Ethylene statistical copolymers

Besides its influence on the crystal unit cell dimension, the presence of noncrystallizable counits can also stabilize crystalline phases that are not commonly observed in homopolymers crystallized at atmospheric pressure [46,47]. X-ray diffraction on a compositionally uniform ethylene statistical copolymer containing... 

This relationship was applied to analyze the crystallization data of six different sets of ethylene statistical copolymers [96]. In all cases, a linear relationship between logA// and logX was observed. Furthermore, the values of m determined for ethylene-olefin copolymers were found to be in the range of 6-13, in good agreement with the critical sequence length proposed by Randall and Ruff based on NMR data and modeling considerations [97]. 

Although it has been known for many years that ethylene oxide and formaldehyde ean form statistical copolymers, it was not until the interest in crown ethers developed that the potential of macrocyclic formals as complexing agents was recognized. 

In some very recent work by Karssenberg et al. [130], attempts have been made to improve the analytical ability of a technique like NMR spectroscopy to effectively predict the distribution of sequence lengths in polyethylene-alkene copolymers. They analyzed the entire [ C-NMR spectrum for homogeneous ethylene-propene copolymers. They used quantitative methods based on Markov statistics to obtain sequence length distributions as shown in Figure 22 [130]. The... 

Production of OBCs by chain shuttling catalysis can result in a copolymer with a melting point more than 50 °C higher than that expected for a statistically random copolymer prepared at equivalent density. Figure 17 shows the typical relationship between density and melting point for random ethylene-LAO copolymers. The circled symbols are several OBCs prepared by chain shuttling catalysis [10]. While a typical random copolymer with density of 0.88 g cm-3 would melt at 60 °C, the OBCs made by chain shuttling do not melt until almost 120 °C. 

Curve El in Fig. 2.21 corresponds to an elastomer (statistic copolymer from ethylene and propylene), characterized by a low value of the elastic modulus... 

Fig. 2.22. Dependence of the elastic modulus E and the mechanical loss factor 6 on temperature for various polymers. Curves 1 elastomer (statistical copolymer of ethylene and propylene) curves 2 isotactic polypropylene (semicrystalline)...

A typical example belonging to this category are undoubtedly the statistical copolymers of ethylene and propylene. Because of their crystalline nature, however, no attempt has yet been made to apply TLC to this copolymer system. Thus, in this... 

Mean-square unperturbed dimensions a and their temperature coefficient, d tin 0) I d T, are calculated for ethylene-propylene copolymers by means of the RIS theory. Conformational energies required in the analysis are shown to be readily obtained from previous analyses of PE and PP, without additional approximations. Results thus calculated are reported as a function of chemical composition, chemical sequence distribution, and stereochemical composition of the PP sequences. Calculations of 0 / nP- are earned out using ( ) r r2 = 0.01, 1.0, 10.0, and 100.0, (ii) p, = 0.95, 0.50, and 0.05, liii) bond length of 153 pm and bond angles of 112°for all skeletal bonds, iv) = 0 and 10°, and (v) statistical weight factors appropriate for temperatures of 248, 298, and 348 K. Matrices used are ... 

With the sole exception of the random ethylene-propylene copolymers, for industrial applications heterogeneous catalysts have been used for alkene polymerisations. Ethylene-propylene statistical copolymerisation has been carried out using homogeneous vanadium-based catalysts [28]. 

In contrast to heterogeneous Ziegler-Natta catalysts, homogeneous catalysts based on biscyclopentadienyl derivatives of group 4 transition metals, which contain cationic metallocene species of formally d° 14-electronic structure, hardly promote the polymerisation of conjugated dienes, since the diene can act as a donor of four electrons rather than of two electrons as in monoolefin polymerisation (let us recall that the polymerisation of conjugated dienes is catalysed by half-sandwich metallocene-based catalysts). However, it has been reported [162] that statistical copolymers of ethylene and butadiene were obtained with the Cp2ZrCl2— [Al(Me)0]x catalyst. 

The alternating copolymers are characterized both by a glass transition temperature (130°C for ethylene/norbornene copolymers) and a melting point (295°C for the totally alternating copolymer). The melting point and the crystallinity of these copolymers may be influenced by choice of the metallocene and the conditions of polymerization. Compared with the statistical copolymers, the alternating structures show better resistance to nonpolar... 

A statistical ethylene-propylene copolymer with the ratio of 4 ethylene units to 3 propylene units (E.P. Rubber) has approximately the same degree of branching as the trimethyl nylon 6/6 of Table II. 

Thus a statistical copolymer of ethylene and propyiene is named poly(ethylene-stef-propylene), and an ABA tri-block copolymer of styrene (A) and isoprene (B) is named polystyrene-block-polyisoprene-block-polystyrene. In certain cases, additional square brackets are required. For example, an alternating, copolymer of styrene and maleic anhydride is named poly[styrene-d/f-(maleic anhydride)]. 

