Search results for "Polymerization"
showing 10 items of 1689 documents
RAFT polymerization of activated 4-vinylbenzoates
2009
The reversible addition fragmentation chain transfer (RAFT) polymerization of five active ester monomers based on 4-vinylbenzoic acid had been investigated. Pentafluorophenyl 4-vinylbenzoate could be polymerized under RAFT conditions yielding polymers with very good control over molecular weight and narrow molecular weight distributions. Following the synthesis of diblock copolymers consisting of polystyrene, polypentafluorostyrene, poly(4-octylstyrene), or poly(4-acetoxystyrene) as an inert block and poly(pentafluorophenyl 4-vinylbenzoate) as a reactive block was successfully performed. The diblock copolymer poly(pentafluoro styrene)-block-poly(pentafluorophenyl 4-vinylbenzoate) had been a…
Polymeric nitrones, 1. Synthesis and modification of polymeric nitrones derived from polymerizable aldehydes
1999
The model compound N,C-diphenylnitrone[N-(benzylidene)aniline-N-oxide] (3) was prepared by condensation of benzaldehyde with phenylhydroxylamine to study its thermal stability. X-ray diffraction analysis of a single crystal established the conformation of the nitrone group. A new monomer 4-(methacryloyloxy)benzaldehyde-phenylnitrone (8) was also prepared and could not be polymerized with 2,2′-azobisisobutyronitrile (AIBN) as initiator at 70°C. Under these conditions the nitrone reacted exclusively in an intermolecular 1,3-dipolar cycloaddition to give oligomeric tetrahydro-1,2-oxazoline derivates. The kinetics of the cycloaddition was investigated. Additionally, different (meth)acryl- and s…
Synthesis and polymerization of active ester monomers based on 4-vinylbenzoic acid
2007
Abstract Nine active ester monomers based on 4-vinylbenzoic acid have been synthesized. Under free radical polymerization conditions these monomers could successfully be polymerized yielding reactive polymers with molecular weights of around M n = 20.000–50.000 g/mol and molecular weight distributions M w / M n of around or below 2 in good yields. Polymer analogous reactions with amines have been investigated by time-resolved FT-IR spectroscopy and it was found that especially poly(pentafluorophenyl 4-vinylbenzoate) featured a significant reactivity, such that polymer analogous reactions proceeded quantitatively with amines within less than 5 min at 0 °C.
Molecular Parameters of Hyperbranched Copolymers Obtained by Self-Condensing Vinyl Copolymerization, 2. Non-Equal Rate Constants
2001
The kinetics, molecular weight averages, and the average degree of branching, DB, are calculated for the self-condensing vinyl copolymerization (SCVCP) of a vinyl monomer M with an "inimer" AB* in the case of different reactivities of active species. Emphasis is given to two limiting cases: formation of "macroinimers" occurs if the monomer M is more reactive than the vinyl groups of inimers or polymer, and "hyperstars" are formed in the opposite case. It is shown that the kinetics, the molecular weight averages, and the average degree of branching strongly depend on the relative reactivities of monomer and inimer. Comparison with experimental data shows that consistent fits of the reactivit…
Poly(4-vinylbenzoyl azide): A New Isocyanato Group Generating Polymer
2007
4-Vinylbenzoyl azide was synthesized from p-vinylbenzoic acid and polymerized by free radical polymerization. The obtained polymer contained acyl azide groups which were thermally transformed to the corresponding isocyanato groups. Reactions on these polymers with ethanol, hydroxyethyl methacrylate and 1-pyrene-butanol proceeded quantitatively. Time-resolved FT-IR studies of the reactions with ethanol were carried out by varying the concentration and temperature. The effect of the solvent polarity on the Curtius rearrangement was investigated.
Ion-Induced Stretching of Low Generation Dendronized Polymers with Crown Ether Branching Units
2009
Synthesis of the first (G1) and second generation (G2) dendronized macromonomers MG1 and MG2 with the dibenzo-24-crown-8 moiety as branching unit is reported. The corresponding dendronized polymers, the polymethacrylates PG1 and PG2, were synthesized by free radical polymerization using AIBN as initiator at 60−80 °C. Static and dynamic light scattering revealed a significant chain expansion upon complexation of these polymers’ crown ether side chains with K+ ions. It is concluded that electrostatic repulsion does not significantly contribute to the chain expansion because of excessive counterion binding even well below the Manning limit, as evidenced by 19F NMR and 1H−19F NOE experiments. R…
Hyperbranched methacrylates by self-condensing group transfer polymerization
1997
The synthesis of hyperbranched methacrylates was achieved by self-condensing group transfer polymerization of 2-(2-methyl-1-triethylsiloxy-1-propenyloxy)ethyl methacrylate (1). “Back-biting” is shown to be the predominant side reaction. In spite of this, the compact nature of the hyperbranched molecules was demonstrated through SEC-viscosity measurements and comparison with a linear analogue. The degree of branching can be controlled by copolymerization with conventional monomers, e.g. MMA, and the living polymers can be used as macroinitiators for star-shaped polymers.
Systematic investigation of functional core variation within hyperbranched polyglycerols
2008
A novel series of hyperbranched polyether polyols with various n-alkyl amine cores (mono- and bifunctional) and photoactive cores (benzylamine and 1-naphthylmethylamine) have been prepared. Polymerization of glycidol was carried out in two ways, starting directly from primary amine initiators and from bisglycidolized amine initiators. NMR spectroscopy and size exclusion chromatography (SEC) showed good control over the molecular weights only, when bisglycidolized amines were used. Molecular weights and polydispersity of the hyperbranched polyglycerols prepared with these initiator-cores were in the range of 1600 to 8400 g/mol and of 1.5 to 2.5, respectively. MALDI-ToF mass spectrometry conf…
Anionic polymerization of methyl methacrylate using tetrakis[tris(dimethylamino)phosphoranylidenamino] phosphonium (P5+) as counterion in tetrahydrof…
2000
A novel metal-free initiator, i.e. the salt of the tetrakis[tris(dimethylamino)phosphoranylidenamino]phosphonium (P5+) cation with the 1,1-diphenylhexyl (DPH–) anion was prepared by cation metathesis. It initiates a very fast and controlled anionic polymerization of methyl methacrylate in THF. Kinetic investigations between –20 and +20°C using a flow tube reactor provide nearly linear first-order time-conversion plots with half-lives below 0.1 s, a linear dependence of the number-average degree of polymerization, and rather narrow molecular weight distributions (Mw/Mn ≈ 1.2). 13C NMR measurements on a model of the active chain end (the P5+ salt of ethyl isobutyrate) in THF-d8 show 15 and 25…
Polymerizations of Cyclic Esters Catalyzed by Titanium Complexes Having Chalcogen-Bridged Chelating Diaryloxo Ligands
2002
A series of titanium complexes having tellurium-bridged chelating bis(aryloxo) ligands, [TiX2{2,2‘-Te(4-Me-6-tBu-C6H2O)2}]2 (5: X = Cl; 6: X = OiPr), catalyzed the ring-opening polymerization of cyclic esters such as e-caprolactone, δ-valerolactone, and l-lactide. The strong dependence of polymerizations on the solvent was observed in this catalytic system. When the polymerizations of e-caprolactone and l-lactide were carried out in toluene at 100 °C, tellurium-bridged bis(aryloxo)titanium complex 5 was found to give polymers with rather broad molecular weight distribution due to back-biting. When the polymerizations of e-caprolactone and l-lactide was carried out in anisole or in dioxane…