A Novel PPh3 Mediated One-Pot Method for Synthesis of 3-Aryl or Alkyl 1,2-Benzisoxazoles.

A novel, efficient, and facile protocol has been developed for transforming 2-hydroxybenzonitriles and bromides into a range of 3-aryl or alkyl substituted 1,2-benzisoxazoles in good to excellent yields mediated by PPh3. The electronic and steric effects of bromides on the reaction are discussed. This is the first example to construct a C-C bond and heterocycle in a Barbier-Grignard-type reaction featuring easier recovery of PPh3 than a metallic catalyst in one step.

Synthesis and wound healing of alternating block polyurethanes based on poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG).

Alternating block polyurethanes (abbreviated as PULA-alt-PEG) and random block polyurethanes (abbreviated as PULA-ran-PEG) based on biodegradable poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG) were prepared. Results showed that alternating block polyurethane gives higher crystal degree, higher mechanical properties, more patterned and rougher surface than the random counterpart, due to the regular and controlled structure. Water absorptions of the polyurethanes were in the range of 620 to 780%. Cytocompatibility of the amphiphilic block polyurethanes (PU) (water static angle 41.4°-61.8°) was assessed by CCK-8 assay using human embryonic kidney (HEK293) cells. Wound healing evaluation of the PU foam scaffolds was carried out by full-thickness SD rat model experiment, with medical gauze as control. It was found that the skin of rat in PU groups was fully covered with new epithelium without any significant adverse reactions and PU dressings give much rapid and better healing than medical gauze. Histological examination revealed that PU dressings suppress the infiltration of inflammatory cells and accelerate fibroblast proliferation. It was also demonstrated that PULA-alt-PEG exhibits obvious better healing effect than PULA-ran-PEG does. This study has demonstrated that without further modification, plain alternating block polyurethane scaffold would help wound recovery efficiently. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1200-1209, 2017.

Rapid Hydrophilization of Model Polyurethane/Urea (PURPEG) Polymer Scaffolds Using Oxygen Plasma Treatment.

Polyurethane/urea copolymers based on poly(ethylene glycol) (PURPEG) were exposed to weakly ionized, highly reactive low-pressure oxygen plasma to improve their sorption kinetics. The plasma was sustained with an inductively coupled radiofrequency generator operating at various power levels in either E-mode (up to the forward power of 300 W) or H-mode (above 500 W). The treatments that used H-mode caused nearly instant thermal degradation of the polymer samples. The density of the charged particles in E-mode was on the order of 1016 m-3, which prevented material destruction upon plasma treatment, but the density of neutral O-atoms in the ground state was on the order of 1021 m-3. The evolution of plasma characteristics during sample treatment in E-mode was determined by optical emission spectroscopy; surface modifications were determined by water adsorption kinetics and X-ray photoelectron spectroscopy; and etching intensity was determined by residual gas analysis. The results showed moderate surface functionalization with hydroxyl and carboxyl/ester groups, weak etching at a rate of several nm/s, rather slow activation down to a water contact angle of 30° and an ability to rapidly absorb water.

Scaffolds from alternating block polyurethanes of poly(ɛ-caprolactone) and poly(ethylene glycol) with stimulation and guidance of nerve growth and better nerve repair than autograft.

Nerve repair scaffolds from novel alternating block polyurethanes (PUCL-alt-PEG) based on PCL and PEG without additional growth factors or proteins were prepared by a particle leaching method. The scaffolds have pore size 10-20 µm and porosity 92%. Mechanical tests showed that the polyurethane scaffolds have maximum loads of 5.97 ± 0.35 N and maximal stresses of 8.84 ± 0.5 MPa. Histocompatiblity of the nerve repair scaffolds was tested in a SD rat model for peripheral nerve defect treatment. Two types of treatments including PUCL-alt-PEG scaffolds and autografts were compared in rat model. After 32 weeks, bridging of a 12 mm defect gap by the regenerated nerve was observed in all rats. The nerve regeneration was systematically characterized by sciatic function index (SFI), electrophysiology, histological assessment including HE staining, immunohistochemistry, ammonia sliver staining, Masson's trichrome staining and TEM observation. Results revealed that nerve repair scaffolds from PUCL-alt-PEG exhibit better regeneration effects compared to autografts. Electrophysiological recovery was seen in 90% and 87% of rats in PUCL-alt-PEG and autograft groups respectively. Biodegradation in vitro and in vivo shows good degradation match of PUCL-alt-PEG scaffolds with nerve regeneration. It demonstrates that plain nerve repair scaffolds from PUCL-alt-PEG biomaterials can achieve peripheral nerve regeneration satisfactorily.

