Polyethylene block

Couman W.J., Heikens D., and Sjoerdsma S.D., Dilatometric investigation of deformation mechanism in polystyrene-polyethylene block copolymer blend Correlation between Poisson ratio and adhesion. 

Polar Polyethylene block Polar polymer blockb Unit... 

IR absorption spectra were superimposable onto those of the physical mixtures of the respective homopolymers. The molar ratio of the poly(MMA) and polyethylene blocks, however, decreased as the Mn of the prepolymer increased, especially when it exceeded ca. 12 000 at which polyethylene began precipitating as fine colorless particles. It is noteworthy that smooth block copolymerization of ethyl acrylate or methyl acrylate to the growing polyethylene chain (Mn = 6 600-24 800) can be realized by the sequential addition of the two monomers. 

The physical properties of this block copolymer are improved by hydrogenation using cobalt-copralactam reduced by tri-i sobutyl alumimium. This homogeneous catalyst reduces the 1,2 double bond at a rate four times faster than it reduces the 1,U double bond. The saturated 1,U double bond, yields polyethylene block and while saturating the 1,2 double bond, yields an elastomer with... 

The block copolymers shown in both Table V and VI were hydrogenated. The B-lU block produced polyethylene and the polyisoprene block produced ethylene propylene alternating copolymer. The physical properties of this copolymer, composed of crystalline polyethylene block and a soft elastomeric segment made of an EPR block, is tabulated in Table VII. The data in this table illustrate the fact that a diblock of hydrogenated polybutadi ene-polyisoprene gave excellent physical properties. This is a further illustration of the new concept of soft chain interpenetrating the crystalli zable polyethylene chain via chain folding. 

Easy separation of solids from the solution can be achieved by using a centrifuge (Macrofuge C-4, Heraeus-Christ). The centrifuge can be provided with polyethylene blocks each having a hole just fitting the Schlenk tube. 

The Magazine (Pig. 4) is a polyethylene block with 96 shafts. Each shaft accommodates up to 10 Lanterns. The Magazine enables Lanterns to be... 

Block copolymers can be produced from terminally borane-containing polyolefins. These borane-containing POs can be synthesized by the metallocene-catalyzed (co)polymerization of olefin(s) monomer with 9-BBN as a chain transfer agent or by the metallocene catalyzed copolymerization of olefins with allyl-9-BBN [55,56], as referred to above. Alternatively, borane-containing POs were prepared by hydroboration of terminally unsaturated PO, for instance, terminally vinyl PE and terminally vinylidene PP [33-35,57]. Such method could produce diblock copolymers, such as polyethylene-block-poly(methyl methacrylate) (PE-fo-PMMA), polypropylene-foZock-poly(methyl methacrylate) (PP-fc-PMMA), polypropylene-foZock-poly(butyl methacrylate) (PP-fc-PBMA), and PP-fc-PS. 

Effect of Substrate. Several comparisons were made to establish the effect of substrate on conversion of methylvinylpyridine and acrylonitrile. Relative effectiveness in the ethylene-propylene series were ethylene-propylene copolymer > polyethylene > polypropylene on a relativity scale of 4 3 2. The fact that chains terminated with polyethylene blocks are better substrates than polypropylene blocks suggests that random grafting on the backbone is not a major part of the reaction at low polymerization temperatures. The higher conversion on polyethylene... 

Table 9.1.6 (continued). Compounds identified in the pyrogram of polyethylene-block-poly(ethylene glycol) 20% wt. ethylene oxide M = 575 as shown in Figure 9.1.9. 

