Fluoroelastomer‐MWNT nanocomposites‐1: Dispersion,morphology, physico‐mechanical,and thermal properties

The present article reports the preparation and characterization of fluoroelastomer/multi‐walled nanotube hybrid nanocomposites prepared by conventional rubber mixing using a two‐roll mill. The morphology of the resulting hybrid nanocomposites were characterized by X‐ray diffraction (XRD), scanning (SEM) and transmission electron microscopies (TEM). SEM photographs showed the formation of completely exfoliated and uniformly dispersed nanotubes in the polymer matrix during the high shear mixing process. Magnetic force microscopy (MFM) has been used to further study the topography of the composites which also showed complete exfoliation. The effect of increasing MWNT loadings on the mechanical properties like tensile strength, modulus, elongation at break, hardness, and tear resistance has also been studied. The fracture surface of the composite has been studied by SEM. A “cross hatched pattern” has been observed. The thermal stability of the composites has been studied by TGA and increase in decomposition temperature with increase in MWNT loadings has been observed which was attributed to the antioxidant nature of nanotubes. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.     

Chitosan‐graft‐acrylamide polyelectrolytes: Synthesis,flocculation, and modeling

A series of chitosans have been grafted with quaternary ammonium cationic monomers, as well as acrylamide using Ce(IV) to induce macroradical formation on the polysaccharide backbone. The materials, which have long chain branches per molecule between 0.3 and 5.5, are shown to provide very high specific flocculation efficiency, at the very least equal to the entirely synthetic materials which have been previously documented in the literature. A charge ratio, determined from the polymer concentration at which flocculation takes place, the charge density of the polymer, and the surface charge of the suspended matter are proposed as metrics to evaluate the occurrence of charge neutralization and bridging or charge patch flocculation mechanism. Furthermore, a window of application (WA) for flocculants, which characterizes the region of concentration wherein the polyelectrolyte can remove 99% of the supernatant turbidity, has been defined. It was shown to depend on the square root of the ionic strength and varies inversely with the Debye length, providing a fundamental basis for the concept of the WA. A mathematical expression is presented which links the WA with the salt concentration and the number of branches of the grafted polymer. Grafted chitosans have been shown to be more robust than polyacrylamides in testing against model kaolin suspensions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 885–896, 2006     

Well‐defined polymers containing 1,3‐dichloro‐tetra‐n‐butyl‐distannoxane moiety: Synthesis,mechanism, and applications in catalysis

A series of well‐defined different chain lengths polymers, which contain the organometallic 1,3‐dichloro‐tetra‐n‐butyl‐distannoxane core in the main chain, was obtained in one‐pot via a novel 1,3‐dichloro‐tetra‐n‐butyl‐distannoxane (complex A )/azobisisobutyronitrile (AIBN) initiating system used in reverse atom transfer radical polymerization of styrene in different concentrations. The introduction of organotin complex A was supported by ¹H‐NMR, ¹³C–NMR, and the Inductive Coupled Plasma Emission Spectrometer analysis of the organotin‐containing polymer. Moreover, the mechanism of polymerization was investigated by changing the ratio of complex A to AIBN. It was concluded that the complex A not only acted as an important part of the initiator system but also introduced the functional organometallic group into the polymer chain. Additionally, the organotin‐containing polymer could be used as catalyst for esterification, and the reaction products' conversion could reach high up to 99% and does not decrease after four successive cycles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Temperature‐responsive alginate‐g‐poly(N,N‐diethylacrylamide) copolymer: Synthesis,characterization, and swelling behavior

