We have synthesized and characterized a new family of nematic all-aromatic polyesteramide thermosets based on 6-hydroxy-2-naphthoic acid (HNA), terephthalic acid (TA), and 4-acetamidophenol (AAP). In order to incorporate a high concentration of the amide-based monomer (AAP), the melt transition (T_K-N) and melt viscosity had to be lowered in order to maintain melt processable intermediates. Precursor thermoplastic reactive oligomers, end-capped with phenylethynyl functionalities, were prepared using standard melt condensation techniques with a target M_n of 1000–9000 g mol⁻¹. The reactive oligomers with 20–30 mol% AAP could easily be processed into films, and the films exhibit good tensile properties in terms of tensile strength (70–80 MPa) and elongation at break (7–10%). A glass transition of 191°C could be obtained when a 1000 g mol⁻¹ oligomer (HNA/TA/AAP(20)–1 K) was thermally cross-linked. When the AAP concentration reaches 35 mol%, the rigidity of the backbone and the hydrogen bonding interactions are enhanced, which make HNA/TA/AAP(35) polymers difficult to process.

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Thermoplastic and thermoset all-aromatic liquid crystal (LC) (AB)_n-multiblock copoly(ester imide)s based on N-(3′-hydroxyphenyl)trimellitimide (IM), 4-hydroxybenzoic acid (HBA), and 6-hydroxy-2-naphthoic acid (HNA) were investigated as single-component high-temperature (≥250 °C) shape memory polymers (SMPs). A high T_g (∼200 °C) HBA/IM block embedded in a low T_g (∼120 °C) HBA/HNA matrix creates a stable rubbery plateau that can be extended to ∼240 °C by cross-linking. The shape fixation (R_f) and shape recovery efficiency (R_r) of the thermoplastic and thermoset films were investigated using a rheometer in torsion mode. Thermoplastic LC copoly(ester imide) films showed excellent dual SM behavior (R_f and R_r ∼ 100%) at 170 °C. After cross-linking the thermoplastic films a single component system as obtained that exhibited high-temperature (≥250 °C) tunable triple SM and one-way reversible SM behavior.

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A series all-aromatic poly(esterimide)s with different molar ratios of N-(3′-hydroxyphenyl)-trimellitimide (IM) and 4-hydroxybenzoic acid (HBA) (IM/HBA = 0.3/0.7 and 0.7/0.3) was prepared with the aim to design flexible high T_g films. Melt-pressed films, either from high molecular weight polymer or cured phenylethynyl precursor oligomers, exhibit T_gs in the range of 200 °C to 242 °C and are brittle. After a thermal stretching procedure, the films became remarkably flexible and very easy to handle. In addition, the thermally stretched 3-IM/7-HBA and 7-IM/3-HBA films show tensile strengths of 108 MPa and 169 MPa, respectively. Thermal treatment increased the T_g of 3-IM/7-HBA from 205 °C to 248 °C, whereas the T_g of 7-IM/3-HBA increased from 230 °C to 260 °C.

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We have prepared (AB)n-multiblock copolymers based on N-(3′-hydroxyphenyl)trimellitimide (IM), 4- hydroxybenzoic acid (HBA), and 6-hydroxy-2-naphthoic acid (HNA) via a simple one-pot melt condensation method. The blocky nature is the result of phase separation taking place in the early stages of the melt polymerization process. The liquid crystal HBA/HNA fraction phase separates from the isotropic HBA/IM fraction and this phase separation effectively shuts down transesterification reactions, preventing randomization of the polymer backbone. The (AB)n-multiblock copoly- (esterimide)s exhibit two distinct glass transition temperatures (Tgs). The first Tg at ∼120 °C can be assigned to the HBA/HNA rich A-block and the second Tg at ∼220 °C can be assigned to the HBA/IM rich B-block. When introducing imide-based phenylethynyl end-groups, these reactive functionalities end-up exclusively at the termini of the HBA/IM rich B-blocks, effectively forming a phenylethynyl-terminated B(AB)n-reactive oligomer. Upon thermal treatment, cross-linking via the phenylethynyl end-groups results in a thermoset where the Tg of the B-block increases by as much as ∼106 °C. The Tg of the HBA/HNA A-block remains unchanged. Scanning electron microscopy experiments show a gradual change in morphology, from a typical fibrous LCP texture for the HBA/HNA rich polymers to a more consolidated morphology for the HBA/IM rich polymers. Atomic force microscopy images confirm the presence of two distinct domains when 44 mol % of HBA was replaced by IM. The “hard” imide rich B-blocks form domains of ∼100−200 nm that are embedded in the imide poor or “soft” A-blocks. @en