Telomers polymerization

Telomerization. Polymerization of DAP is accelerated by telogens such as CBr, which are more effective chain-transfer agents than the monomer itself (65) gelation is delayed. The telomers are more readily cured in uv than DAP prepolymers. In telomerizations with CCl with peroxide initiator, at a DAP/CCl ratio of 20, the polymer recovered at low conversion has a DP of 12 (66). 

The first purposeful use of ATRA in polymer synthesis was in the production of telomers.26j In this early work, comparatively poor control over the polymerization was achieved and little attempt was made to explore the wider utility of the process. Some analogies may also be drawn with the work of Bamford et al, and others on transition metal/organic halide redox initiation (Sections 3.3,5.1 and 7.6.2).2M... 

Still another, and chains, long or short, may be built up. This is the mechanism of free-radical polymerization. Short polymeric molecules (called telomers), formed in this manner, are often troublesome side products in free-radical addition reactions. 

The molecular weight and chain-end structure of polymers can be modified using the chain transfer reaction [65-68]. When an appropriate chain transfer agent, X-Y, is used in radical polymerization, two types of oligomers or telomers having different end groups, 4 and 5, are formed depending on the value of the chain transfer constant, Ctr> of X-Y used. 

To further exploit the potential usefiilness of this new family of clusters, monoadduct 54 was saponified into 55 (0.05 M NaOH, quant) and condensed to L-lysine methyl ester using 2-ethoxy-l-ethoxycarbonyl-l,2-dihydroquinoline (EEDQ) to give extended dimer 56 in 50 % yield together with monoadduct in 15 % yield [75]. Additionally, tert-butyl thioethers 52 could be transformed into thiols by a two step process involving 2-nitrobenzenesulfenyl chloride (2-N02-PhSCl, HOAc, r.t, 3h, 84%) followed by disulfide reduction with 2-mercaptoethanol (60%). Curiously, attempts to directly obtain these thiolated telomers by reaction with thioacetic acid f ed. These telomers were slightly better ligands then lactose in inhibition of binding of peanut lectin to a polymeric lactoside [76]. 

In the synthesis of all concave acids and bases, a difunctionalized molecule A-A was cyclized with a difunctionalized bridge component B-B. Because telo- and polymerizations are the main side reactions [29] the isolated macrocycles need not be the expected [1 -I- 1] addition products, the (-A-AB-B-)i cycles, [n - - n] Telomers with the general structure (-A-AB-B-) are also possible. These molecules have identical elemental analyses and similar IR and NMR data. Therefore the mass spectral analyses of the macrocycles are very important because this is the only method which can tell [1 -t- 1] and [2 -t- 2] addition products apart. Due to the high molecular weight of the concave acids and bases, special MS techniques were necessary in some cases [30]. In the case of the macrocyclic diamine 7 [R = NEt2, X = CH2(CH20CH2)2CH2], a [2 -t- 2] addition product could be isolated and characterized besides the desired [1 + 1] product [12a]. 

Photolysis of this polymer gives radicals on which side chains can be formed, giving graft polymerization 122, 123, 153). Similarly the polymerization of styrene (152) or vinyl acetate (157) in the presence of bromotrichloromethane gives telomers carrying terminal bromine atoms and trichloromethyl groups. By ultraviolet irradiation (3500 A) in the presence of methyl methacrylate the carbon-bromine links are broken and block copolymers are formed. The telomerization of acrylonitrile and acrylic acid with bromoform is based on the same technique the end groups of both polyacrylonitrile and polyacrylic acid were photolyzed in the presence of acrylamide and afforded polyacrylamide blocks linked to polyacrylonitrile or polyacrylic acid blocks (164, 165). 

Telomers have been prepared by polymerizing acrylonitrile in the presence of agents like CC14. Fox and Field (58) have reviewed this whole subject recently. 

In addition, these fluorinated monofunctional telomers can be interesting precursors of original macromonomers leading to novel polymeric optical fibers [393] or grafted copolymers [134]. 

Telomer Its original meaning is in polymer science, to refer to an extremely small polymer—one whose degree of polymerization is between 2 and 5. 

Telomer Short polymeric molecule containing fewer monomeric units than a polymer, but more than an oligomer. 

Hydroxyl terminated telomers of VDF are prepared in methanol using tert-butyl peroxide as the initiator. Less than 10 mm thick film has been produce using microwave-stimulated, low-pressure plasma polymerization of VDF. An isoregic PVDF polymer with minimized head-to-head placement has been synthesized and reported. Properties and synthesis of perdeuter-ated PVDF have also been pointed out. ... 

The absorption spectra of silylene polymers and telomers have been extensively reported and it has been shown that the position of the absorption maximum shifts to the red with increasing degree of polymerization (6,15-19). We and others have reported the existence of narrow, line like fluorescence with no observed vibrational structure for a number of medium and high molecular weight polymers (2,9,16,20,22). The narrow, line-like fluorescence and the chain length dependence of the absorption spectra both indicate substantial delocalization of the electronic states involved in the transitions. 

Boutevin et al. also incorporated VA into block copolymers, but via a slightly different technique. They utilized chloroform as a transfer agent, which, in the presence of AIBN as an initiator, will produced telomers of VA that are capable of initiating ATRP [247]. Various telomers of pVA (degree of polymerization=l, 9, or 62) were used as the macroinitiators for the ATRP of St, carried out in the presence of the CuCl/bpy catalyst system. The molecular weights increased line-... 

Destarac and Matyjaszewski et al. showed that a-trichloromethylated pVDF telomers could be used as ATRP macroinitiators to prepare block copolymers with various monomers [250]. The polymerization of VDF was carried out using a peroxide initiator in the presence of chloroform, which produced an a-trichlo-romethyl radical capable of adding to the monomer. The subsequent ATRP of St, MMA, MA, or nBA using these macroinitiators resulted in block copolymers with Mn>6000 and Mw/Mn<1.3. GPC traces verified complete consumption of the macroinitiators [250]. 

The W arrangement in all the CH2-C-CH3 groups in a chain requires that one of the methylene protons and the methyl carbon should be in the trans state, that is, that the main-chain backbone should be in the repeated tt conformation. Similar 47(HH) connectivities were reported for the telomers of MMA prepared by radical polymerization in the presence of cobalt(II) tetraphenylporphyrin as chain transfer reagent.269,286... 

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