The Nature of Crosslinking inN-Vinylformamide Free-Radical Polymerization

Gu, Leilei; Zhu, Shiping; Hrymak, Andrew N.; Pelton, Robert

doi:10.1002/1521-3927(200102)22:3<212::aid-marc212>3.0.co;2-b

Cited by 26 publications

(32 citation statements)

References 2 publications

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“…[34] In the case of PNIPA, Gao and Frisken reported that microgels are formed during aqueous dispersion polymerization (in a non-redox system, i.e., without TEMED) at 70 8C (>LCST), and they attributed gel formation to interchain selfcrosslinking through a chain transfer reaction in polymer chains associated into compact nano-aggregates. [7] In addition, they estimated that the likely crosslinking position is the backbone carbon.…”

Section: Structure and Formation Mechanism Of Pnn (N>n ã ) Gelmentioning

confidence: 99%

Gel Formation and Molecular Characteristics of Poly(N‐isopropylacrylamide) Prepared by Free‐Radical Redox Polymerization in Aqueous Solution

Haraguchi

2010

Macro Chemistry & Physics

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The molecular characteristics of poly(N‐isopropylacrylamide) (PNIPA), prepared by free‐radical polymerization using an aqueous redox initiator and reaction conditions comparable to those used in the synthesis of nanocomposite gels, were investigated by altering the monomer concentration ([NIPA]) and the polymerization temperature (Tp) across the transition temperature (LCST). When Tp<LCST, there is a critical [NIPA] (=n*) above which PNIPA partially forms gels in the absence of a chemical crosslinker, and the gel fraction increases with increasing [NIPA] and decreasing Tp. In the range of n<n*, the molecular weight of soluble PNIPA correlated well with [NIPA]. When Tp>LCST, gels were not formed regardless of [NIPA]. The structure and mechanism of formation of self‐crosslinked PNIPA gels are discussed.magnified image

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Section: Structure and Formation Mechanism Of Pnn (N>n ã ) Gelmentioning

confidence: 99%

Gel Formation and Molecular Characteristics of Poly(N‐isopropylacrylamide) Prepared by Free‐Radical Redox Polymerization in Aqueous Solution

Haraguchi

2010

Macro Chemistry & Physics

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“…al, who reported on the radical homopolymerization of VFA in water solutions 49. Gel formation was observed using VFA concentrations higher than 20 wt.‐% and were ascribed to crosslinking reactions of the formamide groups 49. Because of the gel formation, diffusion of free VFA monomer to the surface is strongly prevented.…”

Section: Resultsmentioning

confidence: 99%

Radical Grafting Polymerization of Vinylformamide with Functionalized Silica Particles

Meyer

Spange

Hesse

et al. 2003

Macro Chemistry & Physics

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Two different radical polymerization techniques have been applied to covalently graft vinylformamide (VFA) onto silica particles. Grafting by the polymerization of VFA using an immobilized azo initiator on silica has been found less effective, because monomer conversion is limited in non‐aqueous solvents and grafting yields are low in water. Radical copolymerization of VFA with vinyltriethoxysilane (VTS)‐functionalized silica particles is suitable to produce poly(vinylformamide) (PVFA) silica hybrid particles in respectable yield. The VFA/VTS‐silica ratio determines the degree of grafting. The PVFA‐VTS‐co‐grafted silica particles can be acidically hydrolyzed into poly(vinylamine)‐grafted silica particles. Molecular structures of the surface groups and grafted polymer chains have been confirmed by means of solid state 13C{1H} cross‐polarization magic‐angle spinning (CP MAS) NMR spectroscopy. Zeta potential measurements show the altering of the former silica particles surface charges arising from the introduction of basic groups on the surface.

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“…[20–22, 26, 48] These species are generally formed through hydrogen atom abstraction events yielding tert-C free radicals that are stabilized by their conjugation to adjacent groups. In addition to hydrogen transfer originating from the polymer backbone, sometimes side-chain transfer products need to be considered as well.…”

Section: Resultsmentioning

confidence: 99%

“…[26, 27] Herein, we report on the preparation and characterization of cross-linker-free microgels from poly(ethylene glycol) (PEG) side-chain monomers. These microgel particles can be synthesized by precipitation polymerization of poly/oligo ethylene glycol (meth)acrylates (OEG(M)A).…”

Section: Introductionmentioning

confidence: 99%

Oligo(ethylene glycol)-sidechain microgels prepared in absence of cross-linking agent: Polymerization, characterization and variation of particle deformability

Welsch

Lyon

2017

PLoS ONE

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We present a systematic study of self-cross-linked microgels formed by precipitation polymerization of oligo ethylene glycol methacrylates. The cross-linking density of these microgels and, thus, the network flexibility can be easily tuned through the modulation of the reaction temperature during polymerization. Microgels prepared in absence of any difunctional monomer, i.e. cross-linker, show enhanced deformability and particle spreading on solid surfaces as compared to microgels cross-linked with varying amounts of poly(ethylene glycol diacrylate) (PEG-DA) in addition to self-crosslinking. Particles prepared at low reaction temperatures exhibit the highest degree of spreading due to the lightly cross-linked and flexible polymer network. Moreover, AFM force spectroscopy studies suggest that cross-linker-free microgels constitute of a more homogeneous polymer network than PEG-DA cross-linked particles and have elastic moduli at the particle apex that are ~5 times smaller than the moduli of 5 mol-% PEG-DA cross-linked microgels. Resistive pulse sensing experiments demonstrate that microgels prepared at 75 and 80°C without PEG-DA are able to deform significantly to pass through nanopores that are smaller than the microgel size. Additionally, we found that polymer network flexibility of microgels is a useful tool to control the formation of particle dewetting patterns. This offers a promising new avenue for build-up of 2D self-assembled particle structures with patterned chemical and mechanical properties.

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The Nature of Crosslinking inN-Vinylformamide Free-Radical Polymerization

Cited by 26 publications

References 2 publications

Gel Formation and Molecular Characteristics of Poly(N‐isopropylacrylamide) Prepared by Free‐Radical Redox Polymerization in Aqueous Solution

Gel Formation and Molecular Characteristics of Poly(N‐isopropylacrylamide) Prepared by Free‐Radical Redox Polymerization in Aqueous Solution

Radical Grafting Polymerization of Vinylformamide with Functionalized Silica Particles

Oligo(ethylene glycol)-sidechain microgels prepared in absence of cross-linking agent: Polymerization, characterization and variation of particle deformability

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