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Mesomorphic phases of poly(DI‐n‐alkylsiloxane)s
Author(s) -
Möller Martin,
Siffrin Stefan,
Kögler Gerhard,
Oelfin Dieter
Publication year - 1990
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19900340111
Subject(s) - differential scanning calorimetry , phase transition , molecule , isotropy , phase (matter) , liquid crystal , anisotropy , crystallography , side chain , chemistry , polymer , materials science , thermodynamics , physics , organic chemistry , optoelectronics , quantum mechanics
The phase behavior of poly(dialkylsiloxane)s which are symmetrically substituted with ethyl, n ‐propyl, and n ‐butyl side groups has been investigated by solid state NMR and differential scanning calorimetry. All polymers exhibit disordering transitions before isotropization. The observation of conformational and motional changes is correlated to the different thermal transitions. Diffusive rotation of the chain segments around the molecule long axis is indicated by 29 Si‐NMR below the isotropization transition. The remarkably fluid character is explained in part by the coexistence of anisotropic and isotropic motional states of the ‐OSiEt 2 ‐ segments. Molecular motion below the upper disordering transition is restricted but still fast with respect to the 29 Si‐NMR time scale. Long range reorganization processes have to be considered to explain the difference between α 2 ‐PDES and β 2 ‐PDES. The stepwise disordering at the onset of different motional processes, which results in the formation of a columnar liquid crystalline phase of these highly flexible chain molecules, is discussed with respect to the amphiphilic constitution of the molecules having an inorganic backbone substituted by organic side groups.