyl was oxidized with the formation of quinine and dicarboxylic acid structures. In the end, the possible mechanism of the chemical oxidative degradation of PBI was proposed.

In this work, sulfonic acid functionalized hollow silica spheres (SAFHSS)/Nafion® composite membranes were prepared by a recasting procedure. The influences of temperature on water uptake, swelling degree, and proton conductivity of the composite membranes were studied. In comparison with the pure recast Nafion® membrane, it was found that water uptake of composite membranes increased with increasing SAFHSS loading at all temperature studied. The swelling degree of SAFHSS/Nafion® composite membranes with 10∼15 wt % SAFHSS loading was lower than that of the pure recast Nafion® at all temperatures in the study. The proton conductivity of SAFHSS/Nafion® composite membranes was constantly higher than that of the pure recast Nafion® at all temperatures (50∼130 °C). In a range from 50 to 130 °C, the highest conductivity of composite membranes was obtained when 10 wt % SAFHSS was loaded. The maximum conductivity reached 0.1 S cm−1 at 100% relative humidity and 100 °C, even the temperature reached to 130 °C, the conductivity of the composite membranes with 10 wt % SAFHSS was still as high as 4.4 × 10−2 S cm−1 at 100% relative humidity, whereas the conductivity of the pure recast Nafion® was only 2.2 × 10−3 S cm−1. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2647–2655, 2009

Relatively low thermal stability of second-order nonlinear optical (NLO) coefficient due to the relaxation of dipole orientation is a major problem limiting the practical application of these NLO polymers. NLO polymers with suitable Tg are always important for optical devices. In the present work a synthetic approach to styrene-(N-(4-hydroxyphenyl) maleimide) copolymer (SHMI) with 4-[N-ethyl-N-(2-hydroxyethyl) amino]-4′-nitroazobenzene (DR1) as side chain and chromophores has made it possible to efficiently prepare a NLO polymer. The copolymer with high Tg of 202°C has low relaxation of dipole orientation. The maximum optical loss at the optical communication wavelength is less than 0.9 dB. NLO coefficient r33 is 8.2 pm/V (1550 nm) and its maximum relaxation at room temperature is 18%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Two hyperbranched polyglycerols (PG) (1a: Mn = 2000, 1b: Mn = 8000), both with 61% of the overall hydroxyl groups being transformed into trithiocarbonates (2a, 2b, with 16 and 65 OH groups being replaced by trithiocarbonates, respectively), can be used as a reversible addition-fragmentation chain transfer (RAFT) agent. Polymerization of styrene mediated by 2a/2b was in a living manner, resulting in star-like, amphiphilic, core-shell structured polymers with 16 arms (3a) and 65 arms (3b), respectively. It was found that for system mediated by 2b, more serious side reaction (radical–radical coupling) occurred than that by 2a, most probably due to their difference in shell congestion. A shell-crosslinked polymer could be prepared in the presence of divinylbenzene via a one-pot route at solid content up to 20%, but analysis proved the crosslinking was incomplete. Furthermore, the 65-arm-star polymer (3b) more tended to undergo macroscopic rather than intramolecular crosslinking than the 16-arm-star polymer (3a) did. The phenomenon might again be attributed to their difference in shell congestion. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Homopolymerization of N-pyrimidinyl acrylamide (NPA) was reported for the first time. The polymer (polyNPA) was soluble only in acidic media and fluoroalcohols, and only in fluoroalcohol was homogeneous polymerization of NPA feasible. 1H NMR analysis proved that a 1:1 H-bonding complex could be formed between NPA and α,α-bis(trifluoromethyl)phenyl propan-2-ol (BTMP). Cumyl dithiobenzoate mediated reversible addition-fragmentation chain transfer (RAFT) polymerization of NPA in BTMP was carried out. 1H NMR analyses proved that the molecular weight increased linearly with the monomer conversion. The polymer prepared in conventional solvents was atactic while in protic media the syndiotacticity was slightly enhanced.

The synthesis of a thioether inserted, core-shell structured polymer from the scaffold of hyperbranched polyglycerol (PG) was described. PG was first allyl functionalized, and in the presence of AIBN, the allyl groups further underwent radical addition to thiol compounds, thus thiol functional polyethylene oxide monomether (MPEO) were grafted onto PG. Similarly, 2-mercaptoethy-lammonium chloride was introduced onto PG via thiol addition, and the residual amino groups were further quaternized with decyl bromide, leading to an amphiphilic core-shell structure polymer.

