Original Article Liquid crystalline hyperbranched polyesters with phosphorus functional groups Diana Serbezeanu 1 , Ana-Maria Macsim 1 , Ionela-Daniela Carja 1 , Corneliu Hamciuc 1 , Marius Pislaru 2 and Ta ˘ chit¸a ˘ Vlad-Bubulac 1 Abstract Liquid crystalline hyperbranched poly(aryl ester)s (A 2 B 3 ) were prepared by polycondensation reaction of 2-(6-oxido-6H- dibenz<c,e><1,2>oxaphosphorin-6-yl)1,4-naphthalene diol with 1,3,5-benzenetricarbonyl trichloride, taken in two dif- ferent molar ratios. The chemical structure of the newly synthesized hyperbranched polymers was confirmed by FTIR, 1 H NMR, 13 C NMR spectroscopy. The polymers exhibited high thermal stability with initial decomposition temperature above 410–435  C and char yield at 700  C higher than 40%. Combined differential scanning calorimetry, polarized optical microscopy and wide-angle X-ray diffraction measurements were carried out to closely examine their thermal behavior and phase transitions. Keywords Hyperbranched polymers, phosphorus-containing polymers, dendritic polymer, liquid crystalline properties Introduction In the past decade, the field of arborescent macromolecular architectures (dendrimers, hyperbranched polymers) has been well established with a large variety of synthetic approaches, fundamental studies on structure and proper- ties of these unique materials, and possible applications. 1–4 The most prominent application fields of these classes of polymers emerged from the excellent encapsulating capa- bility along with their excellent biocompatibility and bio- degradability. Thus, in the recent years, hyperbranched polymers have been used as vehicle for drug delivery, 5–7 protein delivery, 8–10 gene transfection, 7,11 encapsulating agents of various inorganic nanoparticles to prepare anti- bacterial 12,13 and/or antifouling materials 14,15 or to design versatile nanoreactors for catalytic applications. 16 Dendrimers are perfectly branched spherical monodis- perse macromolecules consisting of an inner core, assem- ble of molecular building blocks containing the repeating units, all enclosed in a shell ended with tunable terminal functionalities. Dendritic architectures have been prepared following complicated multistep synthetic procedures, either through divergent or convergent approaches, each of them having a sum of advantages and disadvantages, beside time consuming synthetic approach and high pro- duction cost. 17–19 On the other hand, hyperbranched polymers can be prepared by facile and easier one-pot poly- merization strategies, thus, they become promising candi- dates for industrial applications where ultimate perfection in structural uniformity is less needed, while retaining many of the important features of dendritic polymers, such as appreciable number of end groups, which facilitates fur- ther chemical modification, very good solubility, lower intrinsic viscosities in comparison with the linear analogues etc. Hyperbranched polymers are less regular in structure, with degree of branching (DB) typically not exceeding 50% of that of dendritic molecules. They can be generally pre- pared starting from AB x monomers. A wide variety of hyperbranched architectures has been successfully synthe- sized, including polyesters, 20–26 polyamides, polycarbo- nates and polyurethanes. 27 The first AB x branched polyester system was prepared by polycondensation reac- tion of 3,5-bis(trimethylsilyloxy)benzoyl chloride. 28 How- ever, the commercial availability of AB x monomers is 1 “Petru Poni” Institute of Macromolecular Chemistry, Iasi, Romania 2 SC Intelectro IASI S.R.L, Iasi, Romania Corresponding author: Diana Serbezeanu, “Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda, 41A, Iasi 700487, Romania. Email: diana.serbezeanu@icmpp.ro High Performance Polymers 1–11 ª The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0954008320960532 journals.sagepub.com/home/hip