Micellar morphologies of self-associated diblock copolymers in acetone solution

Magnetically Recyclable Nanoscale Zero-Valent Iron-Mediated PhotoRDRP in Ionic Liquid toward Smart, Functional Polymers

A facile method based on recyclable nanoscale zero-valent iron (nZVI)-mediated photoinduced reversible deactivation radical polymerization in ionic liquid (IL) leads to the synthesis of narrow disperse poly(tert-butyl methacrylate) (PTBMA), amphiphilic PTBMA-block-poly(poly(ethylene glycol)methacrylate) diblock copolymer and double hydrophilic poly(methacrylic acid)-block-poly(poly(ethylene glycol)methacrylate) (PMAA-b-PPEGMA) diblock copolymers thereof. Stimuli response of the synthesized PMAA-b-PPEGMA diblock copolymer against variation in pH and temperature is assessed. Recyclability of the nZVI (catalyst) and IL (solvent) is established. Polymerization may be switched ON or OFF, simply by turning the UVA light irradiation ON or OFF, offering temporal control. The diblock copolymer self-aggregates into spherical nanoaggregates which are employed for encapsulation of coumarin 102 (C102, a typical hydrophobic dye), describing their potential application in drug delivery applications. The facile synthesis strategy may open up new avenues for the preparation of intelligent functional polymers for engineering and biomedical applications.

Dual stimuli-responsive nano-structure transition of three-arm branched amphiphilic polymers containing ferrocene (Fc) and azobenzene (Azo) moieties in aqueous solution

Amphiphilic polymers can self-assemble into various nanostructures in solution, which can find applications in many fields such as nanotechnology, drug delivery, and template synthesis. Herein, we report the controlled self-assembly and dual stimuli-responsive nanostructure transition of a class of three-arm branched amphiphilic polymers (AzoFcPEO) containing ferrocene (Fc) and azobenzene (Azo) moieties in aqueous solution. These amphiphilic polymers were synthesized by an esterification reaction of a variety of polyethylene oxide methyl ethers (Me-PEO) with 3-(6-ferrocenyhexyloxyl)-5-(6-azobenzenehexyloxy) benzoic acid. Both the isomerization of Azo and redox of Fc moieties can respectively change the amphiphilicity of these polymers to different degrees. Consequently, these amphiphilic polymers in aqueous solution can self-assemble into various nanostructures, such as spherical micelle, worm-like micelle, spherical compound micelle, rod-like compound micelle and vesicle dependent on the PEO molecular weight, applied stimuli, and polymer concentration. This work can offer tremendous possibilities not only for the fundamental science of the controlled self-assembly but also for establishing a suitable method for regulating the nanostructures of amphiphilic polymers in aqueous solution.

Hierarchical Self-Assembled Structures from Diblock Copolymer Mixtures by Competitive Hydrogen Bonding Strength

In this work we prepared poly(styrene⁻b⁻vinylphenol) (PS-b-PVPh) by sequential anionic living polymerization and poly(ethylene oxide-b-4-vinylpyridine) (PEO-b-P4VP) by reversible addition fragmentation chain transfer polymerization (RAFT) by using poly(ethylene oxide) 4-cyano-4-(phenylcarbonothioylthio)pentanoate (PEO-SC(S)Ph) as a macroinitiator with two hydrogen bonded acceptor groups. When blending with disordered PEO-b-P4VP diblock copolymer, we found the order-order self-assembled structure transition from lamellar structure for pure PS-b-PVPh to cylindrical, worm-like, and finally to PEO crystalline lamellar structures. Taking the advantage of the ΔK effect from competitive hydrogen bonding strengths between PVPh/P4VP and PVPh/PEO domains, it could form the hierarchical self-assembled morphologies such as core⁻shell cylindrical nanostructure.

Hydrogen bonding strength effect on self-assembly supramolecular structures of diblock copolymer/homopolymer blends

The steric hindrance effect on the hydrogen bonding strength and self-assembly supramolecular structures of the PS-b-PVPh diblock copolymer when blended with P4VP and P2VP homopolymers was investigated.

Borinic acid block copolymers: new building blocks for supramolecular assembly and sensory applications

Borinic acid functional groups were incorporated into block copolymers via RAFT polymerization and their supramolecular assembly and sensor applications were investigated.

Fluorinated amphiphilic block copolymers via RAFT polymerization and their application as surf-RAFT agent in miniemulsion polymerization

Preparation of an amphiphilic block copolymer (Am-BCP) based on poly(ethylene glycol) methyl ether methacrylate (PEGMA) and heptafluorobutyl acrylate (HFBA) via RAFT polymerization and application of this Am-BCP as surf-RAFT agent for polymerization of styrene.

An Approach for the Sphere-to-Rod Transition of Multiblock Copolymer Micelles

The shape of polymer micelles is important for pharmaceutical applications as drug delivery. In this article, an approach inducing sphere-to-rod transition of multiblock polyurethane micelles has been developed through introducing a second hydrophilic component phosphatidylcholine group into the polymer chains. Time-resolved dynamic light scattering (DLS), combined with transmission electron microscopy (TEM), was employed to investigate the kinetics of morphology transition. Moreover, a dissipative particle dynamics (DPD) simulation method was applied to study the mechanism of sphere-to-rod transition. These experimental and simulation studies revealed that the hydrophilic phosphatidylcholine groups can create defects on the surfaces of spherical polyurethane micelles, thus, making positive contribution to adhesive collisions and leading to the fusion of spherical micelles into rod-like micelles. This finding provides new insight into the origins of rod-like polymer micelles, which is valuable for the design and preparation of novel polymeric drug carriers with tailored properties.

