Stochastic Simulation of Controlled Radical Polymerization Forming Dendritic Hyperbranched Polymers

Stochastic simulation of the formation process of hyperbranched polymers (HBPs) based on the reversible deactivation radical polymerization (RDRP) using a branch-inducing monomer, evolmer, has been carried out. The simulation program successfully reproduced the change of dispersities (Đs) during the polymerization process. Furthermore, the simulation suggested that the observed Đs (=1.5–2) are due to the distribution of the number of branches instead of undesired side reactions, and that the branch structures are well controlled. In addition, the analysis of the polymer structure reveals that the majority of HBPs have structures close to the ideal one. The simulation also suggested the slight dependence of branch density on molecular weight, which was experimentally confirmed by synthesizing HBPs with an evolmer having phenyl group

極低温高分解能透過型電子顕微鏡による高分子結晶の構造研究

京都大学0048新制・論文博士博士(工学)乙第10315号論工博第3489号新制||工||1163(附属図書館)UT51-2000-C82(主査)教授 粷谷 信三, 教授 梶 慶輔, 教授 伊藤 紳三郎学位規則第4条第2項該当Doctor of EngineeringKyoto UniversityDA

Quantification of Stacking Faults in b-Form Single Crystals of Syndiotactic Polystyrene (STATES AND STRUCTURES-Polymer Condensed States)

The b-form single crystals of syndiotactic polystyrene, each of which inevitably contains the stacking faults, were grown isothermally from dilute solution at a crystallization temperature, Tc, ranging from 150 to 210°C. Theoretical treatment based on our structure model of the fault well explained the characteristic features of the electron diffraction patterns. Then the probability of presence of the fault was estimated for each Tc by measauring the mean half-breadth of the streaked reflections in the patterns. The probability thus estimated was in good agreement with that obtained from the number of the faults in a unit length: the number was counted directly in the high-resolution and/or the dark-field images taken by transmission electron microscopy

Latent orientation in the skin layer of electrospun isotactic polystyrene ultrafine fibers

Isotactic polystyrene was electrospun into ultrafine fibers from the chloroform or tetrahydrofuran solutions. Tubular or ribbon-like fibers with many small pores were obtained from the chloroform solution. Densely stacked lamellae were formed by annealing them. On the other hand, fibers with many small dents on the skin layer were obtained from the tetrahydrofuran solution. The skin layer changed into the densely stacked lamellae by annealing, while the interior was not crystallized under the utilized annealing condition. These results suggested that the skin layer of the as-spun fiber should contain a finite amount of highly-oriented molecular chains, while the interior may be unoriented. Despite the annealing, the orientation of the chains in the skin layer has been preserved and worked as the nuclei for the densely stacked lamellae

Edge-on Lamellae of Polyoxymethylene Crystallized from Solutions Epitaxially onto Alkali Halides (STATES AND STRUCTURES-Polymer Condensed States)

Edge-on crystalline lamellae of polyoxymethylene (POM) were isothermally grown onto the (001) face of NaCl or KCl from 0.1 wt% solutions (solvent: nitrobenzene, acetophenone, benzyl alcohol, mcresol). The thickness of crystalline core in the edge-on lamella increased with decreasing supercooling (DT), but was inevitably smaller than the corresponding lamellar thickness for any DT. Accordingly, the POM edge-on lamella should have a surface layer (20~25% of the lamellar thickness) containing folds on each side of its crystalline core

High-Resolution Observation of Crystal Transformation in Isotactic Polybutene-1 Single Crystals (STATES AND STRUCTURES-Polymer Condensed States)

The crystal transformation in lamellar crystals of polybutene-1 grown from an amyl acetate solution was studied by cryogenic high-resolution transmission electron microscopy. The shape of the transformed trigonal (form-1) crystal domains in the surrounding tetragonal (form-2) crystal was successfully revealed. Along with the nucleation of "untwinned" form-1, the existence of another nucleation mechanism which creates "twinned" form-1 was suspected. The growth of form-1 crystal was thought to progress not stem by stem but by pulling in the molecular chains from the surrounding form-2, creating new stems of form-1. The shape of the form-1 domain was irregular, and no specific crystallographic direction along which the form-1 domain tends to grow was found

Detection of fast and slow crystallization processes in instantaneously-strained samples of cis-1,4-polyisoprene

Cross-linked samples of natural rubber (NR) and synthetic cis-1, 4-polyisoprene (IR) were instantaneously expanded to a predetermined strain ratio, α[s], using a newly-designed high-speed tensile tester. Crystallization behavior after the cessation of deformation was investigated. The high-cycle wide-angle X-ray diffraction (WAXD) measurements could successfully reveal the drastic progress of crystallization within the first a few hundred milliseconds. Quantitative analysis of Cross-linked samples of natural rubber (NR) and synthetic cis-1, 4-polyisoprene (IR) were instantaneously expanded to a predetermined strain ratio, α[s], using a newly-designed high-speed tensile tester. Crystallization behavior after the cessation of deformation was investigated. The high-cycle wide-angle X-ray diffraction (WAXD) measurements could successfully reveal the drastic progress of crystallization within the first a few hundred milliseconds. Quantitative analysis of diffraction intensity clarified coexistence of fast and slow crystallization processes; time constants τ[f] and τ[s], and amplitude I[f] and I[s], respectively, were estimated for these processes. The values of τ[f] were in the range of 50–200 ms, while τ[s] ranged between 2.5 and 4.5 s. Almost linear dependence of [I]f and I[s] on α[s] was clarified. The crystallite size in the directions both parallel and perpendicular to the stretching direction decreased with the increase in time-averaged nominal stress. The crystal lattice deformed almost linearly with the average nominal stress. For the fast process, correlation between crystallization and stress relaxation was not recognized, while linear relationship between them was found for the slow process. In every case, strain-induced crystallization was found to be the major origin of stress relaxation. Based on the results, effects of strain on crystallization of polymer melt were discussed