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131.
Reactivity Ratios and Sequence Distribution Characterization by Quantitative 13C NMR for RAFT Synthesis of Styrene‐Acrylonitrile Copolymers
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Md. Mahbub Alam Hui Peng Kevin S. Jack David J. T. Hill Andrew K. Whittaker 《Journal of polymer science. Part A, Polymer chemistry》2017,55(5):919-927
The kinetics and reactivity ratios of styrene‐acrylonitrile (SA) copolymerization have been studied extensively in bulk and in a variety of solution media using conventional free radical polymerizations (FRPs). Due to the significant difference in the two reactivity ratios for this monomer pair, at certain feed ratios the copolymers display composition drift with conversion due to monomer depletion. In this study, the kinetics of SA copolymerization using Reversible Addition‐Fragmentation Chain Transfer (RAFT) has been studied in bulk at 80 °C. The reactivity ratios for the terminal model were calculated from the comonomer sequence distributions for the RAFT process at low conversion for nine different compositions and found to be in the same range as those reported for conventional FRP of SA. The changes in the composition and sequence distribution with conversion were studied for three feed compositions. The copolymers show compositional drift with conversion, except at the azeotropic composition, and match the predictions from the reactivity ratios obtained at low conversion. From quantitative 13C NMR the triad distributions of these copolymers were estimated and found to match the predicted triad distributions as conversion increased. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 919–927 相似文献
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134.
The Chemistry of 10-Pn-3 Systems1: Tricoordinate Hypervalent Pnictogen Compounds and Related Systems
Anthony J. Arduengo III David A. Dixon Constantine A. Stewart 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):341-344
Abstract The unusual hypervalent tricoordinate pnictogen systems, 10-Pn-3 ADPnO, provide a convenient starting point for the study of a wide range of main group chemistry. Differences in reactivity patterns among the pnictogens are readily apparent from the variety of chemistry exhibited. The ADPnO systems also provide a model for the recently recognized edge inversion mechanism for 3 and 4 coordinate 8-electron main group species. 相似文献
135.
Gregory B. Kharas Emi Hanawa Benjamin L. Hill Salima Atlas Mustapha Raihane 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7):650-655
Copolymerization of 2-phenyl-1,1-dicyanoethylene (PDE) with 4-fluorostyrene and pentafluorostyrene in solution with radical initiation (ABCN) at 70°C yielded random copolymers with PDE alternating units. The composition of the copolymers was calculated from nitrogen analysis and the structure was analyzed by IR, 1H and 13C-NMR. The order of relative reactivity (1/r1) and the tendency toward alternation of monomer units in the copolymer for these two monomers, is 4-fluorostyrene (1.96) > pentafluorostyrene (0.51). Higher glass transition temperature of the copolymers in comparison with that of homopolymers indicates a decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. 相似文献
136.
Gregory B. Kharas Emi Hanawa Benjamin L. Hill Katherine T. Flynn Emily Figueroa Anne M. Roubal 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):423-427
Novel copolymers of trisubstituted ethylene monomers, ring-disubstituted 2-phenyl-1,1-dicyanoethylenes, RC6H3CH=C(CN)2 (where R = 3-Br-4-CH3O, 5-Br-2-CH3O, 2-F-5-CH3, 2-F-6-CH3, 3-F-2-CH3, 3-F-4-CH3, 4-F-2-CH3, 4-F-3-CH3) and 4-fluorostyrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C-NMR. The order of relative reactivity (1/r 1) for the monomers is 3-F-4-CH3(1.64) > 5-Br-2-CH3O (1.62) > 3-Br-4-CH3O (1.36) > 4-F-2-CH3(1.3) > 4-F-3-CH3(1.26) > 3-F-2-CH3(1.11) > 2-F-5-CH3 (0.98) > 2-F-6-CH3 (0.97). High Tg of the copolymers, in comparison with that of poly(4-fluorostyrene) indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 290–400°C range with residue, which then decomposed in 400–800°C range. 相似文献
137.
