Thermo-reversible phase structures of lightly cross-linked PDMS/MQ silicone polymer blends

• Published in: Polymer (Guilford) Vol. 200; p. 122574
• Main Authors: Kishi, Hajime, Nakamura, Takuya, Hagiwara, Seitaro, Urahama, Yoshiaki
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 18-06-2020; Elsevier BV
• Subjects: Chain dynamics; Cooling; Crosslinking; Dispersion; Domains; Magnetic induction; Magnetic relaxation; Molecular motion; NMR; Nuclear magnetic resonance; Oligomers; Phase structure; Poly (dimethyl siloxane); Polydimethylsiloxane; Polymer blends; Polymers; Resins; Scanning probe microscopy; Silicone resins; Silicones; Siloxanes; Spectra; Temperature effects; Phase structure; Poly (dimethyl siloxane); Polymer blends
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2020.122574

The phase structures of lightly cross-linked poly (dimethyl siloxane) (PDMS)/MQ silicone polymer blends were analyzed using scanning probe microscopy (SPM) and pulsed 1H NMR. The MQ silicone resins comprised three-dimensional oligomers made of M units ((CH3)3SiO1/2) and Q units (SiO4/2). The SPM observations demonstrated that these blends had sea/island-type phase structures, in which hard MQ phases were dispersed in a soft matrix. The pulsed 1H NMR showed that the soft matrix was not pure PDMS but rather composed of a PDMS-rich phase incorporating dissolved MQ, whereas the dispersed phase was almost pure MQ. Magnetic relaxation spectra obtained using the pulsed 1H NMR were used to quantify the proportions of the MQ domains and the PDMS-rich matrix and to evaluate the molecular mobility of each component. The molecular motion of the PDMS-rich matrix was found to become more constrained with increases in the proportion of MQ. The effect of temperature on the magnetic relaxation spectra was assessed and the MQ domains were determined to partially dissolve in the PDMS matrix at higher temperatures and then to precipitate on cooling. The spectra obtained during heating and cooling were superimposable at intermediate temperatures, indicating that the phase structures of the blends were thermo-reversible.
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•Sea/island phase structures were observed in poly (dimethyl siloxane) (PDMS)/MQ blends.•Hard MQ domains were dispersed in a soft PDMS-rich matrix.•Pulsed 1H NMR quantified the proportions of the MQ domains and the PDMS-rich matrix.•The MQ domains dissolved partially in the PDMS matrix at higher temperatures.•The change of phase structures of the blends were thermo-reversible.