Semitransparent poly(styrene‐r‐maleic anhydride)/alumina nanocomposites for optical applications

This article presents the development and characterization of transparent poly(styrene‐r‐maleic anhydride) (SMA)/alumina nanocomposites for potential use in optical applications. Chemically treated spherical alumina nanoparticles were dispersed in an SMA matrix polymer via the solution and melt‐compounding methods to produce 2 wt % nanocomposites. Field emission scanning electron microscopy was used to examine the nanoparticle dispersion. When the solution method was used, nanoparticle reagglomeration occurred, despite the fairly good polymer wetting. However, through the coating of the alumina nanoparticles with a thin layer (ca. 20 nm) of low‐molecular‐weight SMA, reagglomeration was absent in the melt‐compounded samples, and this resulted in excellent nanoparticle dispersion. The resultant nanocomposites were semitransparent to visible light at a 2‐mm thickness with improved UV‐barrier properties. Their impact strengths, tensile strengths, and strains at break were slightly reduced compared with those of their neat resin counterpart, whereas a small enhancement in their moduli was achieved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis,structural and spectral properties of an ionic polyacetylene: Poly[N‐(5‐nitro‐2‐furanmethylene)‐2‐ethynylpyridinium bromide]

A new ionic polyacetylene was prepared by the activation polymerization of 2‐ethynylpyridine with 2‐(bromomethyl)‐5‐nitrofuran in high yield without any additional initiator or catalyst. This polymerization proceeded well in a homogeneous manner to give a high yield of the polymer (92%). The activated acetylenic triple bond of N‐(5‐nitro‐2‐furanmethylene)‐2‐ethynylpyridinium bromide, formed in the first quaternerization process, was found to be susceptible to linear polymerization. This polymer was completely soluble in such polar organic solvents as dimethylformamide, dimethyl sulfoxide, and N,N‐dimethylacetamide. The inherent viscosities of the resulting polymers were in the range 0.12–0.19 dL/g, and X‐ray diffraction analysis data indicated that this polymer was mostly amorphous. The polymer structure was characterized by various instrumental methods to have a polyacetylene backbone structure with the designed substituent. The photoluminescence peak was observed at 593 nm; this corresponded to a photon energy of 2.09 eV. The polymer exhibited irreversible electrochemical behaviors between the doping and undoping peaks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(vinyl alcohol) nanocomposites with sepiolite and heat‐treated sepiolites

Poly(vinyl alcohol) (PVA) nanocomposites with pristine sepiolite and heat‐treated (HT) sepiolites were prepared by the method of solution dispersion. The measurements of XRD, FTIR, TEM, and AFM were used for the characterization of the nanocomposites. Furthermore, thermal and optical properties were investigated by TG/DTG/DTA and UV‐visible transmission spectra, respectively. Both the effects of sepiolite/polymer ratio and the structural changes in sepiolite on heating were examined in terms of changes in the properties of the nanocomposites. The addition of sepiolite/HT sepiolites into the PVA matrix resulted in a decrease in the thermal decomposition temperatures of the nanocomposites because of the fact that sepiolite and HT sepiolites facilitated the elimination of the water and acetate groups from the PVA in the second step based on the TG/DTG studies. The HT sepiolites‐PVA nanocomposites had lower thermal stability and more influenced optical clarity than those of the sepiolite PVA, at the same filler levels. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal and optical properties of gelatin/poly(vinyl alcohol) blends

Differential scanning calorimetry, thermogravimetric analysis, X‐ray diffraction, and ultraviolet–visible spectroscopy of gelatin and poly(vinyl alcohol) (PVA) homopolymers and their blended samples were studied. The data revealed that the gelatin and PVA polymers were compatible over the investigated range of compositions; this contributed to the formation of hydrogen‐bonding interaction between their polar groups. The associated enthalpy‐of‐melting transition and thermal stability of the blended samples increased with increasing PVA content. This indicated that the crystalline structure of PVA was not destroyed completely in the blends, which was consistent with the X‐ray diffraction pattern of the 50/50 (wt %/wt %) blended gelatin/PVA sample. The absorption edge and optical band gap for allowed direct transition were determined from ultraviolet–visible spectra. The induced changes in the band structure are elucidated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly(vinyl alcohol) and Polyamide‐66 Nanocomposites Prepared by Electrospinning