Scaffolds from block polyurethanes based on poly(ɛ-caprolactone) (PCL) and poly(ethylene glycol) (PEG) for peripheral nerve regeneration.

Nerve guide scaffolds from block polyurethanes without any additional growth factors or protein were prepared using a particle leaching method. The scaffolds of block polyurethanes (abbreviated as PUCL-ran-EG) based on poly(ɛ-caprolactone) (PCL-diol) and poly(ethylene glycol) (PEG) possess highly surface-area porous for cell attachment, and can provide biochemical and topographic cues to enhance tissue regeneration. The nerve guide scaffolds have pore size 1-5 µm and porosity 88%. Mechanical tests showed that the polyurethane nerve guide scaffolds have maximum loads of 4.98 ± 0.35 N and maximum stresses of 6.372 ± 0.5 MPa. The histocompatibility efficacy of these nerve guide scaffolds was tested in a rat model for peripheral nerve injury treatment. Four types of guides including PUCL-ran-EG scaffolds, autograft, PCL scaffolds and silicone tubes were compared in the rat model. After 14 weeks, bridging of a 10 mm defect gap by the regenerated nerve was observed in all rats. The nerve regeneration was systematically characterized by sciatic function index (SFI), histological assessment including HE staining, immunohistochemistry, ammonia silver staining, Masson's trichrome staining and TEM observation. Results revealed that polyurethane nerve guide scaffolds exhibit much better regeneration behavior than PCL, silicone tube groups and comparable to autograft. Electrophysiological recovery was also seen in 36%, 76%, and 87% of rats in the PCL, PUCL-ran-EG, and autograft groups respectively, whilst 29.8% was observed in the silicone tube groups. Biodegradation in vitro and in vivo show proper degradation of the PUCL-ran-EG nerve guide scaffolds. This study has demonstrated that without further modification, plain PUCL-ran-EG nerve guide scaffolds can help peripheral nerve regeneration excellently.

Alternating block polyurethanes based on PCL and PEG as potential nerve regeneration materials.

Polyurethanes with regular and controlled block arrangement, i.e., alternating block polyurethanes (abbreviated as PUCL-alt-PEG) based on poly(ε-caprolactone) (PCL-diol) and poly(ethylene glycol) (PEG) was prepared via selectively coupling reaction between PCL-diol and diisocyanate end-capped PEG. Chemical structure, molecular weight, distribution, and thermal properties were systematically characterized by FTIR, (1)H NMR, GPC, DSC, and TGA. Hydrophilicity was studied by static contact angle of H2O and CH2I2. Film surface was observed by scanning electron microscope (SEM) and atomic force microscopy, and mechanical properties were assessed by universal test machine. Results show that alternating block polyurethanes give higher crystal degree, higher mechanical properties, and more hydrophilic and rougher (deep ravine) surface than their random counterpart, due to regular and controlled structure. Platelet adhesion illustrated that PUCL-alt-PEG has better hemocompatibility and the hemacompatibility was affected significantly by PEG content. Excellent hemocompatibility was obtained with high PEG content. CCK-8 assay and SEM observation revealed much better cell compatibility of fibroblast L929 and rat glial cells on the alternating block polyurethanes than that on random counterpart. Alternating block polyurethane PUC20-a-E4 with optimized composition, mechanical, surface properties, hemacompatibility, and highest cell growth and proliferation was achieved for potential use in nerve regeneration.

Synthesis, characterization, and biocompatibility of alternating block polyurethanes based on PLA and PEG.

