Search results for "Radical polymerization"
showing 10 items of 184 documents
Liquid Crystalline Elastomers—Characterization as Networks
1994
Abstract This paper summarises the properties of archiral and chiral liquid crystalline (LC) elastomers, the latter of which have found interest due to their piezoelectric properties. In addition the formation of new LC elastomers by a radical polymerization of acrylate groups covalently linked to LC polymers was investigated. This was done concerning the progress of the crosslinking reaction, concerning the influence of the crosslinking on the LC phases and concerning the network properties (swelling ratio and elastic modulus) of the resulting elastomers. It turns out that the networks prepared in this way are very soft and their crosslinking density is low. This can be explained assuming …
Transfer to Polymer and Long-Chain Branching in PLP-SEC of Acrylates
2009
Pulsed laser polymerization (PLP) combined with size exclusion chromatography (SEC) is the method of choice for determining propagation rate coefficients. The influence of the long-chain branching in PLP-SEC is investigated using multiple-detection SEC and a recently developed method to detect long-chain branching [P. Castignolles, R. Grab, M. Parkinson, M. Wilhelm, M. Gaborieau, Polymer 2009, 50, 2373.] While little or no long-chain branching is detected in poly(n-butyl acrylate), the error in relevant molecular weights of poly(2-ethylhexyl acrylate) is large (30-100%) due to long-chain branching. Possible variations of propagation rate coefficient with alkyl groups in alkyl acrylates or w…
Synthesis of CO2-responsive polymers by post-polymerization modification
2014
Abstract We describe a general method to synthesize a double responsive polymer, exhibiting a temperature and CO 2 responsive behavior. The polymer derived from a controlled radical polymerization technique of pentafluorophenyl acrylate (PFPA), followed by a sequential post-polymerization modification of a CO 2 responsive- and thermo-responsive amines. Utilizing this approach three double responsive copolymers were synthesized, poly(3- N′,N′ -dimethylaminopropyl acrylamide- co - N -isopropyl acrylamide) (poly(DMPA- co -NIPAM)), poly( L -Arginine methyl ester acrylamide- co - N -isopropyl acrylamide) (poly(AME- co -NIPAM)) and poly( L -Arginine methyl ester acrylamide- co - N -cyclopropyl ac…
Versatile Responsive Surfaces via Hybrid Polymers Containing Acetal Side Groups
2009
Two hybrid polymers, poly(methylsilsesquioxane)-poly(2,2-diethoxyethyl acrylate) and poly-(methylsilsesquioxane)-poly(1,3-dioxolan-2-ylmethyl acrylate), were synthesized and used for preparation of stable surface coatings. Their acetal side groups could be functionalized via solution-dipping with different primary amines and hydroxylamines after acidic deprotection and thus allowed for flexible modification of the surface hydrophilicity. Functionalization with a thermo-responsive polymer resulted in a thermo-responsive surface with temperature-dependent contact angles. Further, the two types of acetals showed different stability toward acidic treatment and could be addressed independently.
Synthesis of hyperbranched poly(tert-butyl acrylate) by self-condensing atom transfer radical polymerization of a macroinimer
2000
Using 2-hydroxyethyl α-bromoisobuty-rate as initiator, atom transfer radical polymerization (ATRP) of tert-butyl acrylate leads to poly(tert-butyl acrylate) (PtBA) with a hydroxyl group at one and a bromine atom at the other end. Esterification of the hydroxyl group of these heterotelechelic polymers with acryloyl chloride yields PtBA (M n = 3060) with a polymerizable double bond at one end and a bromine atom at the other end which can act as an initiator in ATRP (macroinimer). Self-condensing ATRP of such a macroinimer leads to hyperbranched or highly branched PtBA. The polymer was characterized by GPC viscosity measurements. Even at M w = 78800, a rather low polydispersity index of M w M …
Solution Properties and Potential Biological Applications of Zwitterionic Poly(ε-N-methacryloyl-l-lysine)
2013
Poly(e-N-methacryloyl-l-lysine) (PMALys) was synthesized by free radical polymerization yielding a zwitterionic polymer with Mw = 721 000 g mol–1. The polymer dissolves in pure water as well as in aqueous salt solution up to 5 M NaClO4 and over wide range of pH values (1.3 ≤ pH ≤ 12.7) as single chains without any sign for aggregate formation. The zwitterionic polymer shows an expanded random coil structure at and close to isoelectric conditions and further expands upon addition of acid and base, respectively. The polymer fulfills four major prerequisites for a promising nano carrier in potential biomedical applications: (1) It is biocompatible, indicated by a low cytotoxicity. (2) It does …
Structural Characterization of Glycoconjugate Polystyrene in Aqueous Solution
1999
Maltopentaose-carrying polystyrene was synthesized by the homopolymerization of vinylbenzyl maltopentaose amide. Resulted amphiphilc polymacromonomer was dissolved in 0.1 M urea aqueous solution, and its structure was characterized by small-angle X-ray scattering and molecular modeling. Maltopentaose-carrying polystyrene polymacromonomer was found to be represented by a molecular bottlebrush, composed of a large helix of polystyrene backbone and maltopentaose brushes. The molecular bottlebrush seems to be distributed randomly or many even be broken once or twice in segments with no apparent intersegmental spatial correlation. A large helix of polystyrene backbone is formed by a random seque…
A Versatile Grafting-to Approach for the Bioconjugation of Polymers to Collagen-like Peptides Using an Activated Ester Chain Transfer Agent
2009
DepartmentofMaterials Science and Engineering, University of Delaware, 201DuPont Hall, Newark, Delaware 19716,Received February 24, 2009Revised Manuscript Received April 24, 2009Biohybrid materials consisting of synthetic polymers andbiological moieties have gained more and more interest in therecent years.
Radioactive labeling of defined HPMA-based polymeric structures using [18F]FETos for in vivo imaging by positron emission tomography.
2009
During the last decades polymer-based nanomedicine has turned out to be a promising tool in modern pharmaceutics. The following article describes the synthesis of well-defined random and block copolymers by RAFT polymerization with potential medical application. The polymers have been labeled with the positron-emitting nuclide fluorine-18. The polymeric structures are based on the biocompatible N-(2-hydroxypropyl)-methacrylamide (HPMA). To achieve these structures, functional reactive ester polymers with a molecular weight within the range of 25,000-110,000 g/mol were aminolyzed by 2-hydroxypropylamine and tyramine (3%) to form (18)F-labelable HPMA-polymer precursors. The labeling procedure…
Functionalization of TiO2Nanoparticles with Semiconducting Polymers Containing a Photocleavable Anchor Group and Separation via Irradiation Afterward
2014
The controlled radical polymerization (RAFT polymerization) of semiconducting polymers based on poly(4,4′-dimethyl-triphenylamine) is described. These polymers are afterward end-functionalized with a photocleavable group and an anchor unit (catechol) for oxidic nanoparticles (NPs). Serving as a reference, polystyrene oligomers with the same end groups are also synthesized. Using these polymers allows functionalization of the TiO2-NPs, leading to an improved solubility and miscibility in organic solvents or polymer matrices. Irradiation in the UV region is used to split the photocleavable group and remove the polymer chains from the NPs, which leads to their aggregation.