Applied Petrochemical Research (v.5, #1)
The Herman F. Mark Polymer Chemistry Award by Hamid A. Al-Megren (1-1).
Morphology control in precision polyolefins by Michael D. Schulz; Nicolas F. Sauty; Kenneth B. Wagener (3-8).
Herein, we review the major advances in controlling polyethylene morphology through precise control of branch frequency and identity. This control is made possible by the acyclic diene metathesis reaction.
Keywords: ADMET; Olefin metathesis; Precision polyolefins; Polyethylene
Characterization of single-chain polymer folding using size exclusion chromatography with multiple modes of detection by Peter Frank; Alka Prasher; Bryan Tuten; Danming Chao; Erik Berda (9-17).
We highlight here recent work from our laboratory on the subject of fabricating nanostructures from single polymer chains. These so-called single-chain nanoparticles are synthesized by inducing intra-molecular cross-linking on discrete macromolecules in dilute solution. Among the biggest challenges in this rapidly expanding area of research is reliable and accurate means to characterize this process. In this paper, we review our preferred method of characterization: size exclusion chromatography featuring multiple modes of detection. Multi-angle light scattering in conjunction with a concentration detector can provide absolute molecular weight data; viscometric detection can provide information about solution size and conformation. Correlation of these data provides a simple and robust way to quantify the process by which we fold single polymer coils into architecturally defined unimolecular nanostructures.
Keywords: Single-chain nanoparticles; Polymer folding; TEM; SEC
Functionalized regio-regular linear polyethylenes from the ROMP of 3-substituted cyclooctenes by Henry Martinez; Jihua Zhang; Shingo Kobayashi; Yuewen Xu; Louis M. Pitet; Megan E. Matta; Marc A. Hillmyer (19-25).
We demonstrated that the ring-opening metathesis polymerization (ROMP) of 3-substituted cyclooctenes bearing polar substituents allows the synthesis of highly regio- and stereo-regular polymers. A series of polyalkenamers with 90–99 % head-to-tail/trans configuration were synthetized in good yields (33–87 % yield). Upon saturation of the backbone using diimide, these polymers represent a class of linear polyethylene derivatives where the polar side chain is located on every eighth carbon. The thermal properties of both the saturated and unsaturated polymers depend strongly on the size and polarity of the functional side groups. The results presented here demonstrate that the 3-substituted cyclooctenes can be used not only for the synthesis of precisely functionalized polyethylene derivatives, but also to participate in the ring-opening metathesis copolymerization with unfunctionalized cyclic olefins to generate copolymers with tunable properties.
Keywords: ROMP; Polyethylene; Substituted polyolefin; Metathesis
A review of semi-rigid, stilbene-containing alternating copolymers by Alice M. Savage; Xu Zhou; Jing Huang; S. R. Turner (27-33).
The synthesis and properties of sterically congested, stilbene-containing alternating copolymers are reviewed. Persistence lengths (2–6 nm) determined by size exclusion chromatography and small angle X-ray scattering techniques show that these are semi-rigid copolymers. Fully characterized polyanions and polyampholytes, prepared from organic-soluble precursors were studied, along with their respective salt and pH response behavior resulting from the semi-rigid polymer backbone. The solid-state characterization from these studies reveals a high degree of hindered rotation along the polymer backbone. The contorted structure and the hindered rotation of the polymer backbone generate inefficient chain packing, which leads to an increase of nanoporosity and higher surface areas. The semi-rigid stilbene-containing copolymers are a new class of copolymers where the increased polymer backbone rigidity leads to a wide range of polymer properties not attained with flexible polymers.
Keywords: Stilbene; Alternating copolymers; Copolymerization; Maleic anhydride; Maleimides
Triarylamine-enchained semifluorinated perfluorocycloalkenyl (PFCA) aryl ether polymers by Babloo Sharma; Mohammad Faisal; Shawna M. Liff; Dennis W. Smith Jr. (35-45).
A variety of perfluorocycloalkenyl (PFCA) aryl ether monomers and polymers with enchained triarylamine units were successfully synthesized, characterized and reported here. These polymers are highly thermally stable and show variable thermal properties. Successful conversion of the newly synthesized TAA enchained perfluorocyclopentenyl (PFCP) aryl ether polymers via formylation and EAS demonstrates the synthetic versatility of TAA moiety and provides an excellent option for application specific post polymerization reactions. The cross-linking behavior of PFCP aryl ether polymers was studied under different reaction conditions. The combination of processability, thermal stabilities, and tailorability makes these polymers suitable for a wide variety of applications including electro-optics, proton exchange membranes and super-hydrophobic applications.
Keywords: Semi-fluorinated polymers; Step-growth polycondensation; Addition–elimination reaction; Perfluorocycloalkenes
Process modeling and evaluation of petroleum refinery wastewater treatment through response surface methodology and artificial neural network in a photocatalytic reactor using poly ethyleneimine (PEI)/titania (TiO2) multilayer film on quartz tube by Parvaneh Pakravan; Aazam Akhbari; Hojatollah Moradi; Abbas Hemati Azandaryani; Amir Mohammad Mansouri; Mojtaba Safari (47-59).