A series of alternating block polyurethanes (abbreviated as PULA-alt-PEG) and random block polyurethanes (abbreviated as PULA-ran-PEG) based on poly(L-lactic acid) (PLA) and poly(ethylene glycol) (PEG) were synthesized. The differences of PULA-alt/ran-PEG chemical structure, molecular weight, distribution, thermal properties, mechanical properties and static contact angle were systematically investigated. The PULA-alt/ran-PEG polyurethanes exhibited low T(g) (-47.3 ∼ -34.4°C), wide mechanical properties (stress σ(t): 4.6-32.6 MPa, modulus E: 11.4-323.9 MPa and strain ε: 468-1530%) and low water contact angle (35.4-51.4°). Scanning electron microscope (SEM) observation showed that PULA-alt-PEG film displays rougher and more patterned surface morphology than PULA-ran-PEG does, due to more regular structures of PULA-alt-PEG. Hydrolytic degradation shows that degradation rate of random block polyurethane series PULA-ran-PEG is higher than the alternating counterpart PULA-alt-PEG. PLA segment degradation is faster than urethane linkage and PEG segment almost does not degrade in the buffer solution. Platelet adhesion study showed that all the polyurethanes possess excellent hemocompatibility. The cell culture assay revealed that PULA-alt/ran-PEG polyurethanes were cell inert and unfavorable for the attachment of rat glial cell due to the hydrophilic characters of the materials.

Synthesis, characterizations, and biocompatibility of block poly(ester-urethane)s based on biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) and poly(ε-caprolactone).

A type of block poly(ester-urethane)s (abbreviated as PUBC) based on bacterial copolyester poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) and biodegradable poly(ε-caprolactone) (PCL) was synthesized by melting polymerization using 1,6-hexamethylene diisocyanate (HDI) as the coupling agent, with different 3HB, 4HB and PCL contents and segment lengths. Stannous octanoate (Sn(Oct)(2)) was used as catalyst. The chemical structure, molecular weight and thermal property were characterized by (1)H NMR, FTIR GPC, DSC and TGA. DSC analysis revealed that the PUBC polyurethanes exhibit amorphous to semi-crystalline (20.9% crystallinity degree) with T(g) range from -39.7 to -21.5 °C. The hydrophilicity was investigated by static contact angle of deionized water and CH(2)I(2). The obtained PUBCs are hydrophobic (water contact angle 73.7-90.2°). Platelet adhesion study and plasma recalcification time revealed that the block polyurethanes possess hemastasis ability. CCK-8 assay illuminated that the no cytotoxic polyurethanes maintain rat aortic smooth muscle cells (RaSMCs) good viability. It was found that the 4HB content in the materials is an important factor to affect the sustainable cell viability.

A comparative study on structure-property elucidation of P3/4HB and PEG-based block polyurethanes.

A series of alternating block polyurethanes (abbreviated as PU3/4HB-alt-PEG) and random block polyurethanes (abbreviated as PU3/4HB-ran-PEG) based on biodegradable polyester poly(3-hydroxybutyrate-co-4-hydroxybutrate) (P3/4HB-diol) and poly(ethylene glycol) (PEG) with similar chemical compositions were synthesized using 1, 6-hexamethylene diisocyanate (HDI) as coupling agent. The chemical structure, molecular weight and distribution were characterized by FTIR, (1)H NMR, and GPC. The thermal differences were investigated by DSC. The hydrophilicity was studied by static contact angle and the results revealed that PU3/4HB-alt-PEG is more hydrophilic with a higher surface energy than PU3/4HB-ran-PEG. With SEM observation, PU3/4HB-alt-PEG exhibited a regular characterized microstructure with flower-type patterns on the surface, while PU3/4HB-ran-PEG displayed no regular pattern. A platelet adhesion study illustrated that PU3/4HB-alt-PEG possesses better hemocompatibility due to its more hydrophilic surface and evident surface microstructure. The cell culture assay demonstrated that fibroblasts and rat glial cells were more favorable for attachment on PU3/4HB-alt-PEG films. By comparison, alternating block polyurethanes provides a way to control the exact structure of the biomaterials and tailor better properties to biomedical requirements.

