Formation Of Polymer Chains Research Articles

Cerium Oxide‐Armored Composite Latex Particles by Visible Light Emulsion Photopolymerization: From Synthesis to Film Properties

AbstractCerium dioxide (CeO2) has huge potential in many applications ranging from biochemical engineering to the coating industry. Here, the first example of visible light photo‐mediated Pickering emulsion polymerization of (meth)acrylate monomers is reported using CeO2 nanoparticles (NPs) as solid stabilizer. A ω,ω′−dicarboxylic acid diphenyl disulfide photoinitiator is anchored on the surface of the CeO2 NPs and used to initiate the emulsion polymerization of methyl methacrylate (MMA) and of MMA/n‐butyl acrylate (MMA/BA) under visible light leading to CeO2‐armored latexes. Radicals generated upon light irradiation trigger the formation of polymer chains chemically attached to the CeO2 NPs, promoting their subsequent adsorption on the latex surface. The composite films obtained from the CeO2‐armored P(MMA‐co‐BA) latexes exhibit a unique honeycomb nanostructure with the nanoceria located in the walls giving the materials excellent mechanical, anti‐UV, and photocatalytic properties.

1,8-Diazabicyclo[5.4.0]undec-7-ene as Cyclic Ether Electrolyte Polymerization Inhibition for Wide-Temperature-Range High-Rate Lithium-ion Batteries.

1,3-Dioxolane (DOL), with its broad liquid phase temperature window and low Li+-solvent binding energy, stands out as an ideal solvent candidate for the wide-temperature and high-rate electrolytes. Unfortunately, DOL is susceptible to undergo ring-opening polymerization under common lithium salts, which markedly retards the reaction kinetics. This work introduces the organic basic additive 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) to effectively suppress the polymerization, thus achieving compatibility between LiFSI, LiDFOB lithium salts, and DOL. Furthermore, density functional theory (DFT) calculations are utilized to elucidate the underlying mechanisms of DOL polymerization and to clarify how DBU inhibits its polymerization. The resulting electrolyte, devoid of polymer chain formation, forms a weak solvation structure rich in anions, which demonstrates rapid ion transport kinetics in the bulk electrolyte and excellent electrochemical stability at the electrolyte-electrode interfaces (EEIs) simultaneously. When applied to the LiFePO4||graphite full cell, it exhibits exceptional wide-temperature and high-rate performance, with specific capacities reaching 101.2 mAh g -1 at room temperature (20 C), 36.9 mAh g-1 at -40 °C (0.5 C), and 118.0 mAh g-1 at 60 °C (20 C). This study significantly guides the development of wide-temperature, high-rate electrolytes.

Study and Characterization of Tribofilm based on Activated Carbon-Nanochitosan Modified with Silicone Oil for Application of Self-Healing Coatings on Metal Surfaces

A tribofilm material based on activated carbon and nanochitosan modified with silicone oil has been prepared using the sol gel method with variations in the composition of activated carbon at a mass ratio of 40% wt – 60% wt at 5% wt intervals. Sampling was carried out in two stages. The first stage of the synthesis of activated carbon from palm shells using activation of 7% H3PO4 and nanochitosan derived from shrimp shells using the ionic gelation method. The second stage was mixing the tribofilm material of activated carbon, nanochitosan and silicone oil using the sol gel method to produce a film-forming solution which was then characterized including: physical, chemical, mechanical and thermal properties. The characterization results showed that the most optimum composition was the tribofilm material of activated carbon/nanochitosan/silicone oil in S1 with a mass ratio of 40%wt activated carbon which produced a density of 0.94 x 103 kg/m3, a viscosity of 28.42 cP, and a liquid surface tension of 63.5 mN/m. While the performance characteristics of the metal surface coating produce a surface roughness of 0.162 µm for aluminum metal and 0.156 µm for copper metal, friction coefficient 0.024, wear rate 0.19 mm, thermal conductivity 0.092 W/m.K, corrosion properties 1a (slight tarnish), rate corrosion rate of 2.34 mm/yr in 3.5% NaCl medium, 4.33 mm/yr in seawater medium and 11,476 mm/yr in 3% H2SO4 medium and has good self-healing properties for 3 days on carbon steel metal surfaces with corrosion scratch treatment on 3.5% NaCl media, namely almost all the scratches/cracks covered due to frictional force from galvanic corrosion with active carboxyl, amine and hydroxyl groups with the healing agent aminopropyl siloxane (NH2-R-NH-Si-O-R) which reacts with metal ion particles (M-OH) in the formation of polymer chains for new network layers.

