Materials Science and Engineering Laboratories

Polymeric Nanocomposites Laboratory

Basic Information

Staff

Associate Professor Masami Okamoto

Outline

Synthesis of biopolymer-based nanocomposite materials

We attempt to investigate the intercalation of the polymer chains, self-assembly behavior and surface interaction of the nano-fillers, and to explore the key factors for design of the high performance biopolymer-based
nanocomposite materials.

Research Themes

Nanostructure control of biopolymer?based nanocomposite
Fabrication of Polylactide based Biodegradable Thermoset Scaffolds for Tissue Engineering Applications
Synthesis and Adsorption Characteristics of Hollow Spherule Allophane Nano-particles
DNA-based Nanocomposite Gels

Website

http://www.toyota-ti.ac.jp/Lab/Zairyo/5z50/okamoto.htm

Activities



The preparation and characterization of the nanocomposite hydrogels based on deoxyribonucleic acid (DNA) and syntethic hectorite (SWN), were reported. Wide-Angle X-ray Diffraction (WAXD) and Fourier Transform Infrared Spectroscopy (FTIR) analyses confirmed that the intercalation of water molecules into the silicate galleries took place and the interaction between PO2- groups of DNA and SWN surfaces. DNA/SWN hydrogels exhibited viscoelastic solid-like properties DNA as revealed by rheological measurements. The stress-relaxation behaviors of DNA/SWN and SWN hydrogels in the linear viscoelastic regime and non-linear viscoelastic regime were examined. The incorporation of DNA macromolecules led to the enhancement of the damping behavior of the dispersed silicate particles as compared with SWN hydrogels without DNA. The softening of the nanocomposite hydrogels was supported by the calculated damping function of the stress-relaxation measurements.

Europearn polymer journal,
DOI: 10.1016/j.eurpolymj.2012.10.013

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Isothermal melt crystallization behavior of neat poly(L-lactide) (PLLA) and PLLA / Organically Modified Layered Silicate (OMLS) nanocomposite was studied by using time-dependent infrared (IR) spectroscopy and transmission electron microscopy (TEM). Sets of time-dependent IR spectra reflecting the crystallization from the melt of the neat PLLA and PLLA / OMLS nanocomposite were collected at 105 oC. Fine details of the crystallization behaviors were analyzed by two-dimensional (2D) correlation spectroscopy, and significant differences in the crystallization behaviors depending on the presence of OMLS were revealed. Namely, it was found that the crystalline lamellae of the PLLA nanocomposite grow along the layered silicate, while the orientation of the neat PLLA resulted in more disordered orientation because of the absence of the OMLS. The result derived from the 2D correlation analysis of the time-dependent IR spectra of the PLLA samples showed good agreement with corresponding TEM images.

Vib. Spectrosc., 2012, 60, 158-162

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We have characterized the clay network structure in nylon 6-based nanocomposites (N6CNs) through TEM and FFT analyses. The volume fraction of montmorillonite (MMT) between 0.013 and 0.014 was the percolation threshold value for strong network formation. The volume spanning MMT network led to a very high value of the flow activation energy as compared with that of neat nylon 6, resulting in the pseudo-solid like response under molten state in N6CNs. We conducted the canonical NVT-MD simulation in the system made up by nylon 6 molecules/Si(OH)4-molecules. The formation of the strong interfacial interaction between nylon 6 molecules and Si(OH)4-molecules induced by OH groups was speculated.

Macromol. Mater. Eng., 2012, DOI: 10.1002/mame.201200065


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We reported the fabrication of tissue engineering scaffolds based on the polymerization of crosslinked polylactide (PLA)using leaching method to generate well-controlled and interconnected biodegradable polymer scaffolds.The scaffold fabrication parameters were studied in relation to the interpore connectivity, pore morphology and structural stability of the crosslinked PLA scaffold.In vitro cell culture and in vitro degradation were used to analyze the biocompatibility and biodegradability of the scaffolds. The new crosslinked PLA thermoset scaffolds were favorable for bone tissue engineering applications due to the complex internal architecture, thermal stability and biocompatibility.

Macromol. Mater. Eng., 2013,298 (1) 45-52, DOI: 10.1002/mame.201100436

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We synthesized three allophanes from precursors by a hydrothermal reaction at 100°C for 48h. The precursors were formed from the solutions of Na4SiO4 and AlCl3?6H2O at different Si/Al molar ratios (0.5, 0.75, 1.0). The nanostructure of the synthetic allophanes was compared with that of a natural allophane from New Zealand by using X-ray diffractometry, energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetry/ differential thermal analysis, 29Si and 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR), field emission electron microscopy, and pore-size distribution based on the Cranston-Inkley method. The propensity of the allophanes to adsorb adenine and adenosine-5’-monophosphate (5’-AMP) was assessed by batch experiments. The adsorption data were fitted by the Freundlich equation and the adsorption parameters were discussed in relation to the properties of the natural and synthetic allophanes. The adsorption capacity (Kf) of the natural allophane for 5’-AMP was three times that for adenine. The average Kf value of the three synthetic allophanes for 5’-AMP was more than twice that of the natural allophane, possibly due to the higher purity of the synthetic allophanes. Key words: allophanes, nanoparticles, adenine, 5’-AMP, adsorption.

Appl. Clay Sci., 2011, 56, 77-83

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Solid-state processing for the preparation of polypropylene (PP)-based nano-composites having finely dispersed layered fillers was conducted. The mixture of PP and organically modified layered filler (OMLF) (95:5 wt./wt.) was subjected to the processing using alumina mortar heated 65 °C, below Tm of PP (i.e., PP is still at the solid-state), and ground for 8 h before melt compounding. On X-ray diffraction, the d(001) peak of OMLF was broaden and peak position shifted slightly. The mixture prepared by solid-state processing exhibited disorder and delaminated layer structure with the thickness of 3-7 nm into PP matrix through TEM observations. On the contrary, nano-composite prepared by melt compounding at 180 °C for 3 min (without solid-state processing) showed the large stacked silicate layers in the PP matrix. Furthermore, instead of using alumina mortar, we carried out solid-state processing using internal mixer. X-ray diffraction pattern and TEM observation exhibited similar results. The solid-state processing led to delaminate of the silicate layers and attained the discrete dispersion.

Polymer, 2010, 51,4238-4242

 

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