Summary: PVA and PA‐66 nanocomposite fibers with montmorillonite were prepared by electrospinning. Mixing of the components was conducted in two ways: polymer and montmorillonite were mixed with solvent, or monomer was polymerized in the presence of montmorillonite and was then dissolved in a solvent. Polymer/montmorillonite solutions were then electrospun on a non‐woven substrate. To the unaided eye, the coated area was either continuous coating or well‐defined spots. Characterization of the fiber structure and the particle size and distribution by SEM and elemental analysis showed the nanosized filler to be dispersed through the fiber network of the polymer/nanocomposite regardless of the preparation method. However, the clay particles within the fibers were smaller with the polymerization method than mixing in solvent. Only the PA‐66‐based nanocomposites exhibited large enough coating area on the substrate for measurements of contact angles and the time required for water penetration. Contact angles and the time required for water penetration were increased for most of the PA/nanoclay composites relative to the uncoated substrate.

SEM image of a typical fiber structure of a PVA/nanocomposite obtained by electrospinning under alkaline conditions.     

Breathing‐in/breathing‐out approach to preparing nanosilver‐loaded hydrogels: Highly efficient antibacterial nanocomposites

The key objective of developing novel materials for hygienic living conditions is to lower the risk of transmitting diseases and biofouling. To this end, a number of silver–hydrogel nanocomposite systems are under development. In this study, we attempted a unique strategy to prepare silver‐nanoparticle‐loaded poly(acrylamide‐co‐N‐vinyl‐2‐pyrolidone) hydrogel composites. To load nanosilver particles into such a nonionic hydrogel, a novel breathing‐in/breathing‐out (BI–BO) approach was employed. As the number of BI–BO cycles increased, the amount of the silver nanoparticles loaded into these hydrogels also increased. This behavior was obvious and was confirmed by ultraviolet–visible spectroscopy and thermal analysis. Furthermore, the hydrogel–silver‐nanoparticle composites were confirmed with Fourier transform infrared spectroscopy and transmission electron microscopy studies. Antibacterial studies of these hydrogel–silver nanocomposites showed excellent results against Escherichia coli. The antibacterial activity increased with the number of BI–BO cycles, and samples that underwent three BI–BO cycles showed optimal bactericidal activity. The degree of crosslinking and the silver content had a great influence on the antibacterial efficacy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of an oxygen‐ion beam (O+7, 100 MeV) and γ irradiation on polypyrrole films

Nanostructured polypyrrole films doped with para‐toluene sulfonic acid were prepared by an electrochemical process, and a comparative study of the effects of swift heavy ions and γ‐ray irradiation on the structural and optical properties of the polypyrrole was carried out. Oxygen‐ion (energy = 100 MeV, charge state = +7) fluence varied from 1 × 10¹⁰ to 3 × 10¹² ions/cm², and the γ dose varied from 6.8 to 67 Gy. The polymer films were characterized by X‐ray diffraction, ultraviolet–visible spectroscopy, and scanning electron microscopy. The X‐ray diffraction pattern showed that after irradiation, the crystallinity improved with increasing fluence because of an increase in the crystalline regions dispersed in an amorphous phase. The ultraviolet–visible spectra showed a shift in the absorbance edge toward higher wavelengths, which indicated a significant decrease in the band gap of the polypyrrole film after irradiation. The scanning electron microscopy study showed a systematic change in the surface of the polymer. A similar pattern was observed with the γ irradiation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly(vinyl alcohol)‐g‐lactic acid copolymers and films with silver nanoparticles

