Cationic ring-opening copolymerization of seven-membered cyclic sulfite and oxetane in one-shot feeding

Cationic copolymerization of seven-membered cyclic sulfite, 1,3,2-dioxathiepane-2-oxide (1) and oxetane (2) in one-shot feeding was carried out to obtain the corresponding copolymer. When a mixture of equimolar amount of 1 and 2 reacted at 0°C in the presence of methyl trifluoromethanesulfonate (T fOMe) as a cationic initiator, T fOMe and 2 were completely consumed without the consumption of 1. After rising the polymerization temperature up to 25°C, 1 started to be consumed to obtain the corresponding copolymer of 1 and 2. The obtained copolymer showed a unimodal GPC curve, and it afforded a polyether showing a unimodal GPC after alkaline hydrolysis. These results strongly suggested the occurrence of the block copolymerization in one-shot feeding. From the molecular orbital examination, the formation of block copolymerization in one-shot feeding was discussed to be caused by the much larger polymerizability of 2 than that of 1. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1007–1012, 1997     

Unique fluorescence behavior of perylenetetracarboxydiimides in polyimide systems

Perylenetetracarboxydiimide (PEDI) molecularly dispersed in polyamic acid (PAA) and polyimide (PI) films has unique fluorescence properties. An originally strong fluorescence of PEDI is efficiently quenched in the PAA films. The systematic variation of the chain structure of the PAA matrices revealed that the aromatic amide groups in the PAA chains function as a quencher. When a PAA derived from 3,4,3′4′-biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA), BPDA/PDA, was used as a matrix polymer, the fluorescence of the dye dispersed in the film increased abruptly as imidization of the matrix proceeds. But annealing at temperatures higher than 320°C in the step-heating process caused a gradual decrease in the fluorescence intensity. The decreased intensity results from the dye–PDA units interactions intensified by the denser molecular packing of the matrix polymer chains. PEDI shows significant dependence of the fluorescence intensity on the chain structure of the PI matrices. In the various PI films containing a fixed diamine component, the dye fluorescence intensity reduces linearly with an increase in the intramolecular charge transfer ability of the PI matrices. From the result, we propose a fluorescence quenching mechanism through multistep electron transfer processes. The BPDA/PDA polyimide matrix leads to a strong PEDI fluorescence whereas the pyromellitic dianhydride (PMDA)-based PI matrices do not. For the blends composed of these PIs, the fluorescence of PEDI bound into the main chains provides a valuable indicator of the miscibility on the molecular level. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 827–840, 1998     

Molecular weight determination of acrylonitrile polymers by gel permeation chromatography in N,N-dimethylformamide

Peculiar elution behavior of the GPC of acrylonitrile polymers was investigated. The peculiarity was considered to be due to some substances which form a supermolecular structure with acrylonitrile polymers to cause a large UV absorption, detectable at 280 nm. The Mark-Houwink-Sakurada parameters of acrylonitrile polymers in 0.01M LiBr-DMF at 60°C, needed for GPC universal calibration, were determined to be K=2.12 × 10⁻⁴ and a=0.75. The parameters obtained by us were different from the ones by other investigators, however, these values were reasonable for random coil polymers. The addition of inorganic salt, such as LiBr, in DMF removed the peculiar elution behavior of the GPC. The universal calibration using monodisperse poly(ethylene oxide) standards and the Mark-Houwink-Sakurada parameters could be applied for the determination of the molecular weights. The invalidity of the universal calibration for acrylonitrile polymers in DMF containing LiBr, seems to be caused by the difficulty in the determination of the molecular weight of polyacrylonitrile standards by absolute methods, such as light scattering and osmometry.     

Induction of periodic nanostructures in polythiophene films through block copolymer templating

A new class of periodically nanostructured polythiophene materials with high regularity and numerous morphologies is prepared through the cooperative self‐assembly of polythiophene derivatives with a templating block copolymer (BCP) and poly(1,4‐isoprene)‐block‐poly(methacrylic acid) (PMA). The selection of the hydrophilic and aprotic triethylene glycol (TEG) group as side chains on polythiophene and the use of hydrophilic and protic PMA are crucial to producing well‐ordered nanostructures in polythiophene films, as it enables selective coassembly within the hydrophilic domain through hydrogen bonding. The composite films are shown to have formed hexagonally packed cylinders with 28 nm periodicities based on small‐angle X‐ray scattering and transmission electron microscopy. The formation of hydrogen bonding is revealed by a shift in the carbonyl peak of PMA in the Fourier transform infrared spectra of the composite film relative to the neat film. This suggests that the TEG‐functionalized polythiophene selectively incorporates into PMA. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1105–1112     

Direct Observation of Apatite Formation on Bioglass in Simulated Body Fluid by Atomic Force Microscopy

An in situ atomic force microscope (AFM) combined with surface potential measurement was used to observe the apatite formation on the 45S5 Bioglass-type glass in simulated body fluid (SBF). From the observation, it can be seen that small islands with 5-10 nm size are formed on the glass surface in the initial soaking period within 1 h.     

