13C NMR Characterization of Polychloroprene Microstructure I. Spectral Assignments

Coleman, M. M.; Tabb, D. L.; Brame, E. G.

doi:10.5254/1.3535133

Cited by 38 publications

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“…With the advent of 13 C nmr, a number of additional microstructures were observed. There was good agreement between earlier 1H nmr and 13 C nmr techniques (51,56,(60)(61)(62). Other studies of microstructure have been conducted with the aid of infrared and Raman spectroscopy (63,64).…”

Section: Polymersupporting

confidence: 68%

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Polychloroprene

Glenn¹

2004

Kirk-Othmer Encyclopedia of Chemical Technology

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The active center of the chain transfer agent reacts with the growing chain to stop further chain propagation. A new free radical, A, is formed from the Vol. 0 POLYCHLOROPRENE POLYCHLOROPRENE Vol. 0Chloroprene-Sulfur Copolymerization. The high reactivities of chloroprene and dichlorobutadiene permit copolymerization with sulfur to yield toluene-insoluble and partially gelled copolymers of high molecular weight. Gelled polymers are highly crosslinked polymers that are insoluble in toluene.In solution or aqueous emulsion polymerization, a growing polychloroprene radical reacts with rhombic (nonpolymeric) sulfur (24) or suitable sulfur donors such as 1,2,3,4-tetrasulfocyclohexane (25) or polysulfides (26) to yield a copolymer. Reaction with elemental sulfur involves cleavage of the eight-membered sulfurGraft Polymerization. Graft polymerization is related to block copolymerization. A block copolymer contains long sequences of two monomers (ie, AAA monomer blocks followed by BBB monomer blocks) along the copolymer chain. Graft copolymers consist of long chains of one monomer with occasional branches consisting of long chains of a second (grafted) comonomer. The branched points are normally formed by allylic atom (typically hydrogen) abstraction by free-radical initiators (eg, peroxides) to yield a resonance-stabilized free radical. The free radical initiates the addition polymerization of a second monomer beginning at the locus of the free radical. Generally grafting is performed to significantly modify polymer properties. In the production of emulsion-polymerized acrylonitrilebutadiene-styrene tripolymer, styrene and acrylonitrile are grafted onto rubbery polybutadiene to improve compatibility between the thermoplastic and rubber matrix used in impact modification (12). Methyl acrylate, acrylonitrile, alkyl methacrylates (eg, methyl, octyl, lauryl), fumaronitrile, methacrylic acid, and dichlorobutadiene have been employed in solution and emulsion graft polymerization with polychloroprene. Generally, solvent resistance, heat resistance, and Vol. 0 POLYCHLOROPRENE 7 POLYCHLOROPRENE Vol. 0 POLYCHLOROPRENE Vol. 0 POLYCHLOROPRENE Vol. 0 9.5. Latex Applications. A good way to remember the applications for latex is to follow the first six letters of the alphabet. A ¼ adhesives, B ¼ binders, C ¼ coatings, D ¼ dipped Goods, E ¼ elasticizers, and F ¼ foam. Vol. 0 POLYCHLOROPRENE 25

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Section: Polymersupporting

confidence: 68%

“…Unsymmetrical diene monomers such as chloroprene polymerize by four reaction pathways: 1,4 head-to-head, 1,4-head-totail, 1,2 and 3,4 polymerization. The concentrations of microstructure vary with polymerization temperature(51). The Z-or trans-configuration predominates at conventional polymerizations carried out in the range of 10 to 45 8C.…”

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confidence: 99%

Polychloroprene

Glenn¹

2004

Kirk-Othmer Encyclopedia of Chemical Technology

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“…Coleman and coworkers21–23 suggested the use of 13 C‐NMR to estimate the percentage of structural isomers in CR. A sample of Baypren 210 was dissolved in CDCl 3 and subjected to the 13 C‐NMR pulse sequence detailed by Coleman et al21 With corrections for the nuclear Overhauser effect in Coleman and Brame,22 it was estimated that the percentage of trans‐1,4‐units was 76.2%, the percentage of cis‐1,4‐units was 16.0%, the percentage of 1,2‐units was 1.45%, and the percentage of 3,4‐units was 1.75%. Coleman et al21 suggested that the resonance at 130.1 ppm was due to isomerized 1,2‐units.…”

Section: Resultsmentioning

confidence: 99%

Vulcanization of polychloroprene rubber. I. A revised cationic mechanism for ZnO crosslinking

Desai

Hendrikse

Woolard

2007

J of Applied Polymer Sci

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Data relating to the vulcanization of mercaptan-grade polychloroprene (CR) by ZnO and MgO (alone or in combination) are examined. Compounds were vulcanized through the isothermal heating of samples at 1408C in a laboratory press and at programmed rates in a differential scanning calorimeter. The reaction was stopped at various points during the heating process. The crosslink densities were determined via swelling. Extractable ZnCl 2 and MgCl 2 were analyzed by atomic absorption spectrometry. Three different crosslinking processes were identified. The first crosslinking process involved the activation of the highly reactive tertiary allylic 1,2-units along the polymer chain, whereas the second and third crosslinking processes were attributed to the activation toward crosslinking of 3,4-and 1,4-units, respectively. The crosslinking reactions of the 1,2-units comprised three distinct steps: isomerization (promoted by ZnO), dechlorination, and crosslinking. ZnCl 2 (which formed during compounding and upon crosslinking) promoted crosslinking, and its addition to formulations decreased but did not eliminate the induction period before crosslinking. MgO retarded the crosslinking process by limiting the formation of ZnCl 2 during mixing. The results of the CR/ZnO system are discussed, and a modified cationic mechanism for crosslinking is proposed.

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“…This is probably also the situation for a Data from Condon [1953], Richardson [1954], Pollock et al [1955]. b Data from Coleman and Brame [1978], Coleman et al [1977], Ebdon [1978]. …”

Section: -10a Radical Polymerizationmentioning

confidence: 90%

Stereochemistry of Polymerization

Odian

2004

Principles of Polymerization

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Constitutional (formerly: structural) isomerism is encountered when polymers have the same overall chemical composition (i.e., same molecular formula) but differ in connectivitythe order in which the atoms are connected to each other. Polyacetaldehyde, poly(ethylene oxide), and poly(vinyl alcohol) are constitutional isomers. The first two polymers are CH CH 3 O C H 2 CH OH CH 2 CH 2 O n n Polyacetaldehyde Poly(ethylene oxide) Poly(vinyl alcohol) n obtained from isomeric monomers, acetaldehyde and ethylene oxide. The third is obtained by hydrolysis of poly(vinyl acetate) since vinyl alcohol does not exist (it is the enol form of acetaldehyde). Poly(methyl methacrylate) and poly(ethyl acrylate) are isomeric polymers CH 2 C CH 3 CO 2 CH 3 CH 2 CH CO 2 C 2 H 5 n n Poly (methyl methacrylate) Poly (ethyl acrylate) formed from isomeric monomers. Poly(E-caprolactam) and poly(hexamethylene adipamide) are isomeric even though the monomers are not isomeric. Similarly, the 1 : 1 copolymer of Principles of Polymerization, Fourth Edition.

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13C NMR Characterization of Polychloroprene Microstructure I. Spectral Assignments

Cited by 38 publications

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Polychloroprene

Polychloroprene

Vulcanization of polychloroprene rubber. I. A revised cationic mechanism for ZnO crosslinking

Stereochemistry of Polymerization

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