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 (¹H 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 °C, T(m) from 110 to 145 °C. The polyurethanes were more hydrophilic (water contact angle centers around 80 °) 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.

Biodegradable block poly(ester-urethane)s based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymers.

A series of block poly(ester-urethane)s (abbreviated as PU3/4HB) based on biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) segments were synthesized by a facile way of melting polymerization using 1,6-hexamethylene diisocyanate (HDI) as the coupling agent and stannous octanoate (Sn(Oct)(2)) as catalyst, with different 4HB contents and segment lengths. The chemical structure, molecular weight and distribution were systematically characterized by (1)H nuclear magnetic resonance spectrum (NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The thermal property was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The hydrophilicity was investigated by static contact angle of deionized water and CH(2)I(2). DSC curves revealed that the PU3/4HB polyurethanes have their T(g) from -25.6 °C to -4.3 °C, and crystallinity from 2.5% to 25.3%, being almost amorphous to semi-crystalline. The obtained PU3/4HBs are hydrophobic (water contact angle 77.4°-95.9°), and their surface free energy (SFE) were studied. The morphology of platelets adhered on the polyurethane film observed by scanning electron microscope (SEM) showed that platelets were activated on the PU3/4HB films which would lead to blood coagulation. The lactate dehydrogenase (LDH) assay revealed that the PU3/4HBs displayed higher platelet adhesion property than raw materials and biodegradable polymer polylactic acid (PLA) and would be potential hemostatic materials. Crystallinity degree, hydrophobicity, surface free energy and urethane linkage content play important roles in affecting the LDH activity and hence the platelet adhesion. CCK-8 assay showed that the PU3/4HB is non-toxic and well for cell growth and proliferation of mouse fibroblast L929. It showed that the hydrophobicity is an important factor for cell growth while 3HB content of the PU3/4HB is important for the cell proliferation. Through changing the composition and the chain-length of P3/4HB-diol prepolymers, the biocompatibility of the poly(ester-urethane)s can be tailored.

Degradation behaviors of bioabsorbable P3/4HB monofilament suture in vitro and in vivo.

The biodegradable behaviors of monofilament suture made from bacterial biopolyester poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) was investigated both in lipase solution and by implant into rat tergal muscles. Results showed that the monofilament suture lost its tensile strength gradually accompanied by decrease of molecular weight. The suture retained approximately 65% of its original strength after lipase degradation for 12 weeks, whereas the molecular weight decreased from 4.5 x 10(5) to 3.8 x 10(5). However, the crystallinity of the suture, after lipase degradation for 12 weeks, increased from 27 to 33%. This may ascribe to improve orientation arrangement of molecular chain in the monofilament after the fragment from amorphous regions dissolved in the buffer solution. The roughness of surface morphology increased with degradation. Rat implantation showed no remarkable tissue responses during in vivo degradation. Foreign body reactions were much milder than chromic catgut, which is one of the most common commercially available sutures.

Synthesis, characterizations and biocompatibility of novel biodegradable star block copolymers based on poly[(R)-3-hydroxybutyrate] and poly(epsilon-caprolactone).

Star block copolymers based on poly[(R)-3-hydroxybutyrate] (PHB) and poly(epsilon-caprolactone) (PCL), termed SPHBCL, were successfully synthesized with structural variation on arm numbers and lengths via coupling reactions and ring opening polymerizations. Arm numbers 3, 4 and 6 of SPHBCL were synthesized by using different multifunctional cores, such as trimethyol propane, pentaerythiritol and dipentaerthritol, respectively. Gel permeation chromatography (GPC) and (1)H and (13)C nuclear magnetic resonance were used to characterize the structure of SPHBCL. GPC failed to produce accurate molecular weights of the SPHBCL due to the discrepancy of star copolymer structures. The melting temperature of SPHBCL decreased with increasing degree of branching. Thermal decomposition temperature was revealed to be lower than that of linear block copolymer LPHBCL counterparts based on PHB and PCL. Films made from various SPHBCL copolymers had different porous or networking surface morphology, and all possessed improved biocompatibility in terms of less blood clotting and more osteoblast cell growth compared with their corresponding homopolymers PHB and PCL. Among them, it was found, however, that the 4-arm star block copolymer 4SPHBCL-25 showed unique surface properties, i.e. a regular nanoravine structure was observed by scanning electron microscopy and atomic force microscopy. This 4-arm star copolymer also showed the best biocompatibility.

