Conversion Of Poly Research Articles

Fabrication of carbon fibers from the cupric ion impregnated and thermally stabilized poly(hexamethylene adipamide) precursor

The conversion of poly (hexamethylene adipamide) or polyamide 66 precursor fiber to carbon fibers was accomplished through thermal stabilization and carbonization processes. Thermal stabilization was conducted of cupric chloride (CuCl2)–ethanol-impregnated polyamide 66 (PA66) fibers in the air. To determine the influence of heating rate on the fiber structure and properties of the resultant carbon fibers, carbonization experiments were performed at selected temperatures of 500, 700, 900, and 1100°C using 2.5 and 5 °C/min heating rates with no dwelling. The results conclusively revealed that the volume density and tensile properties of the PA66 fiber were higher at 2.5 °C/min heating rate. After fixing the heating rate as 2.5°C/min, further carbonization experiments were conducted at temperatures from 500 to 1100°C, using increments of 100°C with no dwelling time. Linear density, volume density, fiber diameter, carbon yield, elemental composition, tensile, and electrical properties exhibited a strong dependence on the carbonization temperature. After taking into account the effects of structural defects (i.e., microvoids), tensile strength, and tensile modulus of the carbon fibers increased to 794 MPa and 92.4 GPa, respectively, when carbonized at 1100°C. X-ray diffraction analysis of the carbon fibers further revealed the existence of a greatly disordered (i.e., amorphous) structure, which developed during the carbonization process. FT-IR analysis confirmed the formation of highly aromatic carbon clusters at temperatures of 500°C and higher. The outcomes of electrical conductivity in this study confirm that the PA66 precursor was converted into a semi-conducting state once it was carbonized.

Smart Fluorescent Hydrogel Glucose Biosensing Microdroplets with Dual-Mode Fluorescence Quenching and Size Reduction

Fluorescent hydrogel glucose biosensor (FHGB) microdroplets were fabricated using a microfluidic method with glass capillaries having a coaxial flow-focusing geometry with cross-linked poly(acrylic acid) (PAAc) immobilized with carbon dots (CDs), glucose oxidase (GOx), and horseradish peroxidase (HRP) after the conversion of poly(acrylamide) to PAAc. The prepared FHGB droplets showed a dual response to glucose of CD fluorescence quenching and droplet size reduction upon bienzymatic reaction with glucose; the reaction of GOx and HRP with glucose produced gluconic acid and -OH radicals, which caused CD fluorescence quenching and size reduction, respectively. These small FHGB droplets showed good sensitivity (linear range of ∼30 mM with the limit of detection of 0.052 mM), high selectivity (against the main ingredients of human blood serum), and long stability (due to dry state during storage). These FHGB droplets were tested with human blood serum, and they maintained sensing performance for a long time in the dry state. Thus, the FHGB droplets demonstrate a new method to detect glucose levels with small sample amounts by the dual-mode response. They can be further applied as implanted continuous-detection biosensor droplets because of their biocompatibility.

Optimization of reaction parameters in the conversion of PET to produce BHET

The conversion of poly(ethylene terephthalate) (PET) was analyzed in order to define the optimal conditions for the Bis(2‐Hydroxyethyl) terephthalate (BHET) yield as regards catalyst use (zinc acetate), glycol (ethylene glycol), reaction time and temperature. These conditions were optimized so as to decrease the consumption of catalyst and glycolytic agents aiming to extend the analysis to achieve continuous recycling at a greater scale. At the same time, an analysis of the activity of different catalysts (zeolites, acid, and basic resins) was performed; no BHET yields of commercial interest were obtained. The results indicate that a very small catalyst/PET mass ratio and a low glycol/PET ratio are necessary. The reactions were carried out at a temperature of 195°C and a reaction time of 1 h: under these conditions, BHET yield is 30% (starting from pure PET) and up to 88.2% (recycling oligomers plus pure PET). POLYM. ENG. SCI., 58:1500–1507, 2018. © 2017 Society of Plastics Engineers

Encapsulation and Release of Doxorubicin from Plasticizer-Transformed Poly(ε-Caprolactone) Microcapsules

ABSTRACTThe manuscript reports plasticizer-mediated conversion of poly(ε-caprolactone) hollow particles into microcapsules followed by encapsulation and sustained release of doxorubicin from the microcapsules through a progressive approach. Plasticizer molecules account for increased mobility of polymer chains. Chloroform was observed to be the best plasticizer for potential transformation of the hollow particles into microcapsules, compared to 1,4-dioxane, and toluene. In the next step, an anticancer drug doxorubicin was encapsulated in the hollow particles in presence of chloroform. In vitro release of drug from the microcapsules in phosphate buffer saline (pH 7.4) demonstrated sustained release pattern over 15 days.

