Self-oscillating AB diblock copolymer developed by post modification strategy

Abstract

We prepared AB diblock copolymer composed of hydrophilic poly(ethylene oxide) segment and self-oscillating polymer segment. In the latter segment, ruthenium tris(2,2'-bipyridine) (Ru(bpy)3), a catalyst of the Belousov-Zhabotinsky reaction, is introduced into the polymer architecture based on N-isopropylacrylamide (NIPAAm). The Ru(bpy)3 was introduced into the polymer segment by two methods; (i) direct random copolymerization (DP) of NIPAAm and Ru(bpy)3 vinyl monomer and (ii) post modification (PM) of Ru(bpy)3 with random copolymer of NIPAAm and N-3-aminopropylmethacrylamide. For both the diblock copolymers, a bistable temperature region (the temperature range; ΔTm), where the block copolymer self-assembles into micelle at reduced Ru(bpy)3(2+) state whereas it breaks-up into individual polymer chain at oxidized Ru(bpy)3(3+) state, monotonically extends as the composition of the Ru(bpy)3 increases. The ΔTm of the block copolymer prepared by PM is larger than that by DP. The difference in ΔTm is rationalized from the statistical analysis of the arrangement of the Ru(bpy)3 moiety along the self-oscillating segments. By using the PM method, the well-defined AB diblock copolymer having ΔTm (ca. 25 °C) large enough to cause stable self-oscillation can be prepared. The periodic structural transition of the diblock copolymer in a dilute solution ([Polymer] = 0.1 wt. %) is closely investigated in terms of the time-resolved dynamic light scattering technique at constant temperature in the bistable region. A macroscopic viscosity oscillation of a concentrated polymer solution (15 wt. %) coupled with the periodic microphase separation is also demonstrated.

Evolved Colloidosomes Undergoing Cell‐like Autonomous Shape Oscillations with Buckling

“…[7,8] To realize autonomous oscillatory behaviors that exist in living systems by using synthetic materials,w eh ave developed "self-oscillating" gels which exhibit autonomous periodic swelling/deswelling changes driven by an oscillatory chemical reaction. [13][14][15][16][17] In addition to our studies,o ther groups have also reported self-oscillating polymer materials. [13][14][15][16][17] In addition to our studies,o ther groups have also reported self-oscillating polymer materials.…”

Fabrication of Self‐Oscillating Micelles with a Built‐In Oxidizing Agent

“…The efficient redox reaction of Ru(bpy) 3 can be induced by the ideally random arrangement of Ru(bpy) 3 from the viewpoint of the thermodynamic stability of charged structures. [20] From these results, it is expected that autonomous transition between micelles and unimers can be induced in the range of the bistable temperature (25-41 8C) by coupling the BZ reaction, even though the A segment is newly designed as a polycationic BrO 3 À containing hydrophilic polymer. Next, we attempted to induce structural oscillation of the diblock copolymer between micelles and unimers driven by the BZ reaction without the external addition of an oxidizing agent.…”

Recent Advances in Self‐Oscillating Polymer Material Systems

“…As described in Section 2.1, the post‐modification (PM) method, that is, random copolymerization of NIPAAm and NAPMAm followed by the modification of Ru(bpy) 3 having succinimidyl ester (Ru(bpy) 3 ‐NHS), enables more precise control of self‐oscillating behaviors than the direct polymerization (DP) of NIPAAm and vinyl monomers of Ru(bpy) 3 . We have systematically prepared self‐oscillating diblock copolymers with various compositions of Ru(bpy) 3 via both the DP and PM methods, and investigated the factors that affect the bistable temperature region (Δ T m ) 71. The relationship between the Δ T m and Ru(bpy) 3 composition incorporated into self‐oscillating segments is shown in Figure a.…”