Synthesis of Star-Shaped Poly(ε-caprolactone)-b-poly(dl-lactic acid-alt-glycolic acid) with Multifunctional Initiator and Stannous Octoate Catalyst

Abstract

Two types of three-arm or four-arm star-shaped hydroxy-terminated poly( -caprolactone) (PCL) were successfully synthesized via the ring-opening polymerization of -caprolactone (CL) with multifunctional initiator, such as trimethylolpropane (TMP) or pentaerythritol (PTOL), and stannous octoate (SnOct 2) catalyst in bulk at 110 °C. The number-average molecular weight of PCL is proportional to the molar ratio of monomer to initiator. 1 H NMR spectroscopy of the resulting PCL indicates that it contains a primary hydroxy end group in each arm. The star-shaped PCL with hydroxy end groups can be used as a macroinitiator for block copolymerization with DL-3-methylglycolide (MG) using SnOct2 catalyst in bulk at 115 °C. 1 H NMR spectra of the resulting block copolymers show that the molecular weights and the unit compositions of the block copolymers were controlled by the molar ratios of MG monomer to hydroxy groups of PCL and MG to CL in feed, respectively. Moreover, the molecular weights of the resulting block copolymers linearly increased with the increase of the molar ratios of MG to CL in feed. The molecular weight distributions of the block copolymers were rather narrow (M w/Mn ) 1.09-1.26). 13 C NMR spectra of the resulting block copolymers clearly show their diblock structures, that is, PCL as the first block and poly(DL-lactic acid-alt-glycolic acid) (DL-PLGA50) with alternating structures of lactyl and glycolyl units as the second block. Therefore, two types of three-arm or four-arm star-shaped diblock copolyesters comprising the first block PCL and the second block DL-PLGA50 were successfully synthesized via the sequential ring-opening polymerization of CL with multifunctional initiator and SnOct2 catalyst and then followed by copolymerization with MG.

The Effect of Branching (Star Architecture) on Poly(d,l-lactide) (PDLLA) Degradation and Drug Delivery

“…Pentaerythritol has been successfully employed as a multifunctional initiator for the bulk polymerization of lactides [22][23][24] , but in pilot experiments we noticed that polyols with higher functionality such as dipentaerythritol and tripentaerythritol (respectively 6 and 8 OH/molecule) were completely insoluble in the monomer. We therefore chose polymerization in a hydrophobic and easy to dry solvent such as toluene, where both pentaerythritol and dipentaerythritol are soluble; tripentaerythritol is only partially soluble and its use as an initiator in refluxing toluene yielded PDLLA with large batch-to-batch variations (although with consistent conversion: 78- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 82%), thus it was not further employed in this study.…”

Mechanistic study of Sn(Oct)2‐catalyzed ε‐caprolactone polymerization using Sn(Oct)2/BF3 dual catalyst

“…They all have a triplet in the vicinity of d ¼ 3.7 ppm, which is due to a ACH 2 OH end, and the multiplets centered at d ¼ 1.4, 1.65, 2.3, 4.05 ppm, which correspond to the main chain protons of PCL. 12,13 The spectrum of the polymer using neat BF 3 catalyst has a triplet at d ¼ 3.4 ppm, which is due to an ether bond formed by the reaction between two hydroxyl end groups. 14 The presence of hydroxyl end groups in the polymer molecules indicated by the NMR spectra is the imprint of water initiator.…”

Synthesis, characterization, and evaluation of paclitaxel loaded in six-arm star-shaped poly(lactic-co-glycolic acid)

“…This means that they are not easily stranded in the blood, which ensures the bioavailability of the drugs encapsulated in them. 9,10 Above all, star-shaped polymers provide more terminal groups that are capable of connecting with targeted molecules. These largely determine the properties of the polymer and transport the encapsulated drugs to the targeted organs and tissues.…”