AbstractConstructing polymeric toroids with a uniform, tunable size is challenging. Reported herein is the formation of uniform toroids from poly(γ-benzyl-l-glutamate)-graft-poly(ethylene glycol) (PBLG-g-PEG) graft copolymers by a two-step self-assembly process. In the first step, uniform rodlike micelles are prepared by dialyzing the polymer dissolved in tetrahydrofuran (THF)/N,N′-dimethylformamide (DMF) against water. With the addition of THF in the second step, the rodlike micelles curve and then close end-to-end to form uniform toroids, which resemble a cyclization reaction.

AbstractConstructing polymeric toroids with a uniform, tunable size is challenging. Reported herein is the formation of uniform toroids from poly(γ-benzyl-l-glutamate)-graft-poly(ethylene glycol) (PBLG-g-PEG) graft copolymers by a two-step self-assembly process. In the first step, uniform rodlike micelles are prepared by dialyzing the polymer dissolved in tetrahydrofuran (THF)/N,N′-dimethylformamide (DMF) against water. With the addition of THF in the second step, the rodlike micelles curve and then close end-to-end to form uniform toroids, which resemble a cyclization reaction.

Spherical nanostructures with striped patterns on the surfaces resembling the essential structures of natural virus particles were constructed through a two-step self-assembly approach of polystyrene-b-oligo(acrylic acid) (PS-b-oligo-AA) and poly(γ-benzyl L-glutamate)-b-poly(ethylene glycol) (PBLG-b-PEG) copolymer mixtures in solution. On the basis of difference in hydrophilicity and self-assembly properties of the two copolymers, the two-step self-assembly process is realized. It was found that PS-b-oligo-AA copolymers formed spherical aggregates by adding a certain amount of water into polymer solutions in the first step. In the second step, two polymer solutions were mixed and water was further added, inducing the self-assembly of PBLG-b-PEG on the surfaces of PS-b-oligo-AA spheres to form striped patterns. In-depth study was conducted for the indispensable defects of striped patterns which are dislocations and +1/2 disclinations. The influencing factors such as the mixing ratio of two copolymers and the added water content in the first step on the morphology and defects of the striped patterns were investigated. This work not only presents an idea to interpret mechanism of the cooperative self-assembly behavior, but also provides an effective approach to construct virus-like particles and other complex structures with controllable morphology.Download high-res image (127KB)Download full-size imageSpherical core-shell virus-like particles with strip-pattern surface are fabricated through a two-step self-assembly of two block copolymers.

Mineralization behaviour of CaCO3 in the presence of polypeptide vesicles self-assembled from poly(L-glutamic acid)-block-poly(propylene oxide)-block-poly(L-glutamic acid) (PLGA-b-PPO-b-PLGA) triblock copolymers was studied. Under the mediation of PLGA-b-PPO-b-PLGA vesicles, CaCO3 fibre clusters were obtained. The structure of fibres could be regulated by the mineralization temperature, copolymer composition, copolymer concentration, and Ca2+ concentration. The investigation of the fibre growth process suggested a solution–precursor–solid mechanism via transient amorphous precursors. Since the polypeptide vesicles could serve as both the modifier and template for the formation of amorphous precursors, the properties of amorphous precursors were affected by the vesicular structure. The variation in the fibre structure was ascribed to the different aggregation and transformation behaviours of amorphous particles. These findings can provide useful information for the design of novel inorganic materials with fibrous structures and enrich our existing knowledge of the crystallization process from the amorphous phase.

Cooperative self-assembly behavior of rod–coil–rod poly(γ-benzyl-l-glutamate)-block-poly(ethylene glycol)-block-poly(γ-benzyl-l-glutamate) (PBLG-b-PEG-b-PBLG) amphiphilic triblock copolymers and hydrophobic gold nanoparticles (AuNPs) was investigated by both experiments and dissipative particle dynamics (DPD) simulations. It was discovered that pure PBLG-b-PEG-b-PBLG copolymers self-assemble into ellipse-like aggregates, and the morphology transforms into vesicles as AuNPs are introduced. When the hydrophobicity of AuNPs is close to that of the copolymers, AuNPs are homogeneously distributed in the vesicle wall. While for the AuNPs with higher hydrophobicity, they are embedded in the vesicle wall as clusters. In addition to the experimental observations, DPD simulations were performed on the self-assembly behavior of triblock copolymer/nanoparticle mixtures. Simulations well reproduced the morphology transition observed in the experiments and provided additional information such as chain packing mode in aggregates. It is deduced that the main reason for the ellipse-to-vesicle transition of the aggregates is attributed to the breakage of ordered and dense packing of PBLG rods in the aggregate core by encapsulating AuNPs. This study deepens our understanding of the self-assembly behavior of rod–coil copolymer/nanoparticle mixtures and provides strategy for designing hybrid polypeptide nanostructures.

Mineralization behaviour of CaCO3 in the presence of polypeptide vesicles self-assembled from poly(L-glutamic acid)-block-poly(propylene oxide)-block-poly(L-glutamic acid) (PLGA-b-PPO-b-PLGA) triblock copolymers was studied. Under the mediation of PLGA-b-PPO-b-PLGA vesicles, CaCO3 fibre clusters were obtained. The structure of fibres could be regulated by the mineralization temperature, copolymer composition, copolymer concentration, and Ca2+ concentration. The investigation of the fibre growth process suggested a solution–precursor–solid mechanism via transient amorphous precursors. Since the polypeptide vesicles could serve as both the modifier and template for the formation of amorphous precursors, the properties of amorphous precursors were affected by the vesicular structure. The variation in the fibre structure was ascribed to the different aggregation and transformation behaviours of amorphous particles. These findings can provide useful information for the design of novel inorganic materials with fibrous structures and enrich our existing knowledge of the crystallization process from the amorphous phase.