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Butterfly patterns in crystalline polymers under uniaxial stretch.
Mikihito Takenaka1, Hirofumi Shimizu, Shotaro Nishitsuji
1Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
Summary
Density fluctuations in crystalline polymers transform from isotropic to a butterfly pattern under uniaxial stretch. This change reveals stress-induced density variations and heterogeneous deformation in polymer materials.
Area of Science:
- Materials Science
- Polymer Physics
- Condensed Matter Physics
Background:
- Crystalline polymers exhibit density fluctuations at the submicron to micron scale.
- Understanding these fluctuations is crucial for predicting material behavior under stress.
Purpose of the Study:
- To investigate the nature of density fluctuations in crystalline polymers before and after uniaxial stretching.
- To characterize the transformation of scattering patterns due to applied stress.
Main Methods:
- Utilizing two-dimensional ultrasmall-angle X-ray scattering (2D USAXS).
- Analyzing scattering patterns to quantify density fluctuations and their anisotropy.
Main Results:
- Before stretching, density fluctuations were isotropic and followed mass fractal behavior with a fractal dimension of 2.6.
- After uniaxial stretch, the scattering pattern changed to a distinct butterfly pattern.
- The butterfly pattern indicates stress-induced density fluctuations and heterogeneous deformation.
Conclusions:
- Uniaxial stretch significantly alters the morphology of density fluctuations in crystalline polymers.
- The observed butterfly pattern is a direct consequence of stress concentration and heterogeneous deformation within crystalline and amorphous regions.
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