LES Study of Turbulent Boundary Layer Over a Smooth and a Rough 2D Hill Model

Large eddy simulation (LES) is carried out to investigate the turbulent boundary-layer flows over a hill-shaped model with a steep or relatively moderate slope at moderately high Reynolds numbers (Re = O(10³)) defined by the hill height and the velocity at the hill height. The study focuses on the effects of surface roughness and curvature. For Sub-grid Scale (SGS) modeling of LES, both the dynamic Smagorinsky model (DSM) and the dynamic mixed model (DMM) are applied. The behavior of the separated shear layer and the vortex motion are affected by the oncoming turbulence, such that the shear layer comes close to the ground surface, or the size of a separation region becomes small because of the earlier instability of the separated shear layer. Appropriate measures are required to generate the inflow turbulence. The methods of Lund et al. (J. Comput. Phys., 140:233–258, 1998) and Nozawa and Tamura (J. Wind Eng. Ind. Aerodyn., 90:1151–1162, 2002; The 4th European and African Conference on Wind Engineering, 1–6, 2005) are employed to simulate the smooth- and rough-wall turbulent boundary layers in order to generate time-sequential data of inflow turbulence. This paper discusses the unsteady phenomena of the wake flows over the smooth and rough 2D hill-shaped obstacles and aims to clarify the roughness effects on the flow patterns and the turbulence statistics distorted by the hill. Numerical validation is conducted by comparing the simulation results with wind tunnel experiment data for the same hill shape at almost the same Re. The applicability of DSM and DMM are discussed, focusing on the recirculation region behind a steep hill.     

Preparation of New Fibrous Organic-Inorganic Layered Compounds Derived from Zinc Hydroxyde

Abstract

A new preparation method of the fibrous organic-inorganic nanohybrids was established by the reaction of Zn(OH)₂ with various organic carboxylic acids. Interlayer spacings of the reaction products of Zn(OH)₂ with benzoic acid and p-phenyl azobenzoic acid were 1.46 and 2.04 nm, and these reaction products have layered structure. In IR spectra, new peaks of RCOO-Zn band appeared at around 1400 cm^?1 and 1550 cm^?1 indicating that hydroxyl groups reacted with organic carboxylic acids. SEM images of these reaction products showed fibrous morphology. The TEM image showed that the layer structure was constructed along the fiber direction.     

Functionalization of polyethylene based on metallocene catalysis and its application to syntheses of new graft copolymers possessing polar polymer segments

The control of hydroxylated polyethylene (PE) structures was investigated in the copolymerization of ethylene with allyl alcohol or 10-undecen-1-ol with a specific metallocene, methylaluminoxane, and trialkyl aluminum catalyst system through changes in the copolymerization conditions. The incorporation of allyl alcohol into the PE backbones was controllable through changes in the trialkyl aluminum, leading to terminally hydroxylated PE or a copolymer possessing hydroxyalkyl side chains. The copolymerization of ethylene with 10-undecen-1-ol gave copolymers with hydroxyalkyl side chains of various contents with a variety of molecular weights through changes in the copolymerization conditions. The obtained copolymers were useful as macroinitiators that allowed polar polymer segments to grow on the PE backbones, leading to the creation of graft copolymers that possessed PE and polar polymer segments. In this way, polyethylene-g-poly(propylene glycol) (PE-g-PPG) and polyethylene-g-poly(ϵ-caprolactone) (PE-g-PCL) were synthesized. The ¹³C NMR analysis of PE-g-PPG suggested that all the hydroxyl groups were consumed for propylene oxide polymerization, and transmission electron microscopy demonstrated nanoorder phase separation and indistinct phase boundaries. ¹³C NMR and gel permeation chromatography analyses indicated the formation of PE-g-PCL, in which 36–80 mol % of the hydroxyl groups worked as initiators for ϵ-caprolactone polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3657–3666, 2003