Propan acid diacid

The stability of polyanhydrides composed of the diacids sebacic acid (SA), bis( -carboxyphenoxy)methane (CPM), l,3-bis(g-carboxyphe-noxy)propane (CPP), l,6-bis( -carboxyphenoxy)hexane (CPH), and phenylenedipropionic acid (PDP), in solid state and in organic solutions, was studied over a 1-year period. Aromatic polyanhydrides such as poly(CPM) and poly(CPH) maintained their original molecular weight for at least a year in both solid state and solution (20). 

Aromatic Polyanhydrides. Aromatic homopolyanhydrides are insoluble in common organic solvents and melt at temperatures above 200°C (29). These properties limit the use of purely aromatic polyanhydrides, since they cannot be fabricated into films or microspheres using solvent or melt techniques. Fully aromatic polymers that are soluble in chlorinated hydrocarbons and melted at temperatures below 100°C were obtained by copolymerization of aromatic diacids such as isophthalic acid (IPA), terephthalic acid (TA), l,3-bis(carboxyphenoxy)propane (CPP), or l,3-bis(carboxyphenoxy)hexane (CPH). 

In the reaction of glycerol, /= 3, with equivalent amounts of several diacids, the gel point was observed [14,15] at an extent of reaction of 0.765. The predicted values of are 0.709 and 0.833 calculated from [13] (Flory, statistical) and [12] (Carothers), respectively. Flory [13] studied several systems composed of diethylene glycol (/=2), 1,2,3-propane-tricarboxylic acid (/ = 3), and either succinic or adipic acid (/ = 2) with both stoichiometric and nonstoichiometric amounts of hydroxyl and carboxyl groups, see Table 1. 

It is interesting to compare the predictions of the two theories with each other and with what happens in practice. Fig. 2.4 shows the variation of p, x and the viscosity tj with time for a reaction between diethylene glycol (a diol), succinic acid (a diacid) and 1,2,3-propane tricarboxylic acid (a triacid). The mixture was found to gel after about 230 min and this was manifested by tj becoming infinite, pc, is about 0.9 and Jf was only 25 at this... 

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