1. SYNTHESIS AND CHARACTERIZATION OF SULFUR-FUNCTIONAL LAYERED
SILICATE FOR USE IN NANOCOMPOSITE ELASTOMERS
Randy Fang, Shigeng Li, and Dr. Harry Ploehn
Department of Chemical Engineering,
University of South Carolina, Columbia, SC 29208
Introduction
Experiments
Results Elemental Analysis
C% H% N% S%
Moles of
CTAB/g of MMT
Moles of
Si69/g of MMT
CTAB-MMT 19.55 4.29 1.27 0 1.2×10-3
0
SMMT 17.48 3.76 1.06 1.81 1.0×10-3
1.9×10-4
Squalene Grafting Reactions
Conclusions
Acknowledgements
Objective
 Prepare clean Na-MMT and functionalize it with sulfur-containing silane coupling agent
(Si69) to produce sulfur-functional MMT (SMMT).
 Assess the potential compatibility of SMMT with elastomers by studying the reaction of
SMMT with squalene, a small-molecule model compound resembling natural rubber.
 Both industry and academia are interested in elastomer nanocomposites – elastomeric
polymers containing inorganic nanoparticles such as layered silicates.
 Small amounts of inorganic layered silicate particles could enhance the properties of
elastomers, such as mechanical strength and toughness, thermal stability, and gas barrier.
 Based on our previous studies, clean sodium montmorillonite (Na-MMT) can be fully
exfoliated in water. However, Na-MMT is not naturally compatible with elastomers.
Clean MMT: Na-MMT was dispersed in water to fully exfoliate into
single platelets and remove any impurities by centrifugation.
SMMT: Si69 was added to react with the edge –OH groups of MMT.
SMMT-Squalene: Squalene, an analog of natural rubber, was reacted with SMMT.
XRD patterns of MMT, CTAB-MMT,
and SMMT:
Low angle peak indicates inter-layer
spacing (d-spacing)
CTAB-MMT d-spacing of 1.94 nm
indicates expansion of relative to MMT
(1.2 nm)
SMMT d-spacing of 1.86 nm is almost
the same as that of CTAB-MMT
Results consistent with SMMT
containing interlayer CTAB and edge-
grafted Si69
TGA of pure MMT
TGA of CTAB-MMT TGA of SMMT
FTIR spectra of clean MMT, CTAB,
CTAB-MMT, SMMT, SMMT-
Squalene:
CTAB-MMT and SMMT spectra include
peaks indicating presence of CTAB
SMMT spectrum does not show unique
peaks from Si69 – hidden by CTAB
peaks
Squalene-SMMT spectrum shows
unique peaks indicating squalene
grafting
MMT structure
110°C, 48hr,
N2 atmosphere
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
Si69/toluene
OH
OH
OH
OH
OH
Squalene, 150°C, 24hr,
N2 atmosphere
OH
OH
0.9 nm
0.2 nm
60°C, 24hr
Na+
Na+ CTAB/H2O
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
TGA of Squalene-SMMTTGA of Squalene-CTAB-MMT
 University of South Carolina
 South Carolina Governor's School for Science and Mathematics
 Dr. Harry Ploehn
 Shigeng Li
 CTAB intercalated and expanded the interlayer of MMT
 The edges of MMT were functionalized with Si69 to produce SMMT
 Squalene successfully grafted onto SMMT via the covalent bond with Si69
 TGA suggests some squalene may intercalate into the SMMT interlayer space, leading to the
increase in d-spacing of squalene-SMMT
TGA data for MMT, CTAB-MMT, SMMT:
MMT: 14.6% loss of water (hydrophilic), 5.7%
dehydroxylation loss
CTAB-MMT: 2% water (hydrophobic), 24% loss from
CTAB, and ~5% dehydroxylation loss. Two peaks:
weakly and strongly adsorbed CTAB
SMMT: 2% water, 27% loss from CTAB and Si69 (no
dehydrox. loss). Organic weight loss may be greater
than in CTAB-MMT due to Si69. Peak shift perhaps due
to presence of Si69.
Nitrogen results: 15-20% decrease in CTAB content after Si69 grafting
Sulfur results: SMMT definitely contains sulfur: about 1:5 ratio of Si69 to CTAB in SMMT
XRD patterns of squalene-CTAB-
MMT and squalene-SMMT:
Squalene-CTAB-MMT control sample
shows d-spacing decrease from 1.94 to
1.8 nm, possibly indicating some CTAB
loss
Squalene-SMMT sample shows d-
spacing increase from 1.86 to 2.1 nm,
due to edge and (possibly) interlayer
squalene grafting
TGA data for squalene-CTAB-MMT and squalene-SMMT:
Squalene-CTAB-MMT: 2% water, 5% dehydrox. loss, and 26.5% loss from CTAB and
squalene. Possibly some squalene intercalation into CTAB-MMT
Squalene-SMMT: 2% water, 45% loss from CTAB, Si69, squalene. Overall weight loss much
larger, presumably due to grafting of squalene onto SMMT.
Fourier-Transform Infrared Spectroscopy (FTIR)
Thermogravimetric Analysis (TGA)
X-Ray Diffraction (XRD)
CTAB-MMT: CTAB was added to expand MMT’s interlayer and make it
more hydrophobic.