Sensing and surface morphological properties of a poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] liquid‐crystalline polymer for optoelectronic applications

The sensing properties of a poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] (F8T2) polymer were investigated at different concentrations and volume percentages. The effects of the concentrations and volume percentages on the sensing parameters were investigated. The sensitivities of F8T2 were found to be 3.190, 1.434, and 0.362 dB/vol % at 290, 580, and 940 nm, respectively. The response of the F8T2 increased with increasing concentration. F8T2 exhibited good sensitivity and response behaviors. Then, the optical parameters based on the refractive indices of the F8T2 at different molarities were calculated. The dispersion energy, moment of the dielectric constant optical spectrum (M_?1, M_?3), oscillator strength, and contrast of the F8T2 increased with increasing molarity, whereas the average excitation energy or single‐oscillator energy decreased with increasing molarity. The surface morphological properties of the F8T2 polymer film were investigated, and the roughness parameters were obtained. The F8T2 polymer could be used in the fabrication of various sensors because of the good solubility, sensitivity, and response behaviors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41659.     

Efficient wound odor removal by β‐cyclodextrin functionalized poly (ε‐caprolactone) nanofibers

Polymer‐cyclodextrin (CD) composite nanofibers, by virtue of the hollow cavities and abundant hydroxyl groups present in CDs, have tremendous potential in a variety of biomedical applications. However, in most cases, especially in aliphatic polyesters, polymer chains thread readily into CD cavities, therefore its potential has not yet been fully realized. Herein, we report the formation of poly(ε‐caprolactone) (PCL)/β‐CD functional nanofibers by electrospinning their mixture from chloroform/N,N‐dimethylformamide (60 : 40). The fiber diameters of the neat PCL and β‐CD functionalized fibers were measured from the images obtained from a scanning electron microscope and were found to be about 500 nm. The efficiency of wound odor absorbance by these composite fibers was studied using a simulated wound odor solution, consisting of butyric and propionic acids in ethanol. Immersion tests indicated that even under less than ideal test conditions, the nanofibers containing β‐CDs were very efficient in masking the odor. The odor masking capability of the β‐CD functionalized PCL nanofibers were further confirmed by thermogravimetric analyses and GC observations, with the former method showing unique degradation patterns. The PCL/β‐CD nanocomposites, by virtue of having their β‐CD cavities free and unthreaded by PCL, could potentially be an ideal substrate for removing wound odors through formation of inclusion compounds with odorants, while providing an ideal environment for the wound to heal. These results suggest tailoring polymer‐CD nanostructures for specific applications in wound odor absorbance, surface grafting of chemical moieties, and vehicles for drug delivery, as examples. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42782.     

New method for fabricating an α‐fetoprotein affinity monolithic polymer array

Bisphenol A based epoxy acrylate (BABEA), a commercial UV‐curable material, was introduced as a crosslinker for the fabrication of an epoxy‐functionalized monolithic polymer array through UV‐initiated copolymerization with glycidyl methacrylate as the functional monomer and poly(ethylene glycol) 200 as the porogen. Scanning electron microscopy images showed that the monolithic poly(bisphenol A based epoxy acrylate‐co‐glycidyl methacrylate) [poly(BABEA‐co‐GMA)] exhibited a well‐controlled skeletal and well‐distributed porous structure. The α‐fetoprotein (AFP) immunoaffinity monolithic polymer array prepared by the immobilization of AFP on epoxy‐functionalized monolithic arrays was used as an immunosensor for chemiluminescent AFP detection. X‐ray photoelectron spectroscopy results indicate that the AFP antibody was successfully immobilized on the monolithic poly(BABEA‐co‐GMA) array. With a noncompetitive immune‐response format, the proposed AFP immunoaffinity array was demonstrated as a low‐cost, flexible, homogeneous, and stable array for AFP detection. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41792.     

Piezoelectric polymer microfiber-based composite for the flexible ultra-sensitive pressure sensor

This study presents a new type of composite consisting of piezoelectric poly(γ-benzyl-α, l -glutamate) (PBLG) polymer fibers, which contain a large dipole moment, and the elastomer polydimethylsiloxane (PDMS) as the matrix material. PBLG microfibers were fabricated and polarized using the electrospinning method and cast in PDMS to form a unidirectional continuous-fiber composite. The PBLG/PDMS composite was characterized based on various aspects such as crystalline structure, mechanical properties, piezoelectricity, and electromechanical response. The piezoelectric charge constants in the transverse and longitudinal modes were measured to be 10.2 and 54 pC/N, respectively, which are the largest piezoelectric coefficients of biocompatible polymers up to date. The thin PBLG/PDMS composite film can produce up to 200 mV peak-to-peak under sinusoidal actuation and exhibit ultra-sensitivity up to 615 mV N⁻¹. These results show the great potential of the highly flexible piezoelectric polymer fiber-based composite for use in a variety of applications such as energy harvesting devices, biomechanical self-powered structures, and force sensors. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48884.     

