Shear induced structure orientation in norbornene block copolymers: In situ Rheo-SAXS investigations

Alignment of microphase separated block copolymers (BCP) has been achieved by shear-fields in order to achieve a deeper understanding of the melt-infiltration of BCP into nanopores (30-400 nm). BCP's composed of different perfluorinated sidechains, namely Am-b-Dn-, A100-b-D100- and A140-b-D60- and Am-b-Cn-BCPs and A50-b-C8 and A50-b-C13 have been studied by rheology coupled to in situ-SAXS. BCP's were prepared by ROMP-methods, generating the BCP's with low polydispersities and the expected molecular weights. A strong macroscopic orientation of the investigated block copolymer domains A50-b-C13 occurs upon applying oscillatory shear forces at temperatures significantly above the Tg's using shear amplitudes of 10% and angular frequencies of 10 rad/s for an already short period of time like 100 s. Coupled Rheology to SAXS-measurements on block copolymer A100-b-D100 at 180 °C revealed a similar picture when sheared at 10% shear amplitude and an angular frequency of 10 rad/s over a time of 100 s. In both BCP's a slow relaxation of the oriented microphases was observed, which can be explained by the nanophase-separation of the respective fluorinated chains.