MOLECULAR-ORIENTATION OF POLY(STYRENE-BLOCK-BUTADIENE-BLOCK-STYRENE) TRIBLOCK COPOLYMER WITH CYLINDRICAL MICRODOMAINS OF POLYSTYRENE

The molecular orientation of poly(styrene-block-butadiene-block-styrene) triblock copolymer with cylindrical microdomains of glassy polystyrene (PS) is investigated by i.r. spectroscopy and is discussed in relation to the structural changes of the microdomains caused by the uniaxial strain. For evaluation of the molecular orientation, the dichroic orientation factor (F(D)) was calculated from the dichroic ratio (D) of the absorption bands at 1493 and 966 cm-1 for PS and polybutadiene (PB), respectively. It was found that PB chains exhibit molecular orientation parallel to the stretching direction whereas there was no orientation for PS chains. The results indicated that PB chains are oriented parallel to the stretching direction but did not imply that the glassy PS microdomains are not deformed by the strain. The reason why the PS orientation was not clearly detected may be ascribed to a bad signal-to-noise ratio for the F(D) of the PS band used to evaluate PS orientation. It was also found that the orientation of PB chains effectively proceeded in an extremely stretched state, which is in good agreement with the results from wide-angle X-ray scattering.