Characterization of the mechanical and thermal properties and morphological behavior of biodegradable poly(L‐lactide)/poly(ε‐caprolactone) and poly(L‐lactide)/poly(butylene succinate‐co‐L‐lactate) polymeric blends

Two series of biodegradable polymer blends were prepared from combinations of poly(L ‐lactide) (PLLA) with poly(?‐caprolactone) (PCL) and poly(butylene succinate‐co‐L ‐lactate) (PBSL) in proportions of 100/0, 90/10, 80/20, and 70/30 (based on the weight percentage). Their mechanical properties were investigated and related to their morphologies. The thermal properties, Fourier transform infrared spectroscopy, and melt flow index analysis of the binary blends and virgin polymers were then evaluated. The addition of PCL and PBSL to PLLA reduced the tensile strength and Young's modulus, whereas the elongation at break and melt flow index increased. The stress–strain curve showed that the blending of PLLA with ductile PCL and PBSL improved the toughness and increased the thermal stability of the blended polymers. A morphological analysis of the PLLA and the PLLA blends revealed that all the PLLA/PCL and PLLA/PBSL blends were immiscible with the PCL and PBSL phases finely dispersed in the PLLA‐rich phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polydimethylsiloxane‐modified polyurethane–poly(ɛ‐caprolactone) nanofibrous membranes for waterproof,breathable applications

In this study, we prepared polydimethylsiloxane (PDMS)‐modified polyurethane–poly(?‐caprolactone) nanofibrous membranes with excellent waterproof, breathable performances via an electrospinning technique. Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and mechanical testing were used to characterize the morphologies and properties of the composite nanofibers. The fiber diameter and porous structure of the membranes were regulated by the adjustment of the temperatures of thermal treatment and the PDMS concentrations. The fibrous membranes obtained at a typical temperature of 70 °C possessed an optimized fibrous structure with a diameter of 514 ± 2 nm, a pore size of 0.55–0.65 µm, and a porosity of 77.7%. The resulting nanofibrous membranes modified with 5 wt % PDMS were endowed with good waterproof properties (water contact angle = 141 ± 1°, hydrostatic pressure = 73.6 kPa) and a high breathability (air permeability rate = 6.57 L m^?2 s^?1, water vapor transmission rate = 9.03 kg m^?2 day^?1). Meanwhile, the membranes exhibited robust mechanical properties with a high strength (breakage stress = 11.7 MPa) and excellent thermal stability. This suggests that they would be promising candidates for waterproof, breathable applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46360.     

Synthesis,characterization, and Pb2+ ion sensing application of hexa‐armed dansyl end‐capped poly(ε‐caprolactone) star polymer with phosphazene core

Novel hexa‐armed dansyl end‐capped poly(ε‐caprolactone) (PCL) star polymer with phosphazene core ( P2 ) was prepared via ring opening polymerization (ROP) and esterification reactions. P2 showed dual fluorescence emission when excited at 328 nm in acetonitrile : water (6 : 4) due to twisted intramolecular charge transfer (TICT) between dimethylamino and naphthalene units in the dansyl moiety. TICT emission band (A band) in the emission spectra red‐shifted with increasing solvent polarity. P2 responded to the addition of Pb²⁺, Hg²⁺, Co²⁺, Cd²⁺, Mn²⁺, and Zn²⁺ metal ions by decreasing TICT emission band with slight bathochromic shifts. The highest quenching efficiency was observed for Pb²⁺ ion with Stern–Volmer constant of 324.74M^?1. The Stern–Volmer plot for Pb²⁺ was rather linear with the increasing concentration of the quencher, indicating a dynamic (collisional) quenching mechanism. Stern–Volmer constants for Hg²⁺, Co²⁺, Cd²⁺, Mn²⁺, and Zn²⁺ ions were found to be 212.33, 189.21, 36.24, 20.84, and 20.69, respectively. Besides, the highest quenching efficiency (94.24%) was attained in the presence of Pb²⁺, suggesting that P2 could be employed as a potential Pb²⁺ chemical probe. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42380.     

