Anionic Polymerization of Nonpolar Monomers

Quirk, Roderic P.

doi:10.1016/b978-0-444-53349-4.00076-5

Cited by 8 publications

(9 citation statements)

References 170 publications

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“…Numerous research studies in such aspects have made the polymerization features of the above nonpolar diene monomers pretty clear. Until now, almost all existing structures of the above three conjugated diene polymers can be precisely achieved by carefully selecting an appropriate ionic/coordination polymerization procedure, as many books summarized. − …”

Section: Introductionmentioning

confidence: 99%

Organocatalyzed Group Transfer Polymerization of Alkyl Sorbate: Polymer Synthesis, Postpolymerization Modification, and Thermal Properties

Liu

Chen

2021

Macromolecules

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The current work presents the organocatalyzed group transfer polymerization (GTP) of alkyl sorbate, the postpolymerization modification at the double bond of the poly(alkyl sorbate) (PAS) backbone, and its thermal properties. The selected alkyl sorbate includes ethyl, n-hexyl, and n-octadecyl sorbate with the carbon number of the n-alkyl side chain being three times between every two neighboring monomers. The polymerization kinetics and mechanisms are briefly discussed for both the t-Bu-P4- and Me3SiNTf2-catalyzed GTPs of ethyl sorbate. Both of the two GTPs only undergo 1,4-addition to produce trans-rich PASs in which the former affords 81.9–85.4% trans content and the latter a much higher value as trans > 96%. The hydrogenation and epoxidation of the internal double bond turn out to be quantitative to provide the hydrogenated and epoxidized polymers, PAS-H2 and PAS-epoxy. The hydrogenation process makes the diastereochemistry and stereoregular structures of the two chiral carbons in the monomeric unit distinguishable by 13C NMR spectra, from which we know that the t-Bu-P4-catalyzed GTP produces erythro-rich PASs (erythro content = ca. 64%), while the Me3SiNTf2-catalyzed GTP gives relatively threo-rich PASs (threo content = 56–58%). However, the diisotactic/disyndiotactic ratios determined by 13C NMR spectra do not show an obvious difference between each other. Thermogravimetric analyses suggest that PAS-H2 shows the highest thermal stability and PAS-epoxy the lowest, due to the different polarity of the newly formed C–C bond in the main chain before and after the chemical modification of the internal double bond. For the amorphous poly(ethyl sorbate) (PES) and poly(n-hexyl sorbate) (PHS), change of the ethyl side group to n-hexyl greatly decreases the glass transition temperature (T g). As for the same PES/PHS series polymers, either the hydrogenation or the epoxidation of the internal double bond drastically changes the T g value of the final polymer product. In addition, the ca. 10% difference in the trans-cis composition for unmodified PES or PHS almost has no effect on T g values, while the erythro/threo content shows a prominent influence for the chemically modified polymers as the T g value can be changed from several to tens of Celsius degree when the same polymer changes from erythro-rich to threo-rich. On the contrary, crystallizable poly(n-octadecyl sorbate) (PODS) and its modified polymers possess melting points (T m) in a pretty narrow temperature range of 34.7–41.4 °C, which is almost the same as the T m of n-octadecyl sorbate. It is likely that the T m values of PODS and its derivative polymers are only determined by the crystallization of the long n-octadecyl side chain, almost irrespective of the chain length, the trans-cis isomerization, the diastereochemistry, and the stereochemistry of the main chain.

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Section: Introductionmentioning

confidence: 99%

Organocatalyzed Group Transfer Polymerization of Alkyl Sorbate: Polymer Synthesis, Postpolymerization Modification, and Thermal Properties

Liu

Chen

2021

Macromolecules

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“…The goal of this research was to develop a novel, efficient synthetic route for making tadpole-shaped polystyrene based on previous work for the synthesis of cyclic polystyrene, , 8-shaped polystyrene and asymmetric star polymers. − Living alkyllithium-initiated polymerization is one of the most reliable synthetic approaches to make polystyrenes with predictable molecular weights, narrow molecular weight distributions, and quantitative chain-end functionalities. ,,− It is known from previous work that using an unsaturated, vinyl-substituted, alkyllithium initiator for living anionic polymerization can ensure that every α-chain end has a vinyl group. , Linking reactions of polymeric organolithium compounds with silyl halides are very efficient. , Utilizing this background, the reaction scheme for the synthesis of tadpole-shaped polystyrene shown in Scheme was proposed. The first step was the preparation of the macromolecular linking agent (ω-methyldichlorosilylpolystyrene, ( 2 ).…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of Well-Defined, Tadpole-Shaped Polystyrene with a Single Atom Junction Point

