Search results for "Radical"
showing 10 items of 1401 documents
Polymerizable and polymeric zwitterionic surfactants: 1. Synthesis and bulk properties
1991
Abstract The synthesis of a series of permanently zwitterionic surfactant monomers based on sulphobetaines and the preparation of their polymers is described. Solubilities, thermal properties and bulk structures of the zwitterionic polymers are studied with respect to their molecular architecture, and compared with cationic analogues. The various solubilities of the polymers can be correlated with their molecular geometry, enabling differentiation into distinct classes. This behaviour is paralleled by the observed bulk structures of the polymers where distinct classes of superstructures are present. However, independently of the molecular geometry, no thermal transition could be detected fo…
Cyclodextrins in Polymer Synthesis: Influence of Acrylate Side Groups on the Initial Rate of Radical Polymerization of Various Acrylate/Methylated β…
2001
Methylated β-cyclodextrin was used to complex the hydrophobic monomers n-propyl acrylate (1), n-butyl acrylate (2), n-pentyl acrylate (3), n-hexyl acrylate (4), and cyclohexyl acrylate (5) respectively yielding the corresponding water-soluble host/guest-complexes 1a−5a. The complexes were polymerized in water by free radical mechanism and the initial polymerization rates (v0) determined. We found that v0 increases as follows: 1a (12.5), 2a (27.5), 3a (44.2), 5a (49.4), 4a (75.8 × 10-6 mol·L-1·s-1). To investigate the influence of the hydrophobic character of the guest monomers on the reaction rate, the water solubilities of the uncomplexed monomers 1−5 were determined by HPLC measurements.…
Core-shell polyacrylate and polystyrene-block-polyacrylate stars
2005
The polymerization of p-(iodomethyl)styrene (PIMS) yields well-defined branched polymers with reactive iodomethyl groups. The branched poly[p-(iodomethyl)styrene] was used as the transfer agent in the iodine mediated radical polymerization of vinyl monomers. The polymerization proceeds in a controlled way and yields polystyrene and poly(t-butyl acrylate) star polymers with reactive groups at the end of their arms. Polymers so obtained were also used to prepare stars with block copolymer arms: polystyrene-block-poly(t-butyl acrylate). The characterization of star structures was performed by NMR and gel permeation chromatography with absolute molar mass detection (MALLS). Preliminary characte…
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 …
Synthesis and characterization of well-defined poly(tert-butyl acrylate) star polymers
2009
Abstract Star polymers with different numbers and lengths of poly(tert-butyl acrylate) (PTBA) arms were obtained via atom transfer radical polymerization. Aliphatic alcohols with different number of hydroxyl groups varying from 3 to 6 and calix[4]arenes based on pyrogallol with 12 and 16 phenol groups were transformed to bromoester derivatives to prepare multifunctional ATRP initiators used as the cores of the stars. The star polymers were characterized by GPC with refractive index, multiangle laser light scattering and viscosimetric detectors. The molar masses of the stars reached 70,000 g/mol and the molar mass dispersities did not exceed 1.2. To elucidate the compact structure of the sta…
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 …
Strukturaufklärung der bei der Addition von 2-Cyano-2-propylradikalen an p-Tolyl- und 4-Cyclohexylphenyl-methacrylat entstehenden Produkte mittels 1H…
1978
The chromatographically pure products, gained on the suppression of polymerisation of p-tolyl or 4-cyclohexylphenyl methacrylates (1, 2) by a great excess of 2-cyano-2-propyl radicals, could be isolated in a total yield of 95 to 100%. The structure of these products was established by 1H NMR and mass spectroscopy. There are p-tolyl or 4-cyclohexylphenyl 4-cyano-2-(2-cyano-2-propyl)-2,4-dimethylvalerate (1a, 2a), p-tolyl or 4-cyclohexylphenyl 2-(2-cyano-2-methylpropyl)acrylate (1b, 2b), p-tolyl or 4-cyclohexylphenyl 4-cyano-4-methyl-2-(2-cyano-2-methylpropyl)valerate (1c, 2c), p-tolyl or 4-cyclohexylphenyl 4-cyano-2,4-dimethylvalerate (1d, 2d), and p-tolyl or 4-cyclohexylphenyl 4-cyano-2,4-d…