Dr.M.Suguna Lakshmi Senior Principal Scientist Polymer Science and Technology Division Central Leather Research Institute (CLRI-CSIR) Adyar Chennai600020 https://clri.org/EmployeProfile/67_Dr.M_Sugunalakshmi_.html
Three isatin derivatives, namely, 1-allyl-3-hydroxy-3-(6-oxocyclohex-1-en-1-yl)indolin-2-one, C 1... more Three isatin derivatives, namely, 1-allyl-3-hydroxy-3-(6-oxocyclohex-1-en-1-yl)indolin-2-one, C 17 H 17 NO 3 , 1-ethyl-3-hydroxy-3-(6-oxocyclohex-1-en-1-yl)indolin-2-one, C 16 H 17 NO 3 , and 5-bromo-3-hydroxy-1-methyl-3-(6-oxocyclohex-1en-1-yl)indolin-2-one, C 15 H 14 BrNO 3 , were synthesized, crystallized by the slowevaporation technique, characterized by 1 H and 13 C NMR spectroscopy, and analysed by the single-crystal X-ray diffraction (XRD) method. Quantum chemical parameters, such as the energy of the highest occupied molecular orbital, energy of the lowest unoccupied molecular orbital, energy gap, electronic energy, ionization potential, chemical potential, global hardness, global softness and electrophilicity index, were calculated. The druglikeness and bioactivity scores of the compounds were calculated. The activities of these isatin derivatives against bacterial strains, such as Eschericia coli, Proteus vulgaris, Shigella flexneri, Staphylococcus aureus and Micrococcus luteus, and the fungal strain Aspergillus niger, were determined using the well-diffusion assay method. Molecular docking studies were carried out to predict the binding mode of the isatin compounds with the penicillin binding protein enzyme and to identify the interactions between the enzyme and the ligands under study.
Polyurethane nanocomposites were synthesized by using a flame retardant compound containing P and... more Polyurethane nanocomposites were synthesized by using a flame retardant compound containing P and N atoms. Nuclear magnetic resonance spectroscopy confirmed the structure for the prepared triethanolaminodiethyl phosphate (P-OH). Effective construction of polyurethane foam was achieved between P-OH and toluene-2,4-diisocyanate with inclusion of polyethylene glycol (PEG) and polydimethylsiloxane (PDMS). It was then characterized by TGA, DSC, AFM, and XRD. The analyses indicated that the foams were amorphous, but reduced PEG/P-OH (w/w) content changes slightly the microphase separation. An increase in PDMS/PEG ratio in the polyurethane has increased glass transition temperature from 168.3 °C to 177.3 °C. The polyurethane systems were considered as being "slow-burning" with a level of UL-94 V-0, and their ignition delay time was estimated to have eight seconds. This polyurethane system can be used successfully in specific applications for energy-saving measures in buildings.
The leftover vegetable oils after frying of food at higher temperature is toxic to environment as... more The leftover vegetable oils after frying of food at higher temperature is toxic to environment as diminutive of technologies for proper disposal and reuse of waste cooking oil. An highly water soluble and emulsifier-free phosphorylated fatliquor with the emulsion stability of more than 60 min from economically cheap deep fried oils on transesterification with highly biodegradable ecologically innocuous and water soluble Poly (ethylene glycol) with p-Toluene Sulphonic acid followed by phosphorylation produces highly water dispersible and stable material for leather applications. The synthesised phosphorylated fatliquors were ascertained for the lubrication of collagen fibres and fibre splitting of goat skin by SEM analysis. The transesterification has confirmed by FT-IR, fat composition oils, COD, BOD, total solid in spent liquor were analysed. Physical characteristics of leathers were analysed by tensile strength, tear strength, elongation and quality assessments by hand evaluation by experts. Acid, iodine, saponification values, particle size of phosphorylated fatliquors, surface wettability, thermal stability of leathers were analysed and the properties compared. The finding can assist an emulsifier-free lubricating process significantly as currently available leather chemicals.
