Ethylene copolymer gels, gelation

Jeong et al. studied the gelation behavior of poly(ethylene glycol)-h-poly(L-alanine) (PEG-h-L-PA) block copolymers in water [117, 118]. They suggested that the P-sheet structure of l-PA plays a critical role in developing a fibrous nanostructure as well as in the sol-to-gel transition of the copolymer solutions (Fig. 14). The conformation of l-PA in water is random coil at low concentrations. As the concentration increases, block copolymers start to aggregate and the conformation... 

Puronic polyols are block copolymers of PEG and poly(propylene oxide). Plutonic copolymers with 70% ethylene oxide and 30% propylene oxide, with an average molecular weight of 11,500, exhibits a reversible thermal gelation in aqueous solution at >20% concentration. The polymer solution at room temperature is liquid, but turns to a gel in the body. This gel has been used as a delivery system for several proteins (80). 

For instance. He and co-workers have shown the potential of an ion gel formed by gelation of poly(styrene-block-ethylene oxideblock-styrene) (SOS) triblock copolymer in l-butyl-3-methylimidazolium hexafluorophosphate.(He et al., 2006) This system has shown interesting conductivity values at room temperature (above 10 S/cirr ). 

The evolution of systems containing double bonds, for example ethylene-octene copolymer in low density polyethylene blends, is illustrative for the materials with unsaturation orient the behavior during UV exposure (Fig. 2). The contribution of this copolymer is evident. If the gelation of samples does not occur for the first 100 h of exposure [20], the accumulation of radicals allow a sudden increase at 200 h. Then the degradation affects the gel fraction by the cleavage of inter-molecular bridges. 

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