Thermal conductivity and morphology of silver-filled multiwalled carbon nanotubes/polyimide nanocomposite films

Electric-Field-Induced Alignment of Functionalized Carbon Nanotubes Inside Thermally Conductive Liquid Crystalline Polyimide Composite Films

The positive liquid crystals, 4'-heptyl-4-biphenylcarbonitrile (7CB), are used to functionalize carbon nanotubes (LC-CNT), which can be aligned in the liquid crystalline polyimide (LC-PI) matrix under an alternating electric field to fabricate the thermally conductive LC-CNT/LC-PI composite films. The efficient establishment of thermal conduction pathways in thermally conductive LC-CNT/LC-PI composite films with a low amount of LC-CNT is achieved through the oriented alignment of LC-CNT within the LC-PI matrix. When the mass fraction of LC-CNT is 15 wt %, the in-plane thermal conductivity coefficient (λ∥ ) and the through-plane thermal conductivity coefficient (λ⊥ ) of the LC-CNT/LC-PI composite films reach 4.02 W/(m ⋅ K) and 0.55 W/(m⋅K), which are 90.5 % and 71.9 % higher than those of the intrinsically thermally conductive LC-PI films respectively, also 28.8 % and 5.8 % higher than those of the CNT/LC-PI composite films respectively. Meanwhile, the thermally conductive LC-CNT/LC-PI composite films also possess excellent mechanical and heat resistance properties. The Young's modulus and the heat resistance index are 2.3 GPa and 297.7 °C, respectively, which are higher than the intrinsically thermally conductive LC-PI films and the thermally conductive CNT/LC-PI composite films under the same amount of CNT.

Interpenetration Networked Polyimide-Epoxy Copolymer under Kinetic and Thermodynamic Control for Anticorrosion Coating

Epoxy (EP) was copolymerized with polyamic acid (PAA, precursor of polyimide (PI)) with termanil monomers of (1) 4,4'-Oxydianiline (ODA) and (2) pyromellitic dianhydride (PMDA) individually to form (PI-O-EP) and (PI-P-EP) copolymers. The FTIR spectrum of PI-O-EP copolymerization intermediates shows that some amide-EP linkages were formed at low temperature and were broken at higher temperature; in additoin, the released amide was available for subsequent imidization to form PI. The curing and imidization of the amide groups on PAA were determined by reaction temperature (kinetic vs. thermodynamic control). In PI-P-EP, the released amide group was very short-lived (fast imidization) and was not observed on FTIR spectra. Formation and breakage of the amide-EP linkages is the key step for EP homopolymerization and formation of the interpenetration network. PI contributed in improving thermal durability and mechanical strength without compromising EP's adhesion strength. Microphase separations were minimal at PI content less than 10 wt%. The copolymerization reaction in this study followed the "kinetic vs. thermodynamic control" principle. The copolymer has high potential for application in the field of higher-temperature anticorrosion.

Ultrahigh Thermal Conductivity of Interface Materials by Silver-Functionalized Carbon Nanotube Phonon Conduits

An ultrahigh thermal conductivity (κ = 160 W m(-1) K(-1) ) of thermal interface materials is achieved with a high enhancement factor (96). A small amount (2.3 vol%) of 1D multiwalled carbon nanotubes (MWNTs) with high κ constructs effective phonon transport pathways between microscale silver-flake islands, and a solid phonon transport junction is realized by the coalescence of silver nanoparticles pre-functionalized on the MWNTs.

Carbon nanotube-poly(lactide-co-glycolide) composite scaffolds for bone tissue engineering applications

Despite their indisputable clinical value, current tissue engineering strategies face major challenges in recapitulating the natural nano-structural and morphological features of native bone. The aim of this study is to take a step forward by developing a porous scaffold with appropriate mechanical strength and controllable surface roughness for bone repair. This was accomplished by homogenous dispersion of carbon nanotubes (CNTs) in a poly(lactide-co-glycolide) (PLGA) solution followed by a solvent casting/particulate leaching scaffold fabrication. Our results demonstrated that CNT/PLGA composite scaffolds possessed a significantly higher mechanical strength as compared to PLGA scaffolds. The incorporation of CNTs led to an enhanced surface roughness and resulted in an increase in the attachment and proliferation of MC3T3-E1 osteoblasts. Most interestingly, the in vitro osteogenesis studies demonstrated a significantly higher rate of differentiation on CNT/PLGA scaffolds compared to the control PLGA group. These results all together demonstrate the potential of CNT/PLGA scaffolds for bone tissue engineering as they possess the combined effects of mechanical strength and osteogenicity.