Ester-functionalised poly(1-vinylpyrrolidin-2-one) (PVP) oligomers obtained by radical polymerisation in methyl propionate, diethyl malonate and diethyl 2-methylmalonate were characterised by NMR spectroscopy, and MALDI-TOF mass spectrometry. The chain-transfer constants were determined as 5.54 x 10(-4), 1.22 x 10(-3) and 1.70 x 10(-2), respectively, by measuring the variation of the number-average molecular weight on conversion. These values were compared with those of methyl isobutyrate (1.65 x 10(-3)) and ethyl lactate (1.03 x 10(-2)), which had been previously determined. A clear dependence was found on the reactivity of the mobile hydrogen atoms alpha with the ester group. All of the macromolecules carried a single ester function. Therefore, the re-initiation step by the CTA-derived radicals overwhelmingly prevailed over initiation by the primary radicals. 相似文献
In an earlier work it was shown that a random long-chain branching structure can be incorporated in polystyrene by copolymerizing styrene with a small amount of monomer that contains a chain transfer group. The use of vinylbenzylthiol as the chain transfer monomer produced a polystyrene with low number-average molecular weight and a degree of branching lower than expected. In this study polymerization kinetics were used to compute the theoretical molecular weight and degree of branching. The results show that if the chain-transfer constant of the chain transfer monomer is as high as that for vinylbenzylthiol the expected molecular weight and degree of branching will indeed be as low as those found experimentally. The theory also predicts that if the chain transfer constant is near one a highly branched bushy structure will result. 相似文献
The phenylmethacrylamide monomer, 1‐(4‐methacrylamidophenyl)‐1‐(4‐nitrophenyl)prop‐1‐en‐3‐one (MPNP) containing a photosensitive group was synthesized by reacting 4‐nitrocinnamoylaniline with methacryloyl chloride in the presence of triethylamine at 0–5°C. The functional monomer, MPNP was polymerized in ethyl methyl ketone (EMK) under nitrogen atmosphere at 70°C using benzoyl peroxide (BPO) as the initiator. The synthesized polymer was characterized by UV, IR, 1H‐NMR and 13C‐NMR spectroscopy. The molecular weight data of the polymer as obtained from gel permeation chromatography suggests a higher tendency for chain termination by radical recombination than disproportionation. The thermal studies of the polymer were obtained from thermogravimetric analysis. The glass transition temperature of the polymer was determined by differential scanning calorimetry. The solubility of the polymer was tested in various organic solvents at room temperature. The photosensitivity of the polymer was investigated in various solvents in the presence and absence of triplet photosensitizers. The effect of the different solvents nature and concentration on the rate of photocrosslinking of the polymer were also examined for using the polymer as negative photoresist materials. 相似文献
Styrene oligomers with perfluoro[1-(2-fluorosulfonyl)ethoxy]ethyl end-groups have been synthesized with moderate to high yields (52-97%) via radical oligomerization by using perfluoro[2-(2-fluorosulfonyl)ethoxy]propyonyl peroxide (PPP) at various reactant ratios of styrene over PPP (80, 160, 240, 300, 360 and 420) and different temperatures (33, 37 and 42 °C), and characterized by FTIR, 1H NMR and 19F NMR. The molecular weight of the oligomers measured by gel permeation chromatography (GPC) is dependent on the reactant ratio and reaction temperature. The polydispersity of the oligomers varies from 1.99 to 3.30. The oligomer obtained at the reactant ratio of 300 has the maximum yield (97%) and much broader polydispersity (3.30). The contact angles of water, θH2O, on the oligomer films are much bigger than that of polystyrene (PS). The glass transition temperature of the oligomers, Tg, increases with the increase of molecular weight and is lower than that of the parent polymer. 相似文献
Summary: A novel functionalised poly(1‐vinylpyrrolidin‐2‐one) (PVP) derivative, carrying a pre‐determined amount of 2‐(2‐pyridinyldithio)ethylamine moieties as side substituents, P(VP‐co‐VP‐SS‐Py), has been prepared from carboxylated VP copolymers, in turn obtained by copolymerising 1‐vinylpyrrolidin‐2‐one with 3,3‐di‐(ethoxycarbonyl)‐1‐vinylpyrrolidin‐2‐one in the presence of radical initiators. Using reaction solvents acting in the mean time as chain transfer agents could control its molecular weight. P(VP‐co‐VP‐SS‐Py) proved to be extremely reactive towards exchange reactions with molecules containing mercapto functions, including bioactive peptides. The exchange derivative with reduced glutathione, chosen as a model compound, was easily prepared.
A method of preparation of isocyanate- or hydroxy-terminated urethane oligomers of narrow molecular weight distribution was developed and the products used for preparation of polyurethane elastomers. The method consists of the controlled step-wise reaction of 2,4- and 2,6-toluene diisocyanate (TDI) with butan-1,4-diol (BD) (in the first step) or with polyoxyethylene glycols of molecular weight varying from 200 to 1000 (following steps). All reactions were carried out in bulk. The clue was that the isocyanate- or hydroxy-terminated oligourethanes obtained in a previous step were used as the substrates in the next preparation step where they reacted with an excess of appropriate glycol or TDI, respectively. The unreacted monomer excess was removed by extraction. The products of subsequent steps characterized by spectral analysis IR and NMR and their molecular weight were determined by matrix-assisted laser desorption ionization-time of flight and electrospray ionization mass spectroscopy and gel-permeation chromatography. The oligomers were cross-linked with trifunctional low-molecular chain extenders yielding polyurethane elastomers. 相似文献
In the first paper of the series, a statistical model for star-branched polycondenzation of AB type monomers in the presence of a polyfunctional agent RAf was completely developed. The analytical expressions obtained for the number-average (D̄P̄n̄) and weight-average (D̄P̄w̄) degree of polymerization, and the dispersion index (D) for whole polymer species, linear and star macromolecular chains, are now derived as function of the feed and of end-group analysis. Also the important molecular parameter, mole fraction of star-branched polymer, can be evaluated. Some numerical examples are presented. It is illustrated that the molecular weight properties of the linear and star-branched polymers in the mixture of the products, very important factors for the application of this kind of polymeric materials, can be determined starting from the feed and terminal group analysis. Polymerization and oligomerization of 6-aminocaproic acid were carried out in the presence of trimesic (T3) acid and 2,2,6,6-tetra(β-carboxyethyl)cyclohexanone (T4) and EDTA as tri- and terra-functional agents. The molecular weights calculated are in good agreement with those obtained by Size Exclusion Chromatography (SEC), end group analysis and NMR spectra. 相似文献
Novel biodegradable polyester block copolymers have been synthesized by using well-defined poly(3-hydroxyoctanoate) (PHO) oligomers having a hydroxyl end group and an ester end group with M(n) values of 800, 2,500, 5,300, 8,000, or 20,000 as an elastomeric soft segment and poly(epsilon-caprolactone) as a more crystalline segment. These PHO oligomers prepared by methanolysis were subjected to block copolymerization with epsilon-caprolactone. The chemical structure of the copolymers was confirmed by (1)H NMR and (13)C NMR spectroscopy. All the copolyesters are semi-crystalline and two T(g) were observed by differential scanning calorimetry when the molecular weight of the PHO block is about 20,000. 相似文献