7 research outputs found
Optical Properties of Some New Azo Photoisomerizable Bismaleimide Derivatives
Novel polythioetherimides bearing azobenzene moieties were synthesized from azobismaleimides and bis-2-mercaptoethylether. Kinetics of trans-cis photoisomerization and of thermal conversion of cis to trans isomeric forms were investigated in both polymer solution and poly(methyl methacrylate) doped films using electronic absorption spectroscopy. Thermal recovery kinetics is well described by a two-exponential relation both in solution and polymer matrix, while that of low molecular weight azobismaleimide fit a first-order equation. The photoinduced cis-trans isomerization by visible light of azobenzene chromophores was examined in solution and in polymer films. The rate of photoinduced recovery was very high for azobismaleimides
Synthesis and characterization of furfural-functionalized poly(vinyl alcohol) cross-linked with maleimide bearing tributyltin groups
Novel Bio-Based Materials: From Castor Oil to Epoxy Resins for Engineering Applications
The paper presents the synthesis and thermal behavior of novel epoxy resins prepared from epoxidized castor oil in the presence of or without trimethylolpropane triglycidyl ether (TMP) crosslinked with 3-hexahydro-4-methylphtalic anhydride (MHHPA) and their comparison with a petroleum-based epoxy resin (MHHPA and TMP). Epoxidized castor oil (ECO) was obtained via in situ epoxidation of castor oil with peroxyacetic acid. The chemical structures of castor oil (CO), ECO, and epoxy matrix were confirmed using FT-IR and 1H-NMR spectroscopy. The morphological and thermal behavior of the resulting products have been investigated. Compared to petroleum-based resins, castor oil-based ones have a lower Tg. Anyway, the introduction of TMP increases the Tg of the resins containing ECO. The morphological behavior is not significantly influenced by using ECO or by adding TMP in the synthesis of resins. The dielectric properties of epoxy resins have been analyzed as a function of frequency (1 kHzā1 MHz) and temperature (ā50 to 200 Ā°C). The water absorption test showed that as Tg increased, the percent mass of water ingress decreased
Synthesis and Characterization of a New Thermoreversible Polyurethane Network
A new polyurethane network was synthesized
by the DielsāAlder
cross-linking reaction of a polyurethane to bisfuryl monomer. Attenuated
total reflectance in conjunction with Fourier transform infrared spectroscopy
(ATR-FTIR) spectra of the network showed the disappearance of the
absorption bands of maleimide and the appearance of new bands attributed
to furan-maleimide cycloadduct. Chemical shifts characteristic to
the cycloadduct appeared in the proton nuclear magnetic resonance
spectra. ATR-FTIR and differential scanning calorimetry (DSC) demonstrated
the thermal reversibility of the material by the reproduction of the
retro-DielsāAlder and DielsāAlder processes upon heating
and cooling. Global kinetic nonisothermal decomposition parameters
in nitrogen were determined by the Flynn-Wall-Ozawa method. A three
successive stage thermal decomposition mechanism depicted by <i>n</i> order reaction model for each stage was proposed. The
validity of the chosen kinetic model and the values of the kinetic
parameters of the individual decomposition stages were determined
by the multivariate nonlinear regression method