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The application of large amplitude oscillatory shear (LAOS) to block polymers near their order-disorder transition temperature (TODT) has previously been shown to induce morphological transitions and to promote domain alignment. To kinetically trap these transient shear-induced morphologies, we have utilized reactive poly(styrene-stat-glycidyl methacrylate)-block-polylactide diblock terpolymers that adopt lamellar morphologies in the quiescent state with thermally accessbile TODT's and can readily be cross-linked near the TODT under LAOS. By maintaining a constant curing temperature in the disordered state while varying the strain amplitude, we observed a shear-induced transition from an isotropic fluctuating disordered morphology at low strain amplitude to an aligned parallel-transverse kinked lamellar morphology at high strain amplitude. Additionally, we investigated the effect that cross-linking temperature (distance from the TODT) at a constant strain amplitude had on the occurrence of shear-induced ordering. The large amplitude of composition fluctuations near the TODT was critical for the transition from a disordered to an ordered morphology under LAOS. Conversely, cross-linking temperatures far above TODT revealed the lack of a shear-induced disorder-order transition, possibly because of smaller amplitude fluctuations and/or rapid curing kinetics. These results suggest that careful selection of the strain amplitude and curing temperature during the cross-linking of lamellar block polymers under LAOS may enable the domain anisotropy and continuity to be precisely tailored for a targeted application.
Bibliographical noteFunding Information:
The authors thank Aaron Lindsay and Daphne Chan for the collection of some of the SAXS data, and Prof. Michelle Calabrese for carefully reading the manuscript. Altasorb generously donated lactide. Funding for this work was provided by the National Science Foundation (DMR-1609459 and DMR-2003454). Hitachi SU8320 SEM was provided by NSF MRI DMR1229263. Parts of this work were carried out in the Characterization Facility, UMN, which receives partial support from NSF through the MRSEC program. Portions of this work were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, E. I. DuPont de Nemours & Co., and The Dow Chemical Company. This research used resources of the APS, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. Data were collected using an instrument funded by the NSF under award number 0960140.
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- Period 7