1052 Research Article Received: 17 July 2009 Revised: 24 September 2009 Accepted: 12 November 2009 Published online in Wiley Interscience: 7 April 2010 (www.interscience.wiley.com) DOI 10.1002/pi.2823 Synthesis and properties of block poly(ether-ester)s based on poly(ethylene oxide) and various hydrophobic segments Gianandrea Quattrociocchi, Iolanda Francolini, Andrea Martinelli, Lucio D’Ilario and Antonella Piozzi * Abstract To obtain biodegradable amphiphilic block polymers for biomedical applications, a series of poly(ether-ester)s based on poly(ethylene oxide) and various hydrophobic/hydrophilic segment ratios were synthesized by the solution polymerization technique. The polyesters were characterized using 1 H NMR spectroscopy, elemental analysis, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis and compression stress – strain measurements. The composition of the poly(ether-ester)s agreed with the feed ratio. A study of the degree of phase segregation in the polymers evidenced that microphase mixing increases with the presence in the hydrophobic segments of polar groups able to establish interactions with the poly(ethylene oxide). This phase mixing increased the thermal stability of the acidic poly(ether-ester)s. Nanospheres for drug delivery with an average diameter of 50 nm were obtained by employing the acidic poly(ether-ester) showing less microphase segregation, while a scaffold structure with a homogeneous and highly interconnected porosity and an average pore size of approximately 15 μm for tissue engineering was prepared using the more hydrophobic copolymer not possessing functional groups. Compression mechanical measurements carried out on the scaffold showed that the more hydrophobic copolymer was suitable for tissue engineering applications. In order to obtain polymers employable both in drug delivery and in tissue engineering a series of block poly(ether-ester)s showing various phase segregations were synthesized by varying the hydrophobic/hydrophilic segment ratio. c  2010 Society of Chemical Industry Keywords: polyesters; amphiphilic block copolymers; nanoparticles; drug delivery; scaffolds; tissue engineering INTRODUCTION Amphiphilic block copolymers have been recently investigated for their application as nanostructured materials since they have an inherent tendency to self-assemble into tunable nanoscale structures. 1 In particular, in aqueous solution they are known to form core – shell-type micelles in which the core is formed by the hydrophobic region of the polymer and the shell is formed by the hydrophilic one. In fact, block copolymers consist of two chemically dissimilar polymer segments, A and B, covalently bonded. Mutual repulsion stemming from the different chemical properties of A and B drives the system to segregate, although bulk phase sep- aration is prohibited by the molecular connectivity that restricts the length scale of the domains to that of the individual polymer molecules. Polymer chains will then organize themselves with the specific equilibrium nanodomain morphology determined by the degree of polymerization, N, the A–B Flory–Huggins interaction parameter, χ , and the relative length of the blocks, f . 2,3 Amphihilic block copolymers find wide application in differ- ent fields of medicine and biology, particularly in developing high-performance medical devices, including scaffolds for tis- sue engineering and nanoparticles for drug delivery systems. At this regard, block copolymers are also attractive because of their chemical composition, molecular weight and easily changeable block-length ratios which allows control of polymer biodegradability and mechanical properties as well as the size and morphology of the particles. 4,5 In this paper, we report the synthesis and the characterization of block poly(ether-ester)s based on poly(ethylene oxide) (PEO) and various hydrophobic segments. PEO, with a molecular weight of 2000 g mol −1 , was chosen as the hydrophilic segment since it possesses unique properties, including a wide range of solubility, lack of toxicity and absence of antigenicity and immunogenicity. Moreover, PEO possesses two-hydroxyl end-groups that can be used as such 6 or suitably functionalized 7 before coupling with ligands of biological relevance. PEO is also employed for the modification of biological molecules by covalent conjugation as a strategy to overcome disadvantages associated with some biopharmaceuticals. In fact, the presence of PEO changes the physical properties of drugs, often resulting in an improvement in the drug pharmacokinetic behaviour. 8 In general, PEO decreases immunogenicity and increases drug solubility, stability and ∗ Correspondence to: Antonella Piozzi, Department of Chemistry, University of Rome ‘La Sapienza’, P le Aldo Moro 5, 00185 Rome, Italy. E-mail: antonella.piozzi@uniroma1.it. Department of Chemistry, University of Rome ‘La Sapienza’, P le Aldo Moro 5, 00185 Rome, Italy Polym Int 2010; 59: 1052–1057 www.soci.org c  2010 Society of Chemical Industry