Ultrafine electrospun polyamide‐6 fibers: Effect of emitting electrode polarity on morphology and average fiber diameter

Electrostatic spinning or electrospinning is now a well‐known process for fabricating ultrafine fibers with diameters in the submicrometer down to nanometer range from materials of diverse origins. The polarity of the emitting electrode (i.e., the one that is in contact with the polymer solution or melt) can be either positive or negative. In the present contribution, the effects of emitting electrode polarity and some processing parameters (i.e., polyamide‐6 (PA‐6) concentration, molecular weight of PA‐6, electrostatic field strength, solution temperature, solvent type, and addition of an inorganic salt) on morphological appearance and average size of the as‐spun PA‐6 fibers were investigated. Scanning electron micrographs showed obvious morphological difference between the fibers obtained under positive and negative polarity of the emitting electrode. The main differences were that the cross section of the as‐spun PA‐6 fibers obtained under the negative electrode polarity was flat, while that of those obtained under the positive one appeared to be round and that the average size of the fibers obtained under the negative electrode polarity was larger than that of those obtained under the positive one. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3699–3712, 2005     

Preparation of polyHIPE via CuAAC “click” chemistry and its application as a highly efficient adsorbent of Cu(II) ions

A hydrophilic emulsion‐templated porous polymer (polyHIPE) is synthesized by CuAAC “click” chemistry. Herein, a 4,4′‐diazidostilbene‐2,2′‐disulfonic acid disodium salt‐4H₂O (DAS) and tripropargylamine in the mixture of water and N,N‐dimethylformamide solution is used as external phase of the high internal phase emulsion template, and paraffin liquid is involved as the internal phase. The resulting polyHIPE has a well‐defined interconnected pore structure, which could be tailored by changing preparation parameters, such as reagent content, internal phase volume fraction, and surfactant concentration. Thermal analysis shows that the polyHIPE is stable under 180 °C. Owing to the presence of a large number of sodium sulfonate groups from the reagent DAS and the triazoles groups produced in the reaction, the polyHIPE is proved to be a highly efficient adsorbent of heavy metal ion (i.e., up to 52 mg/g for Cu(II) ions) in water. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2129–2135     

Improvement in semipermeable membrane performance of wholly aromatic polyamide through an additive processing strategy

A new concept for the method to provide semipermeability in ultrathin and single‐component wholly aromatic polyamide membranes has been developed for the first time. It was found that water molecules could permeate through the membrane prepared not from polyamides containing flexible ether, bulky binaphthyl, or fluorene rigid units, but one with carboxylic acid groups under a reverse osmosis mode. However, the enhancement of water transport properties by introducing the hydrophilic group of polyamide was not substantial. Therefore, polyamide membranes were prepared from the solution containing aqueous additives in order to weaken hydrogen bonds between polymer chains and thereby to suppress the aggregation of the polymer chains. As a result, water flux was dramatically improved with slightly improved NaCl rejection. Our analyses based on attenuated total reflectance Fourier transform infrared spectroscopy and solid‐state carbon polarization and magic angle spinning nuclear magnetic resonance (¹³C CPMAS NMR) spectroscopy confirmed that the aggregation of polymer chains due to the hydrogen bonds among the amide linkages was suppressed by the co‐ordination of the aqueous additives to the amide linkage. The state of water in the membranes analyzed by differential scanning calorimetry also supported the formation of pores. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1275–1281     

Revised insights into templating radical polymerization within nanoreactors

The field of polymer chemistry is currently experiencing major research efforts into development of novel techniques for synthesis of polymers with well‐controlled microstructure. Recently, a new method has been reported [McHale et al., Nat. Chem. 2012, 4, 491–497] whereby high molecular weight and low dispersity polymer can be obtained by a radical polymerization process via the use of solely physico‐chemical interactions. This work was based on the combination of H‐bonding templated polymerization confined within nanoreactors of self‐assembled block copolymers. Herein, this system is thoroughly investigated to fully elucidate the underlying mechanism. Modification of physico‐chemical parameters, kinetic parameters as well as observations of size exclusion chromatography (SEC) results and colloidal behavior in various solvents provide revised insights into the mechanism. Through detailed NMR and SEC investigations, it is demonstrated that the SEC secondary peak originally believed to be the high molecular weight “daughter” polymer actually corresponds to nanoparticles containing the daughter polymer. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1590–1600     

