The polymerization of <i>n</i>‐butyl isocyanate at low catalyst concentrations

Ahmed, Mudrika; Parsons, Ian W.; Haward, R. N.

doi:10.1002/pol.1980.170180139

Cited by 5 publications

(2 citation statements)

References 7 publications

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“…Polyisocyanates, as well as double-helical DNA, poly(aryl amide)s, and cellulose derivatives are well known as typical semiflexible polymers and form liquid crystals because of stiffness of the main chain . A significant amount of experimental data concerning solution properties, liquid crystallinity, and crystal structures of polyisocyanates have been reported. 1a,b,, It had been difficult to control the molecular weight in the polymerzation of isocyanates. 1c, However, Novak and co-workers 6 recently reported that the polymerization of isocyanates with organotitanium compounds proceeds in a living manner.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Conformational Characteristics of Poly(phenyl isocyanate)s Bearing an Optically Active Ester Group

Maeda

Okamoto

1999

Macromolecules

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Optically active phenyl isocyanates (1-9) bearing an optically active ester group were synthesized and polymerized with an achiral anionic initiator. The resulting polymers from 1 and 4-9 showed a much greater specific rotation than that of the corresponding monomer and an intense circular dichroism (CD) band caused by the main-chain absorption, indicating that these polymers have a predominantly one-handed helical conformation in solution. On the other hand, the polymers obtained from 2 and 3 showed a much smaller specific rotation and a weaker CD band than poly-1, which suggests that, as the distance between the polymer main chain and the asymmetric center on the side chain increases, the asymmetric center cannot effectively induce an excess of one helical twist sense of the polymer main chain at room temperature. However, the specific rotation and CD intensity of poly-2 greatly increased because of a predominantly one-handed helical conformation at low temperatures. The polymers obtained from 3-9 did not show such a temperature effect on conformational change. Specific rotation of the copolymers of chiral 8 and achiral 10 changed from a positive to a negative value with an increase in the content of the optically active unit. The helicity of the copolymer may depend on the composition.

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Section: Introductionmentioning

confidence: 99%

Synthesis and Conformational Characteristics of Poly(phenyl isocyanate)s Bearing an Optically Active Ester Group

Maeda

Okamoto

1999

Macromolecules

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“…and Shashoua et al observed that the molecular weight of anionically polymerized n -alkyl isocyanates showed little or no dependence upon the monomer-to-initiator ratio. By carefully performing n -butyl isocyanate polymerizations with high monomer-to-initiator ratios, Ahmed et al did observe a relationship between the molecular weight ( M v ) of the polymer and the monomer-to-initiator ratio . However, the reported absolute molecular weights, on average, were greater than the expected molecular weights by an order of magnitude, and the observed relationship between M v and the monomer-to-initiator ratio was curved and not linear.…”

Section: Introductionmentioning

confidence: 99%

Living Organotitanium(IV)-Catalyzed Polymerizations of Isocyanates

1996

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An organotitanium(IV) compound, TiCl3OCH2CF3, 1, was found to polymerize n-hexyl isocyanate to high yields and without the formation of cyclic trimer. CpTiCl2L (L = −OCH2CF3, −N(CH3)2, −CH3), 2−4, respectively, likewise polymerized n-hexyl isocyanate but also polymerized isocyanates in the presence of donor solvents and isocyanates possessing donor functional groups, activated olefins, and strained olefins. The activity of the organotitanium(IV) catalysts decreased with increasing steric bulk about the metal center and increasing electron donation to the metal center from the ligands. The polymerization of n-hexyl isocyanate using organotitanium(IV) compounds is living. The PDIs of PHIC synthesized using catalysts 1−4 were found to range from 1.05 to 1.2. The molecular weight of the polymer formed in polymerizations of n-hexyl isocyanate using catalysts 1−4 varied linearly as a function of the monomer-to-initiator ratio and the percent conversion of the polymerization. Polymerizations using 2 can be endcapped quantitatively, and well-defined block copolymers can be synthesized using catalysts 1−4. The kinetics for polymerizations using catalysts 1 and 2 are first-order in both monomer and catalyst (k 1 = 8.5 × 10-4 mol L-1 s-1, k - 1 = 3.8 × 10-4 s-1). The active endgroup of a polymerization using 3 was observed using IR spectroscopy, and the frequency of the IR stretch (1548 cm-1) was consistent with an η2-amidate endgroup structure. Finally, the kinetic data for the polymerization of n-hexyl isocyanate and the known chemistry of CpTiCl2L compounds were found to be consistent with a propagation step that occurs via a bifunctional activation mechanism.

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Block copolymers derived from azobiscyanopentanoic acid. V. Block copolymerization initiated with a polyethylene glycol containing scissile azo linkages in its main chain

Ueda

Nagai

1987

J. Polym. Sci. A Polym. Chem.

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The polymerization of n‐butyl isocyanate at low catalyst concentrations

Cited by 5 publications

References 7 publications

Synthesis and Conformational Characteristics of Poly(phenyl isocyanate)s Bearing an Optically Active Ester Group

Synthesis and Conformational Characteristics of Poly(phenyl isocyanate)s Bearing an Optically Active Ester Group

Living Organotitanium(IV)-Catalyzed Polymerizations of Isocyanates

Block copolymers derived from azobiscyanopentanoic acid. V. Block copolymerization initiated with a polyethylene glycol containing scissile azo linkages in its main chain

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