Some Mathematical Formulations of Electrochemical Polymerization KineticsBhadani, S N; Prasad, R S; Parravano, G
doi: 10.1295/polymj.14.1pmid: N/A
Some theoretical aspects of electrochemical polymerization kinetics are discussed in this paper. Mathematical relationships between electrolysis current and the initial rate of polymerization are derived. Also, emphasis is placed on the derivation of mathematical relationships between electrolysis current and the kinetic chain length of polymers. From the Tafel relationship of current and electrode potential, various limiting mechanistic steps in the kinetics of electrochemical initiation by direct electron transfer between monomer and electrode are also illustrated.
Liquid Crystal Polymers. V. Thermotropic Polyesters with Either Dyad or Triad Aromatic Ester Mesogenic Units and Flexible Polymethylene Spacers in the Main ChainOber, C; Jin, J-I; Lenz, R W
doi: 10.1295/polymj.14.9pmid: N/A
The thermal properties of two new series of thermotropic, liquid crystalline polyesters were studied by differential scanning calorimetry and on a hot-stage of a polarizing microscope. The first series contained an aromatic ester triad with a central terephthaloyl and two terminal oxybenzoyl units connected by a flexible polymethylene spacer containing from two to ten methylene units. The second series contained a head-to-head tail-to-tail aromatic ester dyad with one terephthaloyl and one oxybenzoyl unit and either a dimethylene or hexamethylene spacer. The melting temperatures and the transition temperatures for conversion from the mesophase to the isotropic phase (the clearing temperature) of the polyesters in the first series initially decreased in a zig-zag manner for polymers with up to nine methylene units but increased for the decamethylene polymer. The temperature ranges over which the mesophase formation occurred were generally broader for polymers containing an odd number of methylene units than for those with an even number of units. Most, if not all, of the polymers in both series formed nematic states on melting. The enthalpy and entropy changes for the clearing transition both increased with the length of the polymethylene spacer. Polymers of the second series possessed lower transition temperatures and narrower temperature ranges for mesophase formation, as would be expected for the shorter mesogenic unit.
Structural Studies on Linear Polyurethanes. II. Crystal and Molecular Structures of Aliphatic Polyurethanes from Trimethylene Diisocyanate, and Tetra- and Hexa-Methylene GlycolsSaito, Yasushi; Hara, Kazuaki; Kinoshita, Shigetake
doi: 10.1295/polymj.14.19pmid: N/A
The crystal structures of polyurethanes with the formula [InlineEquation not available: see fulltext.] (m=4,6) have been determined by X-ray diffraction analysis. Poly(tetramethylene trimethylene dicarbamate) (4,3-polyurethane) crystallizes in the triclinic space group P1−Ci
1 with a=5.06Å, b=5.04Å, c(fiber axis)=30.10Å, α=112°C, β=113°C, and γ=110°C. Poly(hexamethylene trimethylene dicarbamate) (6,3-polyurethane) crystallizes in the triclinic space group P1−Ci
1, with a=5.04 Å, b=5.04 Å, c=34.65 Å. α=111°C, β=111°C, and γ=111°C. By conformational analysis, we attempted to find structure models that would satisfy the condition of full intermolecular hydrogen bonding. These models were then refined by three dimendional Fourier synthesis to the R values of 0.225 for 4,3- and 0.207 for 6,3-polyurethane. The molecules of both polymers are linked two dimensionally by C=O··· H–N hydrogen bonds. These polymers are the same in structure except for their fiber periods which differ in the length of two methylene groups of the glycols. The hydrogen bonding patterns of these polyurethanes differ from those of other polyurethanes.
Molecular Weight and Conformation of Poly(S-[(3-hydroxypropyl)-carbamoylmethyl]-L-cysteine) in Various SolventsIkeda, Shoichi; Tomiyama, Tetsuo
doi: 10.1295/polymj.14.33pmid: N/A
The number-average and weight-average molecular weights of seven samples of poly(S-[(3-hydroxypropyl)-carbamoylmethyl]-L-cysteine) (poly(Cys[CamPrOH])) have been determined by measurements of osmotic pressure of 0.1% CH3COOH solutions and light scattering of hexafluoro-2-propanol solutions, respectively. A strong tendency of poly(Cys[CamPrOH]) to form the β-conformation is observed in various solvents, including CH3COOH–H2O, DCA, H2O, and D2O. When dissolved in H2O at 70°C, poly(Cys[CamPrOH]) having molecular weight lower than 18,000 is randomly coiled and that having molecular weight higher than 20,000 is subject to the thermally-induced β-coil transition. When dissolved in D2O at 70°C, poly(Cys[CamPrOH]) undergoes the thermally-induced β-coil transition, irrespective of the molecular weight. D2O stabilizes the β-conformation more effectively than does H2O, by the change in the structure of water rather than by the substitution of D for H on the polypeptide.
Glass Transition of Oligostyrene with Different End GroupsHatakeyama, Tatsuko; Serizawa, Mitsuru
doi: 10.1295/polymj.14.51pmid: N/A
Oligostyrenes having butyl groups at both ends, a butyl group at one and a proton at the other, and protons at both ends were prepared. The oligomers obtained were separated into fractions from monomer to octamer by the combined use of vacuum distillation and gel permeation chromatography (GPC). The purity of each fraction was characterized by GPC. The monomer and dimer having butyl groups at both ends were found to crystallize; melting and premelt crystallization were detected by differential scanning calorimeter (DSC). All the oligomer fractions and the monomer became glassy when quenched from the molten state. The glass transition temperatures (T
g’s) of the oligomers having the same number of main chain segments were similar in spite of the difference in molecular weight (Mn). Thus, the values of the constants in the equation of T
g=A–B/Mn (where A and B are constants) varied depending on the type of sample in the range of molecular weight up to 600. This fact indicates that the molecular motion of the end groups cancels out the effect of increasing molecular weight.
Polymerization of Bicyclic Acetals. IX. Cationic Polymerization of 4-Bromo-6,8-dioxabicyclo[3.2.1]octaneOkada, Masahiko; Sumitomo, Hiroshi; Sumi, Akira
doi: 10.1295/polymj.14.59pmid: N/A
Polymerization of the two stereoisomers (1a and 1e) of 4-bromo-6,8-dioxabicyclo[3.2.1]octane was carried out in methylene chloride at different temperatures ranging from −90 to 0°C. Antimony pentafluoride, antimony pentachloride, and trifluoromethanesulfonic acid were found effective for the homopolymerization of the equatorially substituted isomer (1e). Isomerization of 1e to the axially substituted counterpart (1a) occurred during the polymerization at −30°C or above to provide a copolymer of 1e and 1a, especially when trifluoromethanesulfonic acid was used as an initiator. 13C-NMR analysis of the resulting polymers disclosed that the polymer of 1e prepared at −90°C entirely consisted of a structural unit (α-form) in which the exocyclic acetal oxygen atom was axially oriented to the tetrahydropyran ring in a repeating unit. With the rise in polymerization temperaure, the fraction of the other structural unit (β-form) in which the exocyclic acetal oxygen lies in the equatorial position of the tetrahydropyran ring increased appreciably. Polymerization of stereoisomer mixtures of 1a and 1e was induced even with boron trifluoride etherate which is an ineffective initiator for the homopolymerization of 1e. Irrespective of the reaction conditions, the relative reactivity of 1a was higher than that of 1e. The difference in the reactivity between the stereoisomers are discussed in comparison with those of 6,8-dioxabicyclo[3.2.1]octane and anhydrosugar derivatives having the identical skeleton.