Polymerization‐Induced Self‐Assembly for the Synthesis of Poly( N , N ‐dimethylacrylamide)‐ b ‐Poly(4‐ tert ‐butoxystyrene) Particles with Inverse Bicontinuous Phases

Versatile morphology transition of nano-assemblies via ultrasonics/microwave assisted aqueous polymerization-induced self-assembly based on host-guest interaction

Nano-assemblies have wide applications in biomedicine, functional coatings, Pickering emulsifiers, hydrogels, and so forth. The preparation of assemblies mainly utilizes the polymerization-induced self-assembly (PISA) method, which can produce high-concentration nanoscale assemblies in one step. However, the initiation processes of most reported PISA are limited to thermal initiation. Here, we reported two green and efficient methods for synthesizing nano-assemblies with various morphologies using ultrasound (20 kHz)/ microwave (500 W) assisted aqueous-phase RAFT-PISA in 3 h and 1 h. Cyclodextrin (CD) and styrene (St) nucleating monomer were complexed in a 1:1 ratio. Then, using Poly (ethylene glycol) methyl ether as the macromolecular reversible addition-fragmentation chain transfer (RAFT) agent (PEG-CTA) to control the CD/St complexes, the conversion rate of St monomer was respectively 27 %-60 %, 20 %-30 % within 3 h and 1 h under ultrasonics/microwave assisted PISA. Results showed that the morphologies of the assemblies are not only related to the length of PS block, but also to the assistance types and the remaining monomer concentration. The results showed that only PEG45-b-PS90 and PEG45-b-PS241 assemblies prepared by ultrasonics assisted PISA form evolved lamellaes and vesicles (100 nm), which break through the limitation of kinetic freezing. But the ultrasonic reaction on morphology of assemblies is not all favourable. For one thing, it can promote the movement of particles; for another, it makes reverse morphology transformation and sphere is preferred morphology. Therefore, the main reason of morphology evolution is the remaining monomer concentration of PEG45-b-PS90 and PEG45-b-PS241 assemblies reaches to 55 %-65 %, which promoting the segment movement. The results showed that the morphology of the assemblies prepared by microwave assisted PISA changed from spherical micelles to short rods, and finally to vesicles (120-140 nm) as the length of hydrophobic PS block increases. The kinetic freezing problem was solved in microwave-assisted PISA due to the action of microwaves and more remaining monomer concentration. Both them can boost particles movement.

Formation of n-Hexane-in-DMF Nonaqueous Pickering Emulsions: ABC Triblock Worms versus AB Diblock Worms

Nonaqueous Pickering emulsions exhibit promising applications in many industrial areas but have been relatively less studied in the past. In this study, n-hexane-in-DMF nonaqueous Pickering emulsions stabilized by core cross-linked copolymer worms with mixed shells are demonstrated for the first time. Core cross-linked copolymer worms with mixed shells were prepared by seeded reversible addition-fragmentation chain transfer (RAFT) quasi-solution polymerization. Specifically, polystyrene-poly(4-vinylpyridine) (PS-P4VP) diblock copolymer worms were first prepared via RAFT-mediated dispersion polymerization in toluene under the given conditions using PS as both the macro-CTA and the stabilizer block. After the chemical cross-linking of P4VP cores, PS-P4VP diblock copolymer worms were chain-extended with LMA in DMF/toluene (1:9, weight ratio) mixed solvents, producing core cross-linked PS-P4VP-PLMA worms with PS/PLMA mixed shells. The as-prepared core cross-linked PS-P4VP-PLMA worms with mixed PS/PLMA shells were further utilized as Pickering emulsifiers for the generation of nonaqueous n-hexane-in-DMF Pickering emulsions. The emulsifying performances of mixed-shell copolymer worms were compared with those of their spherical and linear analogues with entirely identical chemical compositions as well as PS-P4VP diblock copolymer worm precursors, respectively.

