Conformation of comb-like liquid crystal polymers in isotropic solution probed by small-angle neutron scattering

✍ Scribed by Yiqiang Zhao; Alex M. Jamieson; Brian G. Olson; Ning Yao; Shaosheng Dong; Sergei Nazarenko; Xuesong Hu; Jyotsana Lal

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 861 KB
• Volume: 44
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/polb.20888

✦ Synopsis

Abstract

The conformational characteristics of a comb‐like side‐chain liquid crystal polysiloxane (SCLCP), dissolved in deuterated chloroform, were evaluated by small‐angle neutron scattering (SANS) measurements over a wide q range. SANS studies were carried out on specimens with constant backbone length (DP = 198) and variable spacer length (n = 3, 5, and 11), and with constant spacer length (n = 5) and variable DP (45, 72, 127, and 198). The form factor P(q) at high q was analyzed using the wormlike chain model with finite cross‐sectional thickness (R~c~) and taking into account the molecular weight polydispersity. The analysis generated values of persistence length in the range l~p~ = 28–32 Å, considerably larger than that of the unsubstituted polysiloxane chain (l~p~ = 5.8 Å), with contour lengths per monomer comparable to the fully‐extended polysiloxane backbone (l~m~ = 2.9 Å). This indicates a relatively rigid SCLCP chain due to the influence of the densely attached mesogenic groups. The SCLCP with n = 11 is more flexible (l~p~ = 28 Å) than those with n = 3 and n = 5 (l~p~ = 32 Å). The cross‐sectional thickness increases with spacer length, R~c~ ∼ n^0.21±0.02^ (3 ≤ n ≤ 11), and the contour length per monomer decreases with increasing spacer length, l~m~ ∼ n^−0.35±0.01^. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2412–2424, 2006