Polypyrrole decorated mechanically robust conductive nanocomposites via solution blending and in-situ polymerization techniques

M. Zahra, S. Zulfiqar, C. T. Yavuz, H. S. Kweon, M. I. Sarwar*
Ind. Eng. Chem. Res., 58, 25, 10886-10893 (2019).
DOI: 10.1021/acs.iecr.9b01187

Polypyrrole grafted polystyrene-b-poly(ethylene-ran-butylene)-b-polystyrene (SEBS-g-PPy)/multiwall carbon nanotubes (MWCNTs) conductive nanocomposites were fabricated using two different approaches. The approach of system-I involved primarily the grafting of PPy on SEBS and its subsequent composites with nanotubes. In system-II in situ polymerization/grafting of PPy on SEBS was carried out along with MWCNTs yielding nanomaterials. Presynthesized SEBS-g-PPy and nanocomposites were characterized by Fourier transform infrared spectroscopy, NMR, field emission scanning electron microscopy, transmission electron microscopy, and electrical, mechanical, and thermal properties. The π–π stacking interactions between PPy of SEBS-g-PPy and MWCNTs rendered ample dispersion of the nanotubes in system-II relative to system-I. The electrical conductivity and tensile data showed improvement in these properties of nanocomposites and that system-II nanocomposites can sustain higher stresses, is stiffer, and can absorb more energy before breaking. Thermal stability of both the systems was improved relative to the matrices, and decomposition temperatures were found to increase from 437 to 568 °C. Relative improvement in electrical, thermal and tensile properties were observed for system-II nanocomposites rather than for system-I nanocomposites.

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Influence of interlayer functionalization of kaolinite on property profile of copolymer nanocomposites

S. Zulfiqar*, M. I. Sarwar*, N. Rasheed, C. T. Yavuz
Appl. Clay Sci., 112–113, 25–31, (2015). DOI: 10.1016/j.clay.2015.04.010.

Nanocomposites of co-poly (vinyl chloride–polyvinyl acetate–polyvinyl alcohol) (PVC–PVAc–PVA) and kaolinite were prepared via solution intercalation technique. To improve compatibility among the phases and to expand the interlayer basal spacing, kaolinite was modified using dimethylsulfoxide (DMSO) as a swelling agent. The influence of kaolinite dispersion and interaction between the disparate phases on the properties of nanocomposites were investigated using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), mechanical testing, thermogravimetric analysis (TGA) and water absorption measurements. IR data confirmed the hydrogen bonds formed between DMSO and the surface hydroxyl groups of kaolinite. XRD and microscopic results revealed that clay mineral was intercalated with uniform dispersion at nanoscale in the matrix. Tensile testing of these materials indicated significant improvements in the mechanical properties relative to the pure copolymer. Incorporation of kaolinite into the organic phase enhanced the thermal stability of the nanocomposites. Water absorption of the nanomaterials was reduced upon the addition of modified kaolinite rendering decreased permeability with increasing dispersibility of clay mineral in the copolymer matrix.

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Nanostructure and mechanical properties of aromatic polyamide and reactive organoclay nanocomposites

M. U. Alvi, S. Zulfiqar, C. T. Yavuz, H.S. Kweon, M. I. Sarwar*
Mater. Chem. Phys., 147, 636-643, (2014). [DOI]

Aromatic polyamide/organoclay nanocomposites were synthesized using the solution blending technique. Treatment of montmorillonite clay with p-phenylenediamine produced reactive organophilic clay for good compatibility with the matrix. Polyamide chains were prepared by condensing a mixture of 1,4-phenylenediamine and 4-4′-oxydianiline with isophthaloyl chloride under anhydrous conditions. These chains were end capped with carbonyl chloride using 1% extra acid chloride near the end of reaction to develop the interactions with organoclay. The dispersion and structure–property relationship were monitored using FTIR, XRD, FE-SEM, TEM, DSC and tensile testing of the thin films. The structural investigations confirmed the formation of delaminated and disordered intercalated morphology with nanoclay loadings. This morphology of the nanocomposites resulted in their enhanced mechanical properties. The tensile behavior and glass transition temperature significantly augmented with increasing organoclay content showing a greater interaction between the two disparate phases.

