Dynamic mechanical properties of semi-interpenetrating networks based on poly(styrene-co-maleic anhydride)

Summary

Semi-interpenetrating networks based on linear anionic polystyrene (PS) and poly(styrene-co-maleic anhydride) P(ScoMA) of low MA content are prepared by crosslinking the P(ScoMA) with 4,4′-diphenylmethanediamine (DPMDA). It is demonstrated by dynamic mechanical analysis and by DSC that immiscible semi-IPN's are obtained for MA contents greater 5 wt.-%. In miscible semi-IPN's the relaxation of free PS chains is observed as a second maximum in the loss tangent at higher temperatures. The position of this maximum is shifted to higher temperatures for a polystyrene of molecular weight 500000 compared to a polystyrene of molecular weight 150000. The experimental temperature shift is in good agreement with a M ³ dependence of the terminal relaxation time. In addition the temperature of this second tan δ maximum is shifted to higher temperatures with increasing crosslink density. Again the shift is in good agreement with the theoretical prediction of an increased terminal relaxation time of the relaxing chains with decreasing tube diameter.