BUNSEKI KAGAKU Abstracts

Ultrasonic degradations of polyethylene oxide (PEO), polymethyl methacrylate (PMMA) and polyethylene oxide-block-propylene oxide (PPO) copolymers in aqueous media were studied using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and liquid-chromatography atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS). The ultrasonic degradation of the polymers with a horn-type 28 kHz oscillator was monitored as a function of the ultrasonication duration to examine the structural details of ultrasonic degradation polymers. The ultrasonication of a PEO solution produced five types of oligomers (Mn = ca. 1000 Da) with different end groups, irrespective of the initial average molecular masses (Mn) 2, 6, 20, and 2000 kDa. Several degradation pathways with free radical reactions were suggested to explain these degradation products. On the other hand, ultrasonication of PMMA (Mn 1630 Da) and uniform PMMA (n = 29) generated only one type of degradation oligomer. In addition to chemical reactions with OH · and H · radicals, the results indicated that primary degradation takes place near at the center of the polymer chains by mechanical forces generated around collapsing cavitation bubbles. Ultrasonic degradation of PEO-block-PPO copolymers consisting of a hydrophilic and a hydrophobic portion was studied to determine the location of bonds involved in the initial scission of the copolymers. A detailed structural analysis of the degradation products indicated that the initial bond scissions occurred principally at the boundary regions between the backbones of PEO and PPO chains. Further structural analysis revealed the presence of oxygen adducts in the degradation products. By a comparison with a thermal degradation carried out in a helium atmosphere, one can conclude that the oxygen adducts are formed by radical reactions with water or dissolving oxygen molecules. The study demonstrated that chemical reactions as well as physical bond stress scissions are involved in the ultrasonic degradation of the copolymers.

Phenazasiline (silylene-bridged diphenylamine)-containing polymers (PPhenaz and PAR) were prepared, and an investigation of the effect of the bridging unit was carried out. The use of polymers as functional additives was also carried out. First, the bridging effect of PPhenaz was investigated by a spectroelectrochemical method. The absorption wavelength derived from the cationic spices, which occurred by the oxidation of PPhenaz was longer than which originated from oxidation of poly(diphenylamine). Next, the use of PPhenaz and PAR as functional additives was studied. Even though only 0.001 phr of PPhenaz or PAR was added, the fluorescence of polymer-added resins was much stronger than that of raw resins, suggesting that the polymers are useful as fluorescence additives in the transparent resin. When PPhenaz and PAR were used as additives simultaneously, the FRET effect from PPhenaz to PAR was observed. When the fluorescence spectra of the dumbbell-shaped resins containing PPhenaz and PAR with compatibilizer (LTI) were measured, the change in this type of FRET was observed by the existence of LTI. We could this improve the method for checking the compatibility of two kinds of resins by using this FRET effect. From these results, PPhenaz and PAR were effective as functional additives in resin.

Polyethylene Glycol (PEG) is considered to be environmentally and biologically friendly materials, and has been applied to industrial or biological use as a highly hydrophilic and viscous polymer. PEG-water systems in various molar ratios of ethylene oxide (constitutional repeating unit of PEG) to H₂O were investigated by DSC, NIR (Near infrared spectroscopy) and ¹⁷O NMR, in order to investigate the behavior of water molecules in PEG hydrogel. The results of DSC show good agreement with those of NIR, NMR measurements. In this study, we focused on the PEG - methylcellulose (MC) - water system at the water-rich region. The water state or the dynamic mechanical property was investigated. PEG {PEG 1500, 6000, molar fraction of ethilenoxide (EOX): 0.01 or 0.07} and MC (MC 50cP, 400cP, molar fraction of MC : 1.0 × 10⁻³) were used in this study. The PEG-MC-water system forms a thermo reversible gel in the heating process. We found that the memory of the gel state was kept for 3 days after gelling at room temperature. The period of keeping the memory of the gel state after gelling agreed with the strength of PEG-water interaction. It was found that the interaction was detectable by DSC.