Using a well-designed three-layer onion-like polymer as template, a one-pot procedure that led to stable, narrow-sized and thermoresponsive Pt nanocomposites is described. The polymer consists of an outer shell of thermoresponsive poly( N -isopropylacrylamide), an inner shell of crosslinked poly( N,N -dimethylaminoethyl acrylate) and a hyperbranched polyglycerol core. The core is physically trapped by the shell, with a few thiol groups located on the interface between the core and the shell. The polymer is used as a template for the synthesis of platinum nanoparticles, 1 H NMR and TEM analyses suggest that the in-situ produced, narrow-sized Pt nanoparticle is loaded in the core part of the polymer so that the nanocomposite retains thermoresponsive activity.

Poly(1,2,4-vinyltriazole) (PVTr) and poly(1,2,4-vinyltriazole-co-5-vinyltetrazole-co-acrylonitrile) (P(VTr-VT-AN)) were prepared by normal free radical polymerization and click chemistry, respectively. The structure of the polymers was characterized by FTIR spectra, H NMR spectrum and elemental analysis. Compared with polybenzimidazole (PBI) which is one of the most widely studied anhydrous proton conducting polymers, the solubility of vinyltriazole-based polymers is improved significantly. They are soluble in a lot of polar solvents. The glass-transition temperatures of such kind of polymers are between 70 and 85 °C, thus indirectly indicating the improvement of fabricating properties. In phosphoric acid doped membranes, the higher the basicity of the vinyltriazole-based polymers is, the higher the proton conductivity is. The temperature dependence of the proton conductivity of the acid doped membranes can always be fitted by a simple Arrhenius equation. Transmittance of phosphoric acid doped vinyltriazole-based polymers is above 80% in the range of visual spectra and changes a little with the different structure and basicity of the copolymers.

A continuous glass fiber (GF) roving reinforced polypropylene (PP) tape is prepared with a pin-assisted-melt impregnation set-up. This study originally applied the Taguchi method to statistically assess the effect of selected impregnation parameters on the impregnation process, and to optimize the parameters to realize a high quality impregnated tape. The quality of the impregnated tape is characterized by the degree of impregnation, ratio of the impregnated fiber number to the total fiber number. According to the Taguchi method, impregnation experiments are designed and the experimental results are analyzed. An optimal parameter combination is determined, which led to a degree of impregnation more than 94%. Analysis of variance (ANOVA) was performed on the measured data and S/N (signal to noise) ratios. The results indicated that pulling speed, melt temperature, and the number of impregnation pins are the significant factors in a declining sequence affecting the impregnation process.

The multiwalled carbon nanotubes (MWCNT) covalently bonded by polyvinylimidazole (PVI) (MWCNT-b-PVI) were synthesized and both their chemical and aggregated structures were characterized by means of TEM, IR, XRD and SEM measurements. MWCNT-b-PVI showed enhanced chemical stability in many common solvents and enhanced thermal stability. It will supply a new way to synthesize functional materials with new optical, magnetic and electrical properties, combining excellent mechanics, heat-stabilization, optical, electrical, processing and film forming properties of carbon nanotubes and heterocyclic polymer.

Polybenzimidazole (PBI)/polyimide (PI) and PBI/polyvinylpyrrolidone (PVP) blends were prepared. All of these polymers are suitable for acid doping as a matrix because of the existence of the N-heterocycle in the polymers, which can eventually be used as proton conductors. The miscibility of PBI/PVP blend is confirmed by Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM), while the miscibility of PBI/PI is already reported in references. Temperature dependence of proton conductivity of acid doped PBI/PI and PBI/PVP blends are studied. As the temperature increases, proton conductivity of H3PO4 doped PBI/PVP blends increases. Temperature dependence of proton conductivity of the blends can still be fitted by a simple Arrhenius relation. The proton transport of the blend is similar to that of PBI. The methanol permeability of PBI/PI blends is also studied. Methanol permeability in PBI/PI, PI, and PBI membranes decreases with increasing methanol concentration. POLYM. ENG. SCI., 45:1395–1400, 2005. © 2005 Society of Plastics Engineers

