Dielectric relaxation of various end-functionalized polystyrenes: Plastification effects versus specific dynamics

In this communication, we present first results on the dielectric response of various end-functionalized polystyrenes (PS). The functional polymers have been prepared by using a combination of anionic polymerization techniques and hydrosilation chemistry that gives well-defined polymers where the functional group can be placed with flexibility and high precision. The data show that for rather large functional groups, the overall polymer matrix properties are altered giving rise to a decrease in the glass transition temperature. The trend can be rationalized in terms of free volume effects caused by the bulky functional groups. However, for cyano-functionalized PS, i.e. PS with a CN group at the chain end, the inclusion of the group does not affect the matrix properties. We show that by taking advantage of the strong dipole moment of the CN group, we can obtain a strong dielectric signal that can be used to selectively study the specific dynamics where the group is located. In other words, by appropriately attaching cyano groups at different part of the chains, these can be used as dielectric probes that allow specific contributions to the alpha relaxation.