The first discovery of aggregation-induced emission (AIE), whereby luminogen aggregation plays a ... more The first discovery of aggregation-induced emission (AIE), whereby luminogen aggregation plays a positive role in enhancing the light-emission efficiency, has piqued the interest of many researchers as it opens up a new avenue for the exploration of practically beneficial luminescent materials. Diverse AIEactive luminogens (or AIEgens) with tunable emission colours and very high quantum yields (up to unity) in the solid state have been extensively utilised in a broad range of fields including optoelectronics, energy and bioscience. In this article, we describe novel fluorene-based fluorogens that exhibit bright emission in the solid-state, mechanical stimuli-responsive optical properties and aggregation-induced emissive ability, and were able to modulate their donor and acceptor properties. The target compounds were synthesized by a Knoevenagel condensation followed by Suzuki cross-coupling reaction, which tends to result in good yields. The target cyanostilbenes (4a-4d) show different reversibly switched states with high contrast through morphology modulation and demonstrate solvatochromic, vapochromic, and AIE properties. These results strongly suggest that compound 4d has better properties than the other derivatives (4a-c) due to the presence of extended donor-acceptor ability. Moreover, density-functional theory (DFT) calculations strongly support the UV-Vis and fluorescence spectral studies. The formation of nano-flakes and cuboid-shaped nanocrystals was further confirmed by FE-SEM and AFM studies. The synthesized compound 4d displayed very bright emission in the solid state and in the aggregate state as compared with the other derivatives (4a-4c). These results might be due to the presence of high-color contrast, which is an advantage for elucidation and overcomes the challenges exhibited in live-cell imaging applications. Moreover, an MTT assay on live A549 cells incubated with the target compound (4d) showed very low cytotoxicity even at high concentrations.
A series of thermally stable dicyanate monomers was prepared containing different thermally stabl... more A series of thermally stable dicyanate monomers was prepared containing different thermally stable structural units, namely 2,2 ′-bis(4-cyanatophenyl)propane, bis-4-cyanato-biphenyl, bis-4-cyanato naphthalene, 3,3 ′-bis(4-cyanatophenyl)sulfide and 3,3 ′-bis(4-cyanatophenyl)sulfone, was prepared and the identity of the products was confirmed by Fourier transform infrared and NMR spectral methods. The corresponding cyanate homopolymers were prepared and their properties were evaluated and compared. The composites were analysed for their thermal stability and thermal degradation kinetics. The series of homopolymers exhibit excellent thermal characteristics, e.g. relatively high glass transition temperatures of at least 215 ∘ C, which were inversely proportional to the molecular weight between the crosslinks, high thermal decomposition temperature and high activation energies for the decomposition of cured resins. Determination of their limiting oxygen indices indicates that all the homopolymers are characterized as 'self-extinguishing' materials.
The proposal concerns intentionally added microplastics. It focuses on products which release the... more The proposal concerns intentionally added microplastics. It focuses on products which release the plastic particles to the environment directly or via public wastewater treatment plants. These include cosmetic products (e.g. facial scrubs) and household cleaners (e.g. scouring agents), which are rinsed off during or after use and are disposed of down the drain. The rationale behind it is to reduce the release of poorly biodegradable microplastics into the environment because they are absorbed by organisms and can enter the human food chain. The restriction proposal therefore also forms part of the "EU strategy for plastics (2018)". Some Member States have already enacted similar restrictions, and the EU-wide approach is therefore also seeking to achieve harmonisation. The proposal will continue to allow microplastics in products that do not release the particles. However, there will be labelling and reporting requirements on the fate of the plastics. At this point, the ECHA proposal goes beyond the original mandate and the existing regulations of the Member States. It provides for transition periods for certain products. The labelling requirements will apply 18 months, and the reporting obligations 12 months, after the restriction enters into force (for more information: https://echa.europa.eu/de/registry-of-restriction-intentions/-/dislist/details/0b0236e18244cd73).