Characterization of an Aedes ADP-Ribosylation Protein Domain and Role of Post-Translational Modification during Chikungunya Virus Infection.

Poly ADP-ribose polymerases (PARPs) catalyze ADP-ribosylation, a subclass of post-translational modification (PTM). Mono-ADP-ribose (MAR) moieties bind to target molecules such as proteins and nucleic acids, and are added as part of the process which also leads to formation of polymer chains of ADP-ribose. ADP-ribosylation is reversible; its removal is carried out by ribosyl hydrolases such as PARG (poly ADP-ribose glycohydrolase), TARG (terminal ADP-ribose protein glycohydrolase), macrodomain, etc. In this study, the catalytic domain of Aedes aegypti tankyrase was expressed in bacteria and purified. The tankyrase PARP catalytic domain was found to be enzymatically active, as demonstrated by an in vitro poly ADP-ribosylation (PARylation) experiment. Using in vitro ADP-ribosylation assay, we further demonstrate that the chikungunya virus (CHIKV) nsp3 (non-structural protein 3) macrodomain inhibits ADP-ribosylation in a time-dependent way. We have also demonstrated that transfection of the CHIKV nsP3 macrodomain increases the CHIKV viral titer in mosquito cells, suggesting that ADP-ribosylation may play a significant role in viral replication.

Progress toward Polymerization Reaction Monitoring with Different Dienes: How Small Amounts of Dienes Affect ansa-Zirconocenes/Borate/Triisobutylaluminium Catalyst Systems.

The objectives of this work were to address the fundamental characteristics of ansa-zirconocene catalyzed E/diene copolymerization and E/diene/1-hexene and E/diene/propylene terpolymerizations, and the quantitative relationship between diene structure and polymer chain propagation rate constant in term of quantifiable catalytic active sites. One of the most important but unknown factors in olefins ansa-zirconocene complexes is the distribution of the catalyst between sites actively participating in polymer chain formation and dormant sites. A set of ethylene/dienes copolymerizations, and ethylene/dienes/1-hexene and ethylene/dienes/1-hexene terpolymerizations catalyzed with ansa-zirconocenes/borate/triisobutylaluminium (rac-Et(Ind)2ZrCl2/[Ph3C][B(C6F5)4]/triisobutylaluminium (TIBA) were performed in toluene at 50 °C To determine the active center [C*]/[Zr] ratio variation in the copolymerization of E with different dienes and their terpolymerization with 1-hexene and propylene, each polymer propagation chain ends were quenched with 2-thiophenecarbonyl, which selectively quenches the metal–polymer bonds through acyl chloride. The ethylene, propylene, 1-hexene, and diene composition-based propagation rate constants (kpE, kpP, kp1-H, and kpdiene), thermal (melting and crystalline) properties, composition (mol% of ethylene, propylene, 1-hexene, and diene), molecular weight, and polydispersity were also studied in this work. Systematic comparisons of the proportion of catalytically [Zr]/[C*] active sites and polymerization rate constant (kp) for ansa-zirconocenes catalyzed E/diene, E/diene/1-hexene, and E/diene/propylene polymerization have not been reported before. We evaluated the addition of 1-hexene and propylene as termonomers in the copolymerization with E/diene. To make a comparison for each diene under identical conditions, we started the polymerization by introducing an 80/20 mole ratio of E/P and 0.12 mol/L of 1-hexene in the system. The catalyst behavior against different dienes, 1-hexene, and propylene is very interesting, including changes in thermal properties, cyclization of 1-hexene, and decreased incorporation of isoprene and butadiene, changes in the diffusion barriers in the system, and its effect on kp.

Aldehyde-Functionalized Polymers from the Reverse Iodine Transfer Polymerization of Lignin-Derivable Compounds

