title: Segmental mobility in short-chain grafted-PDMS by homo- and heteronuclear residual dipolar couplings.
abstract: Different homo- ((1)H-(1)H) and heteronuclear ((1)H-(13)C) multiple quantum solid-state NMR experiments were applied to a series of short poly (dimethylsiloxane) (PDMS) chains grafted onto hydrophilic silica. The existence and clear separation of a strongly dipolar coupled region which is attributed to the silica-PDMS interface and a weakly dipolar coupled region attributed to the mobile chain portions outside the interface is evident in all experiments. In a sample series with different average chain lengths the residual dipolar couplings and with that the average order parameters are constant for the interface part and correlate for the mobile part linearly with the average chain length. Temperature dependent studies using (1)H double quantum experiments indicate the different stages of immobilization of the polymer chains. Solid-state NMR techniques therefore can give detailed information about the microscopic structure of this material and especially the effect of chain anchoring. It is also demonstrated that sample rotation influences the mobility of the mobile component and therefore the analysis of such materials should always be done under static conditions.
authors.affiliation: Institute of Technical Chemistry and Macromolecular Chemistry, Worringer Weg 1, 52056 Aachen, Germany. mbertmer@mc.rwth-aachen.de
authors.forename: Marko
authors.initials: M
authors.lastname: Bertmer
authors.forename: Mingfei
authors.initials: M
authors.lastname: Wang
authors.forename: Dan E
authors.initials: DE
authors.lastname: Demco
authors.forename: Bernhard
authors.initials: B
authors.lastname: Blümich