Temperature‐responsive polymers have recently gained importance due to their applications in drug delivery. Herein, temperature‐responsive graft copolymer (Alg‐g‐PDEAAm) of alginate and N,N‐diethylacrylamide was synthesized by microwave‐assisted copolymerization using potassium persulfate/N,N,N′,N′‐tetramethylethylenediamine initiator system. The reaction conditions for the best grafting (331%) have been optimized by changing microwave irradiation time, temperature, N,N‐diethylacrylamide, and alginate concentrations. The spectroscopic characteristic, thermal properties, and surface morphology of the copolymers were investigated by FTIR, ¹H‐NMR, DSC/TGA, XRD, gel permeation chromatography, and SEM. Furthermore, low critical solution temperatures of Alg‐g‐PDEAAm copolymers were detected by UV spectroscopy. Swelling ratio of graft microspheres was carried out at 25, 32, and 37 °C, and microspheres were found exhibiting temperature‐responsive property. Cytotoxicity test indicated the Alg‐g‐PDEAAm copolymer and its microsphere were biocompatible. Therefore, based on the results the synthesized temperature‐responsive copolymer could be considered as a promising biomaterial. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46688.     

New anthracene‐containing phenylene‐ or thienylene‐vinylene copolymers: Synthesis,characterization, photophysics,and photovoltaics

Four new conjugated alternating vinylene‐copolymers, PAP6 , PAT , PA , and TAT , incorporating anthracene rings along the backbone were synthesized by Heck coupling. They were very soluble in common organic solvents and absorbed at the range of 300–500 nm with optical band gaps of 2.38–2.47 eV. They behaved in solution as green emitters, with maximum photoluminescence at 455–518 nm. Finally, these soluble copolymers were used as donor material to realize bulk heterojunction solar cell with (6,6)‐C₆₁‐butyric acid methyl ester as the acceptor. More efficient photovoltaic cells were obtained from the copolymer that carried hexyloxy than dodecyloxy side groups. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal‐ and Photo‐Induced Isomerization of All‐E‐ and Z‐Isomer‐Rich Xanthophylls: Astaxanthin and Its Structurally‐Related Xanthophylls,Adonirubin, and Adonixanthin

The effects of heating and photo‐irradiation on the stability of all‐E‐isomer‐rich and Z‐isomer‐rich xanthophylls, astaxanthin and its structurally related xanthophylls, adonirubin, and adonixanthin, are investigated. The xanthophylls with high Z‐isomer content are prepared from their high‐purity all‐E‐isomers by thermal isomerization and filtering techniques, that is, total Z‐isomer ratios of adonirubin, astaxanthin, and adonixanthin are 80.9%, 89.5%, and 72.5%, respectively. The all‐E‐ and Z‐isomer‐rich xanthophylls dissolved in ethanol are stored at 4, 30, and 50 °C in the dark and at 30 °C under photo‐irradiation using a fluorescent light for 21 days. In the all‐E‐isomer‐rich xanthophylls, as the storage temperature increases, the total Z‐isomer ratio becomes higher, whereas in the Z‐isomer‐rich xanthophylls, the all‐E‐isomer ratio becomes higher. Photo‐irradiation slightly promotes Z‐isomerization in (all‐E)‐xanthophylls, but highly promotes all‐E‐isomerization in Z‐isomer‐rich xanthophylls. In addition, photo‐irradiation prevents thermal Z‐isomerization of (all‐E)‐xanthophylls. Moreover, it is found that some xanthophyll Z‐isomers such as (9Z)‐astaxanthin are more stable than that of the other Z‐isomers against heating and photo‐irradiation. These findings can contribute not only to establishing suitable storage conditions for Z‐isomer‐rich xanthophylls, but also to developing control techniques for the E/Z‐isomer ratio of the xanthophylls. Practical Applications: The fundamental data on the stability of xanthophyll isomers against heating and photo‐irradiation and finding stable xanthophyll Z‐isomers are very important to develop xanthophyll materials rich in the Z‐isomers. Moreover, this study clearly shows that the heat treatment enhances the Z‐isomerization of xanthophylls, whereas the photo‐irradiation enhances the all‐E‐isomerization and prevents thermal Z‐isomerization of them. This information can be utilized in technology for arbitrarily controlling E/Z‐isomerization of xanthophylls.     