Synthesis, characterization and cell compatibility of novel poly(ester urethane)s based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) prepared by melting polymerization.

Novel tailor-made poly(ester urethane)s (PUs) based on microbial polyesters poly(3-hydroxybutyrate-co-4hydroxybutyrate) (P3HB4HB) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) were synthesized by melting polymerization (MP) using 1,6-hexamethylene diisocyanate (HDI) as a coupling agent. A comprehensive characterization using (1)H-NMR, Fourier transform infrared spectroscopy (FT-IR), gel-permeation chromatography (GPC), differential scanning calorimetry (DSC), mechanical properties, static water contact angles, cell proliferation using smooth muscle cells from rabbit aorta (RaSMCs) and immortalized human keratinocytes (HaCat), and blood coagulation behavior were conducted on the synthesized PUs films. DSC showed that PU samples had a low degree of crystallinity at room temperature and became fully amorphous after a melt-quenched process. The series of tailor-made PUs based on different mass ratios of P3HB4HB and PHBHHx revealed a ductile and flexile mechanical property especially for PHBHHx-rich PU, or a hydrophobic property for 4HB-rich PU. A 4 days incubation experiment showed that all PU films had a better cell proliferation than poly(lactic acid) (PLA), polyhydroxybutyrate (PHB), P3HB4HB and PHBHHx. RaSMCs cultured on PU films had a quiescent contractile phenotype, indicating that they were fully functional. HaCat incubated on tailor-made PU films showed a proliferation approximately equal to tissue-culture plates (TCPs). Blood coagulation behavior tests revealed a strong platelet adhesion and a short coagulation time on PU films. This study demonstrated potential medical applications for P3HB4HB and PHBHHx based polyurethane as a hydrophobic wound-healing and hemostatic materials.

Synthesis, characterization and biocompatibility of biodegradable elastomeric poly(ether-ester urethane)s Based on Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and Poly(ethylene glycol) via melting polymerization.

Poly(ether-ester urethane)s (PUs) multiblock co-polymers were synthesized from telechelic hydroxylated poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and poly(ethylene glycol) (PEG) via a melting polymerization (MP) process using 1,6-hexamethylene diisocyanate (HDI) as a non-toxic coupling agent for the first time. The PHBHHx segments and PEG segments in the multiblock co-polymers behaved as a hard, hydrophobic and a soft, hydrophilic part, respectively. Their chemical structures and molecular characteristics were studied by gel-permeation chromatography (GPC), (1)H-NMR and Fourier transform infrared spectroscopy (FT-IR). The PU produced via the MP method showed a higher molecular weight than those resulting from the solvent polymerization (SP) reported previously. Thermal properties showed enhanced thermal stability with semi-crystalline morphology via incorporation of PEG. The segments compositions evaluated from thermogravimetric analysis (TGA) two-step thermal decomposition profiles suggested that MP enhanced the reactivity of PEG compared with the SP process. It was in good agreement with those calculated from (1)H-NMR, as well as the precursor feed ratio, respectively. Water contact angle measurements revealed that surface hydrophilicity of the PUs was enhanced by incorporating the PEG segment into PHBHHx polymer backbone. The mechanical properties assessment of the PUs recorded an improved and adjustable ductility and toughness than pure PHBHHx while preserving the tensile strength. Samples synthesized via MP were resistant to hydrolytic and lipase degradation, yet the multiblock co-polymers incorporating the highest amount of PEG degraded at the highest rate. SEM studies revealed that the surface of the PU films became increasingly porous as the degradation proceeded. Implantation of PU in mouse abdominal cavity indicated that tissue regeneration and tissue compatibility of PU film was better than that of PHBHHx-only film.