Renewable polymers with reactive functionalities become increasingly attractive as they address some critical global concerns related to sustainability. In this work, vanillin methacrylate (VM), an aldehyde-functionalized monomer synthesized by the methacrylation of vanillin (a possible lignin derivative), was polymerized for the first time via reverse iodine transfer polymerization. The influence of various reaction parameters including the polymerization solvent, the initiator-to-iodine ratio, and the polymerization temperature on the induction (or inhibition) period and the molar mass was investigated by 1H NMR spectroscopy and size exclusion chromatography. The lack of a clear and consistent discoloration of the reaction mixture to indicate the end of the induction period in the solvents investigated, i.e., toluene, methyl ethyl ketone (MEK), and N,N-dimethylformamide (DMF), was an indication that iodine was taking part in a side (complexation) reaction with the solvent. When the monomer conversions were followed by 1H NMR spectroscopy, it was found that the induction periods for the reactions carried out in MEK and DMF were significantly shorter due to the consumption of iodine by VM, leading to the formation of a chain transfer agent (CTA), 4-formyl-2-methoxyphenyl-2-iodo-2-methylpropanoate. The formation of polymer chains derived from this CTA was confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. To demonstrate the “livingness” of the polymerization process, PVM was chain-extended with methyl methacrylate, and the formation of block copolymers was confirmed by high-performance liquid chromatography. The application toolbox of these polymers was expanded by the formation of various poly(vanillin methacrylate) Schiff base polymers endowed with additional functional groups.

Influence of gold nanoparticles in polymer nanocomposite on space-temporal-irradiation dependent diffraction grating recording

Following the modern and extremely useful direction of research and development of polymer nanocomposites with combined effects of photopolymerization superimposed by plasmon-induced processes, we investigated acrylate-based nanocomposites with broadband sensitive Irgaqure784 initiator and silicon oxide as well as gold nanoparticles in different regimes of illumination. The details of initiator photodecomposition and polymer chain formation mechanisms at the presence of the gold nanoparticles' (GNPs) plasmon fields and different combinations of irradiation wavelengths or intensities are discussed. These are related to the mechanism and efficiency of holographic volume and surface grating recording based on photopolymerization and mass-transport, diffusion processes of the organic matrix, and nanoparticles. GNP's presence in a monomer nanocomposite influences the recording parameters in a combined way, making preferable the double-wavelength irradiation mode, which may increase the efficiency of the recorded gratings up to two times at decreased exposures. Results may be used for planning fabrication processes of more complex, multifunctional photonic elements.

Ultrafast gelling using sulfonated lignin-Fe3+ chelates to produce dynamic crosslinked hydrogel/coating with charming stretchable, conductive, self-healing, and ultraviolet-blocking properties

Developing an ecological and economical method for fabrication and application of polymer hydrogels is important for the hydrogel/coating electronics. Here, a dynamic oxidation and coordination system composed of sulfonated lignin (SL) and Fe3+ was introduced to assemble multifunctional Fe-SL-g-polyacrylic acid (PAA) hydrogel at 20 ℃ in a time scale of minutes instead of hours. The SL-Fe3+ system can rapidly activate the ammonium persulfate (APS, initiator), and then it instantaneously provides abundant semiquinone and hydroxyl radicals to accelerate the formation of polymer chains. Moreover, the functional SL-Fe3+ chelates can also reversibly crosslink the polymer chains to form multifunctional hydrogels. Surprisingly, the resultant hydrogel obtained charming extension ratio (up to 1680%), conductivity (up to 7.0 × 10-2 S·m−1), and adhesive strength (up to 36.4 kPa). This technology was also applied to rapidly fabricate a transparent (up to 81%, thickness: 2 mm), UV-blocking (up to 99.7%, thickness: 2 mm), adhesive, and conductive hydrogel coating on substrates. Besides, the dynamic coordination inside the hydrogel imparts desirable self-healing capabilities to damaged network, with up to 98.5% recovery in conductivity and 85.7% in extension ratio. In short, this technology based on the sustainable SL-Fe3+ system greatly facilitates the rapid and low-cost preparation of multifunctional hydrogel/coatings, which have promising industrial applications in human–machine electronics.

Controlled/"living" radical polymerization-based signal amplification strategies for biosensing.

Controlled/"living" radical polymerization (CLRP) techniques, such as atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) polymerization, and their variants, have now emerged as a novel class of signal amplification strategies and they have attracted growing attention in biosensing of clinically relevant biomolecules. Through the CLRP-mediated de novo formation of polymer chains, a large amount of signaling probes (e.g., ferrocene) or functional groups (e.g., -NH2, -CHO, and -COOH) that are available for the subsequent introduction of signaling probes can be recruited in the sensing interfaces, outputting a high signal even in the presence of a low abundance of target analytes, thereby greatly improving the detection sensitivity. Compared with conventional strategies based on the use of either catalytic labels (e.g., natural enzymes, biomimetic catalysts, and electrocatalysts) or complex nanomaterials (e.g., surface-functionalized metal nanoparticles), CLRP-based signal amplification strategies have advantages of being low-cost, highly efficient, and relatively easy in operation. By virtue of these merits, CLRP-based signal amplification strategies show great promise for clinical applications and biomedical research studies. In this review, the advantages and disadvantages of various signal amplification strategies have been summarized. Following a brief introduction of the mechanisms of various CLRP techniques, a comprehensive overview of the applications of CLRP-based signal amplification strategies in biosensing of clinically relevant biomolecules such as nucleic acids, enzymes, and antigens is presented. Also discussed herein are the advantages and disadvantages of CLRP-based signal amplification strategies, which are believed to be instructive for their broad application in biosensing.