Encapsulated clay particles in polystyrene by RAFT mediated miniemulsion polymerization

RAFT grafted montmorillonite (MMT) clays [i.e., N,N‐dimethyl‐N‐(4‐(((phenylcarbonothioyl)thio)methyl)benzyl)ethanammonium‐MMT (PCDBAB‐MMT) and N‐(4‐((((dodecylthio)carbonothioyl)thio)methyl)benzyl)‐N,N‐dimethylethanammo‐nium‐MMT (DCTBAB‐MMT)] of various loadings were dispersed in styrene (S) monomer and the resultant mixtures emulsified and sonicated in the presence of a hydrophobe (hexadecane) into miniemulsions. The stable miniemulsions thus obtained were polymerized to yield encapsulated polystyrene‐clay nanocomposites (PS‐CNs). The molar mass and polydispersity index (PDI) of the PS‐CNs depended on the amount of RAFT agent in the system, in accordance with the features of the RAFT process. The morphology of the PS‐CNs ranged from partially exfoliated to an intercalated morphology, depending on the percentage clay loading. The thermomechanical properties of the PS‐CNs were better than those of the neat PS polymer, and were dependent on the molar mass, PS‐CN morphology and clay loading. The similarities and differences of the PS‐CNs prepared here by miniemulsion polymerization were compared to those prepared using the same RAFT agents and polymer system by bulk polymerization (as reported by us in a previous article). © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7114–7126, 2008     

Electrospinning of polyesteramides based on ε-caprolactam and ε-caprolactone from solution

The paper is focused on the preparation of nanofiber layers of polyesteramides with various ratios of ε-caprolactam/ε-caprolactone structural units. We have studied the effect of the system parameters, i.e., the composition of the copolymer, its molar mass and the concentration of the solution on morphology of fiber layers being formed during the electrostatic wet spinning. The process parameters were constant during the processing. Morphology of the fiber layers is given by the composition of the copolymer, i.e., by its polarity, the content of the crystalline phase and thus its separation in the process of evaporating the solvent. Fibers with diameters ranging from 100 to 160 nm were obtained for polyesteramides containing 20 or 40 mol% lactone units during optimizing the system parameters, i.e., the concentration of the solution and molar mass of polyesteramide.     

Thickness‐dependent swelling of molecular layer‐by‐layer polyamide nanomembranes

The thickness‐dependent water vapor swelling of molecular layer‐by‐layer polyamide films is studied via specular X‐ray reflectivity. The maximum swelling ratio of these ultrathin films scale inversely with thickness but more importantly show a dual‐mode sorption behavior characterized by Langmuir‐like sorption at low relative humidity and network swelling at high relative humidity. The thickness‐dependent network parameters are extracted using a proposed model that builds on Painter‐Shenoy network swelling model while taking into account the glass‐like characteristic below a critical swelling ratio, which also scales inversely with thickness. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 412–417     

Use of a trithiocarbonyl RAFT agent without modification as (Co)stabilizer in miniemulsion polymerization

Herein, we demonstrate the effects of using 4‐cyano‐4‐[(dodecylsulfanylthiocarbonyl)sulfanyl] pentanoic acid (CDPA) simultaneously as RAFT chain transfer agent (RAFT‐CTA) and (co)stabilizer in a miniemulsion polymerization process. The novelty of this report includes use this RAFT‐CTA without modification, such as macro‐CTAs, block, or random copolymers. Using an optimized polymerization procedure, it is possible to use distinct formulations and therefore obtain stable latexes comprised of well‐defined spherical nanoparticles. The polymerization kinetics and final polymer properties are directly correlated to the function of the CDPA in the system: RAFT‐CTA and/or (co)stabilizer. Typically, the nanoparticles present average diameters less than 150 nm. The molar mass properties and the kinetic profiles confirm to an expected RAFT process, although some deviations are observable when using the CDPA as only stabilizer. These deviations are a function of the amount of CDPA present within the nano‐droplets, or adsorption on its surface. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1687–1695     

