Thermoplastic-thermosetting merged polyimides via furan-maleimide Diels–Alder polymerization

AbstractNovel thermoplastic-thermosetting merged polyimide system has been developed via Diels–Alder intermolecular polymerization of bisfuran namely, 2,5-bis(furan-2-ylmethylcarbamoyl) terephthalic acid A with a series of bismaleimides B1–4. Thus obtained intermediate Diels–Alder adducts C1–4 were aromatized and imidized (i.e. cyclized) through carboxylic and amide groups to afford thermoplastic-thermosetting merged polyimides D1–4. Bisfuran A was prepared by the condensation of pyromellitic dianhydride with furan-2-ylmethanamine and characterized by elemental, spectral, thermal and LCMS analyses. Synthesized Diels–Alder adducts C1–4 and polyimides D1–4 were characterized by elemental analysis, spectral features, number average molecular weight (Mn‾), degree of polymerization (DP) and thermal analysis. To facilitate the correct structural assessment and to be able to verify the occurrence of the DA adducts and PIs, a model compound 4 was prepared from phthalic anhydride and furan-2-ylmethanamine in a similar way. FTIR spectral features of polyimides D1–4 were compared with model compound 4 and they were found to be quite identical. The ‘in situ' void-free glass fiber reinforced composites GFRC1–4 were prepared from the produced system and characterized by chemical, mechanical and electrical analyses. All the composites showed good mechanical, electrical and thermal properties and good resistance to organic solvents and mineral acids

Synthesis and characterization of interpenetrating polymer networks from transesterified castor oil based polyurethane and polystyrene

AbstractA series of two component interpenetrating polymer networks (IPN) of modified castor oil based polyurethane (PU) and polystyrene (PS) were prepared by the sequential method. Castor oil was modified by triethanolamine by means of transesterification and designated as transesterified castor oil (TCO). The polyurethane network was prepared from transesterified castor oil (TCO) with the isophoronediisocyanates (IPDI) by using dibutyltindilaurate (DBTDL) as catalyst. Simultaneously styrene was added with benzoyl peroxide (BPO) as initiator and N,N′-Dimehtylaniline as coinitiator. Diallylphthalate was added as a crosslinking agent to form IPN and finally cast into films. To cast the film, the mixture (IPN) was poured in the glass cavity with pourable viscosity free from air bubbles. A series of two component interpenetrating polymer networks were prepared by varying % weight ratio of both polyurethane and polystyrene. These films were characterized by FT-IR, dynamic mechanical analysis (DMA), thermogravimetry analysis (TGA), morphology was measured by scanning electron microscopy (SEM). FT-IR have given the conformation of IPN formation. DMA results have shown much increase in the value of tanδ and a decrease in the value of Tg by increasing the anount of Styrene

Leucyl transfer ribonucleic acids and amindacyl transfer ribonucleic acid synthetases in developing pea pods and germinating pea seedlings.

Source: Masters Abstracts International, Volume: 40-07, page: . Thesis (M.Sc.)--University of Windsor (Canada), 1975

A Study on Ocular Manifestations of Diabetes Mellitus

Background: The incidence of detected diabetes in India is rapidly rising and by the time we succeed in preventing the much of a preventable blindness, diabetes is likely to emerge as a leading cause of ocular disease. A large bulk of literature is available describing retinopathy in its various aspects; but the other ocular manifestations of diabetes have been scantily written upon and so their epidemiology is even less well known. Aims: The objective of the study is to find out the incidence of different ocular manifestations of diabetes mellitus. The study is also done to determine the relationship of various risk factors and systemic diseases associated with diabetes mellitus and suggest the measures to prevent various sight threatening complications of diabetes mellitus. Material and Methods: The ocular manifestations were studied in 60 patients attending the eye OPD and the Diabetic Clinic of S. S. G. Hospital, Baroda during a period of 12 months. Results: Cataract was found to be the most common ocular manifestation of diabetes mellitus-35 patients (58.33%).The second most common manifestation was diabetic retinopathy-25 patients (41.66%).Also the most common associated systemic disease was found to be hypertension-20 patients (33.3%). Conclusion: Cataract and retinopathy were the two most common manifestations of diabetes mellitus. Patients having cataract can be very well managed by advanced cataract extraction techniques but to diagnose the early changes of retinopathy is of prime importance. A thorough ocular examination of patients having diabetes is a must, including both anterior and posterior segment examination

Investigation of Ester- and Amide-Linker-Based Porous Organic Polymers for Carbon Dioxide Capture and Separation at Wide Temperatures and Pressures

Organic compounds, such as covalent organic framework, metal–organic frameworks, and covalent organic polymers have been under investigation to replace the well-known amine-based solvent sorption technology of CO2 and introduce the most efficient and economical material for CO2 capture and storage. Various organic polymers having different function groups have been under investigation both for low and high pressure CO2 capture. However, search for a promising material to overcome the issues of lower selectivity, less capturing capacity, lower mass transfer coefficient and instability in materials performance at high pressure and various temperatures is still ongoing process. Herein, we report synthesis of six covalent organic polymers (COPs) and their CO2, N2, and CH4 adsorption performances at low and high pressures up to 200 bar. All the presented COPs materials were characterized by using elemental analysis method, Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (NMR) spectroscopy techniques. Physical properties of the materials such as surface areas, pore volume and pore size were determined through BET analysis at 77 K. All the materials were tested for CO2, CH4, and N2 adsorption using state of the art equipment, magnetic suspension balance (MSB). Results indicated that, amide based material i.e. COP-33 has the largest pore volume of 0.2 cm2/g which can capture up to the maximum of 1.44 mmol/g CO2 at room temperature and at pressure of 10 bar. However, at higher pressure of 200 bar and 308 K ester-based compound, that is, COP-35 adsorb as large as 144 mmol/g, which is the largest gas capturing capacity of any COPs material obtained so far. Importantly, single gas measurement based selectivity of COP-33 was comparatively better than all other COPs materials at all condition. Nevertheless, overall performance of COP-35 rate of adsorption and heat of adsorption has indicated that this material can be considered for further exploration as efficient and cheaply available solid sorbent material for CO2 capture and separation.Qatar National Research Fund, National Priorities Research Program grant (NPRP 5-499-1-088)

