Crystallization and Melting Behavior of Poly(Butylene Succinate) Nanocomposites Containing Silica-Nanotubes and Strontium Hydroxyapatite Nanorods George Z. Papageorgiou, † Dimitrios G. Papageorgiou, ‡ Konstantinos Chrissafis, ‡ Dimitrios Bikiaris,* ,† Julia Will, § Alexander Hoppe, § Judith A. Roether, ⊥ and Aldo R. Boccaccini § † Laboratory of Polymer Chemistry and Technology, Department of Chemistry, Aristotle University of Thessaloniki, 541 24, Thessaloniki, Macedonia, Greece ‡ Solid State Physics Section, Physics Department, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece § Institute of Biomaterials, Department of Materials Science and Engineering, University of Erlangen-Nuremberg, Cauerstrasse 6, 91058 Erlangen, Germany ⊥ Institute of Polymer Materials, Department of Materials Science and Engineering, University of Erlangen-Nuremberg, Martenstrasse 7, 91058 Erlangen, Germany ABSTRACT: The multiple melting behavior of poly(butylene succinate) (PBSu) nanocomposites containing silica nanotubes (SiNTs) and strontium hydroxyapatite nanorods (SrHNRs) was studied with Step Scan DSC. In the reversing signal curves, recrystallization proved to be significant for samples crystallized at low temperature, which lead to large supercooling, favoring fast crystallization and formation of poor crystals that suffer recrystallization on subsequent heating scans. The crystallization study, under both isothermal and nonisothermal conditions, evidenced that only SiNTs act effectively as nucleating agents. Consequently, crystallization of the nanocomposite samples filled with 5 and mainly with 20 wt % SiNTs occurred faster than that of the neat polymeric matrix. The insertion of SrHNRs slightly lowered the crystallization rate of PBSu due to the formation of larger aggregates inside the PBSu matrix, which may inhibit crystallization. The size of crystals was smaller for PBSu/SiNTs samples, as it was proved by wide angle X-ray diffracrion (WAXD), whereas the addition of SrHNRs did not significantly affect the crystalline size of nanocomposites. 1. INTRODUCTION The widespread use of conventional polymers over the last decades has brought up serious environmental problems. Therefore, synthetic aliphatic polyesters have attracted great interest from industry and academia because they can be easily degraded in the environment. 1,2 One of the most promising materials in the category of biodegradable polyesters is poly(butylene succinate) (PBSu) due to its relatively low cost and large production volume. PBSu has already been used in various commercial applications like packaging materials, films and fibers due to its superior biodegradability, and thermal and mechanical properties. 3,4 In addition, PBSu has been used for more advanced applications such as drug delivery systems and tissue engineer- ing. 5-8 Those applications have not stayed unaffected by the continuous growth of polymer nanocomposites and a significant number of biodegradable polyester-based nano- composites has been tested for possible use as drug delivery systems or as a part of tissue engineering methods. Fillers of different geometries and shapes have been tested for the improvement of the final properties of polymer nanocomposites and nanotube-shaped additives have been proved to induce significant enhancements. 9,10 Inorganic nanotubes have been proved an interesting alternative to conventional carbon nanotubes, exhibiting advantages such as easy synthetic access and satisfactory dispersion and adhesion, properties which greatly affect the final materials. 11 For this reason, silica nanotubes (SiNTs) and strontium hydroxyapatite nanorods (SrHNRs) were developed and inserted into a PBSu matrix to observe their effect on the PBSu properties. These nanoparticles were tested for first time in an upcoming publication from our group as appropriate materials for biomedical applications like scaffolds. It was found that SiO 2 nanotubes support cell attachment, whereas Sr 5 (PO 4 ) 3 OH nanorods decrease cell activity, maybe due to its high release concentrations during hydrolysis. Crystallization and melting of various biodegradable polyesters has been presented in numerous publications. 12-17 In our previous study, it was found that the biodegradability of aliphatic polyesters is affected by the polymer crystallinity and, specifically, PBSu exhibited low biodegradation rates compared to other familiar polyesters like poly(propylene succinate) because of its higher crystallinity. 18 Furthermore, it is well- known that the addition of nanofillers, such as those used in the present study, can change the crystallinity of aliphatic polyesters and its hydrolysis rate. 19,20 Therefore, it is very important to study the crystalline content of the prepared PBSu nanocomposites and understand the parameters that affect the polymer crystallization for the Received: September 30, 2013 Revised: December 3, 2013 Accepted: December 11, 2013 Published: December 11, 2013 Article pubs.acs.org/IECR © 2013 American Chemical Society 678 dx.doi.org/10.1021/ie403238u | Ind. Eng. Chem. Res. 2014, 53, 678-692