Lyotropic Morphology Transition of Double Zwitterionic Diblock Copolymer Aqueous Solutions

Abstract

Polymer concentration‐dependent aqueous lyotropic morphology transition of a double zwitterionic diblock copolymer composed of a poly(carboxybetaine methacrylate) (PCB) and poly(sulfobetaine methacrylate) (PSB) is unraveled employing small‐angle X‐ray scattering. Salt‐free aqueous solutions of the well‐defined diblock copolymer produce ordered periodic structure and the morphology transforms from hexagonally close‐packed cylinder to lamellar with decreasing the polymer concentration. The morphology transition is induced by the preferential distribution of water molecules into the PCB domains below threshold polymer concentration because of the limited water capacity of the PSB network domains. The volume fraction modulation causes the instability of phase boundary curvature urging the morphology transition. The precise ordered nanostructure control of the highly biocompatible double zwitterionic block copolymers is valid for responsive biocompatible molecular design in biomaterials.

Modulation of Double Zwitterionic Block Copolymer Aggregates by Zwitterion-Specific Interactions

“…Milli-Q water (Millipore Inc., Billerica, MA) with a resistance of >18 MΩ·cm was used for solution preparation and dialysis. PCB2- b -PSB4 diblock copolymers (Figure ) and PCB2 and PSB4 homopolymers were synthesized through radical addition–fragmentation chain transfer polymerization following the previous report . Because the association of the zwitterionic polymers is sensitive to the residual salt, the product polymers were thoroughly purified through dialysis with regenerated cellulose membrane (MWCO 3500) to remove salts and monomers.…”

“…The SB couples dissociate in aqueous electrolyte solutions due to the charge screening effect. Matsuoka and co-workers reported that block copolymers composed of PCB and PSB chains produce spherical core–shell micellar aggregates in salt-free water, while the micelles dissociate in response to temperature and salts. − We showed the lyotropic microphase separation in high concentration aqueous solutions of a block copolymer composed of poly­(2-[( N -2-methacryloyl­oxyethyl- N , N -dimethyl)­ammonio]­acetate) (PCB2) and poly­(3-[( N -2-methacryl­oyloxyethyl- N , N -dimethyl)­ammonio]­butane-1-sulfonate]) (PSB4) (PCB2- b -PSB4) and the polymer concentration-dependent morphology transition . Thus, the double zwitterionic block copolymers could be regarded as a new type of double hydrophilic block copolymers that produce ordered aggregates; however, the molecular mechanisms in the phase separation have not yet been elucidated.…”

“…PCB2-b-PSB4 diblock copolymers (Figure 1) and PCB2 and PSB4 homopolymers were synthesized through radical addition−fragmentation chain transfer polymerization following the previous report. 27 Because the association of the zwitterionic polymers is sensitive to the residual salt, the product polymers were thoroughly purified through dialysis with regenerated cellulose membrane (MWCO 3500) to remove salts and monomers. The number-average molecular weight (M n ) and molecular weight distribution (M w /M n ) were determined by gel permeation chromatography (GPC).…”

“…) and the polymer concentration-dependent morphology transition. 27 Thus, the double zwitterionic block copolymers could be regarded as a new type of double hydrophilic block copolymers that produce ordered aggregates; however, the molecular mechanisms in the phase separation have not yet been elucidated. Here, we are reminded of the question as to why the PCB2-b-PSB4 diblock copolymers render phase separation in water despite the similarity of chemical structure; both blocks are hydrophilic polymethacrylate with zwitterion pendant groups.…”

Phase Behavior of Double Zwitterionic Block Copolymers in Water: Morphology Transition through Concentration Dependent Selectivity of Water Partitioning

“…[ 16 ] We reported a lyotropic microphase separation in concentrated aqueous solutions of a double zwitterionic diblock copolymer (PCB2 43 ‐ b ‐PSB4 166 ), which is composed of a poly(carboxybetaine methacrylate) (PCB2) and a poly(sulfobetaine methacrylate) (PSB4) chains ( Figure ). [ 27 ] The morphology depended on the polymer concentration due to the limited water capacity of the PSB4 phase. This copolymer can be regarded as a new type of double hydrophilic block copolymer composed of polyzwitterions that is valid for biomedical platforms.…”