Computer modeling studies polyethylene

Experimental information on the valence levels comes essentially from photoemission XPS and UPS measure densities of states (DOSs) convoluted with absorption cross sections, and these DOS values can be compared with those computed from VEH valence-band structures [195]. This has now been done for several CPs and the agreement is good. It would be more instructive to compare the actual band structure to angle-resolved (ARUPS) measurements, but this has never been done. What comes nearest is an ARUPS study of a series of long alkanes taken as models for polyethylene, a nonconjugated polymer [196]. 

A computational model based on molecular dynamics was developed to predict the miscibility of indomethacin in the carriers polyethylene oxide (PEO), glucose, and sucrose (Gupta et al. 2011). The cohesive energy density and the solubility parameters were determined by simulations using the condensed-phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field. The simulations predicted miscibility for indomethacin with PEO (A5 < 2), borderline miscibility with sucrose (A5 < 7), and immiscibility with glucose (A5 > 10 Table 2.2). 

In several publications, Brown and co-workers [82] developed the idea that the reduction in growth rate in polyethylene due to incorporation of branches relates to a difference in the tie molecules in the initial structure. The extensive studies of Capaccio and coworkers [80] confirmed by the computer model of Ward et al. suggest that the critical factor is the creep failure of the fibrils in the craze and is not related directly to the initial morphology [83]. 

The technology and role of photodegradable plastics is considered and computer models are described to evaluate strategies for litter abatement, and experimental studies of the synthesis and biodegradation of conventional and photodegradable polyethylene, polypropylene, poly(ethylene terephthalate), and polystyrene. 

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