Morphology and packing behavior of model ethylene/propylene copolymers with precise methyl branch placement

Lieser, Günter; Wegner, Gerhard; Smith, Jason A.; Wagener, Kenneth B.

doi:10.1007/s00396-004-1091-6

Cited by 66 publications

(95 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…WAXD patterns for PE21Cl, PE19Cl, and PE15Cl are very similar and characterized by sharp, strong reflections at ∼19°a nd ∼22.5°. Taking as reference a similar diffractogram found in methyl-branched analogues, 20 this pattern is associated with a triclinic lattice for which reflections at 19°and ∼22.5°c orrespond to planes (100) and (010) respectively. In reference to the unsubstituted chain, the drastic change in WAXD patterns of precisely substituted polymers suggests a homopolymer crystallization led by the precise regularity of the substitution, as demonstrated in our previous work.…”

Section: Resultsmentioning

confidence: 63%

“…For example, the triclinic unit cell of a homopolymer analogous to PE21Cl, with methyl side groups and a similar WAXD pattern, requires a long c axis with a length that spans over two repeating units (∼53 Å). 20 It is thus conceivable that increasing the crystallite thickness along the chain axis requires a significant chain segment length. This may only be found at very low undercoolings, those corresponding to T c s too close to T m for observation of crystallites.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Crystallization of Polyethylenes Containing Chlorines: Precise vs Random Placement

et al. 2008

View full text Add to dashboard Cite

The crystallization behavior and crystalline structure of a series of chlorine-containing polyethylenes (PEs) with either a random or a precise placement of the Cl atom on each and every 21st, 19th, 15th, and 9th backbone carbon have been studied by DSC, NMR, Raman spectroscopy, WAXD, SAXS and AFM in samples cooled from the melt at 1°C/min. All precision Cl-substituted PEs crystallize as homopolymers based on their DD/MAS solid-state 13 C NMR spectra that reveal a uniform distribution of the content of halogen between crystalline and noncrystalline regions. In addition, unique WAXD crystallographic patterns that differ from those of the linear PE and random polymers, relatively large crystal thicknesses, and sharp crystallization and melting peaks also support this homopolymer pattern in precision systems. In contrast, a high concentration of Cl in the noncrystalline regions in the case of the random systems suggest that the crystallization process for randomly substituted samples is being led by the selection of the most crystalline sequences, resulting in broad thermal transitions and lower crystallinities. Increasing chlorine content in both precision and random systems decreases crystallinity, melting temperature, heat of fusion, and crystallite thicknesses suggesting that Cl atoms are defects that hinder the crystallization of these polyolefins. Both systems are found to exhibit a lamellar crystalline morphology. Precision substituted polyethylenes form long, straight, and stacked lamellae with axialitic (PE21Cl, PE19Cl, and PE15Cl) or spherulitic (PE9Cl) organization as typical of homopolymers of similar molar mass. In contrast, the lamellae of random analogs are curved and more segmented as found in other PE random copolymers. The distribution of Cl within the crystalline regions of systems with precision substitution is strongly affected by the sequence length of the methylene groups. Packing around the substitution point of PE21Cl, PE19Cl, and PE15Cl render nearly all-trans conformations and asymmetric Cl distribution, while close staggering of Cl atoms in the crystals of PE9Cl exert conformational distortions as observed by a strong increase of TG conformers in the Raman spectra.

show abstract

Section: Resultsmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 99%

Crystallization of Polyethylenes Containing Chlorines: Precise vs Random Placement

et al. 2008

View full text Add to dashboard Cite

show abstract

“…Second, in the precisely controlled copolymers PE1M and PEIM-22 have a crystalline, lamellar morphology of a thickness of 3-4 layers of repeating units. 7,8 The orthorhombic crystal structure of HDPE was not observed in these copolymers. 1 Instead, all samples have different, paraffin-like lateral packing, such as the frequently discussed hexagonal, monoclinic or triclinic polyethylene and paraffin structures.…”

Section: Introductionmentioning

confidence: 87%

Crystallization and melting of a branched polyethylene with precisely controlled chemical structure

Qiu¹,

Pyda²,

Nowak-Pyda³

et al. 2006

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

ABSTRACT:The heat capacity of a linear polyethylene with dimethyl branches, at every 21st backbone atom was analyzed by differential scanning calorimetry (DSC) and quasiisothermal temperature-modulated DSC. This novel copolyethylene (PE2M) is relatively difficult to crystallize from the melt. On subsequent heating, a first, sharp melting peak is followed by a sharp cold-crystallization and crystal perfection and a smaller endotherm, before reaching the main melting at 315-320 K, close to the melting temperatures of eicosane and tetracontane. The low-temperature melting is sensitive to the cooling rate and disappears below 1.0 K min À1 . The cold crystallization can be avoided by heating with rates faster than 80 K min À1 . The PE2M exhibits some reversing and reversible melting, which is typical for chain-folded polymers. The glass transition of semicrystalline PE2M is broadened and reaches its upper limit at about 260 K (midpoint at about 0.355 K). Above this temperature, the crystals seem to have a heat capacity similar to that of the liquid. A hypothesis is that the melting transition can be explained by changes in crystal perfection without major alteration of the crystal structure and the lamellar morphology.

show abstract

“…When methyl groups are incorporated on every 21st carbon, they are indeed included in the crystal lattice; however, there is a change to a triclinic lattice with a hexagonal subcell of methylene groups. Using transmission electron microscopy (TEM), we determined that the lamella thickness in this material is between 10 and 20 nm [24].…”

Section: Effect Of Branch Identitymentioning

confidence: 99%

Morphology control in precision polyolefins

2013

Self Cite

View full text Add to dashboard Cite

show abstract

Morphology and packing behavior of model ethylene/propylene copolymers with precise methyl branch placement

Cited by 66 publications

References 30 publications

Crystallization of Polyethylenes Containing Chlorines: Precise vs Random Placement

Crystallization of Polyethylenes Containing Chlorines: Precise vs Random Placement

Crystallization and melting of a branched polyethylene with precisely controlled chemical structure

Morphology control in precision polyolefins

Contact Info

Product

Resources

About