National Metrology Institute of Japan has been developing certified reference materials (CRMs) for molecular weights of synthetic polymers : polystyrene, poly(ethylene glycol), poly(ethylene glycol) nonylphenyl ether. These CRMs are produced with the certified values of the mass and number fractions as well as the averaged molecular weights, for the first case in the reference materials. In the analyses of common synthetic polymers and oligomers, the molecular-weight distribution in a sample often makes it difficult to precisely measure the physical properties. In order to avoid the effects of polydispersity, which is an essential property of synthetic polymers, uniform oligomers having no molecular weight distributions were used. Uniform oligomers are quite useful in determining the exact molecular weight dependence of the sensitivity of detectors. Supercritical fluid chromatography (SFC) is one method to separate the uniform oligomers. First, we separated the uniform oligomers with various degrees of polymerization from commercial polymer samples by means of preparative SFC. Next, we prepared exact equimass mixtures of the uniform oligomers. The calibration curves for the detectors were determined for the molecular weight by using the equimass mixtures of uniform oligomers with various degree of polymerization indices. Through the use of the calibrated detectors, we are able to make accurate determinations not only of the averaged molecular weight, but also all of mass and number fractions of components. This CRM can be used to calibrate the measuring instruments, to control the measurement precision, and to confirm the validity of the measurement methods when determining the molecular-weight distributions and averaged molecular weights. Especially, it is suitable for calibration against both the masses and intensities for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Chemical structures in terminal-modified and branched bisphenol A (BPA) type polycarbonate (PC) samples were characterized by pyrolysis-gas chromatography in the presence of tetramethylammonium hydroxide using ca. 50 μg samples. In the case of terminal-modified PC samples, methyl derivatives of the main component (BPA), the ordinary p-tert-butylphenoxy (PTBP) terminal, and the modified p-tert-cumylphenoxy terminal were quantitatively formed through thermally assisted hydrolysis and methylation of the polymer chain, and quantitatively observed in the pyrograms. The chemical compositions including end groups and number-average molecular weights (M_n) of the PC samples were calculated from the relative peak intensity of these products with less than 5% of relative standard deviations, and were consistent with those obtained by ¹³C-NMR and size exclusion chromatography (SEC), respectively. Similarly, the methyl derivative of the branching component, 1,1,1-tri(4-hydroxyphenyl)ethane, was clearly observed in the pyrogram of the branched PC sample, together with those of the BPA main chain and PTBP terminal units. The chemical composition of the branched PC sample estimated from the relative intensities of these methyl derivatives, PTBP : BPA : THPE = 3.7 : 95.8 : 0.5 (mol%), was in good agreement with that by an HPLC analysis of the hydrolyzates of the PC sample. In addition, the average numbers of terminals and branching in a PC molecule were calculated to be 2.3 and 0.33, respectively, based on the relationship between the PTBP and THPE contents. Combining the chemical composition and the average branch number, M_n of the branched PC was estimated to be 1.6 × 10⁴, which was comparable to that by SEC. Meanwhile, the average branch number, 0.33, suggests that an average of ca. one third PC molecules have one branching in a molecule, while the remaining two thirds should be linear molecules without any branching in the branched PC sample.

A simple and rapid method to provide a 2-dimensional liquid chromatogram (LCxLC) was developed for the characterization of synthetic polymers using liquid chromatography coupled with electrospray ionization mass spectrometry (LC-ESI-MS). Two sets of LC-MS chromatogram data using two different LC columns were prepared in property. The elution time of each chromatogram was plotted based on ions with the same m/z values, to give a scattering diagram of pseudo 2D-chromatogram. The application of this method was discussed to separate and identify a mixture of ten different polyethers.

Femto-second laser photodegradations of polyethylene oxide (PEG), poly(ethylene oxide-b-propylene oxide) copolymer and polydimethylsiloxane (PDMS) were studied to investigate the degradation mechanism. MALDI-TOFMS and LC-APCI-MS were used for detail structural analysis of the degradation products. The results indicated that laser photodegradation proceeds within a few minutes in both aqueous and organic solutions. The degradation products of laser irradiation were identical to those of ultrasonic irradiation, but were not to those of thermal degradation in an aqueous solution using high-resolution mass spectrometry. Therefore, it is suggested that the mechanism of laser photodegradation of the polymers is due to the physical bond scissions through cavitation, just like ultrasonic degradation and the chemical reactions of the polymer chains with radicals formed from solvent or dissolved oxygen in laser-ablation.

Evolved gas analyses by pyrolysis were carried out for 10 kinds of polymers using a newly developed prototype of Skimmer interface-connected [TG/DTA]/[Ion Attachment Ionization-TOFMS]. This prototype has an advantage of the real-time monitoring of pyrolyzed species because of no transformation of the evolved species with the skimmer interface and no fragmentation during ionization by the Ion Attachment Ionization technique. On the other hand, the combination of TG/DTA results and mass spectra offers the discrimination of polymers with the same chemical structure and different thermal properties. Examples were presented in this study.

