5187-23-5Relevant academic research and scientific papers
Contributions from interfacial polarization, conductivity and polymer relaxations to the complex permittivity of a film of poly[(5-ethyl-1,3-dioxan-5-yl)methyl acrylate] containing ionic impurities
Sorensen, Torben Smith,Diaz-Calleja, Ricardo,Riande, Evaristo,Guzman, Julio,Andrio, Andreu
, p. 2399 - 2411 (1997)
The complex permittivity of a film of the polymer poly[(5-ethyl-1,3-dioxan-5-yl)methyl acrylate] of width 0.4 mm and containing very small amounts of ionic impurities has been studied at a range of frequencies from 0.01 Hz to 100 kHz and at a range of temperatures from -135 to +140°C. Some mechanical determinations of the complex Young modulus have also been performed for the same polymer. To separate the surface polarisation effects and the conductivity effects from the dielectric relaxations of the polymer chains and side-chains we have used the same theoretical methods as earlier described for a film of a copolymer of vinylidene cyanide and vinyl acetate and for a film of poly[4-(acryloxy)phenyl-(4-chlorophenyl)methanone]. The diffusion coefficient of the most rapidly diffusing ion is studied as a function of temperature. The diffusion coefficient follows a non-Arrhenius Vogel relation with the same Vogel temperature as the α-relaxation (glass-rubber). Both phenomena may be interpreted using the Cohen-Turnbull theory of free volume as has previously been done for the diffusion of oxygen through poly(cyclohexyl acrylate). The fractional free volume at the glass transition temperature (ca. 36°C) is found to be 0.031, close to the range normally found (0.025 ± 0.005). A β-relaxation is also found at higher frequencies and lower temperatures. This relaxation shows Arrhenius behaviour with an activation energy E?/R = 5780 K. The α- and β-relaxations seem to merge at ca. 100°C and in addition a relaxation more slow than the α-relaxation is found at even higher temperatures. This relaxation can only be seen after correction of the dielectric loss for conductivity. The mean activation energy of this relaxation in the temperature range 90-140°C is practically identical with the mean activation energy of the α-relaxation in the same range of temperatures (E?/R ≈ 15 000 K). The slow relaxation is probably connected with the motion of the polymer molecule as a whole in the 'virtual tubes' of long-range, topological entanglements, for example by 'reptation'. At very high frequencies (50-100 kHz), isochronous graphs of dielectric loss vs. temperature exhibit a splitting of the α-peak into two peaks.
Broad-band dielectric spectrocopy of polymer chains containing structurally complex side groups
Huang,Saiz,Ezquerra,Guzman,Riande
, p. 1785 - 1790 (2002)
The temperature dependence of the α and β relaxations of poly(2-phenyl-5-acryloxymethyl-5-ethyl-1,3-dioxacyclohexane) is studied by broad-band dielectric spectroscopy. The strength of the α relaxation decrease with increasing temperature, pointing to an onset temperature (Δεα = 0) of ca. 97°C. Seen from the high-temperature side, the α relaxation starts with zero intensity at the onset temperature and steeply increases with decreasing temperature until it levels off in the vicinity of Tg. Whereas in the glassy state the strength of the β relaxation is only slightly dependent on temperature, it undergoes a strong increase at temperature above Tg. Arrhenius plots of both relaxations show that the β process remains operative at temperatures above the onset temperature of the α relaxation. The temperature dependence of the stretch exponent does not show a definite trend, most of the values obtained lying in the interval 0.3-0.5.
Synthesis and bactericidal activity of substituted cyclic acetals
Tugarova,Kazakova,Kamnev,Zlotskii
, p. 1930 - 1933 (2015/02/02)
A series of substituted cyclic acetals were synthesized and tested for their bactericidal activity against bacteria strain Azospirillum brasilense Sp245.
Vinylation of hydroxy-containing cyclic formaldehyde acetals with acetylene
Oparina,Vysotskaya,Parshina,Khil'ko,Gusarova
experimental part, p. 1434 - 1437 (2009/06/08)
Nucleophilic addition of alcohols having cyclic acetal fragments to acetylene smoothly occurs under relatively mild conditions (KOH, 100-125°C, 1-2 h, initial acetylene pressure 11-12 atm) to give the corresponding vinyl ethers in 80-83% yield.
Process for recovering ditrimethylolpropane
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Example 4, (2008/06/13)
The present invention provides processes for recovering ditrimethylolpropane from a still residue obtained by extracting and then distilling off trimethylolpropane from a reaction solution obtained by reacting n-butyraldehyde with formaldehyde in the presence of a basic catalyst.One process comprises acid decomposition of formals in the still residue.A second process comprises removal from the still residue of components having a higher boiling point than that of ditrimethylolpropane followed by crystallization of the resultant product.
Influence of chair-to-chair reversal transitions on the dipole moment of 5-(acetoxymethyl)-5-ethyl-1,3-dioxacyclohexane
Saiz, Enrique,Riande, Evaristo,Guzman, Julio,Iglesias, Maria T.
, p. 3818 - 3824 (2007/10/03)
The synthesis and characterization of 5-(acetoxymethyl)-5-ethyl-1,3-dioxacyclohexane as well as the determination of its dipole moment are described. The critical interpretation of the polarity of this compound by using molecular dynamics (MD) suggests that the trajectories in which the CH3COOCH2 residue is attached in the equatorial position to the C(5) bond of the 1,3-dioxacyclohexane ring exhibit dipole moments which are noticeably smaller than those produced with the residue in the axial position. By calculating the time spent by the residue in each conformation at several temperatures, one finds that the activation energy associated with the chair-to-chair transition is ca. 8.0 kcal mol-1, and the time spent by the ester residue in the axial and equatorial conformations is nearly identical. Hence the mean-square dipole moment at 30°C was obtained by averaging the values of this quantity for the equatorial (2.12 D2) and axial (15.21 D2) trajectories, obtaining 〈μ2〉 = 8.7 D2, in good agreement with the experimental result (9.1 D2).
TRANSACETALISATION DE TRIOLS A PARTIR DU DIMETHOXYMETHANE. SELECTIVITE ET APPLICATIONS SYNTHETIQUES
Gras, Jean-Louis,Nouguier, Robert,Mchich, Mohammed
, p. 6601 - 6604 (2007/10/02)
THe LiBr assisted/acid catalyzed transacetalation of triols from DMM affords a highly selective method for the synthesis of hydroxy compounds bearing a dioxane ring.These compounds might further conveniently be alkylated by phase transfer catalyzis.
