Synthesis, characterizations and biocompatibility of alternating block polyurethanes based on P3/4HB and PPG-PEG-PPG

Block copolymers with exactly controlled structures, that is, alternating block polyurethanes based on poly(3-hydroxybutyrate-co-4-hydroxybutrate) (P3/4HB-diol) and poly (propylene glycol)-poly(ethylene glycol)-poly(propylene glycol) (PPG-PEG-PPG) were synthesized by solution polymerization via specifically selective coupling reaction between terminal hydroxyl P3/4HB segment and isocyanate group end-capped PPG-PEG-PPG segment, using 1,6-hexamethylene diisocyanate (HDI) as end-capped agent. The chemical structure, molecular weight and distribution were systematically characterized by nuclear magnetic resonance spectrum (H-1 NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The thermal property was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis. The hydrophilicity was studied by static contact angle of H2O and CH2I2. DSC revealed that the PU3/4HB-alt-PPG-PEG-PPG exhibited a distinct change from amorphous to 30% crystallinity degree, T-g from -25 to -50 degrees C, T-m from 110 to 145 degrees C. The polyurethanes were more hydrophilic (water contact angle centers around 80 degrees) than the raw PHA materials. The platelet adhesion assay showed that the obtained polyurethanes had a lower platelet adhesion than the raw materials and the amount of platelet adhesion could be controlled by varying the segmental length of P3/4HB-diol. This could be explained by the inclusion of PPG-PEG-PPG between the P3/4HB segments, improving the hemocompatibility of P3/4HB. The cell culture assay revealed that the obtained polyurethanes were cell inert and unfavorable for the attachment of mouse fibroblast cell line L929 and rabbit blood vessel smooth muscle cells (RaSMCs). This suggests that these polyurethanes would be promising candidates as hemocompatibility and tissue-inert materials. (C) 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 98A: 88-99, 2011.