Biodegradable amphiphilic copolymer containing nucleobase: synthesis, self-assembly in aqueous solutions, and potential use in controlled drug delivery

Biodegradable nucleobase-grafted amphiphilic copolymer, the methoxyl poly (ethylene glycol)-b-poly (L-lactide-co-2-methyl-2(3-(2,3-dihydroxylpropylthio) propyloxycarbonyl)-propylene carbonate/1-carboxymethylthymine) (mPEG-b- P(LA-co-MPT)), was synthesized. (1)H NMR titration and FT-IR spectroscopy indicated that the hydrogen-bonding could be formed between mPEG-b-P(LA-co-MPT) and 9-hexadecyladenine (A-C16). The hydrophobic microenvironment of the amphiphilic copolymer can protect the complementary multiple hydrogen bonds between mPEG-b-P(LA-co-MPT) and A-C16 from water effectively. The addition of A-C16 not only lowered the critical aggregation concentration (CAC) of mPEG-b-P(LA-co-MPT)/A-C16 nanoparticles (NPs) in aqueous solution but also induced different morphologies, which can be observed by transmission electron microscopy (TEM). Meanwhile, dynamic light scattering (DLS) and turbidometry was utilized to evaluate the effect of temperature and pH change on the stability of mPEG-b-P(LA-co-MPT)/A-C16 NPs. Cytotoxicity evaluation showed good biocompatibility of the mPEG-b-P(LA-co-MPT)/A-C16 NPs. The in vitro drug release profile showed that with the increase of A-C16 content, the doxorubiucin (DOX) release at pH 7.4 decreased, while the faster release rate was observed with the addition of A-C16 with a pH of 5.0. Importantly, DOX-loaded NPs exerted comparable cytotoxicity against MDA-MB-231 cells. This work provided a new method to stabilize NP structure using hydrogen-bonds and would have the potential to be applied in controlled drug delivery.

On modulating the self-assembly behaviors of poly(styrene-b-4-vinylpyridine)/octyl gallate blends in solution state via hydrogen bonding from different common solvents

We have investigated the complexation-induced phase behavior of the mixtures of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) and octyl gallate (OG) due to hydrogen bonding in different solvents. The Fourier transform infrared spectroscopic result indicates that the hydrogen-bonding was formed between the P4VP blocks and OG in both THF and DMF, implying the P4VP blocks can bind to OG. For PS-b-P4VP/OG mixture in chloroform, the morphological transitions were induced from the unimer configuration to swollen aggregate and complex-micelles by adding OG. Interestingly, the complex-micelles can lead the formation of the honeycomb structure from chloroform solution. The PS-b-P4VP/OG mixture in THF, behaving an amphiphilic diblock copolymer in solution state, exhibited a series of morphological transitions from sphere, pearl-necklace-liked rod, worm-liked rod, vesicle, to core-shell-corona aggregates by increasing the OG content. In contrast, the PS-b-P4VP/OG mixture in DMF maintained the unimer configuration upon adding OG. Therefore, the complexation-induced morphology of the mixtures of PS-b-P4VP and OG can be mediated by adopting different common solvents to affect the self-assembly behavior.

Development of various PS-b-P4VP micellar morphologies: fabrication of inorganic nanostructures from micellar templates

We demonstrate a simple route for preparing various micellar nanostructures, like spheres, cylinders, and vesicles, by spin-coating or drop-casting process of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymer solutions in pure tetrahydrofuran (THF), THF/water, and THF/ethanol mixture. Upon drying, a solvent selectivity plays an important role in determining micellar nanostructures in thin films. In solution, micellar sizes and shapes of these PS-b-P4VP copolymers were investigated by dynamic and static light scattering. Immediately after spin-coating the polymer solutions, surface and internal morphologies of the films were observed by atomic force microscopy and transmission electron microscopy. As the polymer concentration in THF or the amounts of water or ethanol added in THF solutions was varied, a remarkable difference in the PS-b-P4VP micellar morphologies was observed, from which spherical or cylindrical or vesicular micelles were developed. These micellar films were used as scaffolds or templates for fabricating metal nanodots or nanowires arrays.

Self-assembly behavior of A-B diblock and C-D random copolymer mixtures in the solution state through mediated hydrogen bonding

We have synthesized poly(methyl methacrylate- b-4-vinylpyridine) (PMMA- b-P4VP) and poly(styrene- r-vinylphenol) (PS- r-PVPh) copolymers by using anionic and free radical polymerizations, respectively. Well-defined micelles through hydrogen bonding have been prepared by mixing PMMA- b-P4VP diblock copolymer and PS- r-PVPh random copolymer in a single solvent. Block copolymers were mixed with random copolymers, with various [N]/[OH] ratios (4/1, 2/1, 1/1, and 1/4) in which "[N]/[OH]" represents the molar ratio of pyridine groups on P4VP to hydroxyl groups on PVPh. The presence distribution of PVPh/P4VP and PVPh/PMMA hydrogen bonding depends on the feeding ratio of PVPh to P4VP. When the PVPh content is lower than that of P4VP, hydrogen bonding occurs only between PVPh and P4VP; with excess PVPh, additional hydrogen bonding between PVPh and PMMA would occur. Furthermore, the effect of the solvent quality on the self-assembly behavior of PMMA- b-P4VP/PS- r-PVPh blends is investigated by considering tetrahydrofuran (THF) and dimethylformamide (DMF) as common solvents. We can mediate the strength of hydrogen bonding in blend systems by adopting different solvents and inducing different morphology transitions.