Mechanical relaxations of poly(β,L‐aspartate)s

The dynamic mechanical thermal properties of a family of poly(α‐alkyl β,L ‐aspartate)s bearing various cyclic, linear, and branched alkoxycarbonyl groups in the side chain were studied. The measurements carried out by dynamic mechanical thermal analysis (DMTA) revealed the significant influence of the constitution of the side chain on mechanical relaxation phenomena. Three relaxations were observed, which are referred to as γ, β, and α, in increasing order of temperature. The first two, γ and β, are related to the local and global motions of the side chain, respectively. Relaxation α is related to the motion of the main chain. Relaxation β, which is associated with the rotation of the side chain, is the most intense. The magnitude and temperature at which this relaxation occurs depends on the volume, the length, and the degree of branching of the ester group of the side chain. A comparison between the dynamic mechanical properties of poly(β,L ‐aspartate)s and poly(α,L ‐glutamate)s revealed that the two methylene groups spacing the ester group from the main chain provides the poly(α‐L ‐glutamate)s with greater mobility, and thus, relaxations α and β occur at lower temperatures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 994–1003, 2006     

Drug‐delivery system based on core–shell‐type nanoparticles composed of poly(γ‐benzyl‐L‐glutamate) and poly(ethylene oxide)

A block copolymer based on poly(γ‐benzyl‐L ‐glutamate) (PBLG) as the hydrophobic part and poly(ethylene oxide) (PEO) as the hydrophilic part was synthesized and characterized. PBLG/PEO/PBLG (GEG) block copolymer nanoparticles were prepared using the dialysis technique. Fluorescence spectroscopy measurement suggested that GEG block copolymers were associated in water to form polymeric micelles and the critical micelle concentration (CMC) value of the GEG‐50 block copolymer was 0.0084 g/L. Particle‐size distribution of the GEG‐50 block copolymer based on the number average was 34.9 ± 17.6 nm. Also, the particle size and drug‐loading contents of GEG nanoparticles were significantly changed with the initial solvent used. From transmission electron microscope (TEM) observations, the GEG polymeric micelle was a nice spherical shape and the sizes ranged from approximately 20–60 nm in diameter. Results from assessing the drug‐loading contents against the initial solvent showed that the use of tetrahydrofuran (THF) or 1,4‐dioxane as the initial solvent resulted in higher drug‐loading contents than those of other solvents. In the drug‐release studies, the higher the molecular weight of the polymer and drug‐loading contents, the slower the drug release. Also, the initial solvent used was significantly affected not only in the drug‐loading contents but also in the drug‐release kinetics. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1115–1126, 2000     

Rapid fabrication of poly(ε‐caprolactone) nanofibers using needleless alternating current electrospinning

Poly(ε‐caprolactone) ( PCL) biopolymer nanofibers and micro‐fibers have been fabricated for the first time at the rates up to 14.0 g per hour using a needleless and collectorless alternating current electrospinning technique. By combining the ac‐voltage, “green” low toxicity glacial acetic acid (AA) as the solvent and sodium acetate (NaAc) as an additive, beadless PCL fibers with diameters tunable from 150 nm to 2000 nm, varying surface morphology and degree of self‐bundling are obtained. In this new approach, the addition of NaAc plays a crucial role in improving the spinnability of PCL solution and fiber morphology. NaAc reveals the concentration‐dependent effect on charge transfer and rheological properties of the PCL/AA precursor, which results in broader ranges of spinnable PCL concentrations and ac‐voltages suitable for rapid manufacturing of PCL‐based fibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43232.     

N,N‐Dimethylformamide Additions to the Solution for the Electrospinning of Poly(ε‐caprolactone) Nanofibers

Summary: Additives that exhibit polyelectrolyte behavior such as N,N‐dimethylformamide (DMF) may improve the electrospinning characteristics of viscoelastic polymer solutions. DMF additions to the solution lead to extensive jet splaying, thereby reducing the fiber diameter significantly. Nanofibrous structures with diameters of the order of 150 nm can be produced by the addition of about 10 vol.‐% DMF to the solvent (chloroform). DMF additions also yield a narrow, unimodal distribution of fibers, compared to the bimodal distribution typically detected in electrospun polymers.

Jet breakdown without (left) and with DMF addition to the solution.     

