Browsing by Subject "Thermosets"

Now showing 1 - 3 of 3

Open Access
Polyhedral oligomeric silsesquioxane-based hybrid networks obtained via thiol-epoxy click chemistry
(Springer, 2017) Bekin Acar, S.; Ozcelik, M.; Uyar, Tamer; Tasdelen, M. A.
A series of hybrid networks based on polyhedral oligomeric silsesquioxane (POSS) were prepared by thiol-epoxy click reaction using commercially available octakis-glycidyl-POSS (G-POSS), trimethylolpropane triglycidyl ether, and trimethylolpropane tris(3-mercaptopropionate) as monomers. The click reaction was simply catalyzed by lithium hydroxide which proceeded readily at ambient conditions in very good yields. The incorporation of G-POSS into the network was clearly determined by transmission electron microscopy, FTIR, and 1H-NMR spectroscopy techniques performed with a model study using 1-butane thiol and G-POSS molecules. The homogeneous distribution of G-POSS up to 5 wt% in the hybrid network was apparently confirmed by morphological investigations. By increasing G-POSS content higher than 5 wt%, the heterogeneous dispersion of G-POSS was determined from the tensile strength measurements. The significant decrease in tensile strength was possible due to the agglomeration of G-POSS. On the other hand, thermal properties of hybrid networks were compared together by thermogravimetric analyses, where all samples exhibited one-step degradation in the range of 220–500 °C. The thermal decomposition of hybrid network led to complete degradation of the organic part and favored the formation of stable carbonaceous and inorganic residues as char. Thus, the char yields of hybrid networks were increased to 6.2, 7.8, 10.1, 12.7, and 15.1% by G-POSS loadings from 0 to 15 wt%. This improvement was also a proof of the incorporation of G-POSS into the hybrid networks that resulted in high heat-resistant POSS-based hybrid networks compared to a sample without G-POSS.
Open Access
Simultaneous photoinduced electron transfer and photoinduced CuAAC processes for antibacterial thermosets
(Elsevier, 2017) Oz, E.; Uyar, T.; Esen, H.; Tasdelen, M. A.
A combination of simultaneous photoinduced electron transfer and photoinduced CuAAC processes enables the in-situ preparation of antibacterial thermosets containing silver nanoparticles (AgNPs) in one-pot. Upon photolysis of photoinitator, the generated radicals not only reduce Cu(II) into Cu(I) activator to catalyst the CuAAC click reaction, but also simultaneously generate AgNPs from AgNO3 through electron transfer reaction. Due to their reduction potentials difference, the polymer matrix is formed before the formation of AgNPs, assisting to eliminate the agglomeration of them. The thermoset structures are confirmed by FT-IR and solubility tests, whereas the presence of AgNPs is proven by transmission electron microscopy with energy dispersive X-ray system analyzer. The samples containing 5 and 10% AgNPs exhibited strong inhibition zones, where all kinds of bacteria (gram-positive (Staphylococcus Aureus) and gram-negative (Escherichia Coli)) were killed in the surrounding of the film samples.
Open Access
Synthesis of polybenzoxazine/clay nanocomposites by in situ thermal ring-opening polymerization using intercalated monomer
(2011) Demir, K.D.; Tasdelen, M.A.; Uyar, T.; Kawaguchi, A.W.; Sudo, A.; Endo, T.; Yagci, Y.
A new class of polybenzoxazine/montmorillonite (PBz/MMT) nanocomposites has been prepared by the in situ polymerization of the typical fluid benzoxazine monomer, 3-pentyl-5-ol-3,4-dihydro-1,3-benzoxazine, with intercalated benzoxazine MMT clay. A pyridine-substituted benzoxazine was first synthesized and quaternized by 11-bromo-1-undecanol and then used for ion exchange reaction with sodium ions in MMT to obtain intercalated benzoxazine clay. Finally, this organomodified clay was dispersed in the fluid benzoxazine monomers at different loading degrees to conduct the in situ thermal ring-opening polymerization. Polymerization through the interlayer galleries of the clay led to the PBz/MMT nanocomposite formation. The morphologies of the nanocomposites were investigated by both X-ray diffraction and transmission electron microscopic techniques, which suggested the partially exfoliated/intercalated structures in the PBz matrix. Results of thermogravimetric analysis confirmed that the thermal stability and char yield of PBz nanocomposites increased with the increase of clay content. © 2011 Wiley Periodicals, Inc.