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Melamine based porous organic amide polymers for CO2 capture

S. Zulfiqar, M. I. Sarwar*, C. T. Yavuz*
RSC Adv., 4, 52263–52269, (2014). [DOI]

Amide based porous organic polymers were synthesized by the reaction of 1,3,5-benzenetricarbonyl trichloride with 2,4,6-triamino-1,3,5-triazine using two different solvents. Polyamide chains were derived from tri-functional monomers and their relative properties were compared in both media. These polymers were subjected to various analyses including FTIR, XRD, TGA, BET surface area and pore size analysis, FESEM and CO2 adsorption measurements. Thermal and chemical stability was achieved through strong amide building blocks in the polymer structure. The basic ring nitrogen and amide groups in the polyamide networks had the affinity to capture CO2. The maximum CO2 uptake of 2.99 cm3 g−1 (0.134 mmol g−1) at 273 K and 1 bar was obtained with the polyamide synthesized in DMAc–NMP (PA-1), revealing better efficiency than the polyamide prepared using 1,4-dioxane (PA-2) due to higher porosity and improved surface area. These thermally stable polyamides are anticipated to be good sorbents for CO2 capture in hostile environments.

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Conductive nanocomposite materials derived from SEBS-g-PPy and surface modified clay

M. Zahra, S. Zulfiqar, C. T. Yavuz, H.S. Kweon, M. I. Sarwar*
Compos. Sci. Technol., 100, 44–52, (2014). [DOI]

Conductive nanocomposites were synthesized from surface modified clay and polypyrrole grafted triblock copolymer, polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS-g-PPy). The grafting of PPy was carried out on SEBS using FeCl₃ as an oxidant and the formation of subsequent materials was monitored by IR, 1H NMR spectroscopy and Gel permeation chromatography (GPC). Surface treatment of the clay was carried out by ion exchange method using the cationic salt of 2,2-bis[4-(4-aminophenoxy)phenyl]propane for better adhesion with the polymer matrix. Thin composite films containing 1–8-wt.% organoclay were investigated by FTIR, XRD, TEM, tensile testing, TGA, DSC and electrical conductivity measurements. The molar mass as determined by GPC was around 37,000. XRD pattern and TEM images described good dispersion of clay platelets in the nanocomposites. Tensile testing revealed improvement in mechanical properties up to 3-wt.% of organoclay. The bulk electrical conductivity was increased up to 7-wt.% with increase in resonance of delocalized electrons of stretched PPy chains due to hydrogen bonding with organoclay in the nanocomposites. Thermal decomposition temperatures of the nanocomposites were in the range 435–448 °C. The decomposition of the nanocomposites was observed at higher temperatures relative to the pure polymer matrix with increasing clay loading. The weight retained after 900 °C was approximately equal to the amount of organoclay added in the composites. These composite materials exhibited improvement in glass transition temperature as compared to SEBS-g-PPy.

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Amidoxime Porous Polymers for CO2 Capture

S. Zulfiqar, S. Awan, F. Karadas, M. Atilhan*, C. T. Yavuz*, M. I. Sarwar*
RSC Adv.,  3 (38), 17203 - 17213, (2013). [DOI] [pdf] [WOS]

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Limitations and high pressure behavior of MOF-5 for CO2 capture

J. Y. Jung,‡ F. Karadas,‡ S. Zulfiqar,‡ E. Deniz, S. Aparicio, M. Atilhan*, C. T. Yavuz*, S. M. Han*
Phys. Chem. Chem. Phys., 15, 14319-14327, (2013). [pdf] [DOI] [WOS] (‡ Equal contribution)

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Influence of aminosilane coupling agent on aromatic polyamide/intercalated clay nanocomposites

M. U. Alvi, S. Zulfiqar*, C. T. Yavuz, H.-S. Kweon, M. I. Sarwar*
Ind. Eng. Chem. Res., 52 (21), 6908–6915, (2013). [DOI] [pdf] [WOS]

Aminosilane grafted and 1,4-phenylene diamine modified reactive montmorillonite was exploited for the generation of aromatic polyamide-layered silicate nanocomposites. For better compatibility between the two disparate phases, the hydrophilic nature of montmorillonite was changed into organophilic by ion-exchange method using 1,4-phenylenediamine as an intercalating agent and the hydroxyl groups present on clay surface and edges were used to graft 3-aminopropyltriethoxysilane (APTS) on clay platelets. The dispersion behavior of reactive organoclay was monitored in the polyamide matrix prepared from a pair of diamines (1,4-phenylenediamine and 4-4′-oxydianiline) with isophthaloyl chloride under anhydrous conditions. The resulting chains were selectively converted into carbonyl chloride ends to interact exclusively with free amine groups of the 1,4-phenylenediamine and APTS grafted on nanoclay. Thin composite films containing 2 to 10-wt. % clay were probed for FTIR, XRD, SEM, TEM, tensile testing, TGA and DSC measurements. XRD and TEM results described ample dispersion and morphology of clay sheets in the nanocomposites. Mechanical measurements revealed that tensile strength increased 110 %, elongation 172 % while modulus and toughness augmented many folds upon the addition of 4-6 wt. % clay in the matrix. Thermal decomposition temperatures of the nanocomposites were in the range 425-480 oC. The glass transition temperature increased up to 142.4 oC with 6-wt. % addition of organoclay in the matrix relative to pure polyamide depicting interfacial interactions among the phases.

