Control of Sequence Distribution of Ethylene Copolymers:  Influence of Comonomer Sequence on the Melting Behavior of Ethylene Copolymers

Hung, Joyce; Cole, and Adam P.; Waymouth, Robert M.

doi:10.1021/ma021779v

Cited by 51 publications

(60 citation statements)

References 67 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, these copolymers might not meet all properties required for the use in plastic industry because they probably lost completely the thermal properties. As a result of the fact that disadvantages of alternating copolymer, which have been found by Hung et al [17] that the polymer with a highly alternating sequence distribution did not exhibit any melting behavior. Based on the result, when the incorporations of comonomers increased, the obtained polymer tended to exhibit more highly alternating copolymer structure (r E r H < 1).…”

Section: Effect Of the Amount Of 1-hexene On Microstructure Of Copolymentioning

confidence: 96%

Ethylene-hexene copolymer derived from [t-butylfluorenylsilyl-amido] dimethyl titanium complex

Chaichana¹,

Khaubunsongserm²,

Praserthdam³

et al. 2010

Express Polym. Lett.

View full text Add to dashboard Cite

Abstract. The copolymers of ethylene and 1-hexene were prepared with half-metallocene titanium complex ([t-BuNSiMe2Flu]TiMe2) and modified methylaluminoxane (MMAO). The initial concentrations of 1-hexene were varied to investigate how the different amounts of comonomer affect on the catalytic activity of copolymerization system and microstructure of the copolymers. It has been found that this catalytic system was not active for hexene polymerization, however, it can be active when ethylene was introduced to perform ethylene-hexene copolymerization. As comonomer, 1-hexene provides positive comonomer effect on the system although very high concentration of 1-hexene was introduced. However, the microstructures of the obtained copolymers, which were examined by 13 C-NMR need to be improved because with highly alternating sequence distribution of comonomer causing them losing some essential specific thermal properties.

show abstract

Section: Effect Of the Amount Of 1-hexene On Microstructure Of Copolymentioning

confidence: 96%

Ethylene-hexene copolymer derived from [t-butylfluorenylsilyl-amido] dimethyl titanium complex

Chaichana¹,

Khaubunsongserm²,

Praserthdam³

et al. 2010

Express Polym. Lett.

View full text Add to dashboard Cite

show abstract

“…DEPT was used because of its prioritized advantages that include enhanced 13 C signal sensitivity; superior spectral editing; and capability to distinguish methyl CH 3 , methylene CH 2 , and methine CH sites, and identify branches. [37,38]. <r E r C > ≈ r E r C confirms terminal model statistical copolymerization mechanism.…”

Section: Copolymer Microstructure and Flory Ethylene Sequence Length mentioning

confidence: 53%

“…Seger and Maciel have highlighted the advantages of this approach. Next, the monad and diad mole fractions, and the copolymer microstructural parameters of our interest were calculated using the relations reported in References [37,38]. The E−4M1P average copolymer compositions and the corresponding microstructural parameters were calculated following the procedure published by Kimura et al [39].…”

Section: Copolymer Microstructure and Flory Ethylene Sequence Length mentioning

confidence: 99%

“…In the literature [38,73], based on experimental data, ethylene−α-olefin copolymers have been classified as follows: (i) random (<r E r α-olefin > = 1); (ii) slightly alternating to random (<r E r α-olefin > = 0.2−1.0); (iii) highly alternating (<r E r α-olefin > = 0.005−0.01); and (iv) blocky character (<r E r α-olefin > >> 1.0), where r is the reactivity ratio. Accordingly, MAO anion 1 (pseudo-homogeneous polymerization) was prone to produce potentially block E−1-H, and alternating to random E−4M1P copolymers.…”