ENPP1 processes protein ADP-ribosylation in vitro.

ADP‐ribosylation is a conserved post‐translational protein modification that plays a role in all major cellular processes, particularly DNA repair, transcription, translation, stress response and cell death. Hence, dysregulation of ADP‐ribosylation is linked to the physiopathology of several human diseases including cancers, diabetes and neurodegenerative disorders. Protein ADP‐ribosylation can be reversed by the macrodomain‐containing proteins PARG, TARG1, MacroD1 and MacroD2, which hydrolyse the ester bond known to link proteins to ADP‐ribose as well as consecutive ADP‐ribose subunits; targeting this bond can thus result in the complete removal of the protein modification or the conversion of poly(ADP‐ribose) to mono(ADP‐ribose). Recently, proteins containing the NUDIX domain – namely human NUDT16 and bacterial RppH – have been shown to process in vitro protein ADP‐ribosylation through an alternative mechanism, converting it into protein‐conjugated ribose‐5′‐phosphate (R5P, also known as pR). Though this protein modification was recently identified in mammalian tissues, its physiological relevance and the mechanism of generating protein phosphoribosylation are currently unknown. Here, we identified ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) as the first known mammalian enzyme lacking a NUDIX domain to generate pR from ADP‐ribose on modified proteins in vitro. Thus, our data show that at least two enzyme families – Nudix and ENPP/NPP – are able to metabolize protein‐conjugated ADP‐ribose to pR in vitro, suggesting that pR exists and may be conserved from bacteria to mammals. We also demonstrate the utility of ENPP1 for converting protein‐conjugated mono(ADP‐ribose) and poly(ADP‐ribose) into mass spectrometry‐friendly pR tags, thus facilitating the identification of ADP‐ribosylation sites.

Development of Iron-Chelating Poly(ethylene terephthalate) Packaging for Inhibiting Lipid Oxidation in Oil-in-Water Emulsions.

Foods such as bulk oils, salad dressings, and nutritionally fortified beverages that are susceptible to oxidative degradation are often packaged in poly(ethylene terephthalate) (PET) bottles with metal chelators added to the food to maintain product quality. In the present work, a metal-chelating active packaging material is designed and characterized, in which poly(hydroxamic acid) (PHA) metal-chelating moieties were grafted from the surface of PET. Biomimetic PHA groups were grafted in a two-step UV-initiated process without the use of a photoinitiator. Surface characterization of the films by attenuated total reflective Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) suggested successful grafting and conversion of poly(hydroxyethyl acrylate) (PHEA) to PHA chelating moieties from the surface of PET. Colorimetric (ferrozine) and inductively coupled plasma mass spectroscopy (ICP-MS) assays demonstrated the ability of PET-g-PHA to chelate iron in a low-pH (3.0) environment containing a competitive metal chelator (citric acid). Lipid oxidation studies demonstrated the antioxidant activity of PET-g-PHA films in inhibiting iron-promoted oxidation in an acidified oil-in-water (O/W) emulsion model system (pH 3.0). Particle size and ζ-potential analysis indicated that the addition of PET-g-PHA films did not affect the physical stability of the emulsion system. This work suggests that biomimetic chelating moieties can be grafted from PET and effectively inhibit iron-promoted degradation reactions, enabling removal of metal-chelating additives from product formulations.

Conversion of poly(lactic acid) to lactide via microwave assisted pyrolysis

Microwave assisted pyrolysis (MAP) of poly(lactic acid) (PLA) was performed using different MW absorbers (tire, carbon, or Fe), apparatus set-up, and MW power, obtaining a liquid rich in 3,6-dimethyl-1,4-dioxan-2,5-dione (lactide) and other oxygenated organic compounds. Pure form of l-lactide was separated from the collected liquids while the meso-form of lactide was present in liquid and identified through GC–MS analysis. Up to 27.7% of lactide was formed and might be recovered. Furthermore simple acids such as acetic acid and propionic acid (up to 17.1%), carbonyl compounds, and fragments of PLA backbone randomly cleaved were present in liquids.The pyrolysis of PLA in the presence of other polymers, which might pyrolyze to aromatic compounds, such as those present in tires, gave cross reactions in the course of the pyrolysis affecting both yield and characteristics of liquid. Aromatic compounds formed from tire pyrolysis prevented the precipitation of lactide.