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Amidoximes: Promising Candidates for CO2 Capture

S. Zulfiqar, F. Karadas, J. Park, E. Deniz, G. D. Stucky, Y. Jung*, M. Atilhan*, C. T. Yavuz*
Energy Environ. Sci., 4, 4528-4531, (2011). [DOI] [pdf]

Monoethanolamine (MEA) dominates power plant carbon dioxide (CO2) scrubbing processes, though with major disadvantages such as a 8–35% energy penalty. Here we report that structurally comparable amidoximes are promising CO2 capture agents based on RIMP2 electronic structure calculations. This was experimentally verified by the synthesis and testing of representative amidoximes for capture efficiencies at pressures as high as 180 bar. Acetamidoxime, which has the highest percent amidoxime functionality showed the highest CO2 capacity (2.71 mmol/g) when compared to terephthalamidoxime (two amidoximes per molecule) and tetraquinoamidoxime (four amidoximes per molecule). Polyamidoxime surpassed activated charcoal Norit RB3 for CO2 capture per unit surface area. Adsorption isotherms exhibit Type IV behavior and acetamidoxime found to increase CO2 capture with temperature, a less observed anomaly. Porous amidoximes are proposed as valuable alternatives to MEA.

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CO2 Adsorption Studies on Hydroxy Metal Carbonates M(CO3)x(OH)y (M = Zn, Zn Mg, Mg, Mg Cu, Cu, Ni, and Pb) at High Pressures up to 175 bar

F. Karadas, C. T. Yavuz, S. Zulfiqar, S. Aparicio-Martinez, G. D. Stucky, M. Atilhan*
Langmuir, 27 (17), 10642–10647 (2011). [DOI] [pdf]

Carbon dioxide (CO₂) adsorption capacities of several hydroxy metal carbonates have been studied using the state-of-the-art Rubotherm sorption apparatus to obtain adsorption and desorption isotherms of these compounds up to 175 bar. The carbonate compounds were prepared by simply reacting a carbonate (CO₃^2-) solution with solutions of Zn²⁺, Zn²⁺/Mg²⁺, Mg²⁺, Cu²⁺/Mg²⁺, Cu²⁺, Pb²⁺, and Ni²⁺ metal ions, resulting in hydroxyzincite, hydromagnesite, mcguinnessite, malachite, nullaginite, and hydrocerussite, respectively. Mineral compositions are calculated by using a combination of powder XRD, TGA, FTIR, and ICP-OES analysis. Adsorption capacities of hydroxy nickel carbonate compound observed from Rubotherm magnetic suspension sorption apparatus has shown highest performance among the other components that were investigated in this work (1.72 mmol CO₂/g adsorbent at 175 bar and 316 K).

 

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Investigation on novel thermoplastic poly(urethane-thiourea-imide)s with enhanced chemical and heat resistance

A. Kausar, S. Zulfiqar, C. T. Yavuz, M. I. Sarwar*
Polym. Degrad. Stabil., 96 (7), 1333-1341 (2011). [DOI] [pdf]

A new generation of segmented thermoplastic poly(urethane-thiourea-imide)s (PUTIs) was synthesized via reaction of polyethylene glycol and thiourea-based prepolymer with dianhydride as chain extenders. NCO-terminated prepolymer was synthesized from a new diisocyanate, 3-(3-((4-isocyanatophenyl)carbamoyl)thioureido)phenyl-4-isocyanatophenylcarbamate (IPCT), as a hard segment and PEG forming soft segment. The starting materials and polymers were characterized by conventional methods and physical properties such as solubility, solution viscosity, molecular weight, thermal stability and thermal behavior were studied. PUTIs showed partially crystalline structures. Weight average molecular weights of PUTIs (GPC measurements) were in the range of 1,68,694-1,97,035. Moreover, thermogravimetric analysis indicated that poly(urethane-thiourea-imide)s were fairly stable above 500 oC having T10 of 521-543 oC. Investigation of the results authenticated the approach of introducing thiourea (using IPCT) and imide structure in polyurethanes for the improvement of thermal stability. In comparison to typical polyurethanes, these polymers exhibited better heat resistance, chemical resistance as well as processability.

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