Vesicles made of PS-PI cyclic diblock copolymers: In situ freeze-drying cryo-TEM and dynamic light scattering experiments

Abstract

We have studied the morphology of self-assembled micelles made of linear and cyclic poly(styrene-b-isoprene) PS-b-PI block copolymers dispersed in selective solvents of the PI block (n-heptane, n-decane). Up to a copolymer concentration of 5 mg mL(-1), the micelles made from linear block copolymer chains adopt a spherical shape. Those arising from cyclic copolymer chains having exactly the same molar mass and volume fraction self-assemble into (i) planar sunflower-shaped particles at low concentration (c < 0.1 mg mL(-1)), (ii) giant wormlike micelles at intermediate concentration (0.1 mg mL(-1) < c < 2 mg mL(-1)) and (iii) vesicles at higher concentration (2 mg mL(-1) < c < 5 mg mL(-1)). Those results were obtained using dynamic light scattering and in situ freeze-drying cryo-transmission electron microscopy. In this contribution, we discuss the effects of concentration and temperature on the morphology of the self-assembled particles made from both linear and cyclic PS-PI copolymers, and highlight the surprising vesicle formation in cyclic block copolymer solutions.

Self-assembly of cyclic polymers

“…Borsali and coworkers reported the self-assembly behaviour of cyclic poly-(styrene)-b-poly(isoprene) (PS x -b-PI y ) copolymers, that possess a significantly longer core-forming PS block than the coronaforming PI block; these assemblies are commonly referred to as "crew-cut". [100][101][102][103][104][105][106] In contrast to the "star-like" assemblies discussed above, these "crew-cut" assemblies exhibited much greater structural and morphological differences with respect to their linear PS x -b-PI y analogues. The linear PS x -b-PI y copolymers were observed to form spherical micelles of consistent size and low dispersities, regardless of polymer concentration, temperature or solvent choice (various n-alkanes selective for the PI block).…”

“…The effect of cyclization on the aggregation behaviour of a crystallization-driven self-assembly 107 has also been investi- gated. Cyclic and linear amphiphilic diblock polypeptoids, poly(N-decylglycine) 10 -b-poly(N-methylglycine) 105 were found to initially form spherical micelles upon self-assembly in methanol, a selective solvent for the poly(N-methylglycine) block. 108 However, a morphological transition from spheres to cylindrical micelles was observed by cryo-TEM for both cyclic and linear polymers as the core-forming poly(N-decylglycine) block crystallized over time.…”

Synthesis and Characterization of Amphiphilic Cyclic Diblock Copolypeptoids from N-Heterocyclic Carbene-Mediated Zwitterionic Polymerization of N-Substituted N-Carboxyanhydride

“…9–12 To verify that the morphological transition observed in the c / l -PNMG- b -PNDG is due to crystallization of the solvophobic block (PNDG), the synthesis of amorphous-amorphous cyclic and linear diblock copolypeptoid analogs and investigation of their solution self-assembly behavior is currently in progress.…”

Self‐assembled, wormlike‐cylinder network of polystyrene‐block‐poly(ethylene oxide) micelles in solution

“…[1][2][3][4][5][6][7][8] A wide range of micelle morphologies of block copolymers in solutions have been recently reported, and these morphologies possess better stability than those formed by small-molecule amphiphiles such as surfactants. [9][10][11][12][13][14][15] These block copolymer micelles can be potentially used in specific biological and medical applications. [16][17][18] To obtain different micelle morphologies of block copolymers in solutions, two sets of parameters need to be taken into account.…”