One-Dimensional Helical Nanostructures from the Hierarchical Self-Assembly of an Achiral "Rod-Coil" Alternating Copolymer

The self-assembly of alternating copolymers (ACPs) has attracted considerable interest due to their unique alternating nature. However, compared with block copolymers, their self-assembly behavior has remained much less explored and their reported self-assembled structures are limited. Here, we report the formation of supramolecular helical structures by the self-assembly of an achiral rod-coil alternating copolymer, poly(quarter(3-hexylthiophene)-alt-poly(ethylene glycol)) (P(Q3HT-alt-PEG)). The copolymer exhibited an interesting hierarchical self-assembly process, driven by the π-π stacking of the Q3HT segments and the solvophobic interaction of the alkyl chains in tetrahydrofuran (THF)-isopropanol (iPrOH) mixed solvents. The copolymer first self-assembled into thin nanobelts with a uniform size, then grew to helical nanoribbons and eventually twisted into helical nanowires with an average diameter of 25 ± 9 nm and a mean pitch of 80 ± 10 nm. Dissipative particle dynamics (DPD) simulation supported the formation course of the helical nanowires. Furthermore, the addition of (S)-ethyl lactate and (R)-ethyl lactate in the self-assembly of P(Q3HT-alt-PEG) resulted in the formation of left-handed and right-handed chiral nanowires, respectively, demonstrating the tunability of the chirality of the helical wires. This study expands the library of ordered self-assembled structures of ACPs, and also brings a new strategy and mechanism to construct helical supramolecular structures. This article is protected by copyright. All rights reserved.

RAFT-mediated polymerization-induced self-assembly (RAFT-PISA): current status and future directions

Polymerization-induced self-assembly (PISA) combines polymerization and self-assembly in a single step with distinct efficiency that has set it apart from the conventional solution self-assembly processes. PISA holds great promise for large-scale production, not only because of its efficient process for producing nano/micro-particles with high solid content, but also thanks to the facile control over the particle size and morphology. Since its invention, many research groups around the world have developed new and creative approaches to broaden the scope of PISA initiations, morphologies and applications, etc. The growing interest in PISA is certainly reflected in the increasing number of publications over the past few years, and in this review, we aim to summarize these recent advances in the emerging aspects of RAFT-mediated PISA. These include (1) non-thermal initiation processes, such as photo-, enzyme-, redox- and ultrasound-initiation; the achievements of (2) high-order structures, (3) hybrid materials and (4) stimuli-responsive nano-objects by design and adopting new monomers and new processes; (5) the efforts in the realization of upscale production by utilization of high throughput technologies, and finally the (6) applications of current PISA nano-objects in different fields and (7) its future directions.

Recent Progress in Polymer Cubosomes and Hexosomes

Polymer cubosomes and hexosomes are polymer colloids with inverted lyotropic liquid crystal phases as internal structures. They are composed of regular networks of water-filled channels surrounded by a bilayer membrane made from amphiphilic block copolymers. Due to the uniform, tunable, and highly ordered porous structure, polymer cubosomes and hexosomes present numerous advantages over polymer micelles and vesicles, such as the high loading volumes for both hydrophilic and hydrophobic substances, large specific surface areas, and good mechanical and chemical stabilities. The polymer chemistry also enables unlimited molecular design to endow these polymer colloids with a lot of adjustable physical and chemical properties. Therefore, polymer cubosomes and hexosomes have attracted increasing attention for their potential applications in materials science and nanotechnology. This review outlines the recent progress in this field with an emphasis on the polymer architectures, the self-assembly conditions and mechanisms, and some application examples which are special for these inverted polymer colloids. It is hoped to provide some practical guidance for researchers interested in polymer cubosomes and hexosomes.

Dual Role of Doxorubicin for Photopolymerization and Therapy

In this study, we report dual roles for doxorubicin (DOX), which can serve as an antitumor drug as well as a cocatalyst for a photoliving radical polymerization. DOX enhances the polymerization rates of a broad range of monomers, including acrylamide, acrylate, and methacrylates, allowing for high monomer conversion and well-defined molecular weights under irradiation with a blue light-emitting diode light (λ_max = 485 nm, 2.2 mW/cm²). Utilizing this property, the photopolymerization of N,N-diethylacrylamide was performed in the presence of a poly(oligo(ethylene glycol) methyl ether acrylate) macroreversible addition-fragmentation chain transfer (macroRAFT) agent to prepare polymeric nanoparticles via aqueous polymerization-induced self-assembly (PISA). By varying the monomer:macroRAFT ratio, spherical polymeric nanoparticles of various diameters could be produced. Most notably, DOX was successfully encapsulated into the hydrophobic core of nanoparticles during the PISA process. The DOX-loaded nanoparticles were effectively uptaken into tumor cells and significantly inhibited the proliferation of tumor cells, demonstrating that the DOX bioactivity was not affected by the polymerization reaction.