Free Volumes in Polymers; Positron Annihilation vs. Other Methods

Okamoto, Katsutomo; Tanaka, Katsutoshi; Katsube, N.; Sueoka, Osamu; Ito, Yasuo

doi:10.4028/www.scientific.net/msf.105-110.1675

Cited by 3 publications

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“…Several groups have recently reported on PAL studies on polyimides; − however, only a few papers focused on moisture absorption . In the present work, we utilize PAL spectroscopy to investigate the effect of water sorption on the free volume in polyimide 6FDA-ODA.…”

Section: Introductionmentioning

confidence: 99%

Water in Local Free Volumes of Polyimides: A Positron Lifetime Study

et al. 1999

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Positron annihilation lifetime (PAL) spectroscopy was used to study the effect of water uptake on the free volume in 6FDA-ODA polyimide (PI2566, DuPont). Orthopositronium (o-Ps) lifetime (τ 3 ) and intensity (I 3) data were analyzed assuming a Gaussian size distribution of preexisting (excess free volume) holes and further assuming that holes occupied by water molecules would not be detected in the measurement. When exposed to humidity, both the mean hole volume and the number of holes not occupied by water molecules decrease with increasing relative humidity, as indicated by decreasing τ 3 and I 3. Our PAL results correlated with humidity-induced mass uptake and volume expansion support a model according to which water absorption in polyimides occurs in two stages. At relative humidities smaller than about 30%, water is absorbed mostly in large, preexisting holes, with each hole typically occupied by a single water molecule. At larger humidities, an increasing fraction of the sorbed water molecules will occupy sites other than preexisting empty holes. A multiple occupation of larger holes by water molecules is discussed as a possible mechanism.

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Section: Introductionmentioning

confidence: 99%

Water in Local Free Volumes of Polyimides: A Positron Lifetime Study

et al. 1999

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Microstructural characterization of semi-interpenetrating polymer networks by positron lifetime spectroscopy

Singh

Pater

Eftekhari

1998

Nuclear Instruments and Methods in Physics Research Section B:

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Thermoset and thermoplastic polyimides have complementary physical and mechanical properties. Whereas thermoset polyimides are brittle and generally easier to process, thermoplastic polyimides are tough but harder to process. A combination of these two types of polyimides may help produce polymers more suitable for aerospace applications. Semi-!nterpenetrating Polymer Networks (S-IPN) of thermoset LaRCTM-RP46 and thermoplastic LaRCTM-IA polyimides were prepared in weight percent ratios ranging from 100:0 to 0:100. Positron lifetime measurements were made in these samples to correlate their free volume features with physical and mechanical properties. As expected, positronium atoms are not formed in these samples. The second lifetime component has been used to infer the positron trap dimensions. The "free volume" goes through a minimum at a ratio of about 50:50, and this suggests that S-IPN samples are not merely solid solutions of the two polymers. These data and related structural properties of the S-IPN samples are discussed.

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Influence of Moisture-Uptake on Mechanical Properties of Polymers Used in Microelectronics

et al. 1998

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Polymers are currently considered as a possible alternative to silicon dioxide in the fabrication of interlevel dielectrics. To penetrate mainstream semiconductor device fabrication polymers have to meet a number of requirements regarding their long-term stability. One aspect is the mechanical stability of integrated polymer films under changing climatic conditions. In the present work, the impact of ambient moisture on the mechanical properties of thin polymer films (PI, BCB, and PFCB) was investigated. The sorption of water molecules in these materials typically causes an anisotropic volume expansion, resulting in increased mechanical film stress if the film is physically constrained by adjacent inorganic structures. Especially polyimides show both considerable moisture uptake and large changes in the mechanical film stress, while BCB and PFCB are virtually insensitive to ambient moisture. In the paper, experimental data (water uptake, in-plane swelling, out-of-plane swelling) are presented and discussed in detail.

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Free Volumes in Polymers; Positron Annihilation vs. Other Methods

Cited by 3 publications

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Water in Local Free Volumes of Polyimides: A Positron Lifetime Study

Water in Local Free Volumes of Polyimides: A Positron Lifetime Study

Microstructural characterization of semi-interpenetrating polymer networks by positron lifetime spectroscopy

Influence of Moisture-Uptake on Mechanical Properties of Polymers Used in Microelectronics

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