Plasticization of poly(styrene-b-isobutylene-b-styrene) ionomers by acid salts of 2-ethylhexyl-p-dimethylaminobenzoate

Poly(styrene-b-isobutylene-b-styrene) block copolymer ionomer (overall mole cular weight = 71,200 g/mole; 25.5 wt % polystyrene, 4.7% sulfonation of ph enyl units, 100% neutralized with KOH) was compounded with various organic and inorganic acid salts of 2-ethylhexyl-p-dimethylaminobenzoate (ODAB) to explore the efficacy of these compounds as ionic plasticizers. Results were compared to the same polymer plasticized by zinc stearate. Plasticizers we re added to the polymer at levels of approximate to 5 wt%. Films were prepa red by solution casting from tetrachloroethylene. Thermogravimetric analysi s (TGA) showed all ODAB derivatives to have lower decomposition temperature s than zinc stearate. Dynamic mechanical analysis (DMA) of the films showed varying degrees of ionic plasticization as evidenced by a lowering of the temperature at which the onset of flow occurred. With the exception of the stearic acid salt of ODAB, all ODAB derivatives were more efficient ionic p lasticizers than zinc stearate. Among the ODAB derivatives, the degree of i onic plasticization varied, with the methane sulfonic and p-toluene sulfoni c acid salts being most effective, leading to the conclusion that processin g temperatures could be tailored to specific applications by choice of plas ticizer and level of incorporation.