New polymer syntheses. XCVII. Hyperbranched LC-polyesters based on 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: 353 KB
• Volume: 36
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(19980715)36:9<1397::aid-pola7>3.0.co;2-q

✦ Synopsis

Two classes of liquid crystalline hyperbranched copolyesters were prepared by the copolycondensation of silylated 3,5-bis(acetoxy)benzoic acid with mixtures of mesogenic difunctional monomers. The first class of LC-copolyesters was obtained from 1 : 1 mixtures (molar ratio) of silylated b-(4-acetoxyphenyl)propionic acid and silylated 4-acetoxybenzoic acid (poly(HPPA/HBA)). The second class of LC-copolyesters was obtained by additional copolycondensation of silylated 6-acetoxy-2-naphthoic acid. The hyperbranched copolyesters of this ternary system poly(HPPA/HBA/HNA) proved to be less crystalline in contrast to the binary system. In both classes of LC-copolyesters the degree of branching was varied via the feed ratio of 3,5-dihydroxybenzoic acid. A minimum segment length of 6 difunctional monomer units between the branching points is required to establish a nematic phase. However, a greater segment length is needed to obtain a homogeneous LC-phase. The poly(HPPA/HBA) copolyesters were also characterized by melt rheology.