Poly(vinyl alcohol) (PVA), a well‐known synthetic biodegradable, biocompatible, and hydrophilic polymer is susceptible to several structural modifications, due to the presence of hydroxyl groups in its backbone. PVA was grafted with L (+)‐lactic acid (LA) in molar ratios VA/LA (1/1, 1.5/1, and 2.2/1), manganese acetate as catalyst, by solution polycondensation procedure, resulting the poly(vinyl alcohol)‐g‐lactic acid copolymers. Aqueous solutions of copolymers with glycerol as plasticizer, silver nanoparticles (Ag^o), and sodium tetraborate as crosslinking agent were used for films casting. The copolymers were characterized by FTIR and ¹H RMN spectroscopy, gel permeation chromatography, thermal analyses (DTG and DSC), silver particles size, while films were characterized by mechanical properties and mechanodynamic analyses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrical conductivity and thermal properties of poly(m‐aminophenyl acetic acid) and its copolymers with aniline

Poly(m‐aminophenyl acetic acid) was synthesized under different conditions from the respective monomer, using ammonium persulfate as oxidizing agent in both the presence and the absence of CuCl₂ in HCl(aq). Moreover, the copolymers between aniline and m‐aminophenyl acetic acid were prepared at several feed mol ratios (f₁) of aniline. Copper was introduced by the Batch method in the homo‐ and copolymers of different compositions. The polymers were characterized by FTIR and UV‐vis spectroscopy, elemental analysis, thermal analysis, and electrical conductivity. The thermal stability and the content of copper increased as the content of aniline was increased in the copolymers. Moreover, the copolymers showed a high thermal stability; at 400°C a weight loss < 10% was observed. The electrical conductivity was increased with a higher content of aniline in the copolymers, achieving semiconduction values. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1484–1492, 2003     

Comparative investigation of the ultraviolet stabilization of polycarbonate/poly(acrylonitrile–butadiene–styrene) with different ultraviolet absorbers

When polycarbonate (PC)/poly(acrylonitrile–butadiene–styrene) (ABS) blends are exposed to outdoor conditions, they are mainly degraded by sunlight; this is known as photodegradation. It is the ultraviolet radiation in the sunlight that is responsible for the degradation of the blend. To stabilize the blend against the harmful ultraviolet radiation, ultraviolet absorbers (UVAs) are used. In this study, three different UVAs—Tinuvin 1577 (a hydroxyphenyl triazine type), Cyasorb 5411 (a benzotriazole type), and Uvinul 3030 (a cyanoacrylate type)—were compounded with a PC/ABS blend at 240°C with a twin‐screw extruder. Accelerated aging of the compounded sample was done by an Atlas Suntest containing xenon lamp. The degradation studies were performed with ultraviolet–visible spectroscopy, attenuated total reflectance/Fourier transform infrared spectroscopy, and yellowing index measurements. The molecular weight of the compounded sample was determined by gel permeation chromatography. It was found that hydroxyphenyl triazine type UVA showed the best results for decreasing the degradation products, oxidation rate, and yellowing of the PC/ABS blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Facile Incorporation of Silver Nanoparticles into Quaternized Poly(2‐(Dimethylamino)Ethyl Methacrylate) Brushes as Bifunctional Antibacterial Coatings

A simple strategy to fabricate bifunctional antibacterial coatings via in situ synthesis and incorporation of silver nanoparticles (AgNPs) into quaternized poly(2‐(dimethylamino)ethyl methacrylate) (qPDMAEMA) brushes without using any reducing agents is reported. PDMAEMA brushes are prepared on Si wafer substrates via surface‐initiated reverse atom transfer radical polymerization, which then are quaternized with ethyl bromide and hexyl bromide, respectively. The resulting qPDMAEMA‐AgNP nanocomposite coatings are characterized by using Fourier‐transform infrared spectroscopy (FT‐IR), X‐ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE‐SEM), and Raman spectroscopy. FE‐SEM and Raman results indicate that the AgNPs with an average diameter of 35 nm are successfully loaded into the qPDMAEMA brushes. Furthermore, the antibacterial activities of the qPDMAEMA‐AgNP nanocomposite coatings against Gram‐positive Staphylococcus aureus and Gram‐negative Escherichia coli are investigated by both disc diffusion and colony‐forming unit methods. The results show excellent antibacterial properties of the nanocomposite coatings. The influence of the length of the quaternization agents on their antibacterial properties is also investigated.