Alternative block polyurethanes based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and poly(ethylene glycol).

A series of amphiphilic alternative block polyurethane copolymers based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) and poly(ethylene glycol) (PEG) were synthesized by a coupling reaction between P3/4HB-diol and PEG-diisocyanate, with different 3HB, 4HB, PEG compositions and segment lengths. Stannous octanoate was used as catalyst. The chemical structure, alternative block arrangement, molecular weight and distribution were systematically characterized by FTIR, (1)H NMR, GPC and composition analysis. The thermal property was studied by DSC and TGA. Platelet adhesion study revealed that the alternative block polyurethanes possess excellent hemocompatibility. CCK-8 assay illuminated that the non-toxic block polyurethanes maintain rat aortic smooth muscle cells (RaSMCs) good viability. The in-vitro degradation of the copolymers in PBS buffer solution and in lipase buffer medium was investigated. Results showed that the copolymer films exhibit different degradation patterns in different media from surface erosion to diffusion bulk collapsing. The synthetic methodology for the alternative block polyurethanes provides a way to control the exact structure of the biomaterials and tailor the properties to subtle requirements.

Block poly(ester-urethane)s based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and poly(3-hydroxyhexanoate-co-3-hydroxyoctanoate).

A series of block poly(ester-urethane) poly(3/4HB-HHxHO) urethanes (abbreviated as PUHO) based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB-diol) and poly(3-hydroxyhexanoate-co-3-hydroxyoctanoate) (PHHxHO-diol) segments were synthesized by a facile way of melting polymerization using 1,6-hexamethylene diisocyanate (HDI) as the coupling agent, with different 3HB, 4HB, HHxHO compositions and segment lengths. The chemical structure, molecular weight and distribution were systematically characterized by (1)H, (13)C nuclear magnetic resonance spectrum (NMR), two-dimensional correlation spectroscopy (COSY ((1)H, (13)C) NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The thermal property was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The hydrophilicity was investigated by static contact angle of water and CH(2)I(2). DSC revealed that the poly(3/4HB-HHxHO) urethanes are almost amorphous with a little crystallinity (less than 6%) and T(g) from -23 degrees C to -3 degrees C. The polyurethanes are more hydrophobic (water contact angle 88 degrees -117 degrees ) than the P3/4HB and PHHxHO raw materials. The lactate dehydrogenase (LDH) assay and platelet adhesion determination showed that the obtained polyurethanes have much higher platelet adhesion property than raw materials and common biodegradable polymers polylactic acid (PLA) and poly(3-hydroxybutyrate) (PHB). Hydrophobicity and crystallinity degree are important factors to affect the platelet adhesion. All the properties can be tailored by changing the composition and segment length of prepolymers P3/4HB-diol and PHHxHO-diol.

Characterization, biodegradability and blood compatibility of poly[(R)-3-hydroxybutyrate] based poly(ester-urethane)s.

Poly(ester-urethane)s (PUs) were synthesized using hexamethylene diisocyanate (HDI) or toluene diisocyanate (TDI) to join short chains (M(n) = 2000) of poly(R-3-hydroxybutyrate) (PHB) diols and poly(epsilon-caprolactone) (PCL) diols with different feed ratios under different reaction conditions. The multiblock copolymers were characterized by nuclear magnetic resonance spectrometer (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), X-ray diffraction (XRD), and scanning electron microscope (SEM). XRD spectra and second DSC heat thermograms of the multiblock copolymers revealed that the crystallization of both PHB and PCL segments was mutually restricted, and, especially, the PCL segment limited the cold crystallization of the PHB segment. The SEM of platelet adhesion experiments showed that the hemocompatibility was affected to some extent by the chain flexibility of the polymers. Hydrolysis studies demonstrated that the hydrolytic degradation of PUs was generated from the scission of their ester bonds or/and urethane bonds. Simultaneously, the rate of ester bond scission was determined to some extent by the crystallization degree, which was further affected by the configuration of polymer chains. These highly elastic multiblock copolymers combining hemocompatibility and biodegradability may be developed into blood contact implant materials for biomedical applications.