Preparation and Characterization of Micro and Nano Metal Doped Polymer Composites

Polyaniline (PA) was synthesized by in-situ chemical oxidative polymerization method using K2Cr2O7 as an oxidant and H2SO4 as a dopant. Then the micro and nano copper were doped to enhance its electrical conductivity. The micro and nano composites were characterized using FT-IR and Raman spectroscopic method for identify the chemical interactions between the molecules. The formation of polymer chain and incorporation of Cu metal were confirmed by these spectroscopic analysis. The crystallographic patterns (XRD) shows the crystalline structure in the composites whereas the pure PA exhibits an amorphous structure. The clearly visible morphological changes and elemental analysis were investigated using SEM-EDS. The flower petals and star like structure were observed after doping Cu into PA matrix. The A.C. electrical conductivity of pure and doped PA with micro and nano copper were attained by two probe setup. The one order increase in conductivity between doped and pure PA was observed.

Electrochemical synthesis of polypyrrole in powder form

Novel approach to synthesis of conjugated oligomers/polymers is proposed. This approach combines all advantages of electrochemical methods: variation of the oxidation potential in wide range with high precision, direct control of the process rate and product yield, variation of both the doping anion/cation nature and the composition of polymerization medium, absence of chemical oxidative reagents in reaction mixture. Contrary to the conventional use of this synthetic method, it has been exploited in our study for generation of polymeric products outside the electrode surface. This goal has been implemented via oxidation of the monomer at porous electrode with simultaneous pumping of the polymerization medium (monomer in background electrolyte solution) through porous electrode with a certain rate. It leads to electrochemical generation of active intermediates (cation radicals) at the electrode surface with their recombination and subsequent accumulation of the products not only as film on the electrode surface but also as a colloid in solution outside the porous medium. Since this reaction path toward bulk solution products should evidently be favored by slow steps in the course of the polymer formation, this approach has been tested for pyrrole oxidation (both in its pure monomer solution and in the presence of the bromide redox mediator) since this monomer is known of its high rate of polymer chain formation.

Zinc bis-pyrrolide-imine complexes: Synthesis, structure and application in ring-opening polymerization of rac-lactide

A series of bis-ligated zinc complexes with pyrrole-imine ligands were successfully synthesized and characterized by 1H and 13C{1H} NMR, and by X-ray crystallography for Zn1 and Zn3. These zinc complexes were used as catalysts for the ring-opening polymerization of rac-lactide in a toluene solution, under bulk conditions, in the presence and absence of benzyl alcohol. The complexes proved to be active in the presence of benzyl alcohol as co-initiator and chain transfer agent. Polymers were formed with high conversions and with well-matched experimental and calculated molar mass values. Under solvent-free conditions, high conversions were obtained after 1 h with good molecular control and satisfactory polydispersity. The homo-decoupled 1H NMR spectra of the methine regions of the PLA samples were consistent with the formation of polymer chains with slightly tendency to heterotacticity.

Initiated‐Chemical Vapor Deposition of Polymer Thin Films: Unexpected Two‐Regime Growth

AbstractInitiated‐chemical vapor deposition (iCVD) is a very promising technique which has demonstrated the ability to deposit a large variety of polymers that can be integrated in micro‐nanotechnology applications. However, studies on the underlying growth mechanisms responsible for the formation of these thin films remain scarce in the literature. This work shows that the iCVD growth follows surprisingly two regimes: in the first stage of the growth, the deposition rate is relatively slow then increases with the deposition time until a linear growth is reached. The presence of these two growth regimes can be interpreted by taking into account, as the iCVD growth progresses, that the synthesized polymer chains help the monomer adsorption on the substrate which locally increases the concentration of monomers available for the polymerization and thus the growth rate. This increase of the local concentration of monomer consistently correlates with the formation of polymer chains with higher molar mass.

