Control on the Morphology of ABA Amphiphilic Triblock Copolymer Micelles in Dioxane/Water Mixture Solvent

This work offers a typical understanding of the factors that govern the nanostructures of poly（4-vinyl pyridine）-b-polystyrene-bpoly（4-vinyl pyridine）（P4 VP-b-PS-b-P4 VP） block copolymers（BCs） in dioxane/water, in which water is a selective solvent for the P4 VP block. It is achieved through an investigation of the amphiphilic triblock copolymer micelles by variation of three different factors, including water content（above CWC but under the immobile concentration）, temperature（ranging from 20 °C to 80 °C）, and copolymer composition（low and high PS block length）. Transition of bead-like micelles to vesicles is observed with the increase of water content due to the increase of interfacial energy between the copolymer and the solvent. Effect of temperature superposed on that of water content results in various morphologies, such as beads, fibers, rods, capsules, toroids, lamellae, and vesicles. The interfacial tension between the BC and the solvent increases with the increase of water content but decreases with the increase of temperature, indicating that the micellar morphologies are resulted from the competitive interplay between the temperature and the water content and always change in a direction that decreases the interfacial energy. Based on the micellar structures obtained in this work and the effects of temperature superposed on water concentration, a diagram of phase evolution of different micellar morphologies is illustrated here, covering the temperature range from 20 °C to 80 °C and the water content changing from 20 vol% to 35 vol%. For the investigation of BC composition, morphological transition of vesicle-to-fiber, for high PS length, is observed as compared with bead-to-capsule for low PS length, as the temperature changes from 20 °C to 80 °C. Our research complements the protocols to control over the morphologies and the phase diagram describing P4 VP-b-PS-b-P4 VP micellar nanostructures in aqueous solution.

DEFORMATION OF COPOLYMER MICELLES INDUCED BY AMPHIPHILIC DIMER PARTICLES

Combining self-consistent-field theory and density-functional theory, we systematically study the deformation of copolymer micelles induced by the presence of amphiphilic dimer particles. Due to the amphiphilic nature, dimer particles tend to accumulate onto the interface of the copolymer micelle. With increasing concentration of the symmetric dimer particles, which are made of two identical spherical particles, the micelle deforms from the initial sphere to ellipse, dumbbell, and finally separates into two micelles. Furthermore, asymmetric dimer particles, composed by two particles with different sizes, are considered to investigate the influence of geometry of dimer particles on the deformation of the micelle. It is found that the micelle inclines to deform into dumbbell due to the additional curvature originating in the gathering of asymmetric dimer particles onto the interface of the micelle. The present study on the deformation of micelles is useful to understand the possible shape variation in the course of cell division/fusion.

Organic Templates for Inorganic Nanocrystal Growth

Nanocrystals provide a variety of size and shape-dependent properties with applications in a wide range of areas, gaining much attention in the past few years. However, due to the nature of the kinetic nanocrystal growth, the procedures often require strict experimental conditions and the shape and size of nanocrystals are difficult to control. In such context, organic templates, which are artificially modified or synthesized, can direct inorganic nanocrystal nucleation and growth to achieve desired shape, size and ultimately properties. In this review article, two general categories of organic templates used for making inorganic nanomaterials are discussed:biotemplates(e.g., peptide, lipid, DNA, and capsid) and block copolymer templates(e.g., block copolymer micelles, star-like block copolymer unimicelles). The goal of this review is to bridge these gaps and help foster a greater awareness of the range and applicability of different organic templating techniques within the field of nanotechnology.

Micelle-crosslinked hydrogels with stretchable,self-healing,and selectively adhesive properties:Random copolymers work as dynamic yet self-sorting domains

The design of crosslinking domains is a vital factor to create functional hydrogels with controlled physical,mechanical,and adhesive properties.This paper demonstrates versatile synthetic systems of micelle-crosslinked hydrogels with highly stretchable,self-healing,and selectively adhesive properties.For this,methacrylate-bearing random copolymer micelles are designed as physical and covalent crosslink domains via the self-assembly of amphiphilic random copolymers carrying hydrophilic poly(ethylene glycol)(PEG),hydrophobic butyl or dodecyl groups,and methacrylate-terminal PEG in water.The size,aggregation number,and pendant methacrylate number of the micelles are controlled by the composition and degree of polymerization.Hydrogels are efficiently obtained from the free radical polymerization of hydrophilic monomers such as PEG acrylate and acrylamide in the presence of the micelle crosslinkers in water.Owing to the dynamic yet selective chain exchange properties of the micelle domains,the hydrogels are highly stretchable up to over 1000%and show self-healing and selectively adhesive properties.The self-healing of hydrogels is promoted upon heating due to the fast chain exchange of the micelle domains,whereas hydrogels consisting of micelles with different alkyl groups are never adhesive because of their self-sorting properties.

Preparation of ABA triblock copolymer assemblies through “one-pot” RAFT PISA

Poly(N,N-dimethyl acrylamide)-block-poly(styrene)-block-poly(N,N-dimethyl acrylamide)(PDMAc-bPSt-b-PDMAc)amphiphilic triblock copolymer micro/nano-objects were synthesized through reversible addition-fragmentation chain transfer(RAFT)dispersion polymerization of St mediated with poly(N,Ndimethyl acrylamide)trithiocarbonate(PDMAc-TTC-PDMAc)bi-functional macromolecular RAFT agent.It is found that the morphology of the PDMAc-b-PSt-b-PDMAc copolymer micro/nano-objects like spheres,vesicles and vesicle with hexagonally packed hollow hoops(HHHs)wall can be tuned by changing the solvent composition.In addition,vesicles with two sizes(600 nm,264 nm)and vesicles with HHHs features were also synthesized in high solid content systems(30 wt%and 40 wt%,respectively).Besides,as compared with typical AB diblock copolymers(A is the solvophilic,stabilizer block,and B is the solvophobic block),ABA triblock copolymers tend to form higher order morphologies,such as vesicles,under similar conditions.The finding of this study provides a new and robust approach to prepare block copolymer vesicles and other higher order micelles with special structure via PISA.

