A pH-sensitive double [60]fullerene-end-capped polymers via ATRP: Synthesis and aggregation behavior

Precise synthesis of double-armed polymers with fullerene C60 at the junction for controlled architecture

We report the first successful synthesis of the polymer-attached 1,2-hydrofullerene and the double-armed 1,4-bisadducts in a regioselective manner via controlled radical reactions.

Hierarchical self-assembly of polyhedral oligomeric silsesquioxane end-capped stimuli-responsive polymer: from single micelle to complex micelle

Responsive polymeric micelles have been widely studied because of their potential use in nanocontainers and nanocarriers. In this study, polyhedral oligomeric silsesquioxane (POSS) end-capped poly[2-(dimethylamino)ethyl methacrylate] (POSS-PDMAEMA), a stimuli-responsive organic-inorganic hybrid polymer, was synthesized via atom transfer radical polymerization (ATRP) using POSS-Br as a macroinitiator. The self-assembly behaviors of POSS-PDMAEMA in aqueous solution were studied by fluorescence probe, transmission electron microscopy (TEM), dynamic light scattering (DLS), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). The results revealed two self-assembly processes of POSS-PDMAEMA. First they self-assembled into a single micelle with the POSS molecules forming a crystal core and the PDMAEMA chains stretching as a corona. Then the single micelles, as building blocks, were able to reversibly form a hierarchical micelle-on-micelle structure (complex micelle) under external stimuli.

Synthesis and self-assembly of stimuli-responsive poly(2-(dimethylamino) ethyl methacrylate)-block-fullerene (PDMAEMA-b-C60) and the demicellization induced by free PDMAEMA chains

Well-defined poly(2-(dimethylamino) ethyl methacrylate)-block-fullerene [60] ((PDMAEMA)-b-C(60)) with a galactose targeting moiety was prepared by atom-transfer radical polymerization (ATRP). This copolymer was designed for possible use as a targeted drug carrier. The chemical composition and the self-assembly behavior were characterized using different techniques, including GPC, NMR, UV, and DLS. The self-assembly of the galactose-functionalized PDMAEMA-b-C(60) structure in aqueous solutions was investigated using dynamic light scattering (DLS) under different pH conditions. At pH 3 and 10, the DLS results showed the presence of both polymeric micelles and unimers. However, a smaller R(h) was observed at pH 10 than at pH 3 because of electrostatic repulsion at low pH values. In addition, free PDMAEMA chains induced the demicellization of self-assembled nanostructures caused by the formation of a charge-transfer complex between PDMAEMA and C(60.) This phenomenon offers possible applications for free-polymer-triggered drug release.

New concepts and applications in the macromolecular chemistry of fullerenes

A new classification on the different types of fullerene-containing polymers is presented according to their different properties and applications they exhibit in a variety of fields. Because of their interest and novelty, water-soluble and biodegradable C(60)-polymers are discussed first, followed by polyfullerene-based membranes where unprecedented supramolecular structures are presented. Next are compounds that involve hybrid materials formed from fullerenes and other components such as silica, DNA, and carbon nanotubes (CNTs) where the most recent advances have been achieved. A most relevant topic is still that of C(60)-based donor-acceptor (D-A) polymers. Since their application in photovoltaics D-A polymers are among the most realistic applications of fullerenes in the so-called molecular electronics. The most relevant aspects in these covalently connected fullerene/polymer hybrids as well as new concepts to improve energy conversion efficiencies are presented.The last topics disccused relate to supramolecular aspects that are in involved in C(60)-polymer systems and in the self-assembly of C(60)-macromolecular structures, which open a new scenario for organizing, by means of non-covalent interactions, new supramolecular structures at the nano- and micrometric scale, in which the combination of the hydrofobicity of fullerenes with the versatility of the noncovalent chemistry afford new and spectacular superstructures.

Adsorption of Cr(VI) using silica-based adsorbent prepared by radiation-induced grafting

Silica-based adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto the silanized silica followed by a protonation process. The FTIR spectra and XPS analysis proved that DMAEMA was grafted successfully onto the silica surface. The resultant adsorbent manifested a high ion exchange capacity (IEC) of ca. 1.30 mmol/g and the Cr(VI) adsorption behavior of the adsorbent was further investigated, revealing the recovery of Cr(VI) increased with the adsorbent feed and the equilibrium adsorption could be achieved within 40 min. The adsorption capacity, strongly depended on the pH of the solution, reached a maximum Cr(VI) uptake (ca. 68 mg/g) as the pH was in the range of 2.5-5.0. Furthermore, even in strong acidic (4.0 mol/L HNO(3)) or alkaline media (pH 11.0), the adsorbent had a sound Cr(VI) uptake capacity (ca. 22 and 30 mg/g, respectively), and the adsorption followed Langmuir mode. The results indicated that this adsorbent, prepared via a convenient approach, is applicable for removing heavy-metal-ion pollutants (e.g. Cr(VI)) from waste waters.