Fish populations are declining around the world, and many countries are trying to conserve them b... more Fish populations are declining around the world, and many countries are trying to conserve them by regulating their fishing industries. However, controlling fishing locally may not do enough to strengthen fish populations. Often one nation's fish stocks depend on the spawning grounds of a neighboring country, where fish release eggs and sperm into the water and larvae hatch from fertilized eggs. We do research on oceans, climate and fisheries. In a recent study, we showed that global fisheries are even more tightly connected than previously understood. The world's coastal marine fisheries form a single network, thanks to the drift of larvae along ocean currents. This suggests that country-by-country fishery management may be fundamentally insufficient. If a fish species that provides food to one country should decline, the amount of fish spawn, or eggs and larvae, riding the ocean currents from there to other countries would also decline dramatically, resulting in further loss of fish elsewhere.
Three isatin derivatives, namely, 1-allyl-3-hydroxy-3-(6-oxocyclohex-1-en-1-yl)indolin-2-one, C 1... more Three isatin derivatives, namely, 1-allyl-3-hydroxy-3-(6-oxocyclohex-1-en-1-yl)indolin-2-one, C 17 H 17 NO 3 , 1-ethyl-3-hydroxy-3-(6-oxocyclohex-1-en-1-yl)indolin-2-one, C 16 H 17 NO 3 , and 5-bromo-3-hydroxy-1-methyl-3-(6-oxocyclohex-1en-1-yl)indolin-2-one, C 15 H 14 BrNO 3 , were synthesized, crystallized by the slowevaporation technique, characterized by 1 H and 13 C NMR spectroscopy, and analysed by the single-crystal X-ray diffraction (XRD) method. Quantum chemical parameters, such as the energy of the highest occupied molecular orbital, energy of the lowest unoccupied molecular orbital, energy gap, electronic energy, ionization potential, chemical potential, global hardness, global softness and electrophilicity index, were calculated. The druglikeness and bioactivity scores of the compounds were calculated. The activities of these isatin derivatives against bacterial strains, such as Eschericia coli, Proteus vulgaris, Shigella flexneri, Staphylococcus aureus and Micrococcus luteus, and the fungal strain Aspergillus niger, were determined using the well-diffusion assay method. Molecular docking studies were carried out to predict the binding mode of the isatin compounds with the penicillin binding protein enzyme and to identify the interactions between the enzyme and the ligands under study.
Polyurethane nanocomposites were synthesized by using a flame retardant compound containing P and... more Polyurethane nanocomposites were synthesized by using a flame retardant compound containing P and N atoms. Nuclear magnetic resonance spectroscopy confirmed the structure for the prepared triethanolaminodiethyl phosphate (P-OH). Effective construction of polyurethane foam was achieved between P-OH and toluene-2,4-diisocyanate with inclusion of polyethylene glycol (PEG) and polydimethylsiloxane (PDMS). It was then characterized by TGA, DSC, AFM, and XRD. The analyses indicated that the foams were amorphous, but reduced PEG/P-OH (w/w) content changes slightly the microphase separation. An increase in PDMS/PEG ratio in the polyurethane has increased glass transition temperature from 168.3 °C to 177.3 °C. The polyurethane systems were considered as being "slow-burning" with a level of UL-94 V-0, and their ignition delay time was estimated to have eight seconds. This polyurethane system can be used successfully in specific applications for energy-saving measures in buildings.
The leftover vegetable oils after frying of food at higher temperature is toxic to environment as... more The leftover vegetable oils after frying of food at higher temperature is toxic to environment as diminutive of technologies for proper disposal and reuse of waste cooking oil. An highly water soluble and emulsifier-free phosphorylated fatliquor with the emulsion stability of more than 60 min from economically cheap deep fried oils on transesterification with highly biodegradable ecologically innocuous and water soluble Poly (ethylene glycol) with p-Toluene Sulphonic acid followed by phosphorylation produces highly water dispersible and stable material for leather applications. The synthesised phosphorylated fatliquors were ascertained for the lubrication of collagen fibres and fibre splitting of goat skin by SEM analysis. The transesterification has confirmed by FT-IR, fat composition oils, COD, BOD, total solid in spent liquor were analysed. Physical characteristics of leathers were analysed by tensile strength, tear strength, elongation and quality assessments by hand evaluation by experts. Acid, iodine, saponification values, particle size of phosphorylated fatliquors, surface wettability, thermal stability of leathers were analysed and the properties compared. The finding can assist an emulsifier-free lubricating process significantly as currently available leather chemicals.
