Polyethylene, considered structure

When polarization of light is taken into account, other forms of contrast appear. For instance, let us consider spherolites in solid polyethylene. These structures are clusters of crystallites which can be seen under an ordinary microscope. However, they appear3 much more clearly if a polarizing microscope is used, the sample being observed between crossed polarizers. Here, the contrast is related to the optical anisotropy of the material. 

A polyethylene-like structure is considered to consist of more than 10 ethylene oxide units in the main chain and ladder-like polymer... 

At the end of the 1970s considerable interest developed in what became known as linear low density polyethylenes (LLDPE) which are intermediate in properties and structure to the high pressure and low pressure materials. While strictly speaking these are copolymers it is most convenient to consider them alongside the homopolymers. The LLDPE materials were rapidly accepted by industry particularly in the manufacture of film. The very low density polyethylenes (VLDPE) introduced by Union Carbide in 1985 were closely related. 

A further class of ethylene-vinyl acetate copolymer exists where the vinyl acetate content is of the order of 3 mole %. These materials are best considered as a modification of low-density polyethylene, where the low-cost comonomer introduces additional irregularity into the structure, reducing crystallinity and increasing flexibility, softness and, in the case of film, surface gloss. They have extensive clearance as non-toxic materials. 

Acetylene (ethyne), C2H2, can be polymerized, (a) Draw the Lewis structure for acetylene and draw a Lewis structure for the polymer that results when acetylene is polymerized. The polymer has formula (CH), where n is large, (b) Consider the polymers polyacetylene and polyethylene. The latter has the formula (CH2)W and is an insulating material (plastic wrap is made of polyethylene), whereas polyacetylene is a darkly colored material that can conduct electricity when properly treated. On the basis of your answer to part (a), suggest an explanation for the difference in the two polymers. 

Several studies have considered the influence of filler type, size, concentration and geometry on shear yielding in highly loaded polymer melts. For example, the dynamic viscosity of polyethylene containing glass spheres, barium sulfate and calcium carbonate of various particle sizes was reported by Kambe and Takano [46]. Viscosity at very low frequencies was found to be sensitive to the network structure formed by the particles, and increased with filler concentration and decreasing particle size. However, the effects observed were dependent on the nature of the filler and its interaction with the polymer melt. 

Conformational energy estimates are employed to determine the conformational characteristics of polyfvinyl fluoride) (PVF), polyfluoromethylene (PFM), and polytrifluoroethylene (PTF3). Effects of stereoconfiguration and, in the case of PVF and PTF3, the presence of head-to-head tail-to-tail (HH TT) defect structures are considered. The calculated results are compared to corresponding values found for polyfvinylidene fluoride), polytetrafluoroethylene, and polyethylene, and the equilibrium flexibilities of PVF, PFM, and PTF3 are discussed on this basis. 

Isomorphism in copolyalkenamers was reported by Dall Asta, Motroni, and Carella (27). These copolymers may be considered as constituted by an unbranched polyethylene chain containing, at irregular intervals, fra s-intemal double bonds. It is known 28) that the crystal structure of the homo-fraws-polyalkenamers depends on the number of methylene groups existing between two subsequent double bonds the odd series crystallizes in an orthorhombic unit cell, similar to that of... 

Poly(ethylene oxide). The synthesis and subsequent hydrolysis and condensation of alkoxysilane-terminated macromonomers have been studied (39,40). Using 29Si-nmr and size-exdusion chromatography (sec) the evolution of the silicate structures on the alkoxysilane-terminated polyethylene oxide) (PEO) macromonomers of controlled functionality was observed. Also, the effect of vitrification upon the network cross-link density of the developing inorganic—organic hybrid using percolation and mean-fidd theory was considered. 

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