1992 Fiscal Year Final Research Report Summary
Diffusion of Low Molecular Weight Substances into Single Fiber by Time-resolved Small-angle Light Scattering Technique
| Project/Area Number |
03650726
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
高分子物性・高分子材料（含機械材料）
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| Research Institution | HYOGO UNIVERSITY OF TEACHER EDUCATION |
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Principal Investigator |
FUKUDA Mitsuhiro Hyogo University of Teacher Education, Associate Professor, 学校教育学部, 助教授 (40183587)
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| Project Period (FY) |
1991 – 1992
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| Keywords | Case II diffusion / Light scattering from a coaxial cylinder / Glassy polymer |
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| Research Abstract |
We demonstrated a simple optical diffraction technique to measure the diffusion rate of small molecules in a polymer fiber. The diffusion of acetone vapor into a polystyrene fiber(25mum in diameter) was observed in detail at 20ﾟC. Sorption curves at different vapor pressure showed that the diffusion was apparently an anomalous type. However, the shrinkage of the fiber was occurred at the last stage of the diffusion in the vapor pressure range higher than 0.75. Optical microscopy measurement showed that the front position of the acetone proceeds with time at higher vapor pressure near saturation, strongly suggesting the Case II diffusion. And we found that the moment when the core was just disappeared, the fiber began to shrink. The shrinkage seemed to a kind of relaxation process in the rubbery state. A small angle light scattering apparatus was used to measure the intensity distribution from a monofilament. The Mie scattering from the infinite length of a coaxial cylinder was calculated from a model refractive index profile consisting of a glassy core and a rubbery shell. The decrease in the radius of core was determined by fitting the theoretical curves to the observed one. The results from the optical microscopy measurement showed in good agreement with that from the light scattering method. Thus it is evident that the method of observing the change in small angle light scattering from a fiber during its absorption of solvent is a simple and convenient way of studying diffusion of solvents into polymer. The method can be extended to Fickian diffusion in which the boundary region is large and an extended concentration gradient.
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