Highly efficient and charge-selective adsorption and desorption of peptides at trace level by a solid-phase adsorbent is described. The adsorbent of SiO2@PEI is synthesized by covalent immobilization of branched polyethylenimines (PEI) exclusively on the outer surface of the porous silica particles (∼300 μm). For aqueous peptides (Mw = 600-3000 Da), SiO2@PEI can capture the negatively charged ones and leave the positively charged ones intact, and by adjusting pH of the system peptides with different isoelectric points (pIs) can be well separated. Targeted peptide at low abundance (at least as low as 0.1 mol % with respect to the highest one) can be well separated. The association constants of K10(12) M(-1) at pHpI and K10(4) M(-1) at pHpI are found; that is, selectivity10(8) is generally available. Thus, a peptide even at sub-femtomolar level can be extracted and eluted for analysis, and efficient recovery (79-92%) of the peptides is found. The extraction is mainly promoted by multisite electrostatic interaction, and the hydrophilic and cationic properties of PEI at low pH play a unique role in desorption efficiency and selectivity. The unbiased nature of this method renders the adsorbent applicable to the efficient separation of a broad spectrum of peptides, including those with similar pIs.

The temperature and pressure dependent conductivities of poly(4-vinylimidazole) (P4VI) blended with H 3 PO 4 or H 2 SO 4 have been studied. The influence of the temperature on the conductance and activation volume is discussed. The temperature dependent conducti samples in the glassy state can be fitted with a simple Arrhenius relation. The logarithm of relative conductance for P4VI blended with H 3 PO 4 decreases linearly with increasing pressure. With decreasing temperature the conductance decrease becomes more pronounced. It is proposed that the proton transport in P4VI with low acid concentrations is mainly controlled by a proton hopping mechanism. At high acid levels the proton transport is controlled by both proton hopping and segmental motion of the polymer. The glass transition marks a change in the proton transport mechanism, which is also reflected in the abnormal behavior of the activation volume of the conductance. The conductivities of P4VI blended with H 3 PO 4 and H 2 SO 4 are compared. The conductivity of H 3 PO 4 blended P4VI is lower than that of H 2 SO 4 blended P4VI at the same acid concentrations.

Polycarbonate (PC)/polystyrene (PS) blend is a typical immiscible system. It is, however, still transparent. In this paper, this irregular phenomenon is clarified experimentally and theoretically. A new method of obtaining birefringence-free polymers without sacrificing orientation in materials is proposed. This involves combining suitable amounts of PC and PS in the form of a blend. The observed drastic reduction in birefringence is the result of the compensation of positive and negative contributions to the overall birefringence. ©1997 SCI

Polycarbonate (PC)/polystyrene (PS) blend is an immiscible system. The use of copolymers as compatibilizers in blends of immiscible polymers is one approach which is being developed within the larger field of polymer blends and alloys. The methods for preparing PC–PS copolymers are difficult and complicated. In this paper, a new method for preparing PC–PS graft copolymer, PC-g-PS, by radiation grafting is proposed. The structure of the graft copolymer was confirmed by IR spectroscopy. Various factors which can be used to control the reaction have been studied. The molecular weight of the PS graft chain was determined by gel permeation chromatography after degrading the copolymer in aqueous sodium hydroxide and dichloromethane. The thermal properties of the copolymer have also been measured. © 1997 SCI.

A new single-/two-photon sensitive monomer, (E)-5-(4-ethoxystyryl)−2-nitrobenzyl methacrylate (ENbMA), was synthesized and copolymerized with methyl methacrylate (MMA) to form a series of photosensitive copolymers P(ENbMA–MMA)s that were well characterized by 1H NMR and GPC. The photochemical and photophysical properties of both photosensitive monomer and copolymers upon visible light irradiation were studied by UV–Vis, FTIR, and HPLC spectra, which confirmed that 5-(4-ethoxystyryl)-2-nitrobenzyl ester can be photolyzed effectively with generation of the corresponding 5-(4-ethoxystyryl)-2-nitrosobenzaldehyde and carboxylic acid groups. The successful photocleavage endowed the optimized copolymers with excellent micropatterning property due to the effective generation of alkaline-soluble carboxylic acid groups. Moreover, the high two-photon absorption cross-sections (over 20 GM at 800 nm) and the comparable photolysis upon two-photon NIR light irradiation of the chromophores provided the copolymers with significant application in two-photon microfabrication. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4099–4106, 2013