Implementation of P-Controller in Computational Fluid Dynamics (CFD) Simulation of a Pilot Scale Outlet Temperature Controlled Spray Dryer

[EN] Most of the CFD simulations of spray dryers reported in the literature utilizes a fixed air inlet temperature numerical framework. In this paper, a numerical framework was introduced to model spray drying as an outlet air temperature controlled process. A P-controller numerical framework was introduced which allows the inlet temperature to be automatically adjusted based on the required outlet temperature set point. This numerical framework was evaluated with a simulation of a two-stage pilot scale spray drying system at the Davis Dairy Plant (South Dakota State University) which is used for commercial contract spray drying operation.Afshar, S.; Jubaer, H.; Metzger, L.; Patel, H.; Selomulya, C.; Woo, MW. (2018). Implementation of P-Controller in Computational Fluid Dynamics (CFD) Simulation of a Pilot Scale Outlet Temperature Controlled Spray Dryer. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 155-162. https://doi.org/10.4995/IDS2018.2018.7536OCS15516

Advanced Polymeric Materials with Exceptional Carbon Dioxide Capture Capacities

Carbon dioxide (CO2) emissions resulting from combustion of fossil based fuels increasing the atmospheric CO2 concentration (currently at 393 ppm) is indubitably an alarming environmental issue such as an irreversible increase in the acidity levels of the oceans. In order to manage current CO2 emissions, several technologies exist such as chemical solvent absorption, physical adsorption, cryogenic fractionation, membrane separation, biological fixation as well as the oxi-fuel combustion process. Solvent-based absorption technology, especially amine-based solvents, is still the most widely used technique for CO2 removal in industry. However, it is a known fact that amine based acid gas removal technologies have severe drawbacks to the process such as corrosion, amine recovery and CO2 uptake capacity. Therefore, in an effort to develop the new possibilities on environmentally friendly and effective CO2 capturing materials in clean energy applications, we recently synthesized a new class of polymers with high CO2 adsorption capability termed cyanuric organic polymers (COPs). These compounds do not include metal complexes resulting in a lighter and more stable porous structure that is essential for high CO2 capture capacity at high pressures. High accuracy CO2 adsorption tests were made at pressures up to 200 bars at three isotherms 318 K, 328 K, and 338 K on three COPs called KAIST-1, KAIST-2 and QATAR-1 by using magnetic suspension based sorption apparatus. Moreover, MOF-5 and activated carbon Norit-RB3 were also experimented for comparison purposes since they are well known porous materials used for CO2 adsorption. Our CO2 adsorption studies at 318 K revealed a capacity of 127.60 mmol/g (5616 mg/g) for KAIST-1, 47.41 mmol/g (2086 mg/g) for KAIST-2 and 74.86 mmol/g (3294 mg/g) for QATAR-1. In order to put into perspective, KAIST-1 can hold more than five times what dry ice has in CO2 considering that COPs show modest surface areas. Here we report robust, inexpensive and reproducible synthesis of cyanuric organic polymers (COPs) with CO2 adsorption capacities up to 5616 mg/g. To the best of our knowledge, this is the highest CO2 adsorption capacity to date.qscienc

Discrete Dimers of Redox-Active and Fluorescent Perylene Diimide-Based Rigid Isosceles Triangles in the Solid State

The development of rigid covalent chiroptical organic materials, with multiple, readily available redox states, which exhibit high photoluminescence, is of particular importance in relation to both organic electronics and photonics. The chemically stable, thermally robust, and redox-active perylene diimide (PDI) fluorophores have received ever-increasing attention owing to their excellent fluorescence quantum yields in solution. Planar PDI derivatives, however, generally suffer from aggregation-caused emission quenching in the solid state. Herein, we report on the design and synthesis of two chiral isosceles triangles, wherein one PDI fluorophore and two pyromellitic diimide (PMDI) or naphthalene diimide (NDI) units are arranged in a rigid cyclic triangular geometry. The optical, electronic, and magnetic properties of the rigid isosceles triangles are fully characterized by a combination of optical spectroscopies, X-ray diffraction (XRD), cyclic voltammetry, and computational modeling techniques. Single-crystal XRD analysis shows that both isosceles triangles form discrete, nearly cofacial PDI–PDI π-dimers in the solid state. While the triangles exhibit fluorescence quantum yields of almost unity in solution, the dimers in the solid state exhibit very weak—yet at least an order of magnitude higher—excimer fluorescence yield in comparison with the almost completely quenched fluorescence of a reference PDI. The triangle containing both NDI and PDI subunits shows superior intramolecular energy transfer from the lowest excited singlet state of the NDI to that of the PDI subunit. Cyclic voltammetry suggests that both isosceles triangles exhibit multiple, easily accessible, and reversible redox states. Applications beckon in arenas related to molecular optoelectronic devices