Cadmium(ii) terephthalates based on trinuclear units {Cd3(bdc)3}: control of coordination structure dimensionality and luminescence properties

Two metal-organic coordination polymers based on cadmium(ii) ions and terephthalic (1,4-benzenedicarboxylic) acid were synthesized in dimethylformamide or a mixture of dimethylformamide and methanol: [Cd3(bdc)3(dmf)4] (1, bdc is 1,4-benzenedicarboxylate, dmf is N,N´-dimethylformamide) and [Cd3(bdc)3(dmf)2] (2), respectively. According to the single-crystal X-ray diffraction data, both compounds are built up by the trinuclear carboxylate units {Cd3(O2CR)6}. Compound 1 has a layered structure, whereas compound 2 has a three-dimensional structure due to the presence of additional coordination interactions between adjacent trinuclear units and the formation of polymer chains {Cd3(dmf)2(μ2-O2CR-κ1,κ1)2(μ2-O2CR-κ2,κ1)4(O2CR-κ1)2}. The synthesized compounds were characterized by IR spectroscopy, thermogravimetric analysis, elemental analysis, and powder X-ray diffrac- tion. The luminescence properties of these compounds provide evidence for the existence of both intraligand and charge-transfer transitions. The luminescence quantum yields for both compounds are 10%.

Synthesis of MgB4O7 and Li2B4O7 crystals by proteic sol–gel and Pechini methods

Magnesium-tetraborates and lithium-tetraborates are excellent detectors for ionizing radiation. However, manufacturing these crystalline structures is challenging as it involves multi-step chemical processes and toxic reagents. Over the past decades, alternative production methods for crystals have been studied aiming at lowering production costs and environmental impact and at increasing production yield and reproducibility. Among these is the Pechini method, based on the formation of polymer chains containing uniformly distributed metal ions. Another method is a modified proteic sol–gel process using edible gelatins or coconut water instead of the alkoxides used in conventional processes. In this work, we searched optimal conditions for the synthesis of dosimetry-grade MgB4O7 and Li2B4O7 crystals with the Pechini and the proteic sol–gel methods. The crystal phases were characterized by X-ray diffraction and by thermal analyses. We determined that MgB4O7 can be synthesized either by calcination of the reagents at 900 °C for 2 h with the sol–gel approach, or at just 800 °C for 2 h with the Pechini method. Single-phase Li2B4O7 can be synthesized either by calcination of the reagents at 650 °C for 2 h with the sol–gel approach, or at just 600 °C for 2 h with the Pechini method. Our synthesis times and temperatures are lower than those reported in the literature, which reduces significantly production costs and environmental impact.

Synthesis and characterization of poly (acrylonitrile‐co‐acrylic acid) as precursor of carbon nanofibers

Synthesis of a co‐polymer of polyacrylonitrile (PAN) producing a carbon nanofiber out of PAN and co‐polymer of PAN and comparison between these products were examined. Free‐radical solution copolymerization of acrylonitrile (AN) with acrylic acid (AA) was studied. In this perspective, AA, and AN were used as a precursor for polymerization reactions; then copolymers were synthesized by using ammonium persulfate (APS) as an oxidant and carried in water/dimethylformamide (DMF) mixture. These polymers were used to obtain corresponding electrospun nanofibers. Synthesized P(AN‐co‐AA) was investigated by Fourier transform infrared spectroscopy‐attenuated total reflection (FTIR‐ATR) spectroscopy, and characteristic peaks for AN unit, AA were achieved. Thermal behavior was examined by using differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA), and results indicated that addition of monomers to AN unit reduced the Tg value of homopolymer PAN compared to P(AN‐co‐AA), which provides improvement to the cyclization and the formation of a thermally stable aromatic ladder polymer chain formation. In order to prevent the shrinkage and maintain the molecular orientation on nanofiber webs during stabilization, tension was applied to the samples, and thermal oxidation varies at 200–300°C for different duration of times. Surface morphology of the fibers was observed with scanning electron microscope (SEM), and average nanofiber diameter was found 550 nm, and after carbonization it was reduced to 320 nm for homopolymer PAN, and for poly(AN‐co‐AA) average nanofiber diameter was found as 220 nm and reduced to 130 nm, respectively. Copyright © 2016 John Wiley & Sons, Ltd.