Oriental lacquer has been used as a durable and beautiful coating material in Asian countries for more than 7,000 years. However, lacquer ware is susceptible to damage by light and therefore is usually stored in a dark, cool environment. This research focused on volatilized constituents from raw lacquer film by ultraviolet irradiation. This paper discussed research that examined volatile deterioration products generated when the lacquer film, which was not proved although the existence was pointed out until now, was irradiated with ultraviolet rays. We analyzed about the volatile deterioration product of the lacquer film using newly developed on-line ultraviolet/thermal degradation-gas chromatography/mass spectrometry. In particular, this research examined the ultraviolet exposure conditions to the raw lacquered film. As a result, it was suggested that the oxidative cleavage reaction was triggered because oxygen combines the volatilization ingredient following ultraviolet exposure with the portion which the double combination of the urushiol origin that remains on a lacquer film activated in connection with the allylic rearrangement by ultraviolet rays is the cause. Thus, the present work, we considered the reaction of the oxidative cleavage that starts in the case of ultraviolet ray degradation by analysis using newly developed equipment to the volatilization output from the lacquered film which was not started until now, and acquired the fixed view on an ultraviolet-ray-degradation mechanism.

The estimated thermal-oxidation degree and corresponding thermal aging times at practical temperatures with poly(butylene terephthalate) [PBT] mold parts taken from used cars was investigated by applying the time-temperature superposition principle. Methyl 4-methoxybutyrate (MMB), based on the reactive pyrolysis-GC/MS method, was used as an index of the thermal-oxidation degree. This method was applied for pars taken from the engine compartment of the used cars with mileage of 46000 km ; the amount of MMB was 0.0071 wt%. The thermal aging times converted at a thermal history temperature of 84°C by the DSC method and 100°C were 4200 hours and 3500 hours, respectively. Based on the fact that the thermal-oxidation degree can now be represented as a thermal aging time for any assumed temperature, the thermal-oxidation degree can be more accurately evaluated through the relationship between the amount of MMB and t₁₀₀ than through mileage. The lifetime of parts can also be estimated by adding the mechanical properties. The dependency of the thermal-oxidation rate on the sample thickness and the diffusion controll over the thermal-oxidation rate were mentioned.

The effects of copper-based metals on thermal oxidative degradation and the evaluation methods to analyze different degrees of thermo oxidative degradation with polypropylene (PP) wrere invesigated. In the state of inserting the terminal into the connector of molded PP, thermal aging took place at 140°C for 120 hours. Four types of terminal components (cartridge brass, high copper alloy, tinning cartridge brass, and tinning high copper alloy) and PP with different thermal stability were used. From SEM observations of tin-copper alloy in the tinning layer and the ICP quantification of copper in PP, the influence of the PP thermal stability and terminal components on PP thermo oxidative degradation could be quantitatively identified. The convenient high-temperature GPC, ATR-FTIR, Oxidation Onset Temperature (OOT) with DSC, and iodometric hydroperoxide determination were used as methods to analyze oxidative degradation. Due to the master curve for the degree of degradation, OOT was effective for evaluating the degree of PP thermo oxidative degradation, ranging from the initial to increased degradation and correlated with the molecular-weight change behavior. Rapid decreases of the molecular weight could be sensitively predicted by the iodometric method in a simple manner.

Rosin-glycerol ester, terpene resin, terpene phenolic resin, coumarone resin and petroleum resin, which are major commercial tackifiers, were analyzed by field desorption-mass spectrometry (FD-MS) in the region of m/z 150〜1600. Each resin showed a characteristic mass spectrum that was related to the monomer composition, and the grades of some resins were differentiated by comparing the mass spectra. Packaging adhesive tapes were treated with organic solvent, and some tackifiers, except for aromatic petroleum resin and coumarone resin, which were mixed with aliphatic petroleum resin, were identified simultaneously in the extracts. It has been shown that FD-MS is an effective and easy method to identify tackifiers and those in adhesives.

A certified reference material (CRM, NMIJ CRM 8108-b) of polystyrene resin containing decabrominated diphenyl ether (DBDE) was developed. The form of the CRM was a disk with 30 mm diameter and 2 mm thickness. Homogeneity tests of the CRM disks by X-ray fluorescence spectrometry analysis indicated that the Br concentrations were almost constant both in a disk and among the disks. The DBDE concentration in CRM was determined by two analytical methods ; GC-MS combined with the isotope dilution method (the primary method of measurement) and HPLC-UV detection using the standard addition method. The analytical results obtained by these two methods agreed within the uncertainty. Considering additional sources of uncertainty, such as the water content and stability, the concentration of DBDE in CRM was certified as 312 mg/kg, and its expanded uncertainty was 16 mg/kg with a coverage factor of k = 2.