The first discovery of aggregation-induced emission (AIE), whereby luminogen aggregation plays a ... more The first discovery of aggregation-induced emission (AIE), whereby luminogen aggregation plays a positive role in enhancing the light-emission efficiency, has piqued the interest of many researchers as it opens up a new avenue for the exploration of practically beneficial luminescent materials. Diverse AIEactive luminogens (or AIEgens) with tunable emission colours and very high quantum yields (up to unity) in the solid state have been extensively utilised in a broad range of fields including optoelectronics, energy and bioscience. In this article, we describe novel fluorene-based fluorogens that exhibit bright emission in the solid-state, mechanical stimuli-responsive optical properties and aggregation-induced emissive ability, and were able to modulate their donor and acceptor properties. The target compounds were synthesized by a Knoevenagel condensation followed by Suzuki cross-coupling reaction, which tends to result in good yields. The target cyanostilbenes (4a-4d) show different reversibly switched states with high contrast through morphology modulation and demonstrate solvatochromic, vapochromic, and AIE properties. These results strongly suggest that compound 4d has better properties than the other derivatives (4a-c) due to the presence of extended donor-acceptor ability. Moreover, density-functional theory (DFT) calculations strongly support the UV-Vis and fluorescence spectral studies. The formation of nano-flakes and cuboid-shaped nanocrystals was further confirmed by FE-SEM and AFM studies. The synthesized compound 4d displayed very bright emission in the solid state and in the aggregate state as compared with the other derivatives (4a-4c). These results might be due to the presence of high-color contrast, which is an advantage for elucidation and overcomes the challenges exhibited in live-cell imaging applications. Moreover, an MTT assay on live A549 cells incubated with the target compound (4d) showed very low cytotoxicity even at high concentrations.
A series of thermally stable dicyanate monomers was prepared containing different thermally stabl... more A series of thermally stable dicyanate monomers was prepared containing different thermally stable structural units, namely 2,2 ′-bis(4-cyanatophenyl)propane, bis-4-cyanato-biphenyl, bis-4-cyanato naphthalene, 3,3 ′-bis(4-cyanatophenyl)sulfide and 3,3 ′-bis(4-cyanatophenyl)sulfone, was prepared and the identity of the products was confirmed by Fourier transform infrared and NMR spectral methods. The corresponding cyanate homopolymers were prepared and their properties were evaluated and compared. The composites were analysed for their thermal stability and thermal degradation kinetics. The series of homopolymers exhibit excellent thermal characteristics, e.g. relatively high glass transition temperatures of at least 215 ∘ C, which were inversely proportional to the molecular weight between the crosslinks, high thermal decomposition temperature and high activation energies for the decomposition of cured resins. Determination of their limiting oxygen indices indicates that all the homopolymers are characterized as 'self-extinguishing' materials.
The proposal concerns intentionally added microplastics. It focuses on products which release the... more The proposal concerns intentionally added microplastics. It focuses on products which release the plastic particles to the environment directly or via public wastewater treatment plants. These include cosmetic products (e.g. facial scrubs) and household cleaners (e.g. scouring agents), which are rinsed off during or after use and are disposed of down the drain. The rationale behind it is to reduce the release of poorly biodegradable microplastics into the environment because they are absorbed by organisms and can enter the human food chain. The restriction proposal therefore also forms part of the "EU strategy for plastics (2018)". Some Member States have already enacted similar restrictions, and the EU-wide approach is therefore also seeking to achieve harmonisation. The proposal will continue to allow microplastics in products that do not release the particles. However, there will be labelling and reporting requirements on the fate of the plastics. At this point, the ECHA proposal goes beyond the original mandate and the existing regulations of the Member States. It provides for transition periods for certain products. The labelling requirements will apply 18 months, and the reporting obligations 12 months, after the restriction enters into force (for more information: https://echa.europa.eu/de/registry-of-restriction-intentions/-/dislist/details/0b0236e18244cd73).
