Applications frontal polymerization

One of the most promising applications of nonlinear dynamics to polymer science is the phenomenon of frontal polymerization (Section III). Frontal pol)mierization is a process of converting monomer into polymer via a localized reaction zone that propagates through the monomer. There are two modes of frontal polymerization. 

P-67). Curing of thick composites may also be a useful application (62,63). In chapter 9, Pojman et al. review nonlinear dynamics in frontal polymerization. 

Isothermal Frontal Polymerization (IFP), also called Interfacial Gel Polymerization, is a slow process in which polymerization occurs at a constant temperature and a localized reaction zone propagates because of the gel effect (64,65). Using IFP (27), one can control the gradient of an added material like a dye, to generate materials useful, for example, in optical applications (66,67). Lewis et al. provide experimental and theoretical results in chapter 14. 

In 2000, we have begun our research on this topic paying particular attention to the possibility of finding new chemical systems able to frontally polymerize and new FP applications. Specifically, we have studied polyurethanes (19, 20), polyester tyrene resins (21), polydicylopentadiene (22) and its BPNs with polyacrylates (23), Furthermore, we were able to prepare films (24) and to apply FP to the consolidation of porous materials (i.e. stones, woods, flaxes, papers), in particular -but not only- those having a historical-artistic interest (24), In this chapter we present a brief overview of these recent findings. 

Frontal polymerization is a mode of converting monomer into polymer via a localized exothermic reaction zone that propagates through the coupling of thermal diffusion and Arrhenius reaction kinetics. Frontal polymerization was discovered in Russia by Chechilo and Enikolopyan in 1972 (63). The macrokinetics and dynamics of frontal polymerization have been examined in detail (5) and applications for materials synthesis considered (64,65). 

Photofrontal polymerization produces fronts whose positions depend logarithmically on time if the initiator continues to absorb light and linearly on time if the initiator is photo-bleached. It is limited in application to unfilled systems. IFP propagates on the order of 1 cm day" and only for total distances of about 1 cm. Thermal frontal polymerization has the widest range of velocities and types of chemistries that can be used. 

Arrhenius kinetics and is highly exothermic can support localized polymerizations that propagate. Frontal polymerization has been studied with many different polymerization mechanisms but free-radical polymerization is the most studied. Most of the work has focused on the dynamics of the process, but recently applications have been studied. Hydrogels have been prepared frontally, which have superior properties to those prepared by conventional methods. 

The major advantage of thermal frontal polymerization is the high rate of conversion. Cure-on-demand applications appear to be the most promising use for this approach. 

Frontal free-radical polymerization applications to materials synthesis. Polym. News, 28, 303-310. 

Bidali et al performed frontal atom transfer radical polymerization (ATRP) with tri(ethylene glycol dimethacrylate). They used CBr4, tris(2-aminoethyl)amine, and CuBr. When the components were dissolved in the monomer, the solution was cooled to 0 ° C to prevent bulk polymerization, which did not react for at least 3 h. Samples were heated to 25 ° C before fronts were then initiated, which propagated with velocities of about 0.5 cm min" The major advantage of this system compared to a typical peroxide-based system was the lack of bubbles. However, because the system reacted relatively quickly at room temperature, the system has limited applicability. 

---