Effect of polymer matrix on the performance of pressure‐sensitive paint comprising 5,10,15,20‐tetrakis(pentafluorophenyl)porphinato platinum(II) and poly(1,1,1,3,3,3‐hexafluoroisopropyl‐co‐tert‐butyl methacrylates)

Copolymers of 1,1,1,3,3,3‐hexafluoroisopropyl methacrylate (HFIPM) and tert‐butyl methacrylate (TBM) were prepared by conventional radical copolymerization as a novel binders for pressure‐sensitive paints (PSP). The monomer reactivity ratios r_HFIPM and r_TBM were determined as 0.45 and 0.67, respectively. The glass transition temperature of the copolymers increased from 77 to 126°C with increasing mole fraction of TBM units in the copolymer. The PSP were formed by combining the resulting copolymers and 5,10,15,20‐tetrakis(pentafluorophenyl)porphinato platinum(II). The pressure and temperature sensitivities of the PSPs were measured at air pressures ranging from 5 to 120 kPa and at temperatures ranging from 0 to 60°C. Modified Stern–Volmer plots indicated slight increases in the pressure sensitivity, but significant decrease in the temperature sensitivity as the mole fraction of HFIPM units increased in the copolymer. Applying a theoretical model to our calibration data, we inferred that luminescence quenching is primarily responsible for increasing the temperature sensitivity in the resulting copolymers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43316.     

Polymeric piezoelectric fiber with metal core produced by electrowetting‐aided dry spinning method

An electrowetting‐aided dry spinning method is developed to produce morphologically stable polymeric piezoelectric fibers with a metal core covered by a beta‐phase poly(vinylidene fluoride) [or poly(vinylidene‐trifluoroethylene)] layer. Each fiber consists of a 100 μm copper core (enameled with 6 μm polyester‐imide), a 3–10 μm piezoelectric layer, and a sputtered 100 nm gold electrode. The morphological properties of the fibers are analyzed with scanning electron microscopy, X‐ray diffraction, and a step profiler. The piezoelectric properties are tested in a vibration‐detecting application. Both morphological observation and piezoelectric testing demonstrate that the electrowetting‐aided dry spinning helps in forming high‐quality polymeric piezoelectric fibers. Moreover, this method can also be applied in different fabrications, where adhesion between a liquid and solid surface needs to be enhanced. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43968.     

Mechanical characterization of high‐performance graphene oxide incorporated aligned fibroporous poly(carbonate urethane) membrane for potential biomedical applications

In this article, we report the development of graphene oxide (GO) reinforced electrospun poly(carbonate urethane) (PCU) nanocomposite membranes intended for biomedical applications. In this study, we aimed to improve the mechanical properties of PCU fibroporous electrospun membranes through fiber alignment and GO incorporation. Membranes with 1, 1.5, and 3% loadings of GO were evaluated for their morphology, mechanical properties, crystallinity, biocompatibility, and hemocompatibility. The mechanical properties were assessed under both static and dynamic conditions to explore the tensile characteristics and viscoelastic properties. The results show that GO presented a good dispersion and exfoliation in the PCU matrix, contributing to an increase in the mechanical performance. The static mechanical properties indicated a 55% increase in the tensile strength, a 127% increase in toughness for 1.5 wt % GO loading and the achievement of a maximum strength reinforcement efficiency value at the same loading. Crystallinity changes in membranes were examined by X‐ray diffraction analysis. In vitro cytotoxicity tests with L‐929 fibroblast cells and percentage hemolysis tests with fresh venous blood displayed the membranes to be cytocompatible with acceptable levels of hemolytic characteristics. Accordingly, these results highlight the potential of this mechanically improved composite membrane's application in the biomedical field. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41809.     

Electrospinning core‐shell nanofibers for interfacial toughening and self‐healing of carbon‐fiber/epoxy composites

This article reports a novel hybrid multiscale carbon‐fiber/epoxy composite reinforced with self‐healing core‐shell nanofibers at interfaces. The ultrathin self‐healing fibers were fabricated by means of coelectrospinning, in which liquid dicyclopentadiene (DCPD) as the healing agent was enwrapped into polyacrylonitrile (PAN) to form core‐shell DCPD/PAN nanofibers. These core‐shell nanofibers were incorporated at interfaces of neighboring carbon‐fiber fabrics prior to resin infusion and formed into ultrathin self‐healing interlayers after resin infusion and curing. The core‐shell DCPD/PAN fibers are expected to function to self‐repair the interfacial damages in composite laminates, e.g., delamination. Wet layup, followed by vacuum‐assisted resin transfer molding (VARTM) technique, was used to process the proof‐of‐concept hybrid multiscale self‐healing composite. Three‐point bending test was utilized to evaluate the self‐healing effect of the core‐shell nanofibers on the flexural stiffness of the composite laminate after predamage failure. Experimental results indicate that the flexural stiffness of such novel self‐healing composite after predamage failure can be completely recovered by the self‐healing nanofiber interlayers. Scanning electron microscope (SEM) was utilized for fractographical analysis of the failed samples. SEM micrographs clearly evidenced the release of healing agent at laminate interfaces and the toughening and self‐healing mechanisms of the core‐shell nanofibers. This study expects a family of novel high‐strength, lightweight structural polymer composites with self‐healing function for potential use in aerospace and aeronautical structures, sports utilities, etc. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Electrospinning of flux‐enhanced chitosan–poly(lactic acid) nanofiber mats as a versatile platform for oil–water separation