Fish populations are declining around the world, and many countries are trying to conserve them b... more Fish populations are declining around the world, and many countries are trying to conserve them by regulating their fishing industries. However, controlling fishing locally may not do enough to strengthen fish populations. Often one nation's fish stocks depend on the spawning grounds of a neighboring country, where fish release eggs and sperm into the water and larvae hatch from fertilized eggs. We do research on oceans, climate and fisheries. In a recent study, we showed that global fisheries are even more tightly connected than previously understood. The world's coastal marine fisheries form a single network, thanks to the drift of larvae along ocean currents. This suggests that country-by-country fishery management may be fundamentally insufficient. If a fish species that provides food to one country should decline, the amount of fish spawn, or eggs and larvae, riding the ocean currents from there to other countries would also decline dramatically, resulting in further loss of fish elsewhere.
The intercalation of captopril (CP) into the interlayers of montmorillonite (MMT) affords an inte... more The intercalation of captopril (CP) into the interlayers of montmorillonite (MMT) affords an intestine-selective drug delivery system that has a captopril-loading capacity of up to ca. 14 %w/w and which exhibits near-zero-order release kinetics.
Abstract Appropriate selection of implant biomaterial is a key factor for long-term success of im... more Abstract Appropriate selection of implant biomaterial is a key factor for long-term success of implants. The biologic environment does not accept completely just any material so to optimize biological performance; implants should be selected to reduce the negative biologic response while maintaining adequate function. Prior to developing an implant, a clinician should have sound knowledge about the different biomaterials and its properties. An implant made up of Ti-based alloys provides fruitful performance due to their excellent mechanical, physical, and biological properties. Despite the existence of different types of Ti-based alloys, low modulus β-type Ti-based alloys have superior performance in comparison with other types. Providing good biological fixation through bone tissue in growth into the porous network is the main feature of it. Similar to titanium, the elements belonging to group VI of the Periodic table are found to be suitable for the development of implants. Of which, zirconium has high corrosion resistance and low thermal conductivity. To withstand the longer life of an implant in a biological medium, it possesses high corrosion resistance as well as tissue in growth. The implants made from titanium and zirconium compound yields better solutions. For this modified alloy design, an improvement of strength is expected by combining metal rather than individual metal. Effort has been taken to summarize the various applications of the biomaterials which were used in the past as well in the current world.
The present study focuses on the synthesis of phosphorus-containing epoxy resins, and their use a... more The present study focuses on the synthesis of phosphorus-containing epoxy resins, and their use as reactive flame retardants for epoxy. Phosphorus-functionalized epoxy resins were synthesized using different aliphatic diols. Firstly, phosphorus was grafted by reacting phosphoryl chloride with three different aliphatic diols: 1,5-pentanediol, 1,4-butanediol, or 1,3-propanediol. The ensuing phosphorus-triol compounds were then epoxidized with epichlorohydrin in an alkaline medium. Fourier transform infrared and nuclear magnetic resonance spectroscopies confirmed the presence of the epoxy-end group in the structure of synthesized epoxy resins. The phosphorus-containing epoxy resins were mixed with diglycidylether of bisphenol A at a fixed mass ratio of 9:1, and the hybrid formulations were cured with triethylenetetramine as a hardener. Their thermal behaviour was assessed by differential scanning calorimetry and thermogravimetric analysis. Furthermore, the hybrid epoxy resins were blended with nano-clay and applied as a finishing coating on the grain surface of the leather. Thermal analyses of coated leather showed an enhancement of thermal performance with an increase of statistical heat resistant index temperature from 100 to 121 °C. The flame retardation properties were also assessed and found that after coating leather with epoxy nanocomposites, the limiting oxygen index of leather increased from 26.7 ± 0.5% to 28.6 ± 0.7%; meanwhile, ignition time went from 6.0 to 8.1 sec. Consequently, all the coated leather with phosphorus-based epoxy nanocomposites exhibited a self-extinguishing behaviour due to the synergistic effect of P atoms and clay nanoparticles.
