Untreated Silica Nanoparticles Containing Poly(acrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid) Composite—Effect of Copolymer Composition

Abstract

Poly(acrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid)/Silica [Poly(AM-co-AMPSA)/SiO₂] core-shell composite nanogels with silica as core and hydrophilic polymer with functional groups such as sulfonic acid, amido, as shell were prepared by microemulsion polymerization without surface treatment of silica and upto 5.5 mole% of AMPSA in feed to control the particle size as well as morphology. The synthesized intercalated composites were produced with controllable sizes ranging from 44–77 nm in diameter. The repared sulfonic acid based silica core-shell composite nanogels were characterized by dynamic light scattering, transmission electron microscope, Fourier transform infrared spectrophotometer, thermogravimetric analyzer, differential scanning calorimeter, scanning electron microscope and X-ray diffraction. The encapsulation of functional polymer shell onto the silica particles was driven by the hydrogen-bonding interaction between sulfonic acid and amido groups of AMPSA with Si-O linkages. The onset degradation temperature is increased from 227°C to 262°C in copolymer-silica composites which indicates improved thermal stability. The shifting of glass transition temperature from 194°C to 203°C in copolymeric composite nanogels further confirms the existence of strong interactions of silica filler with copolymer chains. Also the chemical composition of polymeric chains and the affinity of polymer chains and silica influenced the morphology.

Keywords:

• 2-Acrylamido-2-methyl-1-propanesulfonic acid
• Acrylamide
• Composite nanogels
• Microemulsion polymerization
• Silica

ACKNOWLEDGMENT

We thank Council of Scientific and Industrial Research (CSIR), New Delhi, India for providing senior research fellowship (no. 09/806 (16) 09/ EMR – I) to P.B.