Conversion of Poly(Ethylene Terephthalate) Waste into Activated Carbon: Chemical Activation and Characterization

AbstractDue to its high carbon content, low impurities, low cost and easy availability, poly(ethylene terephthalate) (PET) waste is considered as a suitable precursor for the production of activated carbon. The chemical activation of PET wastes using different chemical agents such as H3PO4, H2SO4, ZnCl2, and KOH was investigated. KOH‐ and ZnCl2‐activated PET were found to be the best choices for the adsorption of small and large molecules. The capacities of the adsorbents towards I2, methylene blue, N2, CH4, and CO2 followed the order KOH‐PET >H3PO4‐PET > ZnCl2‐PET > H2SO4‐PET; however, in the molasses uptake and selective adsorption of CO2 compared to CH4, ZnCl2‐PET performed better than the other adsorbents.

Hydrothermal Conversion of Poly(ethylene naphthalate) to Naphthalene Dicarboxylic Acid and Ethylene Glycol in the Presence of Trimethylamine

Hydrothermal Conversion of Poly(ethylene naphthalate) to Naphthalene Dicarboxylic Acid and Ethylene Glycol in the Presence of Trimethylamine

2-(Pyridin-2-yl)ethanol as a protecting group for carboxylic acids: chemical and thermal cleavage, and conversion of poly[2-(pyridin-2-yl)ethyl methacrylate] to poly(methacrylic acid)

In this communication, we show that 2-(pyridin-2-yl)ethanol is a good protecting group for methacrylic acid (MAA), which can be selectively removed, after polymerization, either chemically under alkaline conditions or thermally at or above 110 °C, while it is stable under acidic conditions and resists catalytic hydrogenolysis. To this end, the monomer 2-(pyridin-2-yl)ethyl methacrylate was synthesized, purified, and homo- and co-polymerized via two controlled polymerization methods, group transfer polymerization (GTP) and reversible addition–fragmentation chain transfer (RAFT) polymerization, to obtain homopolymers and diblock copolymers with methyl methacrylate (GTP) and styrene (RAFT), whose 2-(pyridin-2-yl)ethyl groups could be readily cleaved by chemical or thermal treatment, yielding diblock copolymers with polyMAA segments. The 2-(pyridin-2-yl)ethyl protecting group is one of the very few moieties that can be hydrolyzed under alkaline conditions, and, owing to the commercial availability and relatively low cost of 2-(pyridin-2-yl)ethanol, the present group is expected to find extensive use by the polymer community.

Conversion of poly(ethylene-alt-tetrafluoroethylene) copolymers into polytetrafluoroethylene by direct fluorination: A convenient approach to access new properties at the ETFE surface

Direct fluorination of poly(ethylene-alt-tetrafluoro- ethylene) copolymer (ETFE) was carried out on commercially available ETFE films with pure fluorine gas at ambient atmos- phere. Reaction temperature was either 95 � C or 150 � C and ex- posure time was 20 hours. Analysis of the fluorinated samples was performed by attenuated total reflection Fourier transform Infrared, confocal micro-Raman and 1 H and 19 F magic angle spinning nuclear magnetic resonance spectroscopies, scanning electron microscopy, electron diffraction and X-Ray photoelec- tron spectroscopies, contact angle determination, atomic force microscopy and nanoindentation measurements, and com- pared to those of the virgin ETFE copolymer. Integrity of the bulk materials was verified by investigating the thermal behav- ior of the polymers by thermogravimetric analysis and differen- tial scanning calorimetry. Evidence for the formation of a homogeneous layer of polytetrafluoroethylene with a thickness of several microns at the surface of the copolymers with no degradation of the materials was observed. V C 2011 Wiley Peri- odicals, Inc. J Polym Sci Part A: Polym Chem 49: 1517-1527, 2011

Synthesis of Some New Resins From Poly (Phenol-Furfural ) And Cyclic Anhydride

:In this work , the synthesis of some new resins from conversion of poly (2 or 3 or 4- nitro phenol- furfural) to poly (2 or3 or 4-amino pheunol- furfural), by reaction with cyclic anhydride, where explored . The obtained new resins containing an amic acids residue were characteristized with IR, UV, 1HNMR, CHN analysis, Intrinsic viscosities and S.P where by polymers or resins. Will have an intermediate molecular weight might be proved .

