New polymer syntheses. XCVI. Star-shaped LC-polyesters derived from β-(4-hydroxyphenyl)propionic acid and 4-hydroxybenzoic acid

✍ Scribed by Hans R. Kricheldorf; Thomas Stukenbrock; Christian Friedrich

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 329 KB
• Volume: 36
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(19980715)36:9<1387::aid-pola6>3.0.co;2-q

✦ Synopsis

Star-shaped polyesters were prepared by polycondensation of tetraacetoxyspirobis(indane) and a 1 : 1 mixture of silylated b-(4-acetoxyphenyl)propionic acid and silylated 4-acetoxybenzoic acid. The lengths of the star arms were systematically varied, and the influence of the star center on the stability of the nematic phase was studied. It was found that on the average more than 10 monomer units per star arm are required to stabilize a homogeneous LC-phase. Furthermore, a second class of star-shaped polyesters consisting of b-(4-hydroxyphenyl)propionic acid (HPPA), 4hydroxybenzoic acid (HBA), and 6-hydroxy-2-naphthoic acid (HNA) was prepared. This ternary copolyester proved to reduce the crystallinity but to stabilize the LCcharacter. A homogeneous nematic melt was obtained with 6 monomer units per star arm. This interpretation is based on optical microscopy which provides a static picture of the biphasic situation. Therefore, a preliminary study of the melt rheology was included, which proved that the typical LC-character of the melt was detectable at even shorter star arms due to the shear orientation.