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Titolo:
Positron annihilation properties of copolyimides and copolyamides with microphase-separated structures
Autore:
Fang, JH; Tanaka, K; Kita, H; Okamoto, K; Ito, Y;
Indirizzi:
Yamaguchi Univ, Fac Engn, Dept Adv Mat Sci & Engn, Ube, Yamaguchi 7558611,Japan Yamaguchi Univ Ube Yamaguchi Japan 7558611 , Ube, Yamaguchi 7558611,Japan Univ Tokyo, Nucl Sci & Technol Res Ctr, Tokai, Ibaraki 3191195, Japan UnivTokyo Tokai Ibaraki Japan 3191195 Ctr, Tokai, Ibaraki 3191195, Japan
Titolo Testata:
JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS
fascicolo: 9, volume: 38, anno: 2000,
pagine: 1123 - 1132
SICI:
0887-6266(20000501)38:9<1123:PAPOCA>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
LIFETIME SPECTROSCOPY MEASURE; STYRENE-MALEIC ANHYDRIDE; HOLE SIZE DISTRIBUTION; FREE-VOLUME; AMORPHOUS POLYMERS; MAXIMUM-ENTROPY; COPOLYMERS;
Keywords:
positron annihilation lifetime; ortho-positronium; polyimide; polyamide; microphase separation; poly(dimethylsiloxane); poly(ethylene oxide);
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
28
Recensione:
Indirizzi per estratti:
Indirizzo: Okamoto, K Yamaguchi Univ, Fac Engn, Dept Adv Mat Sci & Engn, Ube, Yamaguchi 7558611,Japan Yamaguchi Univ Ube Yamaguchi Japan 7558611 guchi 7558611,Japan
Citazione:
J.H. Fang et al., "Positron annihilation properties of copolyimides and copolyamides with microphase-separated structures", J POL SC PP, 38(9), 2000, pp. 1123-1132

Abstract

The positron annihilation lifetime (PAL) of a series of copolyimides and copolyamides with microphase-separated structures was measured to investigate the effects of different hard-segment polymers on the PAL properties of soft-segment domains of poly(dimethyl-siloxane) (PDMS) and poly(ethylene oxide) (PEG). The lifetime (tau(3)) and intensity (I-3) of the long-lived component are given as a function of the PDMS or PEG content for a series of copolymers, of which the density roughly obeys the additive rule except for the PDMS-segmented copolyamides. The PDMS-segmented copolyimides and copolyamides show much smaller I-3 values than those estimated from the additive rule. The lifetime distribution of the long-lived component for the PDMS-segmented copolyamides is composed of two components. The longer-lifetime component is attributed to pure PDMS domains, and the shorter-lifetime component is attributed to the polyamide domains, intermediate phases, and PDMS domains containing small amounts of short amide blocks. Despite the high PDMS content, the latter component is rather large. Thus, the positronium formation in the PDMS domains of the copolyimides and copolyamides is effectivelyreduced. This can be explained by the combination of the difference in theelectron affinity of the PDMS and polyimide or polyamide segments and the incomplete phase separation. The PEG-segmented copolyimides show much smaller I-3 values than those predicted from the additive rule. This is likely attributable to the effects of the intermediate phases. (C) 2000 John Wiley & Sons, Inc.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 14/08/20 alle ore 04:58:45