Novel aromatic polyamides containing 2‐diphenylamino‐(9,9‐dimethylamine) units as multicolored electrochromic and high‐contrast electrofluorescent materials

A series of electrochromic and photoluminescence‐active polyamides 4a‐4e were prepared from a novel dicarboxylic acid, N,N‐di(4‐carboxyphenyl)‐2‐amino‐9,9‐dimethylfluorene, and five diamines via a condensation polymerization. These polyamides were amorphous and readily soluble in many solvents. The glass transition temperatures were in the range of 281–339 °C and the 10% weight loss temperatures in nitrogen were in excess of 490 °C. The polyamides exhibited strong fluorescence in either solution or solid states. The polyamides 4a‐4d showed reversible electrochemical redox with color changing from colorless to grey‐green. Specially, the polyamide 4e with 2‐diphenylamino‐(9,9‐dimethylamine) group in both diamine and dicarboxylic acid residues exhibited multicolored electrochromic behaviors. Furthermore, the fluorescence of these polyamides could be reversibly electroswitched with a high contrast up to 221.4, enabling their potential applications in dual‐switching electrochromic/electrofluorescent materials. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 213–222     

Covalent fixed multicyclic polystyrene conformers

Covalent fixed multicyclic polystyrene conformers were synthesized from inconvertible polystyrene conformers based on p‐tert‐butylthiacalix[4]arene by azidation and subsequent click coupling. Selective 1D NOESY analyses confirmed that the spatial structures of star polystyrene precursors and multicyclic polystyrenes were preserved during the azidation and click coupling processes. The conformation of star polymers affected degree of decrease in the hydrodynamic volume after cyclization but had little effect on glass transition behavior. The rigid core of star polymer increased the T_g but in the case of multicyclic polymer, this influence of core structure was reduced. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 4020–4026     

Controlled radical polymerization of N‐acryloylglycinamide and UCST‐type phase transition of the polymers

N‐Acryloylglycinamide was polymerized via the reversible addition fragmentation transfer process without sacrificing its key property, the upper critical solution temperature in water. This could be achieved by choosing an appropriate nonionic initiator [2,2′‐azobis(4‐methoxy‐2.4‐dimethyl valeronitrile) (V‐70)] and nonionic chain‐transfer agent (cyanomethyl dodecyl trithiocarbonate). A good molar mass control was accomplished as proved by the linear increase of molar mass with conversion, a chain extension experiment, and low dispersity. The influence of molar mass, polymer end groups, or salt concentration on the cloud point was analyzed by turbidimetry. Polymer end groups exerted a distinct effect on the cloud points, whereas the influence increased with decreasing molar masses. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Group contribution method for the swelling behavior of thermo‐responsive hydrogels

A group contribution method is introduced to describe the swelling behavior of thermo‐sensitive hydrogel systems. The accuracy of group contribution calculations is strongly dependent on the choice of thermodynamic model. Therefore, we revise the modified double lattice (MDL) model and develop a new expression for the interaction energy parameter using the association theory of Sanchez to take into account complex polymer/solvent mixing. The net Helmholtz energy for a hydrogel is established by combining the revised MDL model and modified Flory–Rehner elastic model. Group parameters are generated by fitting to experimental swelling data from both homopolymer and copolymer gel systems. The effect of salt on the volume phase transition is modeled by introducing an additional salt‐specific parameter to investigate various stimuli‐response swelling behavior. Calculated swelling equilibria using the new group contribution method shows excellent agreement with experimental data and various stimuli‐response volume phase transitions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 455–463     