The intercalation of captopril (CP) into the interlayers of montmorillonite (MMT) affords an inte... more The intercalation of captopril (CP) into the interlayers of montmorillonite (MMT) affords an intestine-selective drug delivery system that has a captopril-loading capacity of up to ca. 14 %w/w and which exhibits near-zero-order release kinetics.
Polyurethane nanocomposites were synthesized by using a flame retardant compound containing P and... more Polyurethane nanocomposites were synthesized by using a flame retardant compound containing P and N atoms. Nuclear magnetic resonance spectroscopy confirmed the structure for the prepared triethanolaminodiethyl phosphate (P-OH). Effective construction of polyurethane foam was achieved between P-OH and toluene-2,4-diisocyanate with inclusion of polyethylene glycol (PEG) and polydimethylsiloxane (PDMS). It was then characterized by TGA, DSC, AFM, and XRD. The analyses indicated that the foams were amorphous, but reduced PEG/P-OH (w/w) content changes slightly the microphase separation. An increase in PDMS/PEG ratio in the polyurethane has increased glass transition temperature from 168.3 °C to 177.3 °C. The polyurethane systems were considered as being "slow-burning" with a level of UL-94 V-0, and their ignition delay time was estimated to have eight seconds. This polyurethane system can be used successfully in specific applications for energy-saving measures in buildings.
The leftover vegetable oils after frying of food at higher temperature is toxic to environment as... more The leftover vegetable oils after frying of food at higher temperature is toxic to environment as diminutive of technologies for proper disposal and reuse of waste cooking oil. An highly water soluble and emulsifier-free phosphorylated fatliquor with the emulsion stability of more than 60 min from economically cheap deep fried oils on transesterification with highly biodegradable ecologically innocuous and water soluble Poly (ethylene glycol) with p-Toluene Sulphonic acid followed by phosphorylation produces highly water dispersible and stable material for leather applications. The synthesised phosphorylated fatliquors were ascertained for the lubrication of collagen fibres and fibre splitting of goat skin by SEM analysis. The transesterification has confirmed by FT-IR, fat composition oils, COD, BOD, total solid in spent liquor were analysed. Physical characteristics of leathers were analysed by tensile strength, tear strength, elongation and quality assessments by hand evaluation by experts. Acid, iodine, saponification values, particle size of phosphorylated fatliquors, surface wettability, thermal stability of leathers were analysed and the properties compared. The finding can assist an emulsifier-free lubricating process significantly as currently available leather chemicals.
The first discovery of aggregation-induced emission (AIE), whereby luminogen aggregation plays a ... more The first discovery of aggregation-induced emission (AIE), whereby luminogen aggregation plays a positive role in enhancing the light-emission efficiency, has piqued the interest of many researchers as it opens up a new avenue for the exploration of practically beneficial luminescent materials. Diverse AIEactive luminogens (or AIEgens) with tunable emission colours and very high quantum yields (up to unity) in the solid state have been extensively utilised in a broad range of fields including optoelectronics, energy and bioscience. In this article, we describe novel fluorene-based fluorogens that exhibit bright emission in the solid-state, mechanical stimuli-responsive optical properties and aggregation-induced emissive ability, and were able to modulate their donor and acceptor properties. The target compounds were synthesized by a Knoevenagel condensation followed by Suzuki cross-coupling reaction, which tends to result in good yields. The target cyanostilbenes (4a-4d) show different reversibly switched states with high contrast through morphology modulation and demonstrate solvatochromic, vapochromic, and AIE properties. These results strongly suggest that compound 4d has better properties than the other derivatives (4a-c) due to the presence of extended donor-acceptor ability. Moreover, density-functional theory (DFT) calculations strongly support the UV-Vis and fluorescence spectral studies. The formation of nano-flakes and cuboid-shaped nanocrystals was further confirmed by FE-SEM and AFM studies. The synthesized compound 4d displayed very bright emission in the solid state and in the aggregate state as compared with the other derivatives (4a-4c). These results might be due to the presence of high-color contrast, which is an advantage for elucidation and overcomes the challenges exhibited in live-cell imaging applications. Moreover, an MTT assay on live A549 cells incubated with the target compound (4d) showed very low cytotoxicity even at high concentrations.