Wet‐spun,photoinitiator‐modified polyacrylonitrile precursor fibers: UV‐assisted stabilization

The role of dilute concentrations (～1 wt %) of a photoinitiator, 4,4 ′ ‐bis(diethylamino)benzophenone, on the processability and properties of the resulting wet‐spun polyacrylonitrile (PAN) fibers are reported. Rheology measurements show no adverse effect on the viscosities of solutions by the addition of the photoinitiator. Fibers containing photoinitiator were successfully wet‐spun from PAN – DMSO solution. FTIR results prove that 4,4 ′ ‐bis(diethylamino)benzophenone was retained in the fibers after coagulation and post‐stretching. SEM micrographs show no deterioration of the post‐stretched fiber microstructure due to the presence of photoinitiator. Tensile testing results show a small reduction in the strain‐at‐break of post‐stretched fibers containing photoinitiator when compared with pure (control) PAN fibers. After UV treatment, fibers with 4,4 ′ ‐bis(diethylamino)benzophenone display a higher tensile modulus compared with the other sets. Wide‐angle X‐ray diffraction results show no significant decrease in interplanar spacing and size of the crystals within the fibers containing photoinitiator, but such fibers retain a higher extent of molecular orientation after being UV treated. Conversion indices were measured from the WAXD spectra and compared with conventional thermal stabilized fibers. This correlation confirms that the addition of 1 wt % photoinitiator to PAN followed by 5 min of UV treatment leads to a conversion index that is observed in control fibers after more than an hour, which could reduce the conventional thermo‐oxidative stabilization time significantly. These results indicate the potential of the dual stabilization route in generating precursor fibers with higher molecular orientation, and possibly reducing the thermo‐oxidation time during carbon fiber processing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2494–2503, 2013     

High‐performance copoly(benzimidazole‐benzoxazole‐imide) fibers: Fabrication,structure, and properties

Novel high‐performance copolyimide (co‐PI) fibers containing benzimidazole and benzoxazole ring in the main chain were prepared by a two‐step spinning via the poly(amic acid)s. Effects of the incorporated benzimidazole and benzoxazole units on the micro‐structure and properties of co‐PI fibers were investigated. Fourier transform infrared (FTIR) results indicated that hydrogen bonding is formed in the co‐PI fibers. The co‐PI fibers exhibited discernible crystallization peaks at 14°～15° and 23°～26° (2θ), showing crystalline‐like structure. Moreover, the packing type of benzimidazole‐imide units determined the macromolecules packing of co‐PIs. It was amazedly found that the co‐PI fibers exhibited higher tensile strength and initial modulus than those of corresponding homo‐PI fibers, reaching tensile strength of 2.2–2.6 GPa, initial modulus of 99.1–113.2 GPa. The results of dynamic mechanical analysis (DMA) indicated co‐PI2 fiber had a positive T_g deviation due to the presence of strong intermolecular hydrogen bonding between benzimidazole‐imide and benzoxazole‐imide units, which maybe lead to the effective stress transfer between benzimidazole‐imide units and benzoxazole‐imide units. In addition, the obtained PI fibers exhibited excellent thermal properties with the 10% weight loss temperatures under N₂ in the range of 574–585°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42001.     

Positive‐tone,aqueous‐developable,polynorbornene dielectric: Lithographic,and dissolution properties

A positive‐tone, aqueous base soluble, polynorbornene (PNB) dielectric formulation has been developed. The photolithographic solubility switching mechanism is based on diazonaphthoquinone (DNQ) inhibition of PNB resin functionalized with pendent fluoroalcohol and carboxylic acid substituents. The optical contrast (at 365 nm) was found to be 2.3. The maximum height‐to‐width aspect ratio of developed line and space features was 3 : 2. The sensitivity, D₁₀₀, of a formulation containing 20 pphr of DNQ photoactive compound (PAC) was calculated to be 408 mJ cm^?2. The effects of the PAC molecule structure on miscibility and dissolution of the photosensitive films in aqueous base developer were studied. The effect of the monomer composition of the PNB polymer on the dissolution rate of the formulated PNB resin was evaluated. A unique dissolution and swelling behavior was observed. The effect is attributed to a copolymer synthesized with two monomers each of which is susceptible to deprotonation in aqueous base. FTIR measurements showed that the pure PNBFA has a small percentage of free hydroxyl groups, which did not change appreciably by the addition of PAC to the mixture. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dial‐a‐size: Precision quantum dot nanopatterning using cheap,off‐the‐shelf copolymers

