Octa-armed star-shaped poly(e-caprolactone)s with a phthalocyanine core by ring-opening polymerization: Synthesis and characterization Ahmet Bilgin ⇑ , Çig ˘dem Yag ˘cı Kocaeli University, Umuttepe Campus, 41380, Turkey article info Article history: Received 25 August 2014 Received in revised form 19 September 2014 Accepted 13 October 2014 Available online 30 October 2014 Keywords: Ring-opening polymerization Polymer-containing phthalocyanine Star polymer Aggregation DSC abstract A series of hydroxyl-terminated octa-armed star-shaped poly(e-caprolactone)s (8SPCL1–3, represented as 5, 6 and 7, respectively) with an initiator core of 2,3,9,10,16,17,23,24- octakis(3-hydroxypropylmercapto)phthalocyaninatozinc(II) (4) was synthesized by the ring-opening polymerization of e-caprolactone using tin(II) 2-ethylhexanoate as the catalyst. The obtained star-shaped polymers were characterized by FT-IR, 1 H NMR, GPC and UV–vis spectroscopy. The measured intrinsic viscosities of all polymers were used to calculate the number-average molecular weight. The fluorescence of polymers 5–7 was studied. The changes in the visible spectra of 7 were investigated by increasing the concentration and adding methanol and cations such as Ag + , Hg 2+ , or Pb 2+ . The electrical conductivities of the polymers measured in vacuum and in air were between 10 9 and 10 6 Sm 1 . DSC and polarized optical microscopy techniques were used to evaluate the crystalline behavior of 5–7. The thermal stability of 5–7 was investigated by TGA. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Aliphatic polyesters are of significant interest owing to their unique biodegradability, biocompatibility and hydro- lyzability [1]. Among these polyesters, poly(e-caprolac- tone) (PCL), poly(lactide) (PLA), poly(glycolic acid) (PGA), and their copolymers are especially fascinating because of their potential applications as biomedical materials [2– 4]. The ring-opening polymerization (ROP) of lactides, and lactones is gaining increasing importance again as a major synthetic method after the discovery of organome- tallic compounds, such as oxides, carboxylates, and alkox- ides, as a starting material for the synthesis of polyesters [5]. Also, stannous and zinc derivatives [6–9] and enzymes [10] have been used as catalysts for ROP. For hydroxyl-end group-containing compounds used as initiators in the synthesis, tin(II) 2-ethylhexanoate (SnOct 2 ) is the most extensively used catalyst [11,12]. SnOct 2 is commercially available, and can produce polymers in high yield with controlled molecular weight and narrow distribution. Fur- thermore, it can prevent transesterification and possesses diminished biologic toxicity [13]. On the other hand, among the polyesters, PCL offers special advantages in medical applications [14–16]. The hydrophobic, semi- crystalline nature and slow degradation of PCL make it suitable for long-term drug delivery systems and scaffolds for tissue engineering [17,18]. Compared with their linear analogues, highly branched polymers, such as star-shaped PCL, exhibit particular fea- tures due to the higher segment density within the dis- tance of gyration radius [19]. Recently, star-shaped PCLs with well-defined architectures have been extensively investigated by different research groups using multifunc- tional small molecules and/or dendritic molecules [20–23]. http://dx.doi.org/10.1016/j.eurpolymj.2014.10.009 0014-3057/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: abilgin@kocaeli.edu.tr (A. Bilgin). European Polymer Journal 61 (2014) 240–252 Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj