Oligomerization Stereochemistry of Vinyl Monomers. 1. A Steroselective Synthesis of meso-2,4-Di(2-pyridyl)-pentane

Tien, C. F.; Hogen‐Esch, Thieo E.

doi:10.1021/ma60053a035

Cited by 17 publications

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“…Vinyl pyridine polymers are particularly important as polyelectrolytes and polymeric reagents, and have a range of electrical applications. The presence of the heteroatom on the pyridine ring also results in interesting mechanistic implications during anionic or radical polymerization of vinyl pyridines 49–57. Anionic polymerization of 2‐vinyl pyridine carried out by conventional strong nucleophiles as initiators, apart from reacting with the vinyl bond, also attacks the aromatic ring of the monomer as well as the growing polymer chain.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of poly(2‐vinyl pyridine)‐b‐poly(n‐hexyl isocyanate) amphiphilic coil‐rod block copolymer by anionic polymerization

Shin

Han

Samal

et al. 2004

J. Polym. Sci. A Polym. Chem.

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A well-defined amphiphilic coil-rod block copolymer, poly(2-vinyl pyridine)b-poly(n-hexyl isocyanate) (P2VP-b-PHIC), was synthesized with quantitative yields by anionic polymerization. A low reactive one-directional initiator, potassium diphenyl methane (DPM-K), was very effective in polymerizing 2-vinyl pyridine (2VP) without side reactions, leading to perfect control over molecular weight and molecular weight distribution over a broad range of initiator and monomer concentration. Copolymerization of 2VP with n-hexyl isocyanate (HIC) was carried out in the presence of sodium tetraphenyl borate (NaBPh 4 ) to prevent backbiting reactions during isocyanate polymerization. Terminating the living end with a suitable end-capping agent resulted in a P2VP-b-PHIC coil-rod block copolymer with controlled molecular weight and narrow molecular weight distribution. Cast film from a chloroform solution of P2VP-b-PHIC displayed microphase separation, characteristic of coil-rod block copolymers.

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Section: Resultsmentioning

confidence: 99%

Synthesis of poly(2‐vinyl pyridine)‐b‐poly(n‐hexyl isocyanate) amphiphilic coil‐rod block copolymer by anionic polymerization

Shin

Han

Samal

et al. 2004

J. Polym. Sci. A Polym. Chem.

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“…VR and Vc are of order 2m'2 X 2m~2; all their elements are zero except for the gRth and gcth element on the main diagonal which are unity. W'q is now given by U* (10) vx where the supermatrix W is given by where E" is the unit matrix of the same order v as Um(2) and Ur(2). For m-ads that implicitly comprise two different stereosequences the two different matrices W'q obtained from eq 17 for each sequence must be added (e.g., if q is mmmr, W'q is the sum of the two matrices formed by eq 17 with mmmr and rmmm).…”

Section: Table II Matricesmentioning

confidence: 99%

Epimerization of vinyl polymers to stereochemical equilibrium. 1. Theory

Suter¹

1981

Macromolecules

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conventional PGC and PHGC with catalytic hydrogenation.The fact that there exists fairly good agreement between the relative yields before and after hydrogenation supports the validity of the presumption for the assignment of some peaks on the pyrogram in Figure 1A. Thus, the identified peaks in the monomer and the trimer regions on the pyrograms in Figures 1A and IB mostly reflect the H-H and/or the T-T structures. Although the monomer is still most abundant among the products on the pyrogram, its yield only amounts to 20.4%. On the other hand, the formation of a comparable size for the multiplets of the monomer, dimer, and trimer regions suggests that random scission type thermal degradation might be predominant for H-H PS.As was reported in the PMS work on H-H PS by Lüderwald,6 we can also find on the pyrogram in Figure IB a very minor PhCH2Ph peak (peak 10) and a fairly strong PhCH(CH3)Ph peak (peak 35). This suggests either that these structures were incorporated through minor byproducts at the stage of the monomer preparation or that thermal rearrangements took place during the pyrolysis. Furthermore, it is very interesting to note that, even though very minor, PhCH2CH2Ph and PhCH2CHPhCH3 peaks can be observed on the pyrogram of H-T PS (Figure 1C). This fact, which was also pointed out by Alajbeg et al.,13 could be indicative of the existence of H-H linkages even in H-T PS.

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“…3 ) (8). These epimerizations, when carried out on dimers [7] and trimers [ 8 ] , have been shown to produce a statistically expected mixture of stereoisomers without the formation of side products (1,2). It appears, therefore, that the section of the chain close to the 13CH3 end group is highly stereoregular.…”

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confidence: 97%

“…with a cation side approach of electrophile to [13a] (1,2). With larger or more strongly coordinated cations the corresponding nonchelated ion pairs of [13] and [14] should increasingly prevail resulting in a loss of stereoselectivity.…”

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Stereochemistry of anionic oligomerization of vinyl monomers. VI. Low‐molecular‐weight stereoregular polymers of 2‐vinylpyridine prepared with li salts as initiators in THF

Hogen‐Esch

Tien

1979

J. Polym. Sci. B Polym. Lett. Ed.

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We have recently shown that oligomers [7] and [8] of 2-vinylpyridine prepared with Li and Na salts as initiators in THF [eq. (l)] are predominantly Q 95%) isotactic (1,2). -- C2I-C61C7I-C121 C21. C71 n=l; 131. CSI ~2 ; 141.C91 n=3; C51. [lo] 11.5-6; [6]. [ I 1 1 n=6-12 1123 n -Thus, the methylation of and the 2-vinylpyridine addition to anion [2] occurs with the same meso stereochemistry. Moreover, with a 4-pyridyl unit in ultimate position or both ultimate and penultimate positions the methylation of such an anion is not stereoselective. With larger or more extensively coordinated cations the methylation stereoselectivity of [2] is decreased dramatically. These results have been shown to be consistent with the occurrence of diastereomeric ion pairs [13] and [14]. With Li and Na as counterions these ion pairs most likely exist in their respective chelated forms [13a] and [14a] (3): -*qJ paw n+ 2-Py 2-Py 2-Py 2-Py C13Jl C14al Since [13a] should be preferred because of butane gauche and PCHz-chain end pyridine lone-pair interactions, the stereoselectivity [eq. (l)] is consistent

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Oligomerization Stereochemistry of Vinyl Monomers. 1. A Steroselective Synthesis of meso-2,4-Di(2-pyridyl)-pentane

Cited by 17 publications

References 1 publication

Synthesis of poly(2‐vinyl pyridine)‐b‐poly(n‐hexyl isocyanate) amphiphilic coil‐rod block copolymer by anionic polymerization

Synthesis of poly(2‐vinyl pyridine)‐b‐poly(n‐hexyl isocyanate) amphiphilic coil‐rod block copolymer by anionic polymerization

Epimerization of vinyl polymers to stereochemical equilibrium. 1. Theory

Stereochemistry of anionic oligomerization of vinyl monomers. VI. Low‐molecular‐weight stereoregular polymers of 2‐vinylpyridine prepared with li salts as initiators in THF

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