Poly film fragmentation chain

Prompt emission spectra of films irradiated in either vacuum or air indicated the formation of at least two fluorescing species. These species are denoted as Products II and II. The most prominent emission, that of Product II, was highly structured with maxima at about 405, 435, and 455 nm. Product II can be associated with both the polymer chain and low molar mass fragments it was extractable from the photolyzed film with methanol but not with cyclohexane, and it was present in methylene chloride extracts of cross-linked residues of films that had been extracted previously with methanol. The fluorescence spectra are shown in Figure 6 excitation maxima correspond very well with the weak absorption bands noted in the spectra of the irradiated films. Plots of absorbance increases at 350 nm against fluorescence intensity at 435 nm were linear for both vacuum and air irradiations. Therefore, it is concluded that Product II is a major emissive contributor to the yellowing of poly(sty-rene-aft-methyl methacrylate) films subjected to 254-nm irradiation. 

Graft copolymers are polymers produced when molecular fragments belonging to others polymers have been inserted into their side chains (Hazer and Steinbiichel 2007). The condensation reaction between the carboxy-terminal groups of certain PHAs poly[(/ )-3-hydroxybutyrate] poly[(/ )-3-hydroxybutyrate-co-(l )-3-hy-droxyvalerate] or PHO and the amine function of chitosan resulted in grafting of PHA polymers onto chitosan (Fig. 2). These grafted polymers formed opaque, viscous solutions in water and, once dried, afforded strong elastic films (Yalpani et al. 1991 Arslan et al. 2007). 

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