Molecular characterization and effect of shear on the distribution of long branching in poly(vinyl acetate)

Agarwal, Sunita; Jenkins, Robert F.; Poster, Roger S.

doi:10.1002/app.1982.070270113

Cited by 20 publications

(7 citation statements)

References 4 publications

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“…The branching factor tends to increase with the molecular weight of arms and decrease with the number of arms . Similar effects are seen in extensional properties by polymer solution modelling where increasing the number of arms (at constant arm length) results in a later coil‐stretch transition and a lower extensional viscosity even at high strain rates .…”

Section: Future Directionssupporting

confidence: 58%

“…[139,140] Similar effects are seen in extensional properties by polymer solution modelling where increasing the number of arms (at constant arm length) results in a later coil-stretch transition and a lower extensional viscosity even at high strain rates. [141] Similarly, modelling has shown that increasing the arm length (with constant number of arms) leads to a larger extensional viscosity.…”

Section: Future Directionssupporting

confidence: 56%

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Polymeric Drift Control Adjuvants for Agricultural Spraying

Lewis

Evans

Malic

et al. 2016

Macro Chemistry & Physics

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---------The movement of a pesticide or herbicide to an off-target site during agricultural spraying can cause injury to wildlife, plants and contamination of surface water. This phenomenon is known as spray drift and can be controlled by spraying during favorable environmental conditions, and by using low drift nozzles and drift control adjuvants (DCAs). Polymeric DCAs are the most common type of DCA and function by increasing the droplet size produced during spraying. There are, however, two main drawbacks of polymeric DCAs; they are prone to mechanical degradation during spraying which reduces their performance and they can produce oversized drops which reduces the efficacy of the spray. In this review, existing DCA technology is reviewed including the mechanism through which they function.This then provides a platform for the discussion of novel polymeric architectures which have currently not been applied in DCA formulations.-2 -

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Section: Future Directionssupporting

confidence: 58%

Section: Future Directionssupporting

confidence: 56%

Polymeric Drift Control Adjuvants for Agricultural Spraying

Lewis

Evans

Malic

et al. 2016

Macro Chemistry & Physics

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“…Chain transfer to polymer is thought to occur both by abstraction of hydrogens of the polymer backbone and methyl groups in the Ac groups. Uncertainty remains about the actual fraction of each type of transfer, although a dominant abstraction of hydrogen atoms in the Ac groups has been reported. − For simplicity in the present work, only hydrogen abstraction of the methyl group is considered, resulting in pMCRs. The propagation of these radicals results in the formation of LCBs.…”

Section: Kinetic Modelmentioning

confidence: 99%

Interplay of Head, Tail, and Mid-Chain Radicals in Bulk Free-Radical and Reversible Degenerative Addition Fragmentation Chain-Transfer Polymerizations of Vinyl Acetate

et al. 2019

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A detailed kinetic model for isothermal bulk free-radical and degenerative reversible addition−fragmentation chain-transfer (RAFT) polymerizations of vinyl acetate is presented up to monomer conversions of ca. 0.95, considering a distinction between head and tail end-chain radicals and primary and tertiary mid-chain radicals (MCRs). Diffusional limitations are taken into account for conventional initiation and termination, with a reduction of the gel-effect as chain transfer to the monomer lowers the apparent termination reactivities. The tail radicals are essential for the accurate description of backbiting and RAFT deactivation and the primary MCRs for chain transfer to the polymer. The model is based on the application of the method of moments with over 100 macrospecies types and thousands of reactions to obtain the temporal evolution of the monomer conversion, the number and mass average chain length, the number fraction of short-and long-chain branches, the number fraction of unsaturated chains, and the number fraction of chains with head-to-head defects. After a successful model validation of the experimental literature data, the model is applied to understand the complex interplay of the radical types involved and to highlight the control of the branching and unsaturation amounts under RAFT polymerization conditions. Headto-head defects can however not be avoided for realistic average chain lengths.

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“…Most HMPAMs used in enhanced oil recovery are linear polyacrylamides (PAMs). However, recently, it has been confi rmed that side chains of the polymer backbone can enhance its shear stability during turbulent fl ow; this has been attributed to sacrifi cial scission of the branches leading to only a small decrease in the molecular weight [10,11] . In our previous work we have reported the synthesis of a novel class of star PAMs with different arms by photopolymerization [12] .…”

Section: Introductionmentioning

confidence: 99%

Synthesis and solution behaviors of star hydrophobically modified acrylamide copolymers

Zhang

Duan

Fang

et al. 2011

Journal of Polymer Engineering

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Star copolymers of acrylamide and N , N -dimethyl-N -vinylnonadecan-1-aminium chloride (C 18 DMAAC) were synthesized by photopolymerization in water. Solution behaviors of these star hydrophobically modifi ed acrylamide copolymers (SHMPAMs) with different C 18 DMAAC contents and the linear hydrophobically modifi ed acrylamide copolymers (LHMPAMs) were characterized. The increase in C 18 DMAAC content resulted in decreased intrinsic viscosity and increased the Huggins constant for SHMPAMs. Similar results were observed for LHMPAMs. With similar intrinsic viscosity and C 18 DMAAC content, the Huggins constant of SHMPAMs was much higher than that of LHMPAMs, which could be due to the fact that SHMPAMs had much stronger intramolecular interaction in dilute polymer solutions. In semi-dilute solutions, the apparent viscosity of SHMPAMs was increased with increasing C 18 DMAAC content, which was similar to that of LHMPAMs. However, SHMPAMs exhibited higher apparent viscosity than LHMPAMs because it had more arms and thus had more chances to form three-dimensional networks in semi-dilute solutions. In the fl ow-induced scission experiment, SHMPAMs exhibited superior shear stability in comparison with LHMPAMs. When the strain rate was ≈ 40,000 s -1 , the reduction ratios of the apparent viscosities of the four SHMPAMs after the scission were approximately 80 % . By contrast, when the strain rate was ≈ 20,000 s -1 , the reduction ratio of the apparent viscosity of LHMPAM-0.40 had already reached around 80 % .

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Molecular characterization and effect of shear on the distribution of long branching in poly(vinyl acetate)

Cited by 20 publications

References 4 publications

Polymeric Drift Control Adjuvants for Agricultural Spraying

Polymeric Drift Control Adjuvants for Agricultural Spraying

Interplay of Head, Tail, and Mid-Chain Radicals in Bulk Free-Radical and Reversible Degenerative Addition Fragmentation Chain-Transfer Polymerizations of Vinyl Acetate

Synthesis and solution behaviors of star hydrophobically modified acrylamide copolymers

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