Synthesis, characterization, and in vitro degradation of liquid‐crystalline terpolyesters of 4‐hydroxyphenylacetic acid/3‐(4‐hydroxyphenyl)propionic acid with terephthalic acid and 2,6‐naphthalene diol

Abstract

Melt-processable liquid-crystalline terpolyesters of 4-hydroxyphenylacetic acid (HPAA) and 3-(4-hydroxyphenyl)propionic acid (HPPA) with terephthalic acid and 2,6-naphthalene diol were synthesized by one-step acidolysis melt polycondensation followed by postpolymerization and were characterized with viscosity studies, Fourier transform infrared (FTIR) and NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarized light microscopy, and wide-angle X-ray diffraction. The melting behaviors and liquid-crystalline transition temperatures of the terpolyesters were dependent on the composition of the HPAA/HPPA content. The transition temperatures of the polyesters could be effectively reduced by the introduction of an even number of built-in short methylene spacers in combination with the 2,6-naphthalene offset structure. A terpolyester with an HPPA content of 33% (NTP33) showed optimum properties for the glass-transition temperature, around 71°C, and the melting temperature, near 240°C, with a Schlieren nematic texture. The polymer showed excellent flow behavior in a Brabender plasticorder. It was also thermally stable up to 400°C. NTP33 showed 2.5% in vitro hydrolytic degradation in buffer solutions of pH 10 at 60°C after 540 h. Considerable enzymatic degradation was also observed with porcine pancreas lipase/buffer solutions in comparison with Candida rugosa lipase after 60 days. The degradation was also followed with FTIR, DSC, and TGA. Apart from the temperature and pH of the buffer solution, several structural parameters, such as the aromatic content, crystallinity percentage, and composition of the polymer, affected the degradation behavior. FTIR studies indicated the involvement of chain scission during degradation. Scanning electron microscopy studies further showed that surface erosion also played a major role in the degradation.

Highly renewable, thermoplastic tetrapolyesters based on hydroquinone,p‐hydroxybenzoic acid or its derivatives, phloretic acid, and dodecanedioic acid

“…In the case of polyesters based on phloretic acid, little work has been reported on its homopolymer, and most studies have been conducted on its binary copolymers with other aromatic comonomers . The formation of terpolymers of phloretic acid also has been reported . The homopolymer of phloretic acid and its copolyesters with p ‐hydroxybenzoic acid were shown to be liquid crystalline.…”

Challenges for Natural Monomers and Polymers: Novel Design Strategies and Engineering to Develop Advanced Polymers

“…Biodegradability of synthetic polymers has been a great concern for all synthetic polymer chemists and our early attempts at making LC polymers biodegradable were described earlier [193][194][195][196]. We then tried to synthesize biodegradable poly(esteramides) by controlling the crystallinity and aliphatic ester content [221][222][223].…”

“…7. A new monomer 8-hydrooxyphenyl octanoic acid was prepared by phase-transfer-catalyzed permanganate oxidation of cardanol a series homo-polymers and LCPs were prepared and characterized including LCP blends [192][193][194][195][196][197][198][199][200][201][202]. The polymers were shown to hydrolytically degradable.…”

“…In order to tackle this problem, a strategy of using co-monomers consisting of hydroxyphenylalkanoic acids (Fig. 4) such as hydroxyphenyl acetic acid (HPAA), hydroxyphenyl propionic acid acid (HPPA), 8-hydroxyphenyl ocatnoic acid (HPOA) which are characterized by the presence of a short to medium flexible aliphatic group directly attached to the aromatic moiety (this structure is expected to reduce the melting transition without affecting the thermal stability deleteriously) and an aliphatic carbonyl (which are expected to be more sensitive to hydrolytic degradation to induce biodegradability) was adopted [192][193][194][195][196].…”

Hydrolytic and Enzymatic Degradation of Liquid-Crystalline Aromatic/Aliphatic Copolyesters

“…A thorough understanding of structure−property relationships with respect to biodegradability is of fundamental importance for the tailored design of polymeric materials for tissue engineering. Most recently, hydrolytic and enzymatic degradation of aromatic / aliphatic copolyesters in vitro have been reported by several groups. , Nagata et al has presented degradation of thermotropic copolyesters based on terephthalic acid, 3-(4-hydroxyphenyl)propionic acid, and glycol by enzyme. Prasad et al reported in vitro degradation of liquid-crystalline terpolyesters of 4-hydroxyphenylaliphatic acid with terephthalic acid and 2,6-naphthalene diol.…”