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Determination of refractive index increment of synthetic polybutadienes and microstructural control of grafting density and liquid crystalline properties

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Abstract

Polybutadienes (PBs) with microstructural control, i.e., 1,2-olefins ranging from 8% to 94% (mole fractions), were readily synthesized using living anionic polymerization (LAP) by varying the polar additives and their mole ratios over BuLi. Herein, the determination of refractive index increment (dn/dc) and weight-average molecular weight (Mw) of PBs using gel permeation chromatography equipped with differential refractive index (RI) and low angle laser light scattering (LALLS) detectors (GPC-RI/LALLS) is shown, and as expected, the values of dn/dc have a significant dependence on 1,2-olefins of microstructures which is relevant to the glass transition temperature (Tg) of PBs. These PB backbones were subsequently used as precursors for the synthesis of PB-based liquid crystal polymers (LCPs) (PB-M1 and PB-M2) with a microstructural control of grafting densities of 15%, 30% and 50% (moles) after the longitudinal attachment of azobenzene moieties (Azo-M1 and Azo-M2) along PBs. More importantly, the unchanged grafting density (almost 50%) with increasing 1,2-olefin fractions was observed for both PB-M1 and PB-M2 (≥50% 1,2-olefins), which explained the 1,2-olefin microstructural control in terms of phase transitions (mesogenic formation) regardless of whether Azo-M1 or Azo-M2 was used as a side attachment, while DSC curves using different processing temperatures and X-ray analysis with a domain spacing shift over temperature demonstrate a much more variable mesogenic phase and wider ΔT values of PB-M2 compared to PB-M1.

Graphical abstract: Determination of refractive index increment of synthetic polybutadienes and microstructural control of grafting density and liquid crystalline properties

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Article information


Submitted
11 Jan 2020
Accepted
01 Mar 2020
First published
02 Mar 2020

Polym. Chem., 2020, Advance Article
Article type
Paper

Determination of refractive index increment of synthetic polybutadienes and microstructural control of grafting density and liquid crystalline properties

S. Huang, L. Han, H. Ma, L. Lei, R. Zhang, H. Shen, L. Yang, C. Li, S. Zhang and Y. Li, Polym. Chem., 2020, Advance Article , DOI: 10.1039/D0PY00050G

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