et al. 2018

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An efficient method for synthesis of welldefined, well-characterized, tadpole-shaped polystyrene with a single atom junction point that is optimal for the study of dynamics has been developed using anionic polymerization, silicon chloride linking chemistry, and metathesis ring closure. The difunctional macromolecular linking agent, ω-methyldichlorosilylpolystyrene, was formed by reacting sec-butyllithium-initiated poly(styryl)lithium with excess (30×) methyltrichlorosilane to eliminate formation of linear dimer and three-arm star polystyrene. The asymmetric, three-arm, star precursor was formed by linking excess α-4-pentenylpoly(styryl)lithium (α-PSLi) with the macromolecular linking agent, and the excess α-PSLi functionalized with ethylene oxide before termination with methanol to facilitate chromatographic separation. Cyclization of the three-arm, star precursor to form tadpole-shaped polystyrene was effected in methylene chloride at high dilution using the Grubbs first generation catalyst, bis(tricyclohexylphosphine)benzylidene ruthenium(IV) chloride. The tadpole product was uniquely characterized by MALDI-MS using peaks that appeared characteristically 28 m/z units lower than those of the corresponding asymmetric, three-arm, star precursor, which corresponds to the loss of an ethylene unit. MD simulations find a smaller hydrodynamic volume for the tadpole-shaped PS as compared to the three-arm star precursor, in quantitative agreement with GPC results. Incorporating one cycle in the molecule, while leaving one chain end, leads to an increase in T g of only 2.7 °C, much smaller than the increase of 13.6 °C seen when going from the linear chain to cyclic analog with no ends at all. The results are consistent with self-plasticization by free chain ends.

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“…It was envisioned that a new, efficient synthesis of 8-shaped polymers could be developed based on our previous work for the synthesis of macrocyclic polystyrenes utilizing living anionic polymerization, silicon chloride linking chemistry, and metathesis ring closure . Living alkyllithium-initiated polymerization is one of the most reliable methods for the synthesis of polystyrenes with controlled, predictable molecular weights, narrow molecular weight distributions, and quantitative chain-end functionalizations. − The use of 4-pentenyllithium as initiator ensures that every α chain end has a vinyl group . It is known from previous work that the reaction of polymeric organolithium compounds with silyl halides is a very efficient reaction that is not complicated by the competing side reactions that are generally observed for linking reactions with organic halides.…”

Section: Results and Discussionmentioning

confidence: 99%

“…However, a mixture of 2-arm star, 3-arm star, and 4-arm star was obtained; even after several fractionations it was not possible to obtain a pure 4-arm star. Therefore, a more efficient linking agent, 1,2-bis(methyldichlorosilyl)ethane, was chosen for further study because the ethylene spacer between the two silicon groups reduces steric crowding in the linking reaction with poly(styryl)lithium arms; ,− in addition, the presence of protons in the ethylene bridge was found to facilitate the characterization of both the 4- star -polystyrene precursor and 8-shaped polystyrene using 1 H NMR.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Polymerization of styrene was carried out using 5-lithio-1-pentene as the initiator and using benzene as the solvent. 10 equiv of THF was added to the initiator to promote dissociation of the aggregates of this primary organolithium initiator; , lower average degrees of aggregation favor initiation over propagation, promoting formation of narrow molecular weight distribution polymers. − ,, The resulting α-4-pentenyl PSLi chains were linked with 1,2-bis(methyldichlorosily)ethane. A 20% excess of PSLi chain ends relative to the Si–Cl groups in 1,2-bis(methyldichlorosily)ethane was added to drive the linking reaction to completion. ,,, The addition of THF not only increased the rate of initiation to propagation, it also dramatically accelerated the rate of the chlorosilane linking reaction as reported by Burns and Register .…”

Section: Results and Discussionmentioning

confidence: 99%

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Synthesis and Isomeric Characterization of Well-Defined 8-Shaped Polystyrene Using Anionic Polymerization, Silicon Chloride Linking Chemistry, and Metathesis Ring Closure

Mao

Wesdemiotis

et al. 2017

Macromolecules

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A methodology to efficiently synthesize well-defined, 8-shaped polystyrene using anionic polymerization, silicon chloride linking chemistry, and metathesis ring closure has been developed, and the 8-shaped architecture was ascertained using the fragmentation pattern of the corresponding Ag + adduct, acquired with tandem mass spectrometry. The 4-arm star precursor, 4-star-α-4-pentenylpolystyrene, was formed by linking α-4-pentenylpoly(styryl)lithium (PSLi) with 1,2-bis(methyldichlorosilyl)ethane and reacting the excess PSLi with 1,2-epoxybutane to facilitate purification. Ring closure of 4-star-α-4-pentenylpolystyrene was carried out in dichloromethane under mild conditions using a Grubbs metathesis catalyst, bis(tricyclohexylphosphine)benzylidine ruthenium(IV) chloride. Both the 4-arm star precursor and resulting 8-shaped polystyrene were characterized using SEC, NMR, and MALDI-ToF mass spectrometry (MS). Tandem mass spectrometry (MS 2 ) was used for the first time to study the fragmentation pattern of 8shaped polystyrene. The results confirmed the formation of the intra-silicon-linked, 8-shaped polystyrene isomer, but the observed spectra left open the possibility that the inter-silicon-linked, 8-shaped polystyrene isomer was also produced.

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Anionic Polymerization of Nonpolar Monomers

Cited by 8 publications

References 170 publications

Organocatalyzed Group Transfer Polymerization of Alkyl Sorbate: Polymer Synthesis, Postpolymerization Modification, and Thermal Properties

Organocatalyzed Group Transfer Polymerization of Alkyl Sorbate: Polymer Synthesis, Postpolymerization Modification, and Thermal Properties

Synthesis and Characterization of Well-Defined, Tadpole-Shaped Polystyrene with a Single Atom Junction Point

Synthesis and Isomeric Characterization of Well-Defined 8-Shaped Polystyrene Using Anionic Polymerization, Silicon Chloride Linking Chemistry, and Metathesis Ring Closure

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