In the use of block copolymers as templates for nanolithography, deposition, or etching, substantial time and cost savings can be achieved through the use of algebraic models for block copolymer feature size as a function of both the polymer's molecular weight and the relative concentration of a homopolymer additive. Desired average pore diameters and spacing can be achieved on the first try, using off‐the‐shelf polymers in a wide range of molecular weights. This allows precise nanoscopic components such as quantum dots to be patterned over large areas rapidly, repeatably, and at very low cost. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polypropylene nanocomposites with oxo‐degradable pro‐oxidant: Mechanical,thermal, rheological,and photo‐degradation performance

The objective of the study was to generate degradable polypropylene nanocomposites by incorporation of pro‐oxidant and different fillers like silica, silicate, and thermally reduced graphene. Graphene‐based composites exhibited higher crystallinity attributed to better dispersion and high aspect ratio platelets. Graphene composites with 2.5% additive content significantly enhanced the peak degradation temperature to 464°C as compared to 448°C for pure polymer. The processing conditions used for the nanocomposite generation were optimum as a uniform distribution of filler particles (or platelets) was observed in the PP matrix. The tensile modulus of the graphene composite with 2.5% additive content was 80% higher than pure PP, as compared to 60 and 30% for silicate and silica composites, respectively. Similarly, the storage modulus of the graphene nanocomposite with 1% additive content had 30% increment at 40°C as compared to pure PP. PP‐additive blends as well as PP nanocomposites with silica and silicate were observed to attain 100% degree of embrittlement within 6 months of UV exposure at 30°C. Graphene composites, though, had delayed photo‐degradation due to UV absorption by the platelets and high aspect ratio platelets acting as oxygen barrier for PP matrix, but the pro‐oxidant was successful in attaining controlled degradation. POLYM. ENG. SCI., 56:1229–1239, 2016. © 2016 Society of Plastics Engineers     

Surface‐modified sisal fiber‐reinforced eco‐friendly composites: Mechanical,thermal, and diffusion studies

To improve the fiber/matrix interaction, sisal fibers were subjected to various chemical and physical modifications such as mercerization, heating at 100°C, permanganate treatment, benzoylation, and silanization. Polyester composites were fabricated using compression molding. Tensile and flexural properties increased for every treated fiber‐reinforced composites with a reduction in the impact strength. This is attributed to the improved interfacial adhesion between fiber and polyester matrix. An increase in thermal stability was observed for the treated fiber‐reinforced composites especially at lower temperature. Significant reduction in water uptake occurred for the treated fiber‐reinforced composites at 30°C and 90°C. Scanning electron micrograph studies have been used to substantiate the above observations. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Synthesis of poly‐N‐(thiazol‐2‐yl)methacrylamide: Characterization,complexation, and bioactivity

Cu(II) complexes with N‐(thiazol‐2‐yl)methacrylamide (NTM) and its polymer PNTM have been synthesized. The ligands (NTM and PNTM) and their Cu(II) complexes have been characterized by FTIR and ¹H‐NMR. EDX was performed to know the elemental composition and X‐ray powder diffractometry (XRD) analysis was applied to detect the crystallinity of the complexes. The morphology of these complexes was investigated with scanning electron microscopy (SEM) and proves that the monomer complexes have a strongly crystalline structure compared with the polymer complexes, which show that it is only weakly crystalline. These results from SEM are in agreement with results obtained from XRD. Thermal properties of the ligands and their complexes have been studied by thermogravimetric analysis and differential scanning calorimetry. The activity of the ligands and their complexes has been screened against S. aureus, E. coli, Pseudomonas, and Candida albicans. The synthesized compounds have shown good affinity as antibacterial and antifungal agents, which increased on complexation with Cu(II) ion. The results of these studies show the Cu(II) complexes to be more thermal stable as compared with NTM and PNTM. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Addition‐curable propargyl‐containing novolac‐type phenolic resin: Its synthesis,characterization, cure,and thermal properties