Synthesis of glycopeptides from glucosaminic acid

We report on the synthesis of polypeptides with saccharide side chains starting from d ‐glucosaminic acid. The hydroxyl groups were first protected by benzylation, followed by N‐carboxyanhydride formation, which was polymerized by ring opening to form a high molecular weight polyamide. De‐protection of the benzyl groups yields a polypeptide with fully de‐protected saccharide side chains. The resulting new non‐ionic, water soluble, and optically active polymers possessing the properties of both peptides and saccharides have potential use as scaffolds for tissue engineering and drug carriers. The method described here may be extended to any saccharide α‐amino acid. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2657–2662     

Polymerization via the Ugi‐reaction using aromatic monomers

The highly modular Ugi four‐component reaction (Ugi‐4CR) was used to directly obtain polymers of high molar mass bearing aromatic residues in the backbone. By using at least two bifunctional monomers, the Ugi‐4CR can be employed to synthesize polymers through a polycondensation under mild conditions in the absence of catalysts. This highly versatile approach allows the creation of vast libraries of molecules by a comparably small pool of compounds. We investigated the six different possible types of the Ugi four‐component polymerization (Ugi‐4CP) to generate polyamides using commercially available monomers without further purification. After substantial adjustments of reaction parameters, we were able to obtain a polymer of high molar mass, albeit only for one out of the six types of the Ugi‐4CP. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1680–1686     

Ambipolar charge transport in a donor–acceptor–donor‐type conjugated block copolymer and its gate‐voltage‐controlled thin film transistor memory

We demonstrate a fully conjugated donor–acceptor–donor (D–A–D) triblock copolymer, PBDTT–PNDIBT–PBDTT, which contains PBDTT as the donor block and PNDIBT as the acceptor block. The polymer was synthesized by end‐capping each block with a reactive unit, followed by condensation copolymerization between the two blocks. The physical, optical, and electrochemical properties of the polymer were investigated by comparing those of donor‐ and acceptor‐homopolymers (i.e., PBDTT and PNDIBT), which are the oligomeric monomers, and their blends. On using the newly synthesized block copolymer, ambipolar charge transport behavior was observed in the corresponding thin‐film transistor, and the behavior was compared to that of blend film of donor‐ and acceptor‐homopolymers. Owing to the presence of donor and acceptor blocks in a single polymer chain, it was found that the triblock copolymer can store two‐level information; the ability to store this information is one of the most intriguing challenges in memory applications. In this study, we confirmed the potential of the triblock copolymer in achieving distinct two‐stage data storage by utilizing the ambipolar charge trapping phenomenon, which is expected in donor and acceptor containing random and block copolymers in a thin‐film transistor. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3223–3235     

Confinement effects on the thermal stability of poly(ethylene oxide)/graphene nanocomposites: A reactive molecular dynamics simulation study

Nonisothermal and isothermal decomposition of poly(ethylene oxide) (PEO) loaded with different concentrations of pristine graphene (PG) and graphene oxide (GO) nanoplatelets were investigated using reactive molecular dynamics simulation. The onset of nonisothermal decomposition of the PG‐loaded PEO system was the highest among all systems, suggesting that introducing PG to the polymer improves its thermal stability (an effect that increases with an increase in the PG concentration). At low concentration, introducing GO to the polymer brings about a deterioration of the thermal stability of the polymer consistent with experimental findings. On average, the activation energy for the isothermal decomposition of PG‐loaded PEO system increases by 60% over that of the neat PEO system, while it decreases by 40% for the GO‐loaded PEO system. A time‐dependent analysis of the through‐thickness decomposition profile of the above systems reveals that the polymer confined between the PG sheets exhibit a higher thermal stability compared to the bulk polymer. However, an opposite effect is observed with the polymer confined between the GO sheets. The latter observation is attributed to accelerated polymer chain scission in confined regions due to the ejection of reactive hydroxyl radicals from the GO surface during the early stages of thermal decomposition. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1026–1035     

