Reversible Switching of Block Copolymer Nanopatterns by Orthogonal Electric Fields

It is demonstrated that the orientation of striped patterns can be reversibly switched between two perpendicular in-plane orientations upon exposure to electric fields. The results on thin films of symmetric polystyrene-block-poly(2-vinyl pyridine) polymer in the intermediate segregation regime disclose two types of reorientation mechanisms from perpendicular to parallel relative to the electric field orientation. Domains orient via grain rotation and via formation of defects such as stretched undulations and temporal phase transitions. The contribution of additional fields to the structural evolution is also addressed to elucidate the generality of the observed phenomena. In particular solvent effects are considered. This study reveals the stabilization of the meta-stable in-plane oriented lamella due to sequential swelling and quenching of the film. Further, the reorientation behavior of lamella domains blended with selective nanoparticles is addressed, which affect the interfacial tensions of the blocks and hence introduce another internal field to the studied system. Switching the orientation of aligned block copolymer patterns between two orthogonal directions may open new applications of nanomaterials as switchable electric nanowires or optical gratings

Design, Synthesis, and Use of Y‑Shaped ATRP/NMP Surface Tethered Initiator

Heterogeneous polymer brushes on surfaces can be easily formed from a binary initiator on a silicon oxide substrate where two different types of polymers can be grown side-by-side. Herein, we designed a new Y-shaped binary initiator using straightforward chemistry for “grafting from” polymer brushes. This initiator synthesis takes advantage of the Passerini reaction, a multicomponent reaction combining two initiator sites and one surface linking site. This Y-shaped binary initiator can be synthesized in three steps with a higher yield than other similar initiators reported in the literature, and can be performed on a multigram scale. We were able to attach the initiator to a silicon oxide substrate and successfully grow polymer brushes from both initiators (separately and in combination), confirmed by NEXAFS, AFM, and contact angle

Kinetics of Block Copolymer Phase Segregation during Sub-millisecond Transient Thermal Annealing

Early stage phase segregation of block copolymers (BCPs) critically impacts the material’s final structural properties, and understanding the kinetics of these processes is essential to intentional design of systems for practical applications. Using sub-millisecond lateral gradient laser spike annealing and microbeam grazing incidence small-angle X-ray scattering, the ordering and disordering kinetics of cylinder forming poly­(styrene-<i>b</i>-methyl methacrylate) (PS-<i>b</i>-PMMA) were determined for peak annealing temperatures up to 550 °C for dwells (anneal durations) ranging from 250 μs to 10 ms. These temperatures, far in excess of the normal thermal decomposition limit, are enabled by the short time scales of laser annealing. From initially microphase-segregated films, disordering was observed near the equilibrium order–disorder transition temperature (<i>T</i>_ODT) for dwell times above 10 ms but was kinetically delayed by diffusion for shorter time scales, resulting in suppression of observed disordering by over 70 °C. The onset of ordering from initially disordered films was also kinetically limited for short dwells. For anneals with peak temperatures well above <i>T</i>_ODT, the block copolymer fully disorders and quenches to a history-independent final state determined by the quench rate. This kinetic behavior can be represented on an effective <i>T</i>_g and <i>T</i>_ODT phase map as a function of the heating time scale. These results then potentially enable BCP processing to retain or intentionally modify the initial state while accelerating kinetics for other chemical or structural alignment processes

Oxygen-rich poly-bisvanillonitrile embedded amorphous zirconium oxide nanoparticles as reusable and porous adsorbent for removal of arsenic species from water

A new oxygen-rich porous polymer based on bisvanillonitrile was synthesized and characterized. This polymer was employed as support for the anchoring of 14.5 w% amorphous zirconium oxide nanoparticles. The formation of homogeneously dispersed nanoparticles in the poly-bisvanillonitrile (PBVN) host material was confirmed using N2-sorption, XRPD, XPS and electron microscopy. The combination of zirconium oxide nanoparticles having active adsorption sites with the porous supporting material showed excellent adsorption of arsenic species. The resulting adsorption capacities of the hybrid material extend to 245 mg g−1 for arsenite (AsIII) and 115 mg g−1 for arsenate (AsV). Moreover, adsorption kinetics showed a fast removal of both arsenic species with initial adsorption rate h of 0.0646 mg g−1 min−1 for arsenite and 0.0746 mg g−1 min−1 for arsenate. The immobilization was not interfered by the presence of other compounds in solution, indicating the applicability in real working environments. The material could be regenerated in a continuous mode using a 0.1 mol L−1 sodium hydroxide solution at 70 °C to desorb arsenic