In this article, propargyl functionalized novolac resins (PN resins), with varying propargyl contents and varying molecular weights, were synthesized conveniently. The structural characteristics were determined by ¹HNMR and FTIR methods. Thermal cure studies revealed that the uncatalyzed thermal cure was remarkably affected by propargyl extent, while it was hardly affected by molecular weight. The processability of the as‐prepared PN resins was excellent as matrix of composite materials. The cure mechanism was complicated; postcure at high temperature was required to achieve entire crosslink formation. Both dynamic mechanical analysis and thermogravimetric analysis showed that the cured PN resins had substantially improved thermal mechanical properties and thermal stability in comparison to conventional cured phenolics. High propargyl extent was preferred for high thermal stability. The results show that PN resin is one of the ideal candidates for advanced composites matrices in thermostructural and ablative applications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1010–1017, 2006     

1‐amino‐4,5‐8‐naphthalenetricarboxylic acid‐1,8‐lactam‐4,5‐imide‐containing macrocycles: synthesis,molecular modelling and polymerization

Novel macrocycles containing 1‐amino‐4,5‐8‐naphthalenetricarboxylic acid‐1,8‐lactam‐4,5‐imide and 1,4,5‐8‐naphthalenetetracarboxylic bisimide fragments were synthesized by the high‐temperature pseudo‐high‐dilution acylation of the corresponding diols with isophthaloyl chloride, 4,4′‐ and 2,2′‐dichlorocarbonyl biphenyls with up to 60% yield. An important side‐reaction that impedes cyclization was found to be the reaction of diol OH groups with HCl during the acetylation. The ring strain in synthesized macrocyles and model cycles was estimated using the isodesmic reaction approach at the B3LYP/6–311 + G(d,p)//HF/3–21G level of theory. Lactamimide‐containing macrocycles were found to be more strained than bisimide‐containing macrocycles. The ring‐opening polymerization (ROP) of synthesized macrocycles in the molten state shows that the driving force of this process is the strain release on ring‐opening. The ROP of lactamimide‐containing macrocycles was found to be an efficient way to obtain lactamimide‐containing polymers, which are otherwise difficult to synthesize. Copyright © 2003 Society of Chemical Industry     

Polymer Crystallization Studied by Hyphenated Rheology Techniques: Rheo‐NMR,Rheo‐SAXS,and Rheo‐Microscopy

Rheological set‐ups with in situ analytical sensors, combine information on the flow and deformation behavior of soft matter, with simultaneous insights into structural and dynamic features. Furthermore, they permit the study of soft matter under well‐defined flow conditions. Herein are presented hyphenations of rheology and nuclear magnetic resonance (NMR), small angle X‐ray scattering (SAXS), and optical microscopy. They are employed to unravel relationships between the molecular dynamics, morphology, and rheology of crystallizing polymers. The results confirm a physical gelation process during polymer crystallization, mediated by the interaction of growing superstructures at volume fractions of 10–15%. The buildup of row‐nucleated structures during flow‐induced crystallization is found to reduce the time of gelation as detected by the rheological response. These investigations help to clarify the crystallization mechanism, structure–property relationships, and the hardening behavior of crystallizing polymers.     

