Gelation/gels mixed polymer

Kasapis, S., Morris, E. R., Norton, I. X, and Brown, C. R. X 1993a. Phase-equilibria and gelation in gelatin maltodextrin systems. 3. Phase-separation in mixed gels. Carbohydr. Polym. 21 261-268. 

In the context of mixed polymer gelation, it is worth mentioning the observation that the addition of 1% isotactic polystyrene to a 15% solution of atactic polystyrene at room temperature results in the formation of a weak gel under conditions in which neither of the polymers would gel alone. 

The information available on aqueous polymer blends is qualitative in nature because of the lack of a suitable theory to interpret the experimental observations. Mixed gels can be comprised of an interpenetrating network, a coupled network (as discussed above), or a phase-separated network [2]. The latter is the most common as the blends have a tendency to form two phases during gelation. In such cases the miscibility and thermodynamic stability have to be empirically investigated and proper conditions for miscible blends identified. This involves a phase diagram study as is described in [3]. 

Napalm - an infamous gel originally made up of the aluminium salts of napthelenic and palmitic acids mixed with petrol. Used widely by the military from the second world war onwards, burning napalm sticks to its victim causing severe burns and rapid local deoxygenation. Moden napalm uses a polymer additive to achieve gelation. 

Independent Variables. Simultaneous synthesis of two polymer networks is a complex process. Many independent variables are available for study and not all could be explored in a limited investigation. The emphasis in the present study centers on those variables whose predominant effect is to influence the relative rates or gelation times of the reactions. Three independent variables were selected (a) the concentration of di-tert-butyl peroxide initiator was changed to vary the rate of polymerization of n-butyl acrylate (b) the epoxy mix was allowed to prereact for different lengths of time before the acrylate mix was added, and (c) the amount of DEGDM added to the acrylate mix was varied to control the gel time of the acrylate without significantly affecting its rate of polymerization. 

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