     

Influence of LiClO4 on the thermal,mechanical, and morphological properties of P(DMS‐co‐EO)/ P(EPI‐co‐EO) blends

The UV‐vis absorption, thermal analysis, ionic conductivity, mechanical properties, and morphology of a blend of poly(dimethylsiloxane‐co‐ethylene oxide) [P(DMS‐co‐EO)] and poly(epichlorohydrin‐co‐ethylene oxide) [P(EPI‐co‐EO)] (P(DMS‐co‐EO)/P(EPI‐co‐EO) ratio of 15/85 wt %) with different concentrations of LiClO₄ were studied. The maximum ionic conductivity (σ = 1.2 × 10^?4 S cm^?1) for the blend was obtained in the presence of 6% wt LiClO₄. The crystalline phase of the blend disappeared with increasing salt concentration, whereas the glass transition temperature (T_g) progressively increased. UV‐vis absorption spectra for the blends with LiClO₄ showed a transparent polymer electrolyte in the visible region. The addition of lithium salt decreased the tensile strength and elongation at break and increased Young's modulus of the blends. Scanning electron microscopy showed separation of the phases between P(DMS‐co‐EO) and P(EPI‐co‐EO), and the presence of LiClO₄ made the blends more susceptible to cracking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1230–1235, 2004     

Synthesis,characterization, and comparison of self‐doped,doped, and undoped forms of polyaniline,poly(o‐anisidine), and poly[aniline‐co‐(o‐anisidine)]

Polyaniline (PANI), poly(o‐anisidine), and poly[aniline‐co‐(o‐anisidine)] were synthesized by chemical oxidative polymerization with ammonium persulfate as an oxidizing reagent in an HCl medium. The viscosities, electrical conductivity, and crystallinity of the resulting polymers (self‐doped forms) were compared with those of the doped and undoped forms. The self‐doped, doped, and undoped forms of these polymers were characterized with infrared spectroscopy, ultraviolet–visible spectroscopy, and a four‐point‐probe conductivity method. X‐ray diffraction characterization revealed the crystalline nature of the polymers. The observed decrease in the conductivity of the copolymer and poly(o‐anisidine) with respect to PANI was attributed to the incorporation of the methoxy moieties into the PANI chain. The homopolymers attained conductivity in the range of 3.97 × 10^?3 to 7.8 S/cm after doping with HCl. The conductivity of the undoped forms of the poly[aniline‐co‐(o‐anisidine)] and poly(o‐anisidine) was observed to be lower than 10^?5 J/S cm^?1. The conductivity of the studied polymer forms decreased by the doping process in the following order: self‐doped → doped → undoped. The conductivity of the studied polymers decreased by the monomer species in the following order: PANI → poly[aniline‐co‐(o‐anisidine)] → poly(o‐anisidine). All the polymer samples were largely amorphous, but with the attachment of the pendant groups of anisidine to the polymer system, the crystallinity region increased. The undoped form of poly[aniline‐co‐(o‐anisidine)] had good solubility in common organic solvents, whereas doped poly[aniline‐co‐(o‐anisidine)] was moderately crystalline and exhibited higher conductivity than the anisidine homopolymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Synthesis and Properties of Branched Oligo(2‐thienyl)‐ and Oligo(2,2′‐bithien‐5‐yl)‐Substituted Pyridine Derivatives

Starting from easily accessible precursors we describe the preparation of a series of branched oligo(2‐thienyl)‐ and oligo(2,2′‐bithienyl)‐substituted pyridine derivatives. With palladium‐catalyzed cross‐coupling reactions of pyridyl nonaflates/triflates as key steps we synthesized 2,6‐di(2‐thienyl)pyridines bridged by thiophene or benzene rings. By selective bromination of 2,6‐di(2‐thienyl)pyridine and 2,4,6‐tri(2‐thienyl)pyridine and subsequent coupling reactions an access to oligo(2,2′‐bithien‐5‐yl)‐substituted pyridine derivatives was gained. The constitution and solid state conformation of 2,6‐bis(2,2’‐bithien‐5‐yl)pyridine was determined by X‐ray analysis. This series of new pyridine‐thiophene conjugates was systematically investigated by UV/vis spectroscopy. Large Stokes shifts in the neutral and protonated form were observed. The electrochemical oxidation of two typical compounds was studied, however, these oxidations were irreversible forming a polymeric film at the anode. As a selected example, a thiophene‐bridged 2,6‐di(2‐thienyl)pyridine derivative was also investigated by scanning tunneling microscopy showing an interesting self‐assembly into a highly ordered monolayer on highly oriented pyrolytic graphite.

     

Stability constants of polymer‐bound iminodiacetate‐type chelating agents with some transition‐metal ions

A chelating vinyl monomer, glycidyl methacrylate (GMA)–iminodiacetic acid (IDA), was formed by the reaction between GMA and IDA. Three polymeric chelating agents, PGMA–IDA, PGMA–IDA‐co‐methyl acrylate (MA), and PGMA–IDA‐co‐acrylamide (AAm), were also synthesized. Acid dissociation constants and stability constants of these chelating agents with Ni(II), Zn(II), and Co(II) were determined by means of potentiometric titration and ultraviolet–visible spectrophotometry, respectively. The values of K_a1 and K_a2 of all the polymeric chelating agents were smaller than those of GMA–IDA. The stability constants of all the polymeric chelating agents were larger than those of GMA–IDA. Increasing the MA content within PGMA–IDA‐co‐MA affected the stability constant only slightly. A proper molar ratio of AAm in PGMA–IDA‐co‐AAm, stability constants was 30–60 times greater than that of GMA–IDA. However, as the molar content of AAm increased, the stability constant of PGMA–IDA‐co‐AAm decreased. The results obtained in the polymer system are explained in terms of the polymer's stereo and entanglement structure, the neighboring effect, and the hydrophobic/hydrophilic nature of MA or AAm. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1986–1994, 2002     

Co‐poly(vinyl chloride‐vinyl acetate‐vinyl alcohol)‐silica nanocomposites from sol–gel process: Morphological,mechanical, and thermal investigations

Organic–inorganic nanocomposites consisting of co‐poly(vinyl chloride‐vinyl acetate‐vinyl alcohol) and silica were prepared via sol–gel process. Two types of hybrids were prepared, one in which interactions between hydroxyl group present in the copolymer chain and silanol groups of silica network were developed. In the second set, extensive chemical bonding between the phases was achieved through the reaction of hydroxyl groups on the copolymer chains with 3‐isocyanatopropyltriethoxysilane (ICTS). Hydrolysis and condensation of tetraethoxysilane and pendant ethoxy groups on the chain yielded inorganic network structure. Mechanical and thermal behaviors of the hybrid films were studied. Increase in Young's modulus, tensile strength, and toughness was observed up to 2.5 wt % silica content relative to the neat copolymer. The system in which ICTS was employed as binding agent, the tensile strength and toughness of hybrid films increased significantly as compared to the pure copolymer. Thermogravimetric analysis showed that these nanocomposite materials were stable up to 250°C. The glass transition temperature increases up to 2.5 wt % addition of silica in both the systems. Field emission scanning electron microscope results revealed uniform distribution of silica in the copolymer matrix. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Proanthocyanidin‐Induced Horizontal Arrangement in Poly(vinyl alcohol)/Graphene Composites with Enhanced Mechanical Properties

A green approach is employed to prepare mechanically enhanced composites by adding noncovalently proanthocyanidin (PC)‐modified graphene (PC‐rGO) into poly(vinyl alcohol) (PVA). Ascorbic acid (AA) is used as the reducing agent, and PC is used as a dispersant to synthesize low‐defect and fully dispersed graphene. After static treatment, the PC‐rGO sheets in the composite form a horizontally arranged structure. Compared with neat PVA, the Young's modulus of the graphene‐modified composites is significantly enhanced by approximately 79.3% with incorporation of 0.9 wt% PC‐rGO. The composites incorporated with GO or AA‐rGO (without PC) have randomly distributed GO structures and apparent rGO agglomeration, resulting in a weaker mechanical property. The dispersibility, degree of defects, distribution state of graphene, and interactions with the polymer matrix are directly related to the final mechanical performance. This new approach to mechanically enhance graphene‐embedded PVA composites provides the possibility for large‐scale production of graphene‐reinforced composite materials.     

Ligating behavior and metal uptake of N‐sulphonylpolyamine chelating resins anchored on polystyrene‐divinylbenzene beads

Amberlite XAD‐2 has been functionalized by coupling through –SO₂‐with ethylenediamine, propylenediamine, and diethylenetriamine to give the corresponding polyamine chelating resins I–III. The solid metallopolymer complexes of the synthesized chelating resins with Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ were synthesized. The polyamine derivatives and their metal complexes were characterized by elemental analysis, spectral (IR, UV/V, and ESR), and magnetic studies. The batch equilibrium method was utilized for using the chelating polyamines for the removal of Cu⁺², Zn⁺², Cd⁺², and Pb⁺² ions from aqueous solutions at different pH values and different shaking times at room temperature. The selective extraction of Cu⁺² from a mixture of the four metal ions and the metal capacities of the chelating resins were evaluated using atomic absorption spectroscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1839–1846, 2005     

Poly(vinyl alcohol) nanocomposites with different clays: Pristine clays and organoclays

Poly(vinyl alcohol) (PVA)/clay nanocomposites were synthesized using the solution intercalation method. Na ion‐exchanged clays [Na⁺–saponite (SPT) and Na⁺–montmorillonite (MMT)] and alkyl ammonium ion‐exchanged clays (C₁₂–MMT and C₁₂OOH–MMT) were used for the PVA nanocomposites. From the morphological studies, the Na ion‐exchanged clay is more easily dispersed in a PVA matrix than is the alkyl ammonium ion‐exchanged clay. Attempts were also made to improve both the thermal stabilities and the tensile properties of PVA/clay nanocomposite films, and it was found that the addition of only a small amount of clay was sufficient for that purpose. Both the ultimate tensile strength and the initial modulus for the nanocomposites increased gradually with clay loading up to 8 wt %. In C₁₂OOH–MMT, the maximum enhancement of the ultimate tensile strength and the initial modulus for the nanocomposites was observed for blends containing 6 wt % organoclay. Na ion‐exchanged clays have higher tensile strengths than those of organic alkyl‐exchanged clays in PVA nanocomposites films. On the other hand, organic alkyl‐exchanged clays have initial moduli that are better than those of Na ion‐exchanged clays. Overall, the content of clay particles in the polymer matrix affect both the thermal stability and the tensile properties of the polymer/clay nanocomposites. However, a change in thermal stability with clay was not significant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3208–3214, 2003     

Water‐Resistant Poly(vinyl alcohol)‐Silica Hybrids through Sol‐Gel Processing

Poly(vinyl alcohol) (PVA)‐silica hybrids with exceptionally reduced solubility in water were synthesized. The hybrid xerogels were fabricated through sol‐gel processing of a mixture of PVA and the acid‐catalyzed silica precursor tetraethoxysilane. The effects of varying ratios of PVA and silica precursor on the surface structure, thermal properties, crystallinity, and solubility of the hybrids were investigated. Unlike the highly water‐soluble nature of PVA, all the hybrids displayed considerably reduced solubility in water. This anomalous behavior of PVA in the hybrids can be attributed to the unavailability of its pendant –OH groups. Water‐resistant PVA‐silica hybrids can find applications in various technologies requiring biocompatible systems that are stable in aqueous environments.