Stimulated Transitions of Directed Nonequilibrium Self‐Assemblies

Abstract

Near-equilibrium stimulus-responsive polymers have been used extensively to introduce morphological variations in dependence of adaptable conditions. Far-less-well studied are triggered transformations at constant conditions. These require the involvement of metastable states, which are either able to approach the equilibrium state after deviation from metastability or can be frozen on returning from nonequilibrium to equilibrium. Such functional nonequilibrium macromolecular systems hold great promise for on-demand transformations, which result in substantial changes in their material properties, as seen for triggered gelations. Herein, a diblock copolymer system consisting of a hydrophilic block and a block that is responsive to both pressure and temperature, is introduced. This species demonstrates various micellar transformations upon leaving equilibrium/nonequilibrium states, which are triggered by a temperature deflection or a temporary application of hydrostatic pressure.

RAFT‐Mediated Polymerization‐Induced Self‐Assembly

“…The transition temperature is generally sensitive to the molar mass of the polymers, and can thus be tuned by the DP n or by copolymerization. For example, Warren, Plamper, and co‐workers copolymerized NIPAM with tert ‐butyl acrylamide (tBuAAm) to afford PDMAAm‐ b ‐P(NIPAM‐ co ‐tBuAAm) structures, morphological transitions of which could be induced by both temperature and hydrostatic pressure …”

High pressure cell for Bio-SANS studies under sub-zero temperatures or heat denaturing conditions

“…At the NCNR, the LIPSS system offers the unique capability of a broad range of subzero to relatively temperatures: to our knowledge, no other HP-SANS cell offers the combined capability to simultaneously cover the same range of pressure and low temperatures. The Institut Laue Langevin, France, provides HP-SANS cells for up to 500 MPa environments, designed for temperatures above freezing [1,55]. The High Flux Isotope Reactor facilities (Oak Ridge, USA) also offers the possibility of HP environments up to 100 MPa for temperatures above freezing, coupled with the advantage of an HP cell changer that allows for a series of measurements to be pre-programmed on the Bio-SANS instrument [21].…”

RAFT‐vermittelte polymerisationsinduzierte Selbstorganisation (PISA)

“…Ein weiterer wichtiger Parameter, der die finale Morphologie in PISA bestimmt, ist die Monomerkonzentration. Wie bereits erwähnt, fördert eine höhere Monomerkonzentration die Bildung von Morphologien höherer Ordnung durch Plastifizierung der Polymerketten in den Partikeln und eine erhöhte Anzahl von Partikeln pro Volumeneinheit im Reaktionsmedium . Die Polymerisationstemperatur ist ein weiterer zu berücksichtigender Parameter.…”