Solid-state NMR studies on the molecular structure and dynamics of poly(diethylsiloxane) polymorphs

• Published in: Macromolecules 1989-11, Vol.22 (11), p.4190-4197
• Main Authors: Koegler, Gerhard, Hasenhindl, Alfred, Moeller, Martin
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Inorganic and organomineral polymers; Physicochemistry of polymers; Properties and characterization
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma00201a009

Molecular structure and segmental motion of different crystalline modifications of high molecular weight poly(diethylsiloxane) have been investigated by variable-temperature MAS exp 13 C and exp 29 Si NMR experiments. The observations are discussed in correlation to thermodynamic data. Cooperative changes of the motional state of the molecular backbone and the side chains are observed at the solid transitions detected by differential scanning calorimetry (DSC) experiments. Structural differences of the alpha - and beta -polymorph are indicated. Annealing experiments allow determination of the beta -modification as the equilibrium modification. The stepwise loss of long-range order at the onset of different motional processes, which results in the formation of a "liquid crystal" type phase of these highly flexible long chain molecules, is dicussed with respect to the amphiphilic constitution of poly(diethylsiloxane) having an inorganic backbone substituted by organic side groups. . 38 ref.--AA