Study of molecular motion in polysilastyrene by pulsed 1H nuclear magnetic resonance

✍ Scribed by McGarvey, Bruce R. ;Schlick, Shulamith

• Publisher: Wiley (John Wiley & Sons)
• Year: 1982
• Tongue: English
• Weight: 394 KB
• Volume: 20
• Category: Article
• ISSN: 0098-1273
• DOI: 10.1002/pol.1982.180201115

✦ Synopsis

Abstract

Pulsed NMR spectra of protons in polysilastyrene, $ \rlap{--} [{\rm Si(CH}_{\rm 3} {\rm )}_{\rm 2} {\rm  Si(CH}_{\rm 3} )({\rm C}_6 {\rm H}_5 )\rlap{--} ]_n $, with n ≈ 60, have been measured in the temperature range 80–450 K. The linewidth is constant at 7.4 G up to 200 K and narrows considerably above 250 K to a constant value of 0.3 G above 360 K. The motion responsible for this effect has an activation energy of 43.7 kJ/mol and is identified with the large‐scale motion occurring in the vicinity of the glass transition temperature. The spin‐lattice relaxation time T~1~ was measured by the π‐t‐½π pulse sequence as a function of temperature. Two motional minima in T~1~ were observed. The low‐temperature motion has an activation energy of 3.7 kJ/mol and is identified with methyl group reorientation. The high‐temperature motion has an activation energy of 29.1 kJ/mol and might be due to segmental motion.