A new process for producing polyamide from polyester

A new process for producing polyamide from polyester and diamine was proposed. An attempt was made to produce polyamide 6T from polyethyleneterephthalate or dimethylterephthalate with hexamethylenediamine in water, o‐dichlorobenzene and sulfolane. Characterization of the products by IR, elemental analysis, solution viscosity and GPC were carried out. It became clear that high molecular polyamide 6T could be obtained from polyethyleneterephthalate and hexamethylenediamine in sulfolane. The reaction mechanism was discussed from the viewpoint of the polymer effect and solvent effect. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1413–1423, 1999     

Preparation and orthogonal postmodification of dual‐clickable polymer precursors bearing both aldehyde and alkyne groups

A new styrenic monomer 2‐propargyloxy‐5‐vinylbenzaldehyde (PVB) containing both aldehyde and alkyne reactive groups was designed for the synthesis and subsequent orthogonal postfunctionalization of dual‐clickable polymer precursor. Reversible addition‐fragmentation chain transfer polymerization of PVB afforded a structurally well‐defined polymer poly(2‐propargyloxy‐5‐vinylbenzaldehyde) (PPVB) bearing alkyne and aldehyde functionalities that are reactive towards azide ‐ and aminooxy‐containing molecules, respectively. Therefore, the resulting PPVB can be served as a dual‐clickable polymer scaffold for construction of multiple functional polymers via orthogonal alkyne–azide and aldehyde–aminooxy click reactions. Postpolymerization modification of PPVB sequentially with aminooxy‐terminated poly(ethylene oxide)s (H₂NO‐PEO) and azide‐functionalized imidazolium‐type ionic liquid (N₃‐IL·TFSI, having bis(trifluoromethane)sulfonamide, TFSI, counter‐anion) yielded an interesting multicomponent graft polymer PPVB‐g‐(PEO‐and‐IL·TFSI). After anion exchange of hydrophobic TFSI counter‐anion by bromide (Br) anion, the resulting graft copolymer PPVB‐g‐(PEO‐and‐IL·Br) becomes soluble in water, and its imidazolium units can capture negatively charged tetraphenylethylene disulfonate derivative (TPE‐2 ) guest molecule via electrostatic complexation to form in situ self‐assembled fluorescent nanoaggregates with colloidal stability imparted by hydrophilic PEO chains. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2650–2656     

Metalloporphyrin–polyelectrolyte assemblies in aqueous solution: Influence of the metal center and the polyelectrolyte architecture

This study investigates the influence of different metal centers in porphyrins and of different polyelectrolyte architectures on the formation of supramolecular metalloporphyrin–polyelectrolyte assemblies in aqueous solution via electrostatic self‐assembly. Metal‐analogues of the tetravalent anionic meso‐tetrakis(4‐sulfonatophenyl)‐porphyrin (with Zn²⁺, Co²⁺, Ni²⁺, Mn³⁺, and Fe³⁺) are combined with the cationic dendrimer of generation 4 or with the linear polydiallyldimethyl‐ammoniumchloride. Dynamic light scattering and atomic force microscopy reveal that the different molecular geometries of the metalloporphyrins resulting from axial ligands determine the size and the stability of the aggregates. A thermodynamic study elucidates the importance of the polymer architecture in controlling the size of the assembly and the role of the metal center. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 484–500     

Direct arylation polymerization toward ultra‐low bandgap poly(thienoisoindigo‐alt‐diketopyrrolepyrrole) conjugated polymers: The effect of β‐protection on the polymerization and properties of the polymers

Direct arylation polymerization between derivatives of dibromodiketopyrrolopyrrole (DPP) and thienoisoindigo (TIIG) resulted in two π‐conjugated copolymers with average molecular weights up to 24.0 kDa and bandgaps as low as 0.8 eV. The structural analysis of the obtained two polymers revealed well‐defined alternating conjugation backbones without obvious structural defects. The introduction of hexyl‐group in the β‐position of thiophene rings in the DPP units not only reduces the bandgap of conjugated polymer compared to a similar polymer containing bare‐thiophene flanked DPP but also affects polymer morphology in thin films. P‐type charge‐transport characteristics were observed for two polymers in organic field‐effect transistors with comparable hole mobilities. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3205–3213