Use of solution-state deuterium NMR to investigate crosslinking and branching acrylate polymer systems

Wolk, Steven K.; Eisenhart, Eric K.

doi:10.1021/ma00057a032

Cited by 4 publications

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“…The SCB results also give insight into the debate as to whether LCBs from comonomer units are formed by H-abstraction from the main polymer backbone or from the acrylate or acetate side groups. Lovell et al 32 report significant LCB from the main polymer backbone for nBA homopolymer, as do Wolk and Eisenhart; 43 the latter authors also show that branching from the ester group is not detectable. These findings are in accord with the present NMR studysthe hydrogen opposite the acrylate group on the main polymer backbone is very susceptible to abstraction.…”

Section: Discussionmentioning

confidence: 88%

Short-Chain Branching Structures in Ethylene Copolymers Prepared by High-Pressure Free-Radical Polymerization: An NMR Analysis

1997

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It is well-known that short-chain branching (SCB) reactions (intramolecular H-abstraction) play an important role in determining the properties of ethylene homopolymers produced under high pressure by free-radical polymerization. There is little information, however, regarding SCB mechanisms that occur during the synthesis of ethylene copolymers under similar reaction conditions. This work describes SCB structures for a wide range of ethylene copolymers of varying composition (ethylene with n-butyl acrylate (nBA), methyl acrylate (MA), vinyl acetate (VAc), n-butyl methacrylate (nBMA), acrylic acid (AA), and methacrylic acid (MAA)), as determined by proton, 13 C, and 2D NMR techniques. Close examination of the resonances reveals that for many (if not all) of these copolymers, a significant fraction of the SCBs contain comonomer as a result of CH2-radical to CH2 backbiting around a comonomer unit. In addition, SCBs are formed not only by hydrogen abstraction from CH2 polyethylene units but also by abstraction of hydrogen from the comonomer methine units. This latter mechanism does not occur during production of E/VAc, E/nBMA, or E/MAA but is important for E/AA and acrylate (E/MA and E/nBA) copolymers; for these systems 10-20% of the comonomer groups in the polymer are alkylated. Implications of these findings to the polymerization kinetics are discussed.

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Section: Discussionmentioning

confidence: 88%

Short-Chain Branching Structures in Ethylene Copolymers Prepared by High-Pressure Free-Radical Polymerization: An NMR Analysis

1997

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Temperature‐sensitive hydrogel microspheres formed by liquid–liquid phase transitions of aqueous solutions of poly(N,N‐dimethylacrylamide‐co‐allyl methacrylate)

Yin

Stöver

2005

J. Polym. Sci. A Polym. Chem.

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Poly(N,N‐dimethylacrylamide‐co‐allyl methacrylate) (DMA‐co‐AMA) copolymers were prepared by the copolymerization of N,N‐dimethylacrylamide with allyl methacrylate (AMA). The methacryloyl group of AMA reacted preferentially, and this resulted in pendant allyl groups along the copolymer chains. Aqueous solutions of these DMA‐co‐AMA copolymers were thermoresponsive and showed liquid–liquid phase transitions at temperatures that depended on the AMA content. Hydrogel microspheres were prepared from these thermally phase‐separated liquid microdroplets by the free‐radical crosslinking of the pendant allyl groups. The morphologies of the resulting thermoresponsive microspheres as a function of the reaction temperature and the amount of the initiator were examined. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1641–1648, 2005

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The Solution Characterization of Polymers

Bovey

Mirau

1996

NMR of Polymers

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Use of solution-state deuterium NMR to investigate crosslinking and branching acrylate polymer systems

Cited by 4 publications

References 0 publications

Short-Chain Branching Structures in Ethylene Copolymers Prepared by High-Pressure Free-Radical Polymerization: An NMR Analysis

Short-Chain Branching Structures in Ethylene Copolymers Prepared by High-Pressure Free-Radical Polymerization: An NMR Analysis

Temperature‐sensitive hydrogel microspheres formed by liquid–liquid phase transitions of aqueous solutions of poly(N,N‐dimethylacrylamide‐co‐allyl methacrylate)

The Solution Characterization of Polymers

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