Successful functionalization of superporous zeolite templated carbon using aminobenzene acids and electrochemical methods

A novel and selective electrochemical functionalization of a highly reactive superporous zeolite templated carbon (ZTC) with two different aminobenzene acids (2-aminobenzoic and 4-aminobenzoic acid) was achieved. The functionalization was done through potentiodynamic treatment in acid media under oxidative conditions, which were optimized to preserve the unique ZTC structure. Interestingly, it was possible to avoid the electrochemical oxidation of the highly reactive ZTC structure by controlling the potential limit of the potentiodynamic experiment in presence of aminobenzene acids. The electrochemical characterization demonstrated the formation of polymer chains along with covalently bonded functionalities to the ZTC surface. The functionalized ZTCs showed several redox processes, producing a capacitance increase in both basic and acid media. The rate performance showed that the capacitance increase is retained at scan rates as high as 100 mV s−1, indicating that there is a fast charge transfer between the polymer chains formed inside the ZTC porosity or the new surface functionalities and the ZTC itself. The success of the proposed approach was also confirmed by using other characterization techniques, which confirmed the presence of different nitrogen groups in the ZTC surface. This promising method could be used to achieve highly selective functionalization of highly porous carbon materials.

New Insights into the Ring‐Opening Polymerization of β‐Butyrolactone Catalyzed by Chromium(III) Salphen Complexes

AbstractThe heterogeneous nature of β‐butyrolactone (BL) polymerization towards tactic poly(3‐hydroxybutyrate) (PHB) in the presence of chromium(III) salphen (salphen=N,N′‐disalicylidene‐o‐phenylenediamine) complexes is supported by a number of experimental observations. Depending on the substitution pattern, initially soluble chromium(III) salphen chloride complexes can generate microcrystalline agglomerates under the polymerization conditions, driven by formation of μ‐OH bridges between metal centers. Coordinated water molecules are suggested to be the source of such bridging ligands. The formation of these/this heterogeneous species is a prerequisite for the stereocontrolled ring‐opening polymerization (ROP) of BL, whereas both iso‐ and syndioselective enchainment occurs simultaneously. According to the analysis of the 13C NMR spectra of the polymers, the ratio of the corresponding triads depends on a number of parameters in a not yet understood manner. Besides dual stereoselectivity, the heterogeneous chromium(III) salphen species feature catalytic sites with different activities, which is reflected in the very broad molecular mass distribution of the produced PHB. Highly active catalytic sites cause the formation of polymer chains with a high molecular mass at the beginning of polymerization. The described behavior is not inherent to truly homogeneous chromium salphen complexes and is more in line with a bimetallic ROP mechanism proposed earlier, which requires a particular mutual spatial orientation of two salphen complexes for the efficient catalysis of BL polymerization.

Polymer nanocomposites:In situpolymerization of polyamide 6 in the presence of graphene oxide

Polyamide 6 (PA6)/graphene oxide (GO) nanocomposites were prepared via in situ, ring opening polymerization of ε-caprolactam in the presence of both dried powder and colloidally dispersed single layer GO. Characterization of the composites and GO (both as received and after removal from the composites) was carried out using atomic force microscopy (AFM), Fourier transform infra-red spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis, differential scanning calorimetry and tensile testing. Reduction in the GO during polymerization was observed. So too was functionalization of the GO flakes with PA6 chains. FTIR demonstrates the retention of some carbonyl oxygen functionalities after polymerization. AFM imaging indicated the presence of single layer GO and the sheet height increased to ∼4 nm for graphene sheets after polymerization. This suggests the graphene acts as a base for polymer chain formation, leading to good interfacial interaction between the filler and matrix. Raman data show no evidence of the restoration of sp2 hybrid as a result of polymerization. The nanocomposites are thermally stable while molecular weight and crystallinity have both been affected by GO inclusion. A percentage linear increase in Young's modulus was observed as colloidally dispersed GO content increased. POLYM. COMPOS., 38:528–537, 2017. © 2015 Society of Plastics Engineers

Kinetics and modeling of methyl methacrylate graft copolymerization in the presence of natural rubber latex

A graft copolymerization model for using cumene hydroperoxide/tetraethylenepentamine (CHPO/TEPA) as a redox initiator was developed to describe the grafting of methyl methacrylate onto natural rubber latex as a core-shell particle. The model allows estimating the effects of the initiator concentration, monomer-rubber weight ratio, and temperature on the properties of graft product, e.g., % grafting efficiency and the % monomer composition in the graft copolymer and free polymer. The rate expressions of polymer chain formation are developed by taking into account a reduction of CHPO by TEPA and a population event of radicals between core/shell phases. The parameter estimation is performed to find the kinetic parameters. Validation with experimental results demonstrates a good applicability of the proposed model. The model results reveal that the formation of grafted polymer chains rather form by the chain transfer reaction to rubber chains from homopolymer radicals and the initiation reaction of cumyloxy radicals to rubber chains.