Aryl vinyl polymers processes

The objective of this review is to characterize the excimer formation and energy migration processes in aryl vinyl polymers sufficiently well that the excimer probe may be used quantitatively to study polymer structure. One such area of application in which some measure of success has already been achieved is in the analysis of the thermodynamics of multicomponent systems and the kinetics of phase separation. In the future, it is likely that the technique will also prove fruitful in the study of structural order in liquid crystalline polymers. 

Photophysical Species and Monochromophoric Processes in Aryl Vinyl Polymers 34... 

Our motivation for offering a further consideration of excimer fluorescence is that it is a significant feature of the luminescence behavior of virtually all aryl vinyl polymers. Although early research was almost entirely devoted to understanding the intrinsic properties of the excimer complex, more recent efforts have been directed at application of the phenomenon to solution of problems in polymer physics and chemistry. Thus, it seems an appropriate time to evaluate existing information about the photophysical processes and structural considerations which may influence excimer formation and stability. This should help clarify both the power and limitations of the excimer as a molecular probe of polymer structure and dynamics. 

The most widely used nomenclature in the field of luminescence of aromatic molecules is that proposed by Birks. 3) The photophysical species and processes in this scheme which are encountered in rigid systems of aryl vinyl polymers are described in Tables 1-4. Triplet excimers have been omitted since it will be shown later that all triplet states play minor roles in the room-temperature, air saturated P2VN blends studied recently 2). 

Table 3. Monochromophoric Photophysical Processes in Aryl Vinyl Polymers in a Rigid Environment ...

Electronic Energy Migration and Bichromophoric Processes in Aryl Vinyl Polymers... 

We conclude that the difference between the experimental value and the no-transfer value of the fluorescence ratio of P2VN and PS is less in solution than in dilute miscible blends, because energy migration must compete with rotational processes in the generation of excimers in solution. This difference is also present when the effect of molecular weight on aryl vinyl polymers in solution and in dilute miscible blends is considered in the next section. 

Numerous studies of the photophysics of aryl vinyl polymers have shown that the monomer emission intensity can be empirically fit to a triple exponential [15-17]. The immediate conclusion that may be drawn from this observation is that the Birks kinetic scheme [1], which was developed for a collision-induced intermolecular process between small molecules in solution, is inapplicable to intramolecular excimer formation in macromolecules. 

In other applications, phthalides 328-330 were added to the polymerization of MMA and styrene in an effort to add thermostability to the favorable properties of the vinyl polymers. The examples with Cl directly attached to the phthalide ring were found to act principally as chain-transfer agents. Nonhalogenated compounds participated in chain-transfer and initiation processes <2001MI37>. Aryl phthalides 331-333 have been employed as stabilizers for the processing of polymers to limit chain cleavage and oxidation <2001WO132762>. 

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