title: Photocontrol over the disorder-to-order transition in thin films of polystyrene-block-poly(methyl methacrylate) block copolymers containing photodimerizable anthracene functionality.
abstract: Reversible photocontrol over the ordering transition of block copolymers (BCPs) from a disordered state to an ordered state, namely the disorder-to-order transition (DOT), can be used to create long-range ordered nanostructures in self-assembled BCPs over macroscopic distances by photocombing, similar to the classic zone refining used to produce highly pure, large single crystals. Here, we have designed and synthesized an anthracene-functionalized tri-BCP containing deuterated polystyrene (d(8)-PS) and poly(methyl methacrylate) (PMMA) blocks, as well as a short middle block of poly(2-hydroxyethyl methacrylates) (PHEMA) that is randomly functionalized by anthracene. This tri-BCP maintains the order-to-disorder transition-type phase behavior of its parent d(8)-PS-b-PMMA di-BCPs. Under 365 nm UV irradiation, the junction between d(8)-PS and PMMA blocks is photocoupled through the anthracene photodimers, leading to a significant increase in the total molecular weight of the tri-BCP. As a consequence, when the tri-BCP is phase-mixed but close to the boundary of the ordering transition, it undergoes the DOT, as evidenced by small-angle neutron scattering and transmission electron microscopy. The tri-BCP could be reversibly brought through the DOT in thin films by taking advantage of photodimerization and thermal dissociation of anthracene. Currently, anthracene-functionalized d(8)-PS-b-PMMA BCP is one of the most promising candidates for the photocombing process to promote long-range laterally ordered nanostructures over macroscopic distances in a noninvasive manner.
authors: Department of Polymer Science and Engineering, University of Massachusetts-Amherst, Amherst, Massachusetts 01003, USA.
authors: Wei
authors: W
authors: Chen
authors: Jia-Yu
authors: JY
authors: Wang
authors: Wei
authors: W
authors: Zhao
authors: Le
authors: L
authors: Li
authors: Xinyu
authors: X
authors: Wei
authors: Anna C
authors: AC
authors: Balazs
authors: Krzysztof
authors: K
authors: Matyjaszewski
authors: Thomas P
authors: TP
authors: Russell
mesh_terms: D000873:Anthracenes / Q000138:chemical synthesis / Q000737:chemistry*; D019281:Dimerization; D008567:Membranes, Artificial; D008689:Methacrylates / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D010777:Photochemistry; D011137:Polystyrenes / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D000873:Anthracenes; D008567:Membranes, Artificial; D008689:Methacrylates; D011137:Polystyrenes; C522509:polystyrene-block-poly(methyl methacrylate); C034020:anthracene