In this study, poly ethyleneimine (PEI)/Titania (TiO2) multilayer film on quartz tubes have been successfully fabricated via a layer-by-layer (LbL) self-assembly method. Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area analysis were carried out for characterization of the layers on quartz tube. The SEM pictures showed that the film surface is smooth and uniform. The BET characterization verified the formation of multilayer thin film. The photocatalytic activity of the PEI/TiO2 multilayer deposited on the quartz tubes was evaluated in the treatment of raw petroleum refinery wastewater (PRW) under UV light irradiation in three annular photocatalytic reactors. This study examined the impact of initial chemical oxygen demand (COD) concentration, H2O2 concentration, pH and reaction time on the PRW treatment and the results were used to generate both a response surface methodology (RSM) model and an artificial neural network (ANN) model. Maximum COD removal (98 %) was achieved at the optimum conditions (initial COD concentration of 300 mg/l, hydrogen peroxide concentration of 8.8 mM, pH of 5 and reaction time of 120 min). A comparison between the model results and experimental data gave a high correlation coefficient (R ANN 2 = 0.9632, R RSM 2 = 0.943) and showed that two models were able to predict COD removal from PRW by PEI/TiO2/UV process. However, ANN model was superior to RSM model with higher value of coefficient of determination (0.9632ANN > 0.94RSM) and the lower root mean square error (RMSE) (3.377AAN < 3.569RSM). The average percentage error for ANN and RSM models was 0.18 and 0.73, respectively, indicating the superiority of ANN in capturing the nonlinear behavior of the system. It was clear that the best networks were able to predict the experimental responses more accurately than the multiple regression analysis.
Keywords: Petroleum refinery wastewater; Response surface methodology; Artificial neural network; Layer-by-layer self-assembly
Terpolymers for modifying the performance properties of engine oil by Rabab M. Nasser; Nehal S. Ahmed; Amal M. Nassar (61-69).
Nine terpolymers consisting of (jojoba: alkylacrylate: α-olefins) backbone were synthesized via free radical chain addition polymerization and determined using Fourier transform infrared spectroscopy, proton nuclear magnetic resonance and gel permeation chromatography, for determination of weight average molecular weight. The alkylacrylates used were (dodecylacrylate, tetradecylacrylate and hexadecylacrylate), while α-olefins used were (dodecene, tetradecene and hexadecane). The monomers’ ratio used for polymerization was (1:1:1). It was found that the molecular weight increases with increasing the alkyl chain length of both alkylacrylate and α-olefins used. The thermal stability of the synthesized terpolymers was determined using thermal gravimetric analysis and differential scanning calorimetry. The prepared polymers were evaluated as performance modifiers (viscosity index improvers and pour point depressants) for free additives lube oil (SAE-30). It was found that the viscosity index increases with increasing the alkyl chain length, molecular weight and concentration of used terpolymer. The effect of the prepared terpolymers on the pour point of lube oil was studied and it was found that the pour point of lube decreases (more negative) with decreasing the alkyl chain length of both alkylacrylate and α-olefin used.
Keywords: Lube oil additives; Performance modifiers additives; Viscosity index improvers; Pour point depressants; Thermal gravimetric analysis
Catalytic functionalities of Pd catalysts supported on spinel MgAl2O4 for coupling of ethylbenzene dehydrogenation with nitrobenzene hydrogenation by Yengaldas Harikrishna; Vanama Pavan Kumar; Kuna Ramu; Komandur V. R. Chary; Vattikonda Venkat Rao (71-80).
Direct coupling of oxidative dehydrogenation of ethylbenzene with nitrobenzene hydrogenation in a fixed-bed catalytic reactor at atmospheric pressure in the temperature range of 673–823 K over MgAl2O4-supported palladium catalysts has been investigated. Simple dehydrogenation of ethylbenzene (DHEB) is reversible, endothermic and thermodynamically limited. The continuous removal of co-produced hydrogen in DHEB for in situ hydrogenation of nitrobenzene over Pd/MgAl2O4 catalyst improves the performance of the DHEB process. A series of Pd (0.25–4.0 wt%) catalysts supported on MgAl2O4 was prepared. The catalyst samples were characterized by X-ray diffraction (XRD), H2-Temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), CO chemisorption, CO2–Temperature-programmed desorption and BET surface area. Dispersion and particle size of Pd were obtained by CO chemisorption. The reaction profile shows that palladium (0.5 wt%) is an optimum loading to get maximum conversion of ethylbenzene (51.8 %) and nitrobenzene (47.3 %) to give 91.4 and 100 % selectivity of styrene and aniline, respectively.
Keywords: MgAl2O4 spinel; Dehydrogenation; Hydrogenation; Ethylbenzene and nitrobenzene