Even at high styrene incorporation, the co-polymers are formed by ethylene blocks and isolated styrene units.627 Half-sandwich titanium complexes such as 35-39 have also been reported to be active in the ethylene/styrene co-polymerization. The performance of the MAO-activated complex 35 is highly dependent on the Al/Ti ratio. At a ratio of 100, a co-polymer composed of polyethylene blocks with essentially isolated styrene units could be fractionated from the homopolymers. By contrast, at Al/Ti ratios of 1000, a co-polymerization at the same feed ratio resulted in the production of only homopolymers, or co-polymers composed of long PE and sPS blocks at most.628 Subsequent 13C NMR analysis of the co-polymers obtained at 20°C indicated that up to 36 mol% of styrene was incorporated.629 However, under very similar conditions, only formation of the homopolymers was reported.630,631 This may be reasonable since catalytic systems 35/MAO and 36/MAO give rise to several active species with different catalytic properties. Thus, remarkably different results can be obtained with small differences in the experimental procedure. 

PIB), PE and polyethylene-block-polypropylene copolymer (PE-PP) (referred as B20 in the literature). At temperatures <145°C, primary scattering peak and second-order peak are observed at q = 0.07 nm-1 and q2 = 0.14 nm 1, indicative of an ordered lamellar phase with a repeat distance of 90 nm. The experimental intensity near the second peak was fit by Eq. (7.1). 

Langer (13) has also disclosed the use of alkyllithium and dialkyl-magnesium tertiary diamine complexes as catalysts for copolymerization of ethylene and other monomers such as butadiene, styrene, and acrylonitrile to form block polymers. Examples are given in which polybuta-dienyllithium initiates a polyethylene block, as well as vice-versa. Random copolymers of these two were also prepared, and other investigators have used not only tertiary diamines but hexamethylphosphoramide (14) and tetramethylurea (15) as nitrogenous base cocatalysts in such polymerizations. Antkowiak and co-workers (11) showed the similarity of action of diglyme and TMEDA in copolymerizations of styrene and... 

LLDPE linear low density polyethylene block copolymer... 

Balsamo V, Muller AJ, Gyldenfeldt F, Stadler R (1998) Ternary ABC block copolymers based on one glassy and two crystaUizable blocks polystyrene-block-polyethylene-block-poly(e-capro-lactone). Macromol Chem Phys 199 1063—1070... 

Sun L, Liu YX, Zhu L, Hsiao BS, AvUa-Orta CA (2004) Self-assembly and crystallization behavior of a double-crystalline polyethylene-block-poly(ethylene oxide) diblock copolymer. Polymer 45 8181-8193... 

Liao, B., Liang, H., and Pang, Y. 2001. Polymer-layered silicate nanocomposites. 1. A study of poly (ethylene oxide)/Na+—montmorillonite nanocomposites as polyelectrolytes and polyethylene-block-poly(ethylene glycol) copolymer/Na+— montmorillonite nanocomposites as fillers for reinforcement of polyethylene. Polymer 42 10007-10011. 

Ueda et al. [46] have measured the crystalUzation rate of the polyethylene block within polyethylene-6-(atactic polypropylene), PE-6-aPP, with a PE volume fraction of 0.48. The crystaUization of the PE block occurs with a molten aPP block covalently bonded to it. The copolymer is reported to be in the strong segregation limit. They also found a substantially lowered crystalUzation rate as compared to an analog neat PE, which was attributed to a mo-biUty reduction of the chains close to the interphase, and to the presence of non-crystallizable aPP chains close to the growth face which couid hinder the growth process. 

PEG-PE poly(ethylene glycol)-polyethylene block copolymers... 

In block copolymers the polypropylene block(s) constitute the hydrophobic part and the polyethylene block(s) the hydrophilic part. Random copolymers do not have identifiable hydrophobic or hydrophilic parts. 

Balsamo V, Muller AJ, Stadler R (1998) Antinucleation effect of the polyethylene block on the polycaprolactone block in ABC triblock copolymers. Macromolecules 31(22) 7756-7763 Balsamo V, de Navarro CU, Gil G (2003) Microphase separation vs crystallization in polystyrene-b-polybutadiene-b-poly(epsilon-caprolactone) ABC triblock copolymers. Macromolecules 36... 

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