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8 results on '"Yixian Wu"'

4. Graft copolymer of PVAc-g-PIB by cationic polymerization

Author

Yixian Wu, Xu Xu, Guanying Wu, and Jie Lu

Subjects
Isobutylene, Materials science, Polymers and Plastics, General Chemical Engineering, Cationic polymerization, Solution polymerization, General Chemistry, Grafting, chemistry.chemical_compound, chemistry, Polymerization, Polymer chemistry, Materials Chemistry, Vinyl acetate, Copolymer, Molar mass distribution
Abstract

The cationic grafting polymerization of isobutylene (IB) from a poly(vinyl acetate) (PVAc) backbone was initiated by the combination of PVAc with titanium tetrachloride (TiCl4) in methylene chloride (CH2Cl2) solution at –65°C. A mixture of IB homopolymer and PVAc grafted with approximately 9.5% (mol) PIB copolymer was formed. 1H- and 13C-NMR spectra confirmed that IB was successfully grafted from the PVAc backbone. PVAc exhibits both initiation and modification behavior. PVAc acts as a macro-initiator in the polymerization to form the graft copolymer. It also plays a role in the homopolymerization of IB initiated by the combination of residual water with TiCl4 and the product PIB with a narrow molecular weight distribution.

Published
2003
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5. Competitive complexation in the cationic polymerization of isobutylene in a nonpolar medium

Author

Guanying Wu and Yixian Wu

Subjects
Isobutylene, chemistry.chemical_classification, Polymers and Plastics, Organic Chemistry, Cationic polymerization, Solution polymerization, Polymer, chemistry.chemical_compound, chemistry, Polymerization, Polymer chemistry, Materials Chemistry, Molar mass distribution, Lewis acids and bases, Methyl acrylate
Abstract

The cationic polymerization of isobutylene coinitiated by Al(i-Bu)Cl2(Al) was carried out in mixed butane–butene fractions at −50 °C. The expected polymerization processes induced by the trace of moisture with Al system in the presence of a small amount of external electron-donor modifiers, such as methyl acrylate (MA) and dimethyl sulfoxide (DMSO), were obtained. The experimental results showed that these polymerizations produced polymers with relatively high number-average molecular weights and narrow molecular weight distributions (1.5–2.2). That the gel permeation chromatography traces of the polymers depended on the types and concentrations of external donors suggested that there existed competitive complexation reactions of various electron donors (H2O, MA, and DMSO) with the Al Lewis acid. The roles of external electron donors were to take part in the initiation step by competitive complexation and to modify the reactivity of the growing chain ends in the propagation step by mediation and/or solvation, which impaired the high reactivity of the original growing chain ends. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2209–2214, 2002

Published
2002
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6. Kinetic Investigation of the Carbocationic Polymerization of Isobutylene with the H2O/TiCl4/ED Initiating System

Author

Yongxia Tan, Yixian Wu, and Guanying Wu

Subjects
Isobutylene, Reaction mechanism, Order of reaction, Polymers and Plastics, Organic Chemistry, Cationic polymerization, Electron donor, Solution polymerization, Inorganic Chemistry, chemistry.chemical_compound, chemistry, Polymerization, Polymer chemistry, Materials Chemistry, Dichloromethane
Abstract

The cationic polymerizations of isobutylene (IB) initiated by the H2O/TiCl4 in dichloromethane (CH2Cl2) at −30 °C were carried out in the absence and presence of various external electron pair dono...

Published
2002
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7. Electron‐pair‐donor reaction order in the cationic polymerization of isobutylene coinitiated by AlCl3.

Author

Yan Li, Yixian Wu, Xu Xu, Lihu Liang, and Guanying Wu

Subjects
*CHEMICAL reactions, *POLYMERIZATION, *MOLECULAR weights, *ORGANIC compounds
Abstract

The cationic polymerizations of isobutylene (IB) initiated by an H2O/AlCl3 system were carried out in a mixture of n‐hexane/methylene dichloride of 60/40 v/v at −50 °C in the presence of various external electron pair donors (EDs), including methyl benzoate (MB), ethyl benzoate (EB), and methyl acrylate (MA). The effects of the concentrations of EDs ([ED]) and polymerization time on monomer conversion and kinetics of IB polymerization were also investigated. The complexes between AlCl3 and the esters were soluble in the polymerization system at −50 °C. The polymers with high molecular weights and relatively narrow molecular weight distributions were obtained in the presence of the EDs. The rate of polymerization decreased with increasing [ED]. The kinetic orders of the EDs were remarkably dependent on their chemical structure, steric hindrance from moieties, and concentration in the polymerization system. The reaction order of MB was determined to be around −1.3 when [MB] ≤ 0.40 mmol/L, whereas it was −12.9 when [MB] ≥ 0.40 mmol/L. The reaction order of EB was determined to be −1.36 when [EB] ≤ 0.41 mmol/L, whereas it was −3.36 when [EB] ≥ 0.41 mmol/L. The reaction order of MA was determined to be −1.85 when [MA] ≤ 0.48 mmol/L, whereas it was −16.7 when [MA] ≥ 0.48 mmol/L. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3053–3061, 2007 [ABSTRACT FROM AUTHOR]

Published
2007
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