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Fabrication of Ag and Au nanoparticles in cross-linked polymer microgels for their comparative catalytic study

Shah L. A., Sayed M., Siddiq M.

Materials Science Poland

2017

Vol. 35, No. 3

651--659

Three dimensional cross-linked polymer microgels with temperature responsive N-isopropyl acrylamide (NIPAM) and pH sensitive methacrylic acid (MAA) were successfully synthesized by free radical emulsion polymerization with different amounts of MAA. Silver and gold nanoparticles with the size of 6.5 nm and 3.5 nm (±0.5 nm), respectively were homogeneously reduced inside these materials by chemical reduction method at pH 2.78 and 8.36 for the preparation of hybrid materials. The samples were characterized by FT-IR, DLS and TEM techniques. The catalytic activity of the hybrid materials was investigated for the reduction of 4-nitrophenol (4-NP) using NaBH4 as reducing agent by UV-Vis spectroscopy. The hybrid polymer network synthesized at pH 8.36 showed enhanced catalytic efficiency compared to the catalysts synthesized at pH 2.78. In this study, it has been stated that the catalyst activity strongly depends on the amount of MAA, pH value during synthesis and the type of entrapped metal nanoparticles.

Novel mechanically stable, heat resistant and nonflammable functionalized polystyrene/expanded graphite nanocomposites

Kausar A., Ullah W., Muhammad B., Siddiq M.

Advances in Materials Science

2014

Vol. 14, nr 4(42)

61--74

This study examined effect of inclusion of expanded graphite (Exp-G) on morphology, thermal, mechanical and flame retardant properties of PS, nitro-substituted polystyrene (N-PS) and amino-functional polystyrene (A-PS). FESEM showed exfoliated sheet morphology due to intercalation of N-PS and A-PS in expanded galleries. Tensile strength of A-PS materials (31.5-56.9 MPa) was higher than PS and N-PS. 10 % weight loss of A-PS nanocomposites (482-518 °C) was higher relative to pristine polymer and other nanocomposites. Cone calorimetry results revealed that there was lowering in PHHR of A-PS nanocomposites with 0.5 wt.% filler (428 kW/m2), while PS nanocomposites showed PHHR of 443 kW/m2.