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Chitin based polyurethane bio-nanocomposites (PUBNC) were prepared using chitin, Delite HPS bentonite nanoclay enriched in montmorillonite (MMT), 4,4'-diphenylmethane diisocyanate (MDI) and polycaprolactone polyol CAPA 231 (3000 g/mol(-1)). The prepolymers having different concentration of Delite HPS bentonite nanoclay were extended with 2 moles of chitin. The structures of the resulted polymers were determined by FT-IR technique. The effect of nanoclay contents on mechanical properties and in vitro biocompatibility was investigated. The mechanical properties of the synthesized materials were improved with increase in the Delite HPS bentonite nanoclay contents. Optimum mechanical properties were obtained from the PU bio-nanocomposite samples having 4% Delite HPS bentonite nanoclay. The results revealed that the final PU bio-nanocomposite having 2% Delite HPS bentonite nanoclay contents is ideal contenders for surgical threads with on going investigations into their in vitro biocompatibility, non-toxicity, and mechanical properties., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Shape memory polyurethanes (SMPUs) were prepared from polycaprolactone diol 4000 (PCL 4000), 1,4-butanediol (BDO), chitin, dimethylol propionic acid (DMPA), triethylamine (TEA) and 4,4'-diphenylmethane diisocyanate (MDI), and the structures of the synthesized materials were verified by infrared spectroscopy. The effects of chitin and DMPA contents in the polyurethane formulation on surface properties were investigated. DMPA provides function of making hydrophilic polyurethanes. The crystalline structure of chitin enhanced the hydrophobicity of the synthesized materials. Contact angle, water absorption, surface free energy, work of water adhesion and swelling behavior of the synthesized polyurethanes were affected by varying the DMPA and chitin contents. The interactions of the PU films with solvents on the surface were clearly related to the contents of DMPA and chitin in the final polyurethane formulation.

Biodegradable polyurethane elastomers with tunable hydrophobicity were synthesized by step-growth polymerization techniques using poly(epsilon-caprolactone) (PCL) and 4,4'-diphenylmethane diisocyanate (MDI). The prepolymer was extended with different mass ratios of chitin and 1,4-butane diol (BDO). The effect of chitin contents in chain extenders (CE) proportion on surface properties was studied and investigated. Incorporation of chitin contents into the final PU showed decrease in surface free energy and its polar component. Simultaneously, the work of water adhesion to polymer decreases significantly by increasing the chitin contents in the synthesized polymer. Contact angle measurement, water absorption and swelling behavior of the synthesized polyurethane samples were affected by varying the chitin contents in the chemical composition of the final PU. The interactions of the final PU films with solvents on the surface were displayed clear dependent on the contents of chitin in to the final polyurethane formulation. The results of different tests demonstrated that the synthesized products are a potential candidate as non-absorbable suture as previously investigated into their in vitro biocompatibility and non-toxicity [K.M. Zia, M. Zuber, I.A. Bhatti, M. Barikani, M.A. Sheikh, Int. J. Biol. Macromol. 44 (2009) 18-22].

Chitin based polyurethane elastomers with potential as biomedical implants with tunable mechanical properties were synthesized by step growth polymerization techniques using poly(epsilon-caprolactone) (PCL) and 4,4'-diphenylmethane diisocyanate (MDI). The prepolymer was extended with different mass ratios of chitin and 1,4-butane diol (BDO). Molecular characterization was done using FTIR, 1H NMR and 13C NMR techniques. The mechanical properties of these polymers were improved with increase in the chitin contents. Optimum mechanical properties were obtained from elastomers extended with chitin in comparison to elastomers extended with BDO. Cytotoxicity of the synthesized polyurethane samples was affected by varying the chitin contents in the chemical composition of the final polyurethane (PU). It is revealed that the final polymers extended with chitin are preferred candidates for surgical threads with on going investigations into their in vitro biocompatibility and non-toxicity.

Chitin-based polyurethane elastomers (PUEs) were synthesized by step growth polymerization techniques using poly(epsilon-caprolactone) (PCL) varying diisocyanate and chain extender structures. The viscosity average molecular weight (M(v)) of chitin was deduced from the intrinsic viscosity and found; M(v)=6.067 x 10(5). The conventional spectroscopic characterization of the samples with FTIR, (1)H NMR and (13)C NMR were in accordance with proposed PUEs structure. The crystalline behavior of the synthesized polymers were investigated by X-ray diffraction (XRD), differential scanning calorimetery (DSC) and loss tangent curves (tan delta peaks). The observed patterns of the crystalline peaks for the lower angle for chitin in the 2theta range were indexed as 9.39 degrees, 19.72 degrees, 20.73 degrees, 23.41 degrees and 26.39 degrees. Results showed that crystallinity of the synthesized PUEs samples was affected by varying the structure of the diisocyanate and chain extender. Crystallinity decreased from aliphatic to aromatic characters of the diisocyanates used in the final PU. The presence of chitin also favors the formation of more ordered structure, as higher peak intensities was obtained from the PU extended with chitin than 1,4-butane diol (BDO). The value of peak enthalpy (DeltaH) of chitin was found to be 47.13 J g(-1). The higher DeltaH value of 46.35 J g(-1) was found in the samples extended with chitin than BDO (39.73 J g(-1)).

Abstract: Chitin-based polyurethane elastomers (PUEs) constituted on 4,4′-diphenylmethane diisocyanate (MDI), poly(ε-caprolactone) (PCL) and extended with blends of chitin/1,4-butane diol were first synthesized via two step polymerization technique and then irradiated for 50, 100 and 200h in an UV exposure chamber as such the spectral distribution of the light is good match for terrestrial solar radiation. The surface properties of the irradiated PU samples were investigated by contact angle measurements, surface free energy and water absorption (%), total work of water adhesion to polymer and equilibrium degree of swelling. The effects of UV-irradiation time and chitin contents in chain extenders (CE) proportion on surface properties were investigated. Results of the aforementioned surface techniques revealed that the UV-irradiated polyurethane samples were affected by varying the UV exposure period. [Copyright &y& Elsevier]

Abstract: Chitin based polyurethane (PU) elastomers constituted on 4,4´-diphenylmethane diisocyanate (MDI), poly(ε-caprolactone) (PCL) and extended with blends of chitin/1,4-butane diol were synthesized via two step polymerization technique. The synthesized samples were irradiated for 50, 100 and 200h in an UV exposure chamber as such the spectral distribution of the light is good match for terrestrial solar radiation. The crystalline behavior of the irradiated PU samples were investigated by X-ray diffraction (XRD), differential scanning calorimetery (DSC) and dynamic mechanical thermal analysis (DMTA) techniques. The effect of irradiation time and chitin contents on crystallinity were studied and investigated. The maximum decrease in the crystalline behavior of samples after irradiation observed by XRD, DSC and tan δ peaks were found for the PU samples extended with lower contents of chitin (chitin/BDO; 0/100). In comparison with irradiation times the 200h irradiation showed maximum change in the crystalline behavior. [Copyright &y& Elsevier]

Abstract: Shape memory polyurethanes (SMPUs) are playing a prominent role in biomedical, self repairing, aerospace and smart materials. Shape memory polyurethanes (SMPUs) were prepared from polycaprolactone diol 4000 (PCL4000), 1-4-butanediol (BDO), chitin, dimethylol propionic acid (DMPA), triethylamine (TEA), and 4, 4′-diphenylmethane diisocyanate (MDI). Trifunctional characteristics of chitin enhanced the thermal and mechanical properