Effect of γ-Irradiation on the Dielectric Properties of Poly(methyl methacrylate) Doped with Some Luminescent Materials

A systematic dielectric study over the frequency range from 0.1 to 10 MHz has been carried out on pure and doped poly(methyl methacrylate) (PMMA) with tetracyanoquinodimethane (TCNQ) as an acceptor and rhodamine-6G (Rh-6G) and rhodamine-B (Rh-B) as donors before and after being exposed to γ-irradiation. The results indicate that the addition of TCNQ to PMMA increases its ability to withstand γ-irradiation and improves its insulation properties.     

Effect of γ-Irradiation on the Electrical Properties of Poly (Methyl Methacrylate) Doped with Some Transition Metal Complexes

Abstract

The electrical resistivity (p) of pure and doped poly(methyl methacrylate), PMMA, with dithizone (HDZ) and its metal complexes, Zn(HDZ)₂, Cd(HDZ)₂ and Hg(HDZ)₂ has been investigated before and after γ-irradiation. The results show a phase transition at nearly 323°K. The activation energy of the conduction process has been calculated below and above the transition temperature. Further information concerning the electrical behaviour is obtained by considering the type and mechanism of the conduction process. This has been achieved by studying the effect of temperature and γ-irradiation on the mobility and the number of charge carriers which take part in the conduction process.     

Interfacial Interaction Analysis of Blends of Poly(vinylidene fluoride) and Poly(ethylene–butylacrylate–glycidyl methacrylate) Compatibilized by Poly(butylene succinate): Morphologies,Rheological Behavior,and Mechanical Properties

Poly(vinylidene fluoride) (PVDF) and poly(ethylene–butylacrylate–glycidyl methacrylate) (PTW) are polymers with weak interfacial adhesion. Blends based on PVDF and PTW (50/50?w/w) with poly(butylene succinate) (PBS) (0, 1, 3, 5, 7?wt%) are obtained by compression molding. The estimation of interfacial interaction among PVDF, PTW, and PBS and the properties of PVDF/PTW blends are investigated. The optimal content of PBS to form a co-continuous morphology in PVDF/PTW blends is proposed, indicating that the beneficial effect of PBS (7?wt%) on interfacial adhesion is observed. Overall, estimating interfacial adhesion is a critical issue for designing PVDF/PTW blend with excellent performance, which has a prospect in coating.     

Development and Assessment of Electrospun Poly(ε-caprolactone)–Poly(vinylalcohol) Blend Nanofibers for Pest Control in Stored Products

l-Carvone is a constituent of essential oil consisting of monoterpene ketone that possesses various medicinal properties. In this context, the present study focuses on the fabrication and assessment of electrospun poly(ε-caprolactone)–poly(vinylalcohol blend nanofibers imbibed with l-Carvone (5%, w/v) that served as a suitable polymeric carrier to preserve the antimicrobial and antioxidant activities of l-Carvone for a longer period of time. The fumigant potential of l-Carvone and C-PP fibers were assessed toward saw-toothed beetle, a major pest found in stored products. The prepared fragrant C-PP fibers displayed a promising potential formulation for the control of stored product pest such as saw-toothed beetle.     

Surface Morphology and Properties of Rigid Poly(γ-benzyl L-glutamate) Membrane Modified by Flexible Poly(Vinyl Chloride)

Rigid poly(γ-benzyl L-glutamate)/flexible poly(vinyl chloride) (PBLG/PVC) blend membranes were prepared by casting the polymer blend solution in dichloroethane. Structure and morphologies of the PBLG/PVC blend membranes were investigated by Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PBLG/PVC blend membranes were studied by differential scanning calorimetry (DSC), tensile tests, and other physical methods. It was found that the introduction of PVC could exert marked effects on the morphology and the properties of PBLG membrane.     

Thermo- and pH-Responsive Polymersomes of Poly(α,β-N-substituted-DL-aspartamide)s

Materials that can respond to multiple stimuli, such as temperature and pH changes, are of considerable interest for applications in drug delivery systems. Notably, α,β-[poly(2-hydroxyethyl)-DL -aspartamide] is a potentially useful material for such applications. This study investigated the temperature and pH responsiveness of polymers structurally similar to α,β-[poly(2-hydroxyethyl)-DL -aspartamide], namely, poly(α,β-N-substituted-DL -aspartamide)s, in aqueous media. These polymers were derived from polysuccinimide (PSI), which was first synthesized via acid-catalyzed bulk polycondensation of L -aspartic acid (L-ASP) in the presence of 85% o-phosphoric acid under N2. Two primary amino alcohols, 4-aminobutanol (4AB) and 6-aminohexanol (6AH), were then respectively utilized to modify PSI to form poly (α,β-N-substituted-DL -aspartamide)s via aminolysis. Different ratios of these two amino alcohols were used to modify the polymer to produce a series of copolymers with lower critical solution temperatures ranging from 53–28°C when dispersed in aqueous media. Moreover, the properties of the poly(α,β-N- substituted-DL -aspartamide)s in aqueous solution were affected by pH changes. The morphology of the particles formed by these amphiphilic polymers was observed using scanning electronic microscopy and transmission electronic microscopy, and the particles were found to be polymersomes with shell and hollow core structures and diameters of 0.5–1 μm. Other properties of this series of self-assembly copolymers were also characterized. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Toughening and Compatibilization of Acrylonitrile–Butadiene–Styrene/Poly (Ethylene Terephthalate) Blends Using an Oxazoline-Functionalized Impact Modifier

An oxazoline-functionalized core–shell impact modifier was synthesized between aminoethanol and acrylonitrile/butadiene/styrene high rubber powder. According to the Fourier transform infrared spectroscopy test, the nitrile groups were partially converted into oxazoline groups successfully. The oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder was used as an impact modifier for acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends. The differential scanning calorimeter and rheological tests demonstrated that poly(ethylene terephthalate) was partially miscible with acrylonitrile–butadiene–styrene, because the oxazoline groups of oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder reacted with the end groups of poly(ethylene terephthalate). The results of scanning electron microscopy indicated that the morphology of acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends with proper oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder content was improved significantly. The best mechanical properties were achieved, When 6 wt% oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder was added into acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends.     

Synthesis,Characterization, and Evaluation of Gel‐Type Poly(4‐Vinylpyridine) Resins for Plutonium Sorption

Abstract

Three different cross‐linked (4, 8, and 12%) gel‐type strong‐base poly(4‐vinylpyridine) resins (PVP) have been synthesized and characterized by elemental analysis, IR, exchange capacity, and moisture content. The uptake of plutonium and uranium was measured as a function of nitric acid concentration using all the three PVP resins. Plutonium sorption and elution kinetics experiments were also performed on all three PVP resins and compared with the benchmark, a gel‐type quarternary ammonium type anion‐exchange resin. The plutonium sorption rate decreases with the increase in cross‐linkage of the resin. All the three PVP resins exhibit better elution kinetics compared to the benchmark. The results on kinetic experiments performed on all three‐gel‐type resins indicated 8% gel‐type PVP resin with 50–100 mesh as a better candidate for plutonium processing or purification. Radiation degradation studies were carried out on the 8% PVP resin by gamma irradiation up to 200 MRad. The irradiated resins were characterized by IR, TGA, and SEM.

The exchange capacity, moisture content, and plutonium uptake were also evaluated for the irradiated PVP resins in comparison with the benchmark. The results indicated a better radiation stability for PVP resin over the benchmark.     

Morphological and Thermal Properties of Poly(amide-imide)/ZnO Nanocomposites Derived from 4,4′-methylenebis(3-chloro-2,6-diethyl trimellitimidobenzene) and 3,5-diamino-N-(4-hydroxyphenyl)benzamide

A new nanostructure poly(amide-imide) (PAI) was prepared from the polymerization of 4,4′-methylenebis(3-chloro-2,6-diethyl trimellitimidobenzene) as a diacid with 3,5-diamino-N-(4-hydroxyphenyl)benzamide using triphenyl phosphite as a condensing agent and tetra-n-butylammonium bromide as a green media. The synthesized polymer was used to prepare PAI/ZnO nanocomposites (PZNC)s using nano-ZnO surface-coupled by N-trimellitylimido-L-alanine diacid as a coupling agent through ultrasonic process. The resulting PZNCs were also characterized by FT-IR, powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The TEM and FE-SEM results showed a good dispersion of nanoscale inorganic particles in the polymer matrix.     

Reaction Pathways for the Enzymatic Degradation of Poly(Ethylene Terephthalate): What Characterizes an Efficient PET-Hydrolase?

Bioprocessing of polyester waste has emerged as a promising tool in the quest for a cyclic plastic economy. One key step is the enzymatic breakdown of the polymer, and this entails a complicated pathway with substrates, intermediates, and products of variable size and solubility. We have elucidated this pathway for poly(ethylene terephthalate) (PET) and four enzymes. Specifically, we combined different kinetic measurements and a novel stochastic model and found that the ability to hydrolyze internal bonds in the polymer (endo-lytic activity) was a key parameter for overall enzyme performance. Endo-lytic activity promoted the release of soluble PET fragments with two or three aromatic rings, which, in turn, were broken down with remarkable efficiency (k_cat/K_M values of about 10⁵ M⁻¹s⁻¹) in the aqueous bulk. This meant that approximatly 70 % of the final, monoaromatic products were formed via soluble di- or tri-aromatic intermediates.     

Structure and Performance of Poly(vinyl alcohol)/Poly(γ-benzyl L-glutamate) Blend Membranes

Poly(vinyl alcohol) (PVA)/poly(γ-benzyl L-glutamate) (PBLG) blend membranes with different PBLG wt contents were prepared by pervaporation. Structure and surface morphologies of PVA/PBLG blend membranes were investigated by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PVA/PBLG blend membrane were studied by differential scanning calorimeter (DSC), tensile strength tests, and other physical methods. It was revealed that the introduction of PBLG homopolymer into PVA could exert an outstanding effect on the properties of PVA membrane.     

Synthesis,characterization, and platinum-catalyzed cross-linking of 1,4-bis(1-methyl-1-silacyclobutyl) benzene,co-oligo(1-silacyclobut-1-ylidene-1,4-phenylene), and co-oligo(1-silacyclobut-1-ylidene-4,4′-diphenylene)

1,4-bis(1-Methyl-1-silacyclobutyl)benzene (I) has been prepared by the reaction of 1-chloro-1-methyl-1-silacyclobutane with the di-Grignard reagent prepared fromp-dibromobenzene. In a similar manner, co-oligo(1-silacyclobut-1-ylidene-1,4-phenylene) (II) and co-oligo(1-silacyclobut-1-ylidene-4,4′-biphenylene) (III) have been prepared by condensation oligomerization between 1,1-dichloro-1-silacyclobutane and the di-Grignard reagents prepared fromp-dibromobenzene and 4,4′-dibromobiphenyl, respectively. These have been characterized by¹H,¹³C, and²⁹Si NMR as well as FT-IR and UV spectroscopy. The molecular weight distributions of these co-oligomers have been determined by GPC. Their thermal stabilities have been evaluated by TGA. Thermal degradation of these co-oligomers in nitrogen gives high (60%) char yields. The stability of these chars in air has been determined. TheT _g's of these co-oligomers have been measured by DSC. Platinum-catalyzed ring opening of the silacyclobutane rings ofI,II, andIII cross-links these to thermoset materials. The bending moduli (logE′), tan δ, andT _g's of these materials have been determined by DMTA. The dielectric constant and dissipation factor of cross-linkedII are reported.     

Lipase Catalyzed Synthesis and Thermal Properties of Poly(dimethylsiloxane)–Poly(ethylene glycol) Amphiphilic Block Copolymers

Resin immobilized lipase B from Candida antarctica (CALB) was used to catalyze the condensation polymerization of two difuctional siloxane and poly(ethylene glycol) systems. In the first system, 1,3-bis(3-carboxypropyl)tetramethyldisiloxane was reacted with poly(ethylene glycol) (PEG having a number-average molecular weight, M_n = 400, 1000 and 3400 g mol⁻¹, respectively). In the second system, α,ω-(dihydroxy alkyl) terminated poly(dimethylsiloxane) (HAT-PDMS, M_n = 2500 g mol⁻¹) was reacted with α,ω-(diacid) terminated poly(ethylene glycol) (PEG, M_n = 600 g mol⁻¹). All the reactions were carried out in the bulk (without use of solvent) at 80 °C and under reduced pressure (500 mmHg vacuum gauge). The progress of the polyesterification reactions was monitored by analyzing the samples collected at various time intervals using FTIR and GPC. The thermal properties of the copolymers were characterized by DSC and TGA. In particular, the effect of the chain length of the PEG block on the molar mass build up and on the thermal stability of the copolymers was also studied. The thermal stability of the enzymatically synthesized copolymers was found to increase with increased dimethylsiloxane content in the copolymers.     

