Stereospecific Free-Radical Polymerization of Methacrylates Using Fluoroalcohols as Solvents

Isobe, Yutaka; Yamada, Kenjiro; Nakano, Tamaki; Okamoto, Yoshio

doi:10.1021/ma990811r

Cited by 107 publications

(80 citation statements)

References 11 publications

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“…From the shape and relative intensities of the signals between 0.5 and 1.2 ppm of the methyl group attached to the polymer backbone, the tacticities of the polymers could be estimated. 68 They were very similar for all samples, suggesting roughly a ratio of 3/2 for the syndiotactic (signal centred at about 0.9 ppm) and atactic (signal centred at about 1.1 ppm) triades present, with only a few (<10%) isotactic (signal centred at about 1.25 ppm) triades formed, as encountered typically for the free radical polymerisation of methacrylates at the applied reaction temperature. 68 Notwithstanding that the polymerisations were conducted in a fluorinated alcohol, the spectra gave no indication of an excessive formation of syndiotactic triades.…”

Section: Resultsmentioning

confidence: 55%

Effect of the zwitterion structure on the thermo-responsive behaviour of poly(sulfobetaine methacrylates)

Hildebrand

Laschewsky

Päch³

et al. 2017

Polym. Chem.

135

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A series of new sulfobetaine methacrylates, including nitrogen-containing saturated heterocycles, was synthesised by systematically varying the substituents of the zwitterionic group. Radical polymerisation via the RAFT (reversible addition-fragmentation chain transfer) method in trifluoroethanol proceeded smoothly and was well controlled, yielding polymers with predictable molar masses. Molar mass analysis and control of the end-group fidelity were facilitated by end-group labeling with a fluorescent dye. The polymers showed distinct thermo-responsive behaviour of the UCST (upper critical solution temperature) type in an aqueous solution, which could not be simply correlated to their molecular structure via an incremental analysis of the hydrophilic and hydrophobic elements incorporated within them. Increasing the spacer length separating the ammonium and the sulfonate groups of the zwitterion moiety from three to four carbons increased the phase transition temperatures markedly, whereas increasing the length of the spacer separating the ammonium group and the carboxylate ester group on the backbone from two to three carbons provoked the opposite effect. Moreover, the phase transition temperatures of the analogous polyzwitterions decreased in the order dimethylammonio > morpholinio > piperidinio alkanesulfonates. In addition to the basic effect of the polymers' precise molecular structure, the concentration and the molar mass dependence of the phase transition temperatures were studied. Furthermore, we investigated the influence of added low molar mass salts on the aqueous-phase behaviour for sodium chloride and sodium bromide as well as sodium and ammonium sulfate. The strong effects evolved in a complex way with the salt concentration. The strength of these effects depended on the nature of the anion added, increasing in the order sulfate < chloride < bromide, thus following the empirical Hofmeister series. In contrast, no significant differences were observed when changing the cation, i.e. when adding sodium or ammonium sulfate.

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Section: Resultsmentioning

confidence: 55%

Effect of the zwitterion structure on the thermo-responsive behaviour of poly(sulfobetaine methacrylates)

Hildebrand

Laschewsky

Päch³

et al. 2017

Polym. Chem.

135

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“…This finding corresponds to the typical situation encountered in the free radical polymerisation of methacrylates at a chosen temperature, in spite of the use of a fluorinated alcohol as a reaction medium. 36,37 End-group analysis of the polymers via the intense absorbance band of the naphthalimide chromophore attached to the R-group is advantageous compared to the use of the rather weak 1 H NMR signals of the aromatic end groups (Fig. 3).…”

Section: Paper Polymer Chemistrymentioning

confidence: 99%

Modulating the solubility of zwitterionic poly((3-methacrylamidopropyl)ammonioalkane sulfonate)s in water and aqueous salt solutions via the spacer group separating the cationic and the anionic moieties

2016

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Modulating the solubility of zwitterionic poly((3-methacrylamidopropyl) ammonioalkane sulfonate)s in water and aqueous salt solutions via the spacer group separating the cationic and the anionic moieties Postprint Complementary to the well-established zwitterionic monomer 3-((3-methacrylamidopropyl)dimethylammonio)propane-1-sulfonate (SPP), the closely related monomers 2-hydroxy-3-((3-methacrylamidopropyl)dimethylammonio)propane-1-sulfonate (SHPP) and 4-((3-methacrylamidopropyl)dimethylammonio)-butane-1-sulfonate (SBP) were synthesised and polymerised by reversible addition-fragmentation chain transfer (RAFT) polymerisation, using a fluorophore labeled RAFT agent. The polyzwitterions of systematically varied molar masses were characterised with respect to their solubility in water and aqueous salt solutions. Both poly(sulfobetaine)s show thermoresponsive behaviour in water, exhibiting phase separation at low temperatures and upper critical solution temperatures (UCST). For both polySHPP and polySBP, cloud points depend notably on the molar mass, and are much higher in D 2 O than in H 2 O. Also, the cloud points are effectively modulated by the addition of salts. The individual effects can be in parts correlated to the Hofmeister series for the anions studied. Still, they depend in a complex way on the concentration and the nature of the added electrolytes, on the one hand, and on the detailed nature of the spacer group separating the anionic and the cationic charges of the betaine moiety, on the other hand. As anticipated, the cloud points of polySBP are much higher than the ones of the analogous polySPP of identical molar mass.Surprisingly, the cloud points of polySHPP are also somewhat higher than the ones of their polySPP analogues, despite the additional hydrophilic hydroxyl group present in the spacer separating the ammonium and the sulfonate moieties. These findings point to a complicated interplay of the various hydrophilic components in polyzwitterions with respect to their overall hydrophilicity. Thus, the spacer group in the betaine moiety proves to be an effective additional molecular design parameter, apparently small variations of which strongly influence the phase behaviour of the polyzwitterions in specific aqueous environments.

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“…2 A high syndiotactic-specificity was observed in vinyl acetate (VAc) polymerization in (CF3)3COH (rr =50%) and ethyl methacrylate (EMA) polymerization in (CF3MCH3)COH (rr =87%), and a high heterotactic-specificity was achieved in vinyl pivalate (VPi) polymerization in (CF3h-COH (mr=61%). These results are in contrast to the widely-believed fact that the stereochemistry of a free radical reaction is little affected by solvents.…”

mentioning

confidence: 99%

Electron Spin Resonance Study of Stereospecific Polymerization of Vinyl Esters in Fluoroalcohols

Yamada

Kajiwara

2001

Polym J

Self Cite

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KEY WORDSVinyl Ester/ Vinyl Acetate/ Stereospecific Polymerization/ Radical/ ESR / Fluoroalcohol I Coupling Constant/ We have recently reported that fluoroalcohols have a remarkable stereochemical effect on the radical polymerizations of vinyl esters 1 and methacrylates. 2 A high syndiotactic-specificity was observed in vinyl acetate (VAc) polymerization in (CF3)3COH (rr =50%) and ethyl methacrylate (EMA) polymerization in (CF3MCH3)COH (rr =87%), and a high heterotactic-specificity was achieved in vinyl pivalate (VPi) polymerization in (CF3h-COH (mr=61%). These results are in contrast to the widely-believed fact that the stereochemistry of a free radical reaction is little affected by solvents. The stereochemical effects of the solvents were ascribed to the hydrogen-bonding interaction between the fluoroalcohols and the ester side groups of the monomer and propagating species, which makes the side groups apparently bulkier, thus causing a steric repulsion among them. In addition to the solvent effect, we also reported that the bulkiness of the vinyl ester monomers significantly alters the polymerization stereochemistry, where the structure of the monomers may affect the structure and reactivity of the growing species. Although the solvents and the monomer structure effects have been discussed in our series of publications, we have not yet obtained direct information on the structure of the propagating species in either case, which may give a more detailed picture of the stereochemical mechanisms.Electron spin resonance (ESR) spectroscopy can provide useful information on both the structures and properties of paramagnetic species. 3 The dynamics and electron density of propagating radicals can be learned from ESR spectra using both the line width and hyperfine splitting constant (hfc). If a hydrogen bond is formed in a fluoroalcohol solvent, the hfc may be changed depending on the strength of the interaction between an ester side group and a fluoroalcohol. Many reports concerning the conformation of propagating radicals using the ESR technique have been published, especially for methacrylate radicals, 4 and it is known that temperature can affect the hfc values or line width of the ESR spectra. 4 a), 5 Hence, the ESR spectra of poly(vinyl ester) propagating radicals would provide information about their structures and shed light on the reaction mechanism. Therefore, in the present study, we investigated the effect of the fluoroalcohol and the bulkiness of the monomers on the conformation of the poly(vinyl ester) radicals. The ESR spectra of the propagating radicals of V Ac were clearly observed in both solution polymerization in (CF3)sCOH and bulk polymerization at various temperatures. The spectra were interpreted in conjugation with the stereostructure of the obtained polymers. ESR signals were also obtained for the propagating radicals of VPi and vinyl 2,2-bis(trifluoromethyl)propionate (VF6-Pi).Although the ESR studies of the propagating radical of VAc in bulk or using benzene as a solvent have been reporte...

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Stereospecific Free-Radical Polymerization of Methacrylates Using Fluoroalcohols as Solvents

Cited by 107 publications

References 11 publications

Effect of the zwitterion structure on the thermo-responsive behaviour of poly(sulfobetaine methacrylates)

Effect of the zwitterion structure on the thermo-responsive behaviour of poly(sulfobetaine methacrylates)

Modulating the solubility of zwitterionic poly((3-methacrylamidopropyl)ammonioalkane sulfonate)s in water and aqueous salt solutions via the spacer group separating the cationic and the anionic moieties

Electron Spin Resonance Study of Stereospecific Polymerization of Vinyl Esters in Fluoroalcohols

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