Environmentally friendly chitosan (CS)–poly(lactic acid) (PLA) nanofiber mats were designed and constructed by an electrospinning strategy. Studies on the wettability of the CS–PLA nanofiber mats showed that they possessed excellent hydrophobic and oleophilic properties in the pH range 1–12. A layered oil–water mixture was separated by CS–PLA nanofiber mats, and the oil flux of the mats collected by #10 stainless steel wire mesh (sample P‐10) was up to 511.36 L m^?2 h^?1, which was approximately 25 times higher than that of the mats collected by #0 stainless steel wire meshes (sample P‐N). The superior properties of the CS–PLA nanofiber mats may have been due to their tunable porous structure and fine flexibility. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45830.     

Poly(lactic acid)/poly(3‐hexylthiophene) composite nanofiber fabrication for electronic applications

Fibers of the biopolymer poly(lactic acid) (PLA) and the p‐type semiconducting polymer poly(3‐hexylthiophene) (P3HT) were fabricated using the electrospinning technique at low PLA concentration (5 wt%) in CHCl₃. The fibers were several millimeters long and had diameters in the range 100 nm–4 µm. Nanofibers containing 63%/37% of PLA/P3HT were electroactive, and therefore were used to construct p–n diodes whose ideality parameter was 2.4 and rectification (on/off) ratio was 400 at ±1 V. These diodes were also able to sense UV radiation and remain operable with an increase in the on/off ratio and a lowering of the turn‐on voltage. By fabricating reusable and low‐cost multifunctional diodes from PLA/P3HT, the applications of PLA as a biocompatible and biodegradable polyester are expanded to include electronic device fabrication with low environmental impact. © 2016 Society of Chemical Industry     

Dithieno[2,3‐d:2′,3′‐d′]naphtho[2,1‐b:3,4‐b′]dithiophene based medium bandgap conjugated polymers for photovoltaic applications

Three novel medium band gap (MBG) conjugated polymers (CPs) (named as P1, P2, and P3, respectively) were developed by copolymerizing 2,7‐dibromo‐10,11‐di(2‐hexyldecyloxy)dithieno[2,3‐d:2′,3′‐d′]naphtho[2,1‐b:3,4‐b′]dithiophene (NDT‐Br) with three different units: 2,5‐bis(tributylstannyl)thiophene, 2,5‐bis(trimethylstannyl)thieno[3,2‐b]thiophene and trans?1,2‐bis(tributylstannyl)ethene, respectively. The thermal, optical, and electrochemical properties of the polymers were investigated. All of the polymers have good thermal stability and medium band gap (～ 1.9 eV). Prototype bulk heterojunction photovoltaic cells based on the blend P1/P2/P3 and [6, 6] phenyl‐C61 butyric acid methyl ester (PC₆₁BM) were assembled and the photovoltaic properties were assessed. Power conversion efficiencies (PCEs) of 1.61% ～ 2.43% have been obtained under 100 mW cm^?2 illumination (AM1.5). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43288.     

The use of poly (ε‐caprolactone) to enhance the mechanical strength of porous Si‐substituted carbonate apatite

Poly(ε‐caprolactone) (PCL)/silicon‐substituted carbonate apatite (Si‐CO3Ap) composite derived from the interconnected porous Si‐CO3Ap reinforced with molten PCL was prepared. PCL was used to improve the mechanical properties of a porous apatite by a simple polymer infiltration method, in which the molten PCL was deposited through the interconnected channel of porous Si‐CO3Ap. The PCL covered and penetrated into the pores of the Si‐CO3Ap to form an excellent physical interaction with Si‐CO3Ap leading to a significant increase in diametral tensile strength from 0.23 MPa to a maximum of 2.04 MPa. The Si‐CO3Ap/PCL composite has a porosity of about 50–60% and an interconnected porous structure, with pore sizes of 50–150 μm which are necessary for bone tissue formation. These results could pave the way for producing a porous, structured biocomposite which could be used for bone replacement. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013