There exist many alternating copolymerizations ethylene or propene with alkyl acrylates [244], vinyl acetate with maleic anhydride [245], styrene with acrylonitrile [246], styrene with fumaronitrile [247], vinyl carbazol with fumaronitrile, vinyl ferrocenne with diethylfumarate [248], and further pairs or systems of three monomers [238, 249-253]. External conditions can support or hinder alternation. At not too high temperatures, vinyl acetate forms a donor—acceptor complex with maleic anhydride. Under these conditions (and in the presence of a radical initiator), an alternating copolymer is formed. The concentration of the complex decreases with increasing temperature above 363 K the complex cannot exist. Under these conditions, copolymerization yields a statistical copolymer whose composition depends on the composition of the monomer mixture [245]. 

Ionomers consist of statistical copolymers of a non-polar monomer, such as ethylene, with (usually) a small proportion of ioniz-able units, like methacrylic acid. Ethylene-co-methacrylic acid copolymers (-5% methacrylic acid) are used to make cut-proof golf balls (see Fascinating Polymers opposite). The protons on the carboxylic acid groups are exchanged with metal ions to form salts. These ionic species phase-separate into microdomains or clusters which act as crosslinks, or, more accurately, junction zones (Figure 6-4). (We discuss interactions in a little more detail in Chapter 8.)... 

AES (acrylonitrile-EPDM-styrene) is a blend of SAN and EPDM. SAN is a statistic copolymer of styrene and acrylonitrile. EPDM is an elastomeric terpo-lymer of ethylene, propylene and a nonconjugated diene. The diene studied here was 5-ethylidene-2-norbomene. The total content of EPDM was 34mole% [6]. The diene represented 8 mole% of the EPDM and the SAN phase was composed of 80 mole% of styrene and 20 mol% of acrylonitrile. The AES films were irradiated at / > 300 nm at 60 °C in the presence of oxygen. The photoproducts resulting from the photooxidation of each components of AES were identified by FTIR spectroscopy coupled with the same chemical and physical treatments as mentioned above for the previous studies. As pointed out in the literature [17], the EPDM component is more reactive than the copolymer SAN towards photooxidation. 

Statistical copolymers of the types described in Chapter 8 tend to have broader glass transition regions than homopolymers. The two comonomers usually do not fit into a common crystal lattice and the melting points of copolymers will be lower and their melting ranges will be broader, if they crystallize at all. Branched and linear polyethylene provide a case in point since the branched polymer can be regarded as a copolymer of ethylene and higher 1-olefins. 

Generally, 1,2-disubstituted ethylene derivatives have only a small tendency for radical homopolymerization. An exception is vinylene carbonate (VCA) which can be easily polymerized by chemical as well as radiation initiation. However, the reaction is strongly affected by traces of impurities formed during the synthesis. Inhibition experiments are discussed with regard to the nature of the inhibiting impurities. The copolymerization behavior of VCA with some halo-substituted olefins was studied with chlorotrifluoroethylene (CTFE), a statistical copolymer with a slight tendency for alternation was obtained. 

The solidus denotes an unspecified arrangement of the units within the main chain. " For example, a statistical copolymer derived from styrene and vinyl chloride with the monomeric units joined head-to-tail is named poly(l-chloroethylene/l-phenyleth-ylene) . A polymer obtained by 1,4-polymerization and both head-to-head and head-to-tail 1,2- polymerization of 1,3-butadiene would be named poly(but-l-ene-l,4-diyl/l-vinylethylene/2-vinyl-ethylene) In graphic representations of these polymers, shown in Figure 2, the hyphens or dashes at each end of each CRU depiction are shown completely within the enclosing parentheses this indicates that they are not necessarily the terminal bonds of the macromolecule. 

SAH Sahakaro, K., Chaibundit, C., Kaligradaki, Z., Mai, S.-M., Heatley, F., Booth, C., Padget, J. C., and Shirley, I.M., Clouding of aqueous solutions of difunctional tapered statistical copolymers of ethylene oxide and 1,2-butylene oxide, Eur. Polym. J., 36, 1835, 2000. 

LOU Louai, A., Sarazin, D., Pollet, G., Francois, J., and Moreaux, F., Properties of ethylene oxide-propylene oxide statistical copolymers in aqueous solution. Polymer, 32, 703, 1991. 

Morgado, J., CaciaUi, E, Priend, R., Chuah, B., Rost, H., Holmes, A, 2001a. Light-emitting devices based on a poly(p-phenylenevinylene) statistical copolymer with oligo(ethylene oxide) side groups. Macromolecules 34,3094-3099. 

Patlazhan et al. [11] studied the shear-induced fractal morphology of immiscible reactive polymer blends. The example of grafting and cross-linking multilayer systems of statistic terpolymer of ethylene, butyl acrylate, and maleic anhydride (MAH) and statistic copolymers (CPA) including... 

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