Design and Characterization of Chiral and Thermally Stable Nanostructure Poly(amide-imide)s Containing Different Trimellitylimido-Amino Acid-Based Diacids and 4,4′-Methylenebis(3-chloro-2,6-diethylaniline) Units

In this study new chiral nanostructure poly(amide-imide)s (PAI)s were synthesized via direct polycondensation of different trimellitylimido-amino acid-based diacids and 4,4′-methylenebis(3-chloro-2,6-diethylaniline), using tetra-n-butylammonium bromide and triphenyl phosphite as a green media. The formation of these nanostructure PAIs was confirmed by ¹H-NMR, Fourier transform infrared spectroscopy, specific rotation, elemental analysis, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and thermo gravimetric analysis techniques. The FE-SEM micrographs and XRD patterns showed that, the obtained PAIs are nanostructured with different shapes and noncrystalline polymers.     

Enhancement of Poly(Vinyl Alcohol)–Poly(Vinyl Pyrrolidone) Blend Properties using Modified Copper (II) Oxide and Ultrasonic Irradiation

Copper (II) oxide nanoparticles supported within poly(vinyl alcohol)/poly(vinyl pyrrolidone) films have been successfully prepared through ultrasonication method. It is discernible that before the preparation of blends, the surface of copper (II) oxide nanoparticles was modified with citric acid and vitamin C as biosafe capping agents. X-ray diffraction scans illustrated the semicrystalline nature of the obtained pure blend and exhibited a good combination between the blend and the modified copper (II) oxide nanoparticles. Also, thermal stability of blends was improved in comparison to the pure polymer blend with increasing modified copper (II) oxide nanoparticles.     

Kinetic investigation and regularities during the synthesis of Poly(ε-caprolactam-co-ε-caprolactone) and Poly(ε-caprolactam-co-δ-valerolactone) biodegradable copolymers

Summary Large diversity of tailor-made poly[(ε-caprolactam)-co-(ε-caprolactone)] P[(CLA)-co-(CLO)] and poly[(ε-caprolactam)-co-(δ-valerolactone)] P[(CLA)-co-(VLO)] copolymers have been obtained via activated anionic polymerization of ε-caprolactam (CLA) with sodium caprolactam (NaCL) as a basic initiator. In the present study several poly(ε-caprolactones) (PCLOs) and poly(δ-valerolactone) polyols were employed as effective bifunctional polymeric activators (PACs) and suitable comonomers of CLA. The obtained poly(esteramides) PEAS were isolated and their structure was confirmed by the ¹H NMR and FTIR spectroscopy. The influence of the molecular weight and type of the PACs, the CLA/PAC ratio and polymerization conditions on the conversion, intrinsic viscosity and polymerization kinetic was explored. The results demonstrated that the use of the PACs reduces the polymerization time to several minutes and polymerization process proceeds without induction period at low energy of activation and high yield of copolymers. Evaluation of the PACs activity and the activation energy confirmed that the PACs are highly active compounds efficient to CLA features modification.     

Three three-dimensional supramolecular networks formed by one-dimensional chains of Ag(I) and N,N′-di(3-pyridyl)succinamide via weak intermolecular interactions

Reactions of N,N′-di(3-pyridyl)succinamide (L) with AgOTf, AgTFA and AgNO₃ (OTf = triflate, TFA = trifluoroacetate) produced three coordination polymers {Ag(L)(OTf)·DMF·MeCN}_n (1·DMF·MeCN), {Ag(L)(TFA)·2H₂O}_n (2·2H₂O) and {[Ag(L)]₂(NO₃)₂}_n (3), respectively. In 1, two one-dimensional (1D) [Ag(L)] chains are joined by the Ag⋯Ag, π⋯π and hydrogen-bonding interactions to form a 1D double chain, which is further linked to other equivalent ones via the hydrogen bonding interactions to yield a three-dimensional (3D) structure. In 2, the 1D [Ag(L)] helical chains are connected by the Ag⋯O, π⋯π, CH⋯π and hydrogen-bonding interactions to afford a 3D framework. In 3, two kinds of 1D [Ag(L)] chains are linked by the Ag⋯O and hydrogen-bonding interactions to form a 3D structure. The luminescent properties of 1–3 along with L were also investigated.     

Coordination of cobalt(III), nickel(II), copper(II), palladium(II) and platinum(II) with N-ethyl-N′-(4′-methylthiazol-2′-yl)thiourea (HL)

Coordination complexes of formula [ML₂], [CoL₃], [Pd(HL)Cl₂], [CuLCl(H₂O)] and [CuL₂(H₂O)₂] {L=anion of N-ethyl-N^′-(4^′-methylthiazol-2′-yl)thiourea; M=Pt^II, Pd^II or Ni^II} were prepared and characterized by elemental analyses, magnetic susceptibilities, and by IR, NMR, electronic and mass spectral measurements.