Gregory B. Kharas Emi Hanawa Benjamin L. Hill Katherine Flynn Amy N. Addante Julio C. Argueta 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):197-201
Novel copolymers of trisubstituted ethylene monomers, alkyl ring-substituted 2-phenyl-1,1-dicyanoethylenes, RC6H4CH = C(CN)2 (where R is 2-methyl, 3-methyl, 4-methyl, 4-ethyl, 4-i-propyl, 4-butyl, 4-i-butyl, and 4-t-butyl) and 4-fluorostyrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C-NMR. The order of relative reactivity (1/r 1) for the monomers is 4-ethyl (42.6) > 4-butyl (29.4) > 4-t-butyl (26.7) > 4-i-butyl (1.6) > 4-i-propyl (1.29) > 3-methyl (1.26) > 2-methyl (0.8) > 4-methyl (0.4). High T g of the copolymers, in comparison with that of poly(4-fluorostyrene) indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in 183–500°C range with residue (5–30% wt.), which then decomposed in the 500–800°C range. 相似文献
138.
Abstract Intrareaction occurs between moieties attached to copolystyrene-2% divinylbenzene resin as used in solid phase synthesis even when only 0.5% of the phenyl residues are functionalized. Evidence for this interaction has been obtained from the dimeric products resulting from Dieckmann cyclization of resin bound sebacates and ω-cyanopelargonyl thiol resin esters, from kinetic and product data on radioactivity scrambling during the Dieckmann cyclization of uniquely singly labeled tertiary alkyl pimeloyl resin esters, and from anhydride formation with carboxymethyl resin. The extent to which site-site interactions can occur as a function of the percentage functionalization has been measured quantitatively by radiotracer studies on intraresin anhydride formation from carboxymethyl substituted resin. The synthesis and characterization of the resin bound re-actants is described, and the significance of these observations is discussed. 相似文献
139.
Gregory B. Kharas Emi Hanawa Benjamin L. Hill Katherine T. Flynn Libby Lapson Amanda Mueller 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1055-1058
Novel copolymers of trisubstituted ethylene monomers, ring-substituted 2-phenyl-1,1-dicyanoethylenes, RC6H4CH=C(CN)2 (where R is 4-dimethylamino, 4-diethylamino, 3-phenoxy, 3-benzyloxy, 4-benzyloxy, 4-acetoxy, 2-cyano, 3-cyano, and 4-cyano) and 4-fluorostyrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C-NMR. The order of relative reactivity (1/r 1) for the monomers is 3-benzyloxy (2.9) > 4-cyano (2.7) > 3-phenoxy (1.9) > 4-acetoxy (1.8) > 3-cyano (1.7) > 2-cyano (1.6) > 4-benzyloxy (0.6) > 4-dimethylamino (0.4) = 4-diethylamino (0.4). High T g of the copolymers, in comparison with that of poly (4-fluorostyrene) indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 290–400°C range with residue, which then decomposition in 400–800°C range. 相似文献
140.
Hongli Li Brad Bendiak William F. Siems David R. Gang Herbert H. Hill Jr. 《International Journal for Ion Mobility Spectrometry》2013,16(2):105-115
A high-throughput ion mobility mass spectrometer (IMMS) was used to rapidly separate and analyze peptides and glycopeptides derived from glycoproteins. Two glycoproteins, human α-1-acid glycoprotein and antithrombin III were digested with trypsin and subjected to electro-spray traveling wave IMMS analysis. No deglycosylation steps were performed; samples were complex mixtures of peptides and glycopeptides. Peptides and glycosylated peptides with different charge states (up to 4 charges) were observed and fell on distinguishable trend lines in 2-D IMMS spectra in both positive and negative modes. The trend line separation patterns matched between both modes. Peptide sequence was identified based on the corresponding extracted mass spectra and collision induced dissociation (CID) experiments were performed for selected compounds to prove class identification. The signal-to-noise ratio of the glycopeptides was increased dramatically with ion mobility trend line separation compared to non-trend line separation, primarily due to selection of precursor ion subsets within specific mobility windows. In addition, isomeric mobility peaks were detected for specific glycopeptides. IMMS demonstrated unique capabilities and advantages for investigating and separating glycoprotein digests in this study and suggests a novel strategy for rapid glycoproteomics studies in the future. 相似文献