Dicyanate monomer viz bis-4-cyanato-polydimethylsiloxane(PDMS-CY) containing siloxane known as th... more Dicyanate monomer viz bis-4-cyanato-polydimethylsiloxane(PDMS-CY) containing siloxane known as thermally stable structural unit was prepared. The PDMS-CY/DGEBA- Epoxy/Nanoclay were prepared. They were analysed for their properties such as thermal stability, thermal degradation kinetics and microstructures. Keywords: Cyanate ester; Resins; Nanoclay; Nanocomposite; Flame retardance; Degradation kinetics;
New epoxide and cyanate ester resins with an aromatic ester backbone namely 1, 3-[di-(4-glycidylo... more New epoxide and cyanate ester resins with an aromatic ester backbone namely 1, 3-[di-(4-glycidyloxy diphenyl-2, 2′-propane)]-isophthalate (DGDPI) and 1, 4-[di-(4-cyanato diphenyl-2, 2′-propane)]-terephthalate (DCDPT) were synthesized and the intermediates were ...
The intercalation of captopril (CP) into the interlayers of montmorillonite (MMT) affords an inte... more The intercalation of captopril (CP) into the interlayers of montmorillonite (MMT) affords an intestine-selective drug delivery system that has a captopril-loading capacity of up to ca. 14 %w/w and which exhibits near-zero-order release kinetics.
Polyurethane nanocomposites were synthesized by using a flame retardant compound containing P and... more Polyurethane nanocomposites were synthesized by using a flame retardant compound containing P and N atoms. Nuclear magnetic resonance spectroscopy confirmed the structure for the prepared triethanolaminodiethyl phosphate (P-OH). Effective construction of polyurethane foam was achieved between P-OH and toluene-2,4-diisocyanate with inclusion of poly-ethylene glycol (PEG) and polydimethylsiloxane (PDMS). It was then characterized by TGA, DSC, AFM, and XRD. The analyses indicated that the foams were amorphous, but reduced PEG/P-OH (w/w) content changes slightly the microphase separation. An increase in PDMS/PEG ratio in the polyurethane has increased glass transition temperature from 168.3 °C to 177.3 °C. The polyurethane systems were considered as being "slow-burning" with a level of UL-94 V-0, and their ignition delay time was estimated to have eight seconds. This polyurethane system can be used successfully in specific applications for energy-saving measures in buildings.
The preparation and characterization of blends of a series of dicyanate monomers such as 2,2 0-bi... more The preparation and characterization of blends of a series of dicyanate monomers such as 2,2 0-bis(4-cyanatophenyl) propane (DCDPP), bis-4-cyanato-biphenyl (DCBP), bis-4-cyanatonaphthalene (DCN), 3,3 0-bis(4-cyanatophenyl)sulphide (DCTDP), 3,3 0-bis (4-cyanatophenyl)sulphone (DCDPS), and the diglycidyl ether of bisphenol A are reported. These copolymers are combined with a montmorillionite nanoclay and both epoxy-cyanate blends and epoxy-cyanate blends-nanoclay composites are all analyzed for thermal stability, thermal degradation kinetics, flame retardancy, and impact strength. The nanocomposites are further characterized by X-ray diffraction and SEM to determine morphological features, from which structure-property relationships are determined. Dispersion of the nanoclay is of paramount importance, but its inclusion serves to improve char yield and impact strength, when this is achieved.
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