Amphiphilic Arms Research Articles

Facile Synthesis of Fluorinated Polyacrylate Elastomer via Emulsion Polymerization Using Adjustable Amphiphilic Star Macro‐RAFT Agent as Surfactant

AbstractNovel thermoplastic fluorinated polyacrylate films possessing excellent mechanical performance are prepared by emulsion polymerization latex using adjustable amphiphilic star macro‐reversible addition‐fragmentation chain‐transfer (macro‐RAFT) agent as surfactants in this work. First, star macro‐RAFT agent equipped with six amphiphilic arms is synthesized via two‐step RAFT polymerization of acrylic acid (AA) and 2,2,2‐trifluoroethyl acrylate (TFEA) in the presence of hexa‐functional RAFT agents. The surface activities of the as‐synthesized amphiphilic star macro‐RAFT agents in aqueous solutions are studied. Subsequently, various fluorinated polyacrylate latexes are obtained by conducting emulsion polymerization of 2,2,3,4,4,4‐hexafluorobutyl acrylate (HFBA) and butyl acrylate (BA) using the amphiphilic star macro‐RAFT agents as both RAFT agents and surfactants. The latex particle morphologies are studied by transmission electron microscope (TEM) and particle size is measured by dynamic light scattering (DLS). The effects of PAA segment length, HFBA/BA mole ratio, and TFEA segment length on the surface morphologies of the fluorinated polyacrylate films are illustrated by investigating the surface properties using water contact angle test and atomic force microscopy (AFM). Finally, the elastomeric films obtained by directly casting the prepared fluorinated polyacrylate latexes show excellent comprehensive properties such as tensile strength over 4 MPa, elongation at break ≈700%, permanent deformation below 25%. Water absorption test is also provided as a reference.

UV-cleavable unimolecular micelles: synthesis and characterization toward photocontrolled drug release carriers

UV-cleavable star polymers composed of a well-defined 6-arm amphiphilic block copolymer and a UV-cleavable core with photolabile o-nitrobenzyl groups have been synthesized and characterized. The core of the star polymer is a cyclotriphosphazene, which can biodegrade to phosphate and ammonium ion. The resultant unimolecular micelles can be dissociated in a controlled manner by UV irradiation. The inner lipophilic poly(methyl methacrylate) (PMMA) and the outer hydrophilic poly[poly(ethylene glycol) methyl ether methacrylate] (PPEGMA) were grafted by atom transfer radical polymerization (ATRP), leading to the formation of star-PMMA-PPEGMA with different compositions. The effects of various factors, such as molecular weight, solution concentration, solvents (THF, toluene, and water) and monomers (MMA, PEGMA, and 2-(dimethylamino)ethyl methacrylate (DMA)) on the photodegradation rate of the star polymers were studied by gel permeation chromatography (GPC). The micellar behavior of star-PMMA-PPEGMA was unambiguously demonstrated by dynamic light scattering (DLS), fluorescence techniques and transmission electron microscopy (TEM). The formation of nanoparticles (star-AGG) from the aggregation of the two star-PMMA-PPEGMA polymer micelles in aqueous solution was detected by DLS with hydrodynamic radii of 86 and 111 nm. The critical aggregation concentration (CAC) of star-AGG-2 from star-PMMA179-PPEGMA89-2 was 0.0026 g L−1 and 0.022 g L−1 before and after UV-irradiation indicating the reduced stability of the polymer micellar structures after UV-irradiation due to the detachment of the amphiphilic arms from the cyclotriphosphazene core. As a result, spontaneous dissociation of cleaved micelles can be induced by the dilution effect in the human body for stimulus-controlled drug release.

Nonionogenic star-shaped calix[8]arenes: Synthesis and ionophore properties

New approach to the synthesis of star-shaped polymers based on calix[8]arene with amphiphilic arms of nonionogenic nature is described. The ionophore properties of the resulting polymer with respect to ions of alkali metals, europium, and uranium were studied by an example of a polymer containing residues of ω-cetyloligoethylene oxide as arms.

Synthesis and micellization of star-like hyperbranched polymer with poly(ethylene oxide) and poly(ε-caprolactone) arms

Novel star-like hyperbranched polymers with amphiphilic arms were synthesized via three steps. Hyperbranched poly(amido amine)s containing secondary amine and hydroxyl groups were successfully synthesized via Michael addition polymerization of triacrylamide (TT) and 3-amino-1,2-propanediol (APD) with feed molar ratio of 1:2. H-1, C-13, and HSQC NMR techniques were used to clarify polymerization mechanism and the structures of the resultant hyperbranched polymers

Amphiphilicity-Driven Organization of Nanoparticles into Discrete Assemblies

We present a method for organizing metallic nanoparticles in solution that is based on the hydrophobic effect and does not require either hydrogen bonding or molecular recognition. When amphiphilic V-shaped molecules are attached to a gold cluster, an aggregation process ensues in aqueous solution and leads to the formation of well-defined cylindrical and vesicular nanoarrays of particles. The metallic clusters densely pack at the boundary separating the hydrophobic core from the hydrophilic corona of the hybrid micelle-like aggregates. This design allows one to assemble and disassemble the nanoparticles in a reversible manner and control the size and the morphology of the arrays by changing the conditions of the solution preparation. The versatility of this method is demonstrated by its applicability to different metals with covalently attached amphiphilic arms with various chemical compositions (PS-PEO and PB-PEO) and molecular weights.

Starlike Block Copolymers with Amphiphilic Arms as Models for Unimolecular Micelles

Starlike Block Copolymers with Amphiphilic Arms as Models for Unimolecular Micelles