Thermotropic homopolyesters. I. The preparation and properties of polymers based on 4,4′‐dihydroxybiphenyl

Abstract

A homologous series of polyesters was prepared from 4,4′‐dihydroxybiphenyl and dibasic acids having 5‐12 methylene units. The mesophases formed at elevated temperatures were studied by differential scanning calorimetry and polarized light microscopy. This family exhibits an unusual odd‐even effect when the transition temperatures are plotted as a function of the number of methylene units in the dibasic acid. Not only do the points for odd and even members fall on different curves, but the odd members exhibit a nematic phase over a very short temperature interval, while the even members form a highly ordered smectic phase. For both the odd and even series, the transition temperatures are significantly depressed when the inherent viscosity falls below 0.2 dL/g. The largest depression occurs for the crystal melting transition, so that polymers of low ηinh show anisotropic and biphasic regions over wider temperature ranges. A copolymer formed from an equimolar mixture of sebacic and chiral (+)‐3‐methyl adipic acid forms a cholesteric phase. Evidently copolymerization destabilizes the smectic phase which would have been expected. The results are discussed in terms of existing theory.

Enhanced Thermal Conductivity of Thermoplastics by Lamellar Crystal Alignment of Polymer Matrices

“…These materials were directly used as received. PB‐10, PB‐12, and PB‐18 were synthesized according to a previous report 12. A representative PB‐ n species, PB‐10, was synthesized by the melt condensation of 4,4′‐diacetoxy biphenyl and dodecanedioic acid with sodium acetate as a catalyst.…”

“…Here, we report a novel method for producing polymer materials that are lightweight and highly processable and achieve “unprecedentedly high TCs” afforded by the lamellar crystal alignment of polymer matrices using main‐chain PB‐ n polymers, as shown in Figure 1a. PB‐ n , where n is the even number of methylene units in the spacer moiety, forms a highly ordered smectic liquid crystalline (LC) phase along with a chain‐folding lamellar structure in both smectic and crystalline phases 12–14. We applied information acquired from previous studies showing that shear flow induces the alignment of chain‐folding lamellae of main‐chain smectic LC polymers 15–19.…”

Influence of molecular orientation direction on the in‐plane thermal conductivity of polymer/hexagonal boron nitride composites

“…5 PB-10 polyester forms a smectic I LC phase 6 with 47-nm-thick lamellae stacked regularly along the polymer chain direction. [5][6][7][8][9] Shear flow during injection molding induces lamel-lar crystal alignment, in which the polymer chains are aligned in the normal direction (ND) with respect to the molding surface [ Figure 1(b)], thus leading to a high TC (1.2 W m 21 K 21 ) in the ND [ Figure 1(c)]. In contrast, the TCs in both the machine direction (MD) and the transverse direction (TD) are only modest at 0.30 W m 21 K 21 .…”

Aromatic liquid-crystalline polyesters comprising a 2,5-thiophene unit synthesized and studied by the thin-film polymerization method

“…While BP was purchased from Aldrich (Aldrich Chemical Co., Inc., Milwaukee, WI) and used as received, ABA, ANA, AAA, and DABP were acetylated from p-hydroxybenzoic acid (p-HBA), (Ueno Fine Chemicals Industry, Ltd., Osaka, Japan), 6-hydroxy-2-naphtholic acid (HNA), (Ueno Fine Chemicals Industry, Inc.), p-aminophenol (Aldrich Chemical Co., Inc.), and BP, respectively, according to literature reports. [32][33][34] The success of acetylation was confirmed by the compound's 1 H nuclear magnetic resonance (NMR) spectra.…”