JMSSJ On-line Abstracts, Vol.49, No.2 (2001)

Simultaneous TG-MS Studies on Polymers Derived from Monomers with a Polar Group

English

Jian Ping CHEN,^a) Toshiyuki KODAIRA,^a) Kimio ISA,^*b) and Tetsuya SENDA^c) (^a) Department of Materials Science and Engineering, Faculty of Engineering, Fukui University (Bunkyo 3-9-1, Fukui 910-8507, Japan) ^*b) Department of Natural Science Education, Faculty of Education and Regional Studies, Fukui University (Bunkyo 3-9-1, Fukui 910-8507, Japan) ^c) Rigaku Co., Ltd. (Matsubara 3-9-12, Akishima, Tokyo 196-8666, Japan))

J. Mass Spectrom. Soc. Jpn., 49(2), 41-50, 2001

Thermal degradation behavior of polymers derived from monomers with a polar group was investigated by thermogravimetry interfaced to mass spectrometry (TG-MS) to see its applicability to the investigation on thermal degradations of polymers. The polymers studied were poly(methyl methacrylate) (PMMA), poly(methyl acrylate) (PMA), and polyacrylamide (PAM). Decomposition products of PMMA consist exclusively of methyl methacrylate monomers that were formed through random scissions of main chains followed by depolymerization. Initiation temperature of the random scission of PMMA was strongly influenced by its micro-structures, such as head-to-head and head-to-tail linkages and vinyl terminated chain ends, which suggests that subtle difference of polymer structures can be elucidated by TG-MS studies. This could be the characteristic feature of TG-MS that differentiates from other analytical method. During thermal degradation of PMA, unbuttoning reactions, some portion of unzipping reactions, and random scission of main and side chains occurred to afford a wide variety of products including monomers, oligomers, and some other unknown substances. Intra- and intermolecular imidation reactions between the side chain amide groups proceeded to yield glutarimide rings through main chains and crosslinking, respectively, during the initial stage of heat-treatments of PAM. Then, various low molecular weight compounds such as glutarimide and its analogues were formed by the decomposition on further heat-treatment at elevated temperature. The thermal degradation mechanism of these polymers was discussed in terms of the ceiling temperature of the monomers from which these polymers were derived. The results obtained were in good accordance with those reported using other analytical methods, which indicates that TG-MS could be one of the useful techniques for the investigation of thermal degradations of polymers.

A Study of Alkali Halide Triple Ions by Fast Atom Bombardment and Collisionally Activated Dissociation Mass Spectrometry

English

Nora MARTINEZ,^a) Kimio ISA,^*a) Ryuji NAKATA,^a) and Kazunaka ENDO^b) (^*a) Department of Natural Science Education, Faculty of Education and Regional Studies, Fukui University (Bunkyo 3-9-1, Fukui 910-8507, Japan) ^b) Department of Chemistry, Faculty of Science, Kanazawa University (Kakuma, Kanazawa 920-1192, Japan))

J. Mass Spectrom. Soc. Jpn., 49(2), 51-60, 2001

This work represents a more precise study of the characteristics of A₁XA₂⁺ ions in the gas phase, which can be formed in concentrated electrolyte solutions. In order to obtain the parent ions A₁XA₂⁺, a simple system was used, a mixture of two-alkali halide salts in an aqueous solution. In this system, A₁⁺, A₂⁺ are Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺ and X^- is F^-, Cl^-, Br^-, I^-, respectively. Utilizing Fast Atom Bombardment (FABMS) measurement methods, an A₁XA₂⁺ ion type in the mass spectra was obtained, and from this resulting spectrum, an ion was selected to be used as a precursor ion for the next stage. In this way, the Collisionally Activated Dissociation (CAD) spectra were obtained and the product ions identified.

Highly Sensitive and Precise Measurement of Helium Isotopes
Using a Mass Spectrometer with Double Collector System

English

Hirochika SUMINO,^*a) Keisuke NAGAO,^a) and Kenji NOTSU^a) (^*a) Laboratory for Earthquake Chemistry, Graduate School of Science, University of Tokyo ( 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan ))

J. Mass Spectrom. Soc. Jpn., 49(2), 61-68, 2001

A noble gas mass spectrometer equipped with a double collector system for helium isotopes was improved for the purpose of determining noble gas isotopic composition with extremely low concentration in terrestrial rock samples. Ion beams of ³He and ⁴He are measured at the same time with a Faraday cup and an ion-counting for ⁴He and ³He, respectively. As a result of changing detector to an ion-counting system and modification of a computer program for analysis, we can analyze the helium isotopic ratio (³He/⁴He) with a precision of ±10%, when partial pressure of ³He is in the range of 0.5-5×10^-14 Torr (corresponds to 0.2-2×10^-13 cm³ STP). The detection limit was highly improved to ca. 6×10^-16 cm³ STP of helium as a counting rate of 0.04 cps, which was 1-2 orders of magnitude lower than that before modification: 4×10^-14 cm³ STP. The diminution of detection limit enables us to measure other noble gas isotopes whose abundances are generally low in rock samples, such as neon, krypton and xenon with the mass spectrometer specialized to helium. In order to use HESJ (Helium Standard of Japan) as a working standard for helium isotopic measurement, we determined its ³He/⁴He ratio as 20.77±0.24 times the atmospheric ratio (=1.40×10^-6). In addition, accuracy in helium isotopic ratio measurement with the modified mass spectrometer was checked by comparing them with results obtained by other mass spectrometers in our laboratory.