Synthesis and Characterization of Triptych μ-ABC Star Triblock Copolymers

Solution self-assembly of fluorinated polymers, an overview

The incorporation of fluorinated moieties into a polymer can confer unique properties and often lead in solution to original morphologies endowed with rare properties.

Polyphilicity-An Extension of the Concept of Amphiphilicity in Polymers

Recent developments in synthetic pathways as simple reversible-deactivation radical polymerization (RDRP) techniques and quantitative post-polymerization reactions, most notoriously 'click' reactions, leading to segmented copolymers, have broadened the molecular architectures accessible to polymer chemists as a matter of routine. Segments can be blocks, grafted chains, branchings, telechelic end-groups, covalently attached nanoparticles, nanodomains in networks, even sequences of random copolymers, and so on. In this review, we describe the variety of the segmented synthetic copolymers landscape from the point of view of their chemical affinity, or synonymous philicity, in bulk or with their surroundings, such as solvents, permeant gases, and solid surfaces. We focus on recent contributions, current trends, and perspectives regarding polyphilic copolymers, which have, in addition to hydrophilic and lipophilic segments, other philicities, for example, towards solvents, fluorophilic entities, ions, silicones, metals, nanoparticles, and liquid crystalline moieties.

Synthesis of pH-responsive β-CD-based star polymer and impact of its self-assembly behavior on pectinase activity

A novel type of pH-responsive star polymer based on β-cyclodextrin (β-CD) was synthesized and further covalently conjugated with enzyme. The impact of its self-assembly behavior on enzyme activity was investigated. In our design, azide containing the polymer (N₃ )₇ -β-CD-(PtBA)₁₄ was synthesized via atom transfer radical polymerization of tert-butyl acrylate using (N₃ )₇ -β-CD-(Br)₁₄ as the multifunctional initiator. The final product (N₃ )₇ -β-CD-(PAA)₁₄ was obtained via hydrolysis and covalently conjugating pectinase onto pH-responsive polyacrylic acid (PAA) arms. PAA can change its conformation with the self-assembly by altered pH, leading its nanostructure into micellar nanoparticles in aqueous solution and further affecting the activity of immobilized pectinase. The results were proved by fluorescence spectroscopy and dynamic light scattering. This system proves that the activity of immobilized enzyme can be tailored predictably, and this pH-responsive polymer holds great potential for controllable delivery of enzymes.

Synthesis of ABB′ and ABC star copolymers via a combination of NMRP and ROP reactions

Well-defined miktoarm star copolymers (ABB′ and ABC) were synthesized via a combination of NMRP and ROP using N-(2-hydroxyethyl)maleimide as the branching molecule.

Dual responsive macroemulsion stabilized by Y-shaped amphiphilic AB2 miktoarm star copolymers

Y-shaped amphiphilic PS–(PDMAEMA)₂ miktoarm star copolymers stabilized o/w macroemulsion showed pH-induced demulsification and thermo-induced phase inversion.

New polymethylene-based AB2 star copolymers synthesized via a combination of polyhomologation of ylides and atom transfer radical polymerization

Polymethylene-based AB₂ star copolymers were synthesized. PM-b-(PS)₂ porous films and particles were fabricated via static breath-figure process and electrospraying, respectively.

Synthesis and self-assembly of a novel fluorinated triphilic block copolymer

The morphological evolution of triphilic copolymer P(MMA-co-MAA)-b-PFEMA aggregates self-assembling in DMF/H₂O solutions with an increase in water content.

Synthesis of an amphiphilic PEG-PCL-PSt-PLLA-PAA star quintopolymer and its self-assembly for pH-sensitive drug delivery

A novel amphiphilic ABCDE-type star quintopolymer was achieved via modular synthesis and self-assembled into polymersomes for stimuli-triggered drug release.

Thermo, pH and reduction responsive coaggregates comprising AB2C2 star terpolymers for multi-triggered release of doxorubicin

Novel disulfide-linked PEG(PCL)₂(PNIPAM)₂ and PEG(PCL)₂(PAA)₂ star terpolymers were synthesized and coassembled into mixed micelles or vesicles for multi-triggered drug release.

The effects of polymeric nanostructure shape on drug delivery

Amphiphilic polymeric nanostructures have long been well-recognized as an excellent candidate for drug delivery applications. With the recent advances in the "top-down" and "bottom-up" approaches, development of well-defined polymeric nanostructures of different shapes has been possible. Such a possibility of tailoring the shape of the nanostructures has allowed for the fabrication of model systems with chemically equivalent but topologically different carriers. With these model nanostructures, evaluation of the importance of particle shape in the context of biodistribution, cellular uptake and toxicity has become a major thrust area. Since most of the current polymeric delivery systems are based upon spherical nanostructures, understanding the implications of other shapes will allow for the development of next generation drug delivery vehicles. Herein we will review different approaches to fabricate polymeric nanostructures of various shapes, provide a comprehensive summary on the current understandings of the influence of nanostructures with different shapes on important biological processes in drug delivery, and discuss future perspectives for the development of nanostructures with well-defined shapes for drug delivery.

Functional Polyether-based Amphiphilic Block Copolymers Synthesized by Atom-transfer Radical Polymerization

This review deals with the synthesis, physical properties, and applications of amphiphilic block copolymers based on hydrophilic poly(ethylene oxide) (PEO) or hydrophobic poly(propylene oxide) (PPO). Oligomeric PEO and PPO are frequently functionalized by converting their OH end groups into macroinitiators for atom-transfer radical polymerization. They are then used to generate additional blocks as part of complex copolymer architectures. Adding hydrophobic and hydrophilic blocks, respectively, leads to polymers with amphiphilic character in water. They are surface active and form micelles above a critical micellization concentration. Together with recent developments in post-polymerization techniques through quantitative coupling reactions (‘click’ chemistry) a broad variety of tailored functionalities can be introduced to the amphiphilic block copolymers. Examples are outlined including stimuli responsiveness, membrane penetrating ability, formation of multi-compartmentalized micelles, etc.

Multicompartment micelle morphology evolution in degradable miktoarm star terpolymers

Multicompartment micelles with segmented wormlike structures consisting of alternating poly(ethylethylene) (PEE) and poly(gamma-methyl-epsilon-caprolactone) (PMCL) layers were formed upon dispersing samples of micro-[PEE][poly(ethylene oxide)][PMCL] (micro-EOC) miktoarm star block terpolymers in neutral water. Subjecting these dispersions to a pH 12 aqueous buffer at 50 degrees C led to the hydrolytic degradation of the PMCL chains. After 4 weeks, the majority of the micro-EOC molecules were degraded into PEE-b-poly(ethylene oxide) (EO) diblocks and PMCL homopolymers. Although the resulting EO diblocks were expected to assemble into simple cylindrical micelles, the actual "daughter micelle" morphologies were much richer. The initial segmented wormlike micelles evolved into raspberry-like vesicle structures composed of spherical PMCL subdomains embedded in a PEE matrix. This dramatic change in the morphology of the multicompartment micelles is due to rearrangement of micro-EOC/EO/PMCL composite micelles to a structure that minimizes unfavorable interfacial interactions between the three mutually immiscible polymers. This type of micelle-to-micelle morphological evolution induced by block degradation in a miktoarm star terpolymer system holds promise for the development of "smart" delivery capabilities.

Multicompartment micelles from pH-responsive miktoarm star block terpolymers

We describe the synthesis of pH-responsive miktoarm star block terpolymers mu-[polystyrene][poly(ethylene oxide)][poly(2-(dimethylamino)ethyl acrylate)] (mu-SODA) using a combination of two successive living anionic polymerizations and one reversible addition-fragmentation chain-transfer polymerization. Poly[2-(dimethylamino)ethyl acrylate] (PDMAEA) is a weak polybase that is hydrophilic at low pH and hydrophobic at high pH because of the protonation of the dimethylamino functional group with decreasing pH. In addition, our results suggest that PDMAEA is immiscible with polystyrene (PS), a feature that is desirable for the formation of multicompartment micelles. Using a combination of dynamic light scattering and cryogenic transmission electron microscopy, we demonstrate that mu-SODA micelles formed in water evolve from mixed corona (PEO + PDMAEA corona; PS core) and predominantly spherical micelles to multicompartment (PEO corona; PS + PDMAEA core) micelles with increasing pH.