Plasticization of Poly‐L‐lactide with L‐lactide,D‐lactide,and D,L‐lactide monomers

Poly‐L ‐lactide (PLLA) is being widely considered for repair of damaged tissues, for controlled antibiotic release, and also as scaffolds for cultured cells. PLLA was blended with the lactide monomer in its two enantiomeric forms: D ‐lactide (D ‐la) and L ‐lactide (L ‐la) and with the cyclic dimmer D ,L ‐la, in order to enhance its flexibility and thereby overcome its inherent problem of brittleness. In this work, the crystallization, phase structure, and tensile properties of PLLA and PLLA plasticized with 5, 10, 15, and 20 wt% of D ‐la, L ‐la, and D ,L ‐la are explored. The three plasticizers used were effective in lowering the glass transition temperature (T_g) and the melting temperature (T_m) of PLLA, around 20°C for a plasticizer content of 20 wt%. The tensile strength and modulus of the blends decreased following the increasing content of plasticizers from approximately 58 MPa to values below 20 MPa, and from 1667 to 200 MPa, respectively. Aging the blends at storage ambient temperature revealed that the enhanced flexibility as well as the morphological stability was lost over time due to the migration of the plasticizer to the surface, this being less marked in the case of D ‐la as a result of interactions between the polymer and its enantiomeric monomer of complementary configuration. POLYM. ENG. SCI., 53:2073–2080, 2013. © 2013 Society of Plastics Engineers     

Nonionic water‐soluble polymer: Preparation,characterization, and application of poly(1‐vinyl‐2‐pyrrolidone‐co‐hydroxyethylmethacrylate) as a polychelatogen

The free‐radical copolymerization of water‐soluble poly(1‐vinyl‐2‐pyrrolidone‐co‐hydroxyethylmethacrylate) was carried out with a feed monomer ratio of 75:25 mol %, and the total monomer concentration was 2.67M. The synthesis of the copolymer was carried out in dioxane at 70°C with benzoyl peroxide as the initiator. The copolymer composition was obtained with elemental analysis and ¹H‐NMR spectroscopy. The water‐soluble polymer was characterized with elemental analysis, Fourier transform infrared, ¹H‐ and ¹³C‐NMR spectroscopy, and thermal analysis. Additionally, viscosimetric measurements of the copolymer were performed. The thermal behavior of the copolymer and its complexes were investigated with differential scanning calorimetry (DSC) and thermogravimetry techniques under a nitrogen atmosphere. The copolymer showed high thermal stability and a glass transition in the DSC curves. The separation of various metal ions by the water‐soluble poly(1‐vinyl‐2‐pyrrolidone‐co‐hydroxyethylmethacrylate) reagent in the aqueous phase with liquid‐phase polymer‐based retention was investigated. The method was based on the retention of inorganic ions by this polymer in a membrane filtration cell and subsequent separation of low‐molar‐mass species from the polymer/metal‐ion complex formed. Poly(1‐vinyl‐2‐pyrrolidone‐co‐hydroxyethylmethacrylate) could bind metal ions such as Cr(III), Co(II), Zn(II), Ni(II), Cu(II), Cd(II), and Fe(III) in aqueous solutions at pHs 3, 5, and 7. The retention percentage for all the metal ions in the polymer was increased at pH 7, at which the maximum retention capacity could be observed. The interaction of inorganic ions with the hydrophilic polymer was determined as a function of the pH and filtration factor. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 178–185, 2006     

Modeling of rotational molding process: Multi‐layer slip‐flow model,phase‐change,and warpage

A new multilayer slip‐flow model has been developed to simplify and to overcome current numerical difficulties of two‐dimensional model in predicting the internal air temperature inside a mold during a rotational molding process. The proposed methodology considers a macroscopic “layer‐by‐layer” deposition of a heating polymer bed onto the inner mold surface. A semi‐implicit approach is introduced and applied to compute the complex thermal interactions between the internal air and its surroundings. In the model, the lumped‐parameter system and the coincident node technique are incorporated with the Galerkin finite element model to address the internal air and the deposition of molten polymer beds, respectively. The simple phase‐change algorithm has been proposed to improve the computational cost, numerical nonlinearity, and predicted results. The thermal aspects of the inherent warpage are explored to study its correlation to the weak apparent crystallization‐induced plateau in the temperature profile of the internal air, as in practice. The overall predicted results are in favor with the available experimental data for rotomolded parts of cross‐sectional thicknesses up to 12 mm. POLYM. ENG. SCI. 46:960–969, 2006. © 2006 Society of Plastics Engineers