Synthesis and Morphology of Molecular Brushes with Polyacrylonitrile Block Copolymer Side Chains and Their Conversion into Nanostructured Carbons

Densely grafted brushes with polyacrylonitrile (PAN) di- (AB) and triblock (ABC) copolymer side chains were synthesized first time by ATRP using the “grafting from” technique. Tapping-mode atomic force microscopy showed that these brushes displayed wormlike shapes on mica surface. A necklacelike structure was observed for brushes with poly(n-butyl acrylate)-b-polyacrylonitrile-b-poly(tert-butyl acrylate) triblock copolymer side chains. After conversion of poly(tert-butyl acrylate) side chains to poly(acrylic acid), they were cross-linked with diamine to fix the extended 3-dimensional structure. Such shell-cross-linked molecular brushes showed improved stability during transferring from solution to flat substrates and have been successfully converted into nanostructured carbons through pyrolysis. The pyrolyzed materials exhibited characteristics of partially graphitic carbon.

Synthesis and Characterization of Poly(vinylidene fluoride)-g-poly(styrene) Graft Polymers Obtained by Atom Transfer Radical Polymerization of Styrene

Poly(vinylidene fluoride)-g-poly(styrene) graft copolymers (PVDF-g-PS) were synthesized by the “grafting from” method from a PVDF macroinitiator bearing bromine side groups. This fluorinated macroinitiator was obtained from the radical copolymerization of VDF with 8-bromo-1H,1H,2H-perfluorooct-1-ene (BDFO), and then it was used in the atom transfer radical polymerization (ATRP) of styrene initiated by CuIBr/1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) catalyst. First, the synthesis of a model poly(styrene) was investigated starting from 1-bromoperfluorooctane (C8F17Br) as the initiator to check the reactivity of −CF2−Br in ATRP process. Successful ATRP of styrene in the presence of 1-bromoperfluorooctane was observed from a kinetic study and NMR spectroscopy, and the activation rate constant of this initiator (kact = 35 × 10-3 M-1 s-1 at 35 °C in acetonitrile) was assessed for the first time. In a second part, ATRP of styrene was also studied from poly(VDF-co-BDFO) copolymers as the macroinitiators, taking into account: (i) the effect of the polymerization temperature, (ii) the ligand concentration in the ATRP catalyst, and (iii) the amount of solvent vs the conversion of poly(styrene). The formation of graft copolymers was confirmed by size exclusion chromatography and by 1H and 19F NMR spectroscopies. Interestingly, the linear dependences of both the evolutions of ln([M]0/[M]) vs time and of the molecular weights of the resulting graft copolymers vs the styrene conversions, and the decrease of their dispersity indexes vs the styrene conversions evidenced the controlled behavior of that graft polymerization.

Conversion of polyester into heat‐resistant polyamide by reacting with aromatic diamine compound II. Semibatch reaction by nitrogen gas sweeping process

AbstractThe conversion of poly(ethylene terephthalate) (PET) into heat‐resistant polyamide was carried out in the solid state polycondensation by applying a nitrogen gas sweeping process. The reaction product obtained by the catalyzed and uncatalyzed batch reaction with the specified reaction condition was used as the starting material in the semibatch reaction process. Nitrogen gas was introduced into the reactor to remove a volatile reaction byproduct from the reaction mixture. Effect of the semibatch reaction variables such as temperature, time, and nitrogen gas sweeping rate on the extent of reaction and the heat‐resistant property of polyamide obtained was investigated. A comparison of the extent of reaction in the semibatch reaction process was made between the catalyzed starting material and the uncatalyzed one. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2223–2232, 2004

Structure and properties of polyimide films during a far‐infrared‐induced imidization process

AbstractThe conversion of poly(amic acid) into polyimide (PI) was achieved with far‐infrared radiation (FIR) and conventional thermal treatments. The structure and properties of PI films during different stages of imidization were studied with Fourier transform infrared spectroscopy, weight‐loss analysis during imidization, tensile property measurements, and dynamic mechanical thermal analysis. The effects of the imidization degree, postimidization, and solvent on the thermal and mechanical properties of PI films were quantitatively investigated. The corresponding structural changes were also examined. The experimental results showed that the imidization process proceeded more quickly and more completely in an FIR oven than in a conventional oven. A prolonged FIR treatment at a lower temperature (25–100 °C) accelerated the imidization process. The tensile stress–strain curves had a fanlike distribution with the development of the FIR imidization process and a fishtail distribution with conventional thermal imidization. During FIR imidization, the best tensile properties were obtained at 340 °C, and thermooxidative degradation occurred at about 420 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2490–2501, 2004