Micelle or polymersome formation by PCL-PEG-PCL copolymers as drug delivery systems

Polye-caprolactone）-b-poly（ethylene glycol）-b-poly（e-caprolactone）（PCL-b-PEG-b-PCL,PCEC） triblock copolymers have been widely investigated in last several decades.Here,by altering the weight ratio of monomers in ring-opening polymerization,a series of PCEC triblock copolymers with varying hydrophobicity were synthesized,which were characterized by FTIR,1 H NMR,GPC and DSC.When PCEC copolymers with different weight ratios of PCL/PEG were dispersed in different aqueous solutions,they could self-assemble and form two distinctive nanoparticular structures：micelles or polymersomes.We then chose paclitaxel（PTX） as the model drug and encapsulate PTX into PCEC polymeric micelles and polymersomes.The physicochemical characterizations of the nanoparticles such as morphology,the size and distribution,zeta potential,drug loading content,and encapsulation efficiency were also performed.Our results showed that polymeric micelles or polymersomes from PCEC both displayed narrow size distributions and could achieve high drug loading efficiencies.In vitro cellular uptake results suggested that Nile Red loaded polymeric micelles or polymersomes displayed more internalization after 24 h incubation than those after 4 h incubation.These findings suggest that polymeric micelles and polymersomes based on PCL-b-PEG-b-PCL copolymers have great potential to effectively delivery hydrophobic drugs.

Recent progress on DNA block copolymer

DNA has gained great attention because of its unique structure,excellent molecular recognition property,and biological functions.When married with versatile synthetic polymers,the DNA conjugated polymer hybrids,known as DNA block copolymers（DBCs）,have been launched and well developed for the syntheses of new materials and nanostructures with different functions in the past several decades.Compared to conventional synthetic block copolymers,using DNA as a building block provides several advantages over other polymer candidates,such as molecular recognition,programmable self-assembly,biocompatibility,and sequence-encoded information.In this review,recent developments in this area will be summarized and meaningful breakthroughs will be highlighted.We will discuss representative examples of recent progress in the syntheses,structure manipulations,and applications of DBCs.

Morphology and Thermoresponsive Behavior of Hybrid Micelles of Polystyrene-b-Poly((N-isopropyl acrylamide)-co-(4-vinylbenzyl chloride)) with Prussian Blue

The hybrid micelles of polystyrene-b-poly（（N-isopropyl acrylamide）-co-（4-vinylbenzyl chloride）） block copolymer（PS-b-P（NIPAM-co-VBC）） with Prussian blue（PB） in the corona were prepared by reaction of pentacyano（4-（dimethylamino）-pyridine）ferrate（Fe-DMAP）-attached PS-b-P（NIPAM-co-VBC） with Fe Cl3. The formation of the PB framework inside the micelles was verified by UV-Vis, FTIR and TGA. The morphology of the hybrid micelles was studied by TEM and compared with that of the neat and Fe-DMAP-attached PS-b-P（NIPAM-co-VBC）. It is found that attachment of Fe-DMAP may change the short rod-like micelles of the neat PS-b-P（NIPAM-co-VBC） into spherical ones and lead to a smaller micelle size. The morphology of the hybrid micelles may be altered or remain unchanged after formation of the PB framework, depending on the chain structure of PS-b-P（NIPAM-co-VBC） and starting concentration. The thermoresponsive behavior of different micelles was studied using DLS. It is observed that attachment of Fe-DMAP can improve the hydrophilicity of the P（NIPAM-co-VBC） block, leading to weaker hysteresis of the micelle size during the heating and cooling cycle. However, the crosslinked PB framework in the micellar corona may result in a more evident hysteresis phenomenon and blur the two-stepwise change of the micellar size with temperature.

A Dual Ligand Targeted Nanoprobe with High MRI Sensitivity for Diagnosis of Breast Cancer

Antibody targeted delivery is an effective strategy to improve the diagnostic imaging outcome of nanoscale imaging agents in the focal areas. Dual targeting micelles encapsulating superparamagnetic iron oxide were prepared from the amphiphilic block copolymer poly（ethylene glycol）-poly（e-caprolactone） （PEG-b-PCL） with different targeting ligands cRGD and scFv-ErbB single chain antibody conjugated to the distal ends of PEG block. The breast cancer animal model was established by subcutaneous injecting the BT474 cells into the BALB/c-nu female nude mice and then employed to assess the potential of the dual ligand targeted magnetic micelles as a novel MRI contrast agent on a 1.5 T clinical MR/scanner. The T2 signal intensity of the tumor in animals receiving the dual ligand targeted magnetic micelles via tail vein decreased more significantly than the single ligand targeted and nontargeted magnetic micelles. These results indicate that the dual ligand targeted magnetic micelles, cRGD/scFv-ErbB-PEG-PCL-SPION, have great potential to act as a new type of effective nanoscale MRI contrast agent for early diagnosis of breast cancer.