Search results for "Radical polymerization"

Dispersion polymerization of vinyl monomers in supercritical carbon dioxide in the presence of drug molecules: A one-pot route for the preparation of…

2008

The polymerization of 1-vinyl-2-pyrrolidone in supercritical carbon di- oxide in the presence of ibuprofen as a model drug was investigated as a new one-pot process for the preparation of polymer-based drug delivery systems (DDSs). The com- posites were prepared at 65 � C and P ¼ 31-42 MPa by changing the initial con- centration of the drug and the concentration of a crosslinking agent and that of a hydrophobic comonomer. The effects of these parameters on the performances of the polymerization and on the in vitro release kinetics of ibuprofen were studied. In all the experiments, part of the drug was entrapped inside the polymer particles and dissolved more slowly with respect to the pure …

Liquid-Crystalline Colloidal Particles

2004

Here we report about the synthesis of colloidal particles of nematic and smectic liquid-crystalline polymers. For this purpose mesogen-containing acrylate monomers were synthesized and polymerized in a special modification of a precipitation polymerization called dispection polymerization. By variation of the polymerization conditions colloidal particles of different size and polydispersity could be obtained including very narrowly distributed samples in optimized batches. On azobenzene-containing colloidal particles switching experiments with polarized light were performed. It could be observed that the nematic director of the mesogens within the colloidal particles can be rotated due to t…

Synthesis of Liquid-Crystalline Colloids in Nonpolar Media and their Manipulation in Electric Fields

2009

The first synthesis of anisotropic liquid-crystalline colloids in silicone oil by a direct (radical) polymerization of a monomer in THF/silicone oil mixtures with the help of siloxane containing stabilizers is described. The size of the colloids is in the lower μm range and can be adjusted by varying the mixture. The resulting colloids show a bipolar director configuration if they are small (<1.5 μm) and a radial configuration if they are larger. The colloids are sterically stabilized, and, due to the nonpolarity of the solvent, the disturbing effects of migrating ions are excluded and experiments in the electric field can be conducted. Both line formation in DC fields and a periodic switch…

Microflow Technology in Polymer Synthesis

2012

Microflow technology, i.e., the use of microfluidic devices for continuous flow synthesis, represents a highly useful and increasingly popular method in organic chemistry. Recently, also an increasing number of polymer synthesis protocols attain benefit from this technique. In particular, the control of highly exothermic, fast polymerization reactions can be improved due to the excellent heat and mass transfer within the small dimensions of the microreactors. Continuous flow setups with different micromixer geometries and flow patterns are currently used for the preparation of a variety of macromolecular architectures by ionic and (controlled) radical polymerization techniques. This Perspec…

New Photosensitive Polymers:  Synthesis and Free Radical Polymerization of Oxypyridinium and Oxyisoquinolinium Functionalized Methacrylate and Styren…

2002

Polymerizable hydroxypyridinium and hydroxyisoquinolinium salts 1a−4a, 2d, and 3d have been prepared from vinylbenzyl chloride or glycidyl methacrylate and 3-hydroxypyridine (2), 4- or 5-hydroxyisoquinoline (1, 3), and 8-hydroxyquinoline (4). Radical homo- and copolymerization with styrene or methyl methacrylate of the salts 1a−3a, 2d, and 3d produced (co)polymers 1e, 2e, 2f, 3f, 1g, 2g, 2h, and 3h. The photosensitive dipolar oxypyridinium or oxyisochinolinium betaine structures were generated in solutions with triethylamine from the low molecular weight and polymeric salt precursors. For the model compounds 1b−4b and (co)polymers 1e, 2e, 2f, 3f, 1g, 2g, 2h, and 3h, the degradation of the l…

From Defined Reactive Diblock Copolymers to Functional HPMA-Based Self-Assembled Nanoaggregates

2008

This paper describes the synthesis of functional amphiphilic poly( N-(2-hydroxypropyl) methacrylamide)-block-poly(lauryl methacrylate) copolymers by RAFT polymerization via the intermediate step of activated ester block copolymers (pentafluoro-phenyl methacrylate). Block copolymers with molecular weights from 12000-28000 g/mol and PDIs of about 1.2 have been obtained. The amphiphilic diblock copolymers form stable super structures (nanoaggregates) by self-organization in aqueous solution. The diameters of these particles are between 100 and 200 nm and depend directly on the molecular weight of the block copolymer. Furthermore, we investigated the impact of these nanoaggregates on cell viabi…

Magnetic Molecular Rectangles Constructed from Functionalized Nitronyl‐Nitroxide Ligands and Lanthanide(III) Ions

2020

Metal complexes of a picolinate-based nitronyl nitroxide free radical.

2009

A nitronyl nitroxide free radical containing an appended picolinate moiety was synthesized. The resulting tridentate ligand picNN forms neutral mononuclear metal complexes of formula [M(picNN)(2)].3H(2)O (M = Mn, Co, Ni, Zn). These compounds are isostructural and crystallize in the orthorhombic Pnna space group. The metal complexes have a C(2) symmetric structure, with the metal centers lying on the binary axis and surrounded by two equivalent picNN radicals. The magnetic properties of this family of compounds indicate the presence of very strong metal-radical exchange interactions, ranging from J(Ni-rad) = -193 cm(-1) to J(Mn-rad) = -98 cm(-1). Relatively weak (J(rad-rad) = -15 cm(-1)) thr…

A black-box approach to the construction of metal-radical multispin systems and analysis of their magnetic properties

2020

An interaction of M(hfac)2 (M = Mn or Ni) with N-(bis(4,4,5,5-tetramethyl-3-oxido-1-oxyl-4,5-dihydro-1H-imidazol-2-yl)methylene)-2-methyl-propan-2-amine oxide (a nitronyl nitroxide diradical with theC[double bond, length as m-dash]N(O)-tert-Bu coupler) was investigated under various conditions. It was found that prolongation of reaction time caused transformation of the initial diradical into new diradicals with the uniqueC[double bond, length as m-dash]N-OH coupling unit and formation of binuclear Mn(ii) and Ni(ii) complexes, which were characterized by X-ray diffraction analysis. The resulting binuclear heterospin complexes have a complicated magnetic structure with six paramagnetic cente…

Synthesis, crystal structures and magnetic properties of a P-stereogenic ortho-(4-amino-tempo)phosphinic amide radical and its CuII complex

2021

The synthesis of phosphinic amides containing one 4-amino-TEMPO substituent at the ortho position has been achieved through copper(I) catalyzed cross-coupling reactions of ortho-iodophosphinic amides with 4-amino-TEMPO. The method has been extended to the preparation of the first example of a P-stereogenic ortho-(4-amino-tempo)phosphinic amide radical 10. The reaction of 10 with Cu(hfac)2 afforded the P-stereogenic CuII complex 19. The crystal structure of both chiral compounds is reported. The molecular structure of 10 consists of a supramolecular zig-zag chain formed by intermolecular hydrogen bonds between the NH group of the phosphinic amide moiety and the nitroxide oxygen atom. In comp…