Approach to the composition dependence of the glass transition temperature of compatible polymer blends, 2 The effect of local chain orientation

Abstract

Abstract In a previous publication a new concept has been presented for the composition dependence of the glass transition in compatible polymer blends. The concept starts with the idea that besides conformational energy barriers, contacts due to interaction are responsible for both conformation and “free” volume distribution. In accordance with the Flory‐Huggins lattice theory, the contact probability has been related to the volume fraction of the components, corrected for the different volume expansion coefficients. The concept accounts for both chainspecific and interaction‐specific contributions. It is concluded that local chain orientation due to the increased hetero‐contact interaction may explain the observed molecular weight influences on the composition dependence of T g of polymer blends. Using experimental data for poly(vinyl methyl ether)‐polystyrene (PVME‐PS) blends it is shown that this local chain orientation due to hetero‐interaction is extremely strong in blends of the low molecular weight PS with high MW PVME. Thus, apparently, the stiffer component is dominating the T g behaviour of compatible polymer blends.