Evolution of structural features and mechanical properties during the conversion of poly[(methylamino)borazine] fibers into boron nitride fibers

Poly[(methylamino)borazine] (PolyMAB) green fibers of a mean diameter of 15 μm have been pyrolyzed under ammonia up to 1000°C and heat treated under nitrogen up to 2000°C to prepare boron nitride (BN) fibers. During the polymer-to-ceramic conversion, the mechanical properties of the green fibers increase within the 25–400°C temperature range owing to the formation of a preceramic material and remain almost constant up to 1000°C. Both the crystallinity and the mechanical properties slightly increase within the 1000–1400°C range, in association with the consolidation of the fused-B 3N 3 basal planes. A rapid increase in tensile strength ( σ R) and elastic modulus (Young's modulus E) is observed in relation with crystallization of the BN phase for fibers treated between 1400°C and 1800°C. At 2000°C, “meso-hexagonal” BN fibers of 7.5 μm in diameter are finally obtained, displaying values of σ R=1.480 GPa and E=365 GPa. The obtention of both high mechanical properties and fine diameter for the as-prepared BN fibers is a consequence of the stretching of the green fibers on a spool which is used during their conversion into ceramic.

Electrostatic Spinning, Pyrolysis, and Characterization of Boron Carbide Nanofibers Prepared from Poly(norbornenyldecaborane) - a Polymeric Ceramic Precursor

ABSTRACTElectrostatic spinning is a well-developed technique for the fabrication of fibers in the nanoscale domain. Novel boron carbide nanofibers were generated by the electrostatic spinning and ceramic conversion of poly(norbornenyldecaborane) (PND) - a polymeric ceramic precursor. The prepyrolyzed fibers were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The ceramic fibers were characterized by SEM, X-ray diffraction (XRD), 11B magic-angle spinning nuclear magnetic resonance (MAS NMR) and DRIFT spectroscopy. SEM analysis showed retention of the nanostructure in the pre- and postpyrolyzed fibers.

In vitro and in vivo gene transfer with poly(amino acid) vesicles

Non-viral gene delivery systems utilise either amine lipids or polyamines and although non-viral gene delivery systems are said to have a superior safety profile to viruses, the polyamines such as poly( l-lysine) are toxic when used without derivatisation and usually require specific receptor mediated uptake and/or endosomolytic agents to be effective. However, the conversion of poly( l-lysine) and poly( l-ornithine) polyamino acids into amphiphilic vesicle forming polymers reduces the toxicity of the polyamino acids and enables the resulting polyamino acid vesicles to deliver genes both in vitro and in vivo in the absence of receptor specific ligands and endosomolytic agents. The incorporation of a distearoylphosphatidylethanolamine poly(ethylene glycol)–galactosamine conjugate (with the galactosamine unit at the distal end of the poly(ethylene glycol) moiety) into the polyamino acid formulations improved in vitro gene transfer in the case of the amphiphilic poly( l-ornithine) (POP) although no in vivo targeting was detected with the galactosamine formulations. We conclude that the conversion of poly( l-lysine) and poly( l-ornithine) into amphiphilic colloid forming molecules reduces their toxicity, thus allowing these systems to be used for gene transfer in vivo. It is possible that this approach may be extended to other polyamines.

Preventing gelation in polyisoimide synthesis

The origin of the gel formation during the conversion of poly(amic acid)s to polyisoimides, and methods for its prevention are described. The gelation behaviour was studied as a function of the cyclodehydration temperature, the concentration and end-groups of 4,4′-oxydianiline/4,4′-oxydiphthalic anhydride poly(amic acid) systems, using 1,3-dicyclohexylcarbodiimide as a dehydrating agent. The 1H NMR spectroscopic data showed that gel formation during polyisoimide synthesis results from the amide formation reaction of terminal amine groups with acylated poly(amic acid)s. Dilution of poly(amic acid) solutions and lowering cyclodehydration temperatures retarded gelation. However, complete prevention of gel formation at relatively high concentration (15%) and temperature (20 °C) was achieved only for phthalic anhydride end-capped polyamic systems. © 2000 Society of Chemical Industry