Section: Copolymer Intra-chain Microstructure and Copolymerization Mementioning

confidence: 99%

See 1 more Smart Citation

Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

Adamu

Atiqullah

Malaibari

et al. 2016

Journal of the Taiwan Institute of Chemical Engineers

View full text Add to dashboard Cite

Keywords:Metallocene catalyst Pseudo-homogeneous and in-situ heterogeneous isomeric ethylene−α-olefin copolymerization Hydrodynamic boundary layer mass transfer Inter-and intra-chain backbone composition distribution Lamellar thickness distribution Thermal properties a b s t r a c t This study reports a novel conceptual framework that can be easily experimented to evaluate the effects of hydrodynamic boundary layer mass transfer, methylaluminoxane (MAO) anion design, and comonomer steric hindrance on metallocene-catalyzed ethylene polymerization. This approach was illustrated by conducting homo-and isomeric copolymerization of ethylene with 1-hexene and 4-methyl-1-pentene in the presence of bis(n-butylcyclopentadienyl) zirconium dichloride ( n BuCp) 2 ZrCl 2 , using (i) MAO anion 1 (unsupported [MAOCl 2 ] − ) and pseudo-homogeneous reference polymerization, and (ii) MAO anion 2 (supported Si−O−[MAOCl 2 ] − ) and in-situ heterogeneous polymerization. The measured polymer morphology, catalyst productivity, molecular weight distribution, and inter-chain composition distribution were related to the locus of polymerization, comonomer effect, in-situ chain transfer process, and micromixing effect, respectively. The peak melting and crystallization temperatures and %crystallinity were mathematically correlated to the parameters of microstructural composition distributions, melt fractionation temperatures, and average lamellar thickness. These relations showed to be insightful. The comonomer-induced enchainment defects and the eventual partial disruption of the crystal lattice were successfully modeled using Flory and GibbsThompson equations. The present methodology can also be applied to study ethylene−α-olefin copolymerization, performed using MAO-activated non-metallocene precatalysts.

show abstract

“…Therefore, from the values in Table 3, all the polymer composites were alternating copolymers. Hung et al [30] note that the disadvantage of alternating copolymer is that a polymer with a highly alternating sequence distribution does not exhibit a sharp melting point. This is because the co-monomers in their chain are distributed moderately well along the backbone, and shortens the average backbone sequence length for crystallization and therefore lowers the crystallinity.…”

Section: Characterization Of Lldpe/tio 2 Nanocompositesmentioning

confidence: 99%

LLDPE/TiO2 nanocomposites produced from different crystallite sizes of TiO2 via in situ polymerization

et al. 2012

View full text Add to dashboard Cite

Nano-TiO 2 particles with a range of crystallite sizes were synthesized by a conventional sol-gel method, and then used as nanoparticle substrates in the synthesis of LLDPE/TiO 2 nanocomposites via in situ polymerization of ethylene/1-hexene with zirconocene/MMAO catalyst. It was found that the size of the nano-TiO 2 crystallite nanoparticles can influence the catalytic activity in the polymerization system. The larger nano-TiO 2 crystallites provided better catalytic activity in the polymerization system due to more space for monomer attack. In addition, by thermo-gravimetric analysis, it can be seen that the larger nano-TiO 2 crystallites also exhibited lower interaction with available MMAO. Consequently, the MMAO reacted more efficiently with the zirconocene catalyst during the activation process, and enhanced polymerization catalysis. All the polymer nanocomposites products did not have well defined melting temperature indicating non-crystalline polymers. This is due to the high amount of hexene incorporation (based on 13 C NMR). The difference in crystallite sizes of the nano-TiO 2 also affected how 1-hexene became incorporated into the polymer nanocomposites. The smaller crystallite size of nano-TiO 2 allowed greater 1-hexene incorporation due to depression of the reactivity of the ethylene. The contribution of this work helps develop a better understanding of the role of nano-TiO 2 in the catalytic activity of the polymerization system and in the microstructure of the polymer composite product. However, this study only considers work on the laboratory scale, so for commercial application of these results, it is necessary to scale up the polymerization process. It is only at this stage, that other physical properties, such as the mechanical properties of these materials can be sensibly determined.nanocrystal, polymer nanocomposite, polyethylene, sol-gel, TiO 2 Citation:Chaichana E, Pathomsap S, Mekasuwandumrong O, et al. LLDPE/TiO 2 nanocomposites produced from different crystallite sizes of TiO 2 via in situ polymerization.

show abstract

Control of Sequence Distribution of Ethylene Copolymers: Influence of Comonomer Sequence on the Melting Behavior of Ethylene Copolymers

Cited by 51 publications

References 67 publications

Ethylene-hexene copolymer derived from [t-butylfluorenylsilyl-amido] dimethyl titanium complex

Ethylene-hexene copolymer derived from [t-butylfluorenylsilyl-amido] dimethyl titanium complex

Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

LLDPE/TiO2 nanocomposites produced from different crystallite sizes of TiO2 via in situ polymerization

Contact Info

Product

Resources

About