Synthesis, characterization and morphological study of core-shell structure microgels via pre-emulsified semi-batch emulsion polymerization
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Date
2014
Authors
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Publisher
Universiti Teknologi Malaysia
Abstract
A novel microgel was polymerized using styrene (St), methyl methacrylate (MMA), acrylamide (AAm) and acrylic acid (AAc) monomers in the presence of N,N'- methylenebisacrylamide (MBA) cross-linker. Pre-emulsified monomer was first prepared followed by polymerizing the monomer using semi-batch emulsion polymerization. Fourier Transform Infrared Spectroscopy (FTIR) and 1H Nuclear Magnetic Resonance (NMR) were used to identify the related functional group and to determine the chemical structure. Energy Dispersive X-ray Spectrometer (EDS) was used to detect the elemental compositions of the microgels. The effect of MBA amount on the degree of cross-linking (%), water absorbency, glass transition temperature (Tg) and thermal degradation were studied. Grafting and crosslinking of poly(acrylamideco- acrylic acid)-grafted-poly(styrene-co-methyl methacrylate) [poly(AAm-co-AAc)- g-poly(St-co-MMA)] microgels were verified by the disappearance of bands at 1300 cm-1, 1200 cm-1 and 1163 cm-1 of FTIR spectrum and the appearance of C-H peaks at 5.5 - 5.7 ppm in 1H NMR spectrum. Scanning electron microscope (SEM) images indicated that poly(St-co-MMA) particle had lobed morphology, coated by crosslinked poly(AAm-co-AAc) shell. Furthermore, the SEM results revealed that poly(AAm-co-AAc)-g-poly(St-co-MMA) was a composite particle that consist of ‘raspberry’- shape like structure core. Internal structures of the microgels showed the homogeneous network of pores, an extensive interconnection among pores, thicker pore walls and open network structures. Water absorbency test indicated that sample with particle size of 0.43 |im had lower equilibrium water content (EWC, %) than the sample with particle size of 7.39 |im. Decomposition of poly(AAm-co-AAc)-gpoly( St-co-MMA) was slightly affected by increasing the MBA contents from 1.500 to 2.200 pphm. Tg of poly(AAm-co-AAc)-g-poly(St-co-MMA) was decreased at MBA contents of 1.500 to 1.675 pphm due to increasing in the ordered structure and the crystallinity content, which led to increase in melting temperature (Tm)
Description
Thesis (PhD. (Polymer Engineering))
Keywords
Polymerization, Emulsion polymerization, Microgels