Self-assembly Of Random Copolymers Research Articles

Core-Corona Micelles Formed by Self-Assembly of Random Copolymer and Homopolymer Mixtures: Dissipative Particle Dynamics Simulations

Dissipative particle dynamics simulation was applied to investigate the cooperative aggregation of amphiphilic random copolymer and homopolymer mixtures in selective solvents. The amphiphilic random copolymers were set to contain more hydrophilic segments. The effects of the contents of homopolymers, the chain length of amphiphilic random copolymers, the interaction parameters, as well as the simulation time, on the cooperative aggregation were systematically studied with dissipative particle dynamics simulation method. The results showed that core-corona micelles could be formed with the addition of homopolymers, where the homopolymers accumulate at the core and the amphiphilic random copolymers as the corona. This work demonstrated that the morphology and the size of the micelles could be tuned by the controlled addition of homopolymers in the process of self-assembly.

ChemInform Abstract: Self‐Assembly of Random Copolymers

AbstractReview: 134 refs.

Self-assembly of random copolymers.

Self-assembly of random copolymers has attracted considerable attention recently. In this feature article, we highlight the use of random copolymers to prepare nanostructures with different morphologies and to prepare nanomaterials that are responsive to single or multiple stimuli. The synthesis of single-chain nanoparticles from random copolymers and their potential applications are also discussed in some detail. We aim to draw more attention to these easily accessible copolymers, which are likely to play an important role in translational polymer research.

Synthesis via RAFT polymerization of thermo- and pH-responsive random copolymers containing cholic acid moieties and their self-assembly in water

Here we report the design and synthesis of polymers containing cholic acid pendant groups, a major bile acid synthesized in the liver from cholesterol. Random copolymers derived from 2-(methacryloyloxy)ethyl cholate (MAECA) with polyethylene glycol methyl ether methacrylate (PEGMA) and N,N-dimethylaminoethyl methacrylate (DMAEMA) have been synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. Compositions of co-monomers in the copolymers were determined by 1H NMR spectroscopy, which were further used to determine reactivity ratios of the monomers using the extended Kelen–Tudos method at high conversions. Copolymers from MAECA with PEGMA (P(MAECA-co-PEGMA)) series displayed lower critical solution temperatures (LCSTs) up to 23% MAECA content in the copolymer, which was studied by UV-visible spectroscopy. Both thermo- and pH-responsiveness were observed for the P(MAECA-co-DMAEMA) copolymers with an MAECA unit in the copolymer up to 11.8%. The critical aggregation concentration (CAC) of water soluble copolymers was determined by fluorescence spectroscopy. Self-assembly of random copolymers was investigated by 1H NMR spectroscopy, dynamic light scattering (DLS), atomic force microscopy (AFM) and scanning electron microscopy (SEM), which indicated micellar structures in water from cholic acid based random copolymers. The polymeric aggregates were further explored for their drug encapsulation capabilities in aqueous medium using nile red as a hydrophobic model compound.

Surface Hydrophilicity of Spherical Micelle from Self-Assembly of Random Copolymer: A Dissipative Particle Dynamics Simulation

Coarse-grained models with different ratios of numbers of hydrophilic particles to hydrophobic particles were built for amphiphilic random copolymers. The surface hydrophilicity of spherical micelles formed from self-assembly of amphiphilic random copolymers in solution was investigated via dissipative particle dynamics (DPD) simulations. The simulations showed that solid spherical micelles are formed from self-assembly of amphiphilic random copolymers in selective solvents. The surface hydrophilicity of spherical micelles is related to the content of hydrophilic particles and selectivity of the solvent. The surface hydrophilicity of spherical micelles increases with increasing content of hydrophilic particles. In addition, the surface hydrophilicity of spherical micelles increases with the increase of the repulsion parameters between hydrophobic particles and solvent, which is in good agreement with the experimental results. These findings can provide theoretical guidance for molecular design and experimental studies on self- assembly of amphiphilic random copolymers in solution.

Facile synthesis of nanoparticles via assembly of photopolymerized and self-crosslinked random copolymers in selective organic media

We report the facile synthesis of vesicular nanoparticles via self-assembly of random copolymers in selective organic solvents. The polymers were synthesized via photopolymerization in bulk from acryloyl chloride (AC) containing a small amount of hydrolyzed acrylic acid (AA) at ambient condition. Fourier transform infrared spectroscopy of the photopolymerized product revealed two main chemical components: poly(acryloyl chloride) (PAC) and acid anhydride. The later peak intensified when increasing the initial AA composition in the monomer solution, suggesting that the hydrolyzed AC contributed to the formation of crosslinked anhydride, leading to amphiphilicity of the polymer with solvophobic anhydride and solvophilic PAC chains. At an optimal UV dosage (2000 mJ cm−2), vesicular nanoparticles (∼90 nm in diameter) were obtained from polymers assembled in acetone. The particle size and morphology were confirmed by scanning electron microscopy, transmission electron microscopy, and dynamic and static light-scattering measurements. Further, we found that the random copolymers self-organized into vesicles in merely good solvents of PAC chains, including acetonitrile, tetrahydrofuran, and 1,4-dioxane, but became aggregated and precipitated out in poor solvents of PAC, such as isopropanol, ethanol, toluene, xylene, and hexane. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Nanospheres Prepared by Self-Assembly of Random Copolymers in Supercritical Carbon Dioxide

The synthesis of spherical particles was attained by the direct self-assembly of poly[2-(perfluorooctyl)ethyl acrylate-random-acrylic acid], P(POA-r-AA), and by the indirect self-assembly poly[POA-random-2-(dimethylamino)ethyl acrylate], P(POA-r-DAA), with dicarboxylic acids in supercritical carbon dioxide (scCO2). The copolymers formed spherical particles with hundreds of nanometer diameters in a heterogeneous state at pressures lower than the cloud point pressure. The formation of spherical particles was also dependent on the temperature. The formation of spherical particles could be optimized through varying the solvent quality by the manipulation of the CO2pressure and temperature for the different copolymer compositions. The dynamic light scattering and1H NMR studies demonstrated that the nanospheres had the micellar structures consisting of the CO2-philic POA shells and the CO2-phobic AA or DAA cores including the main chain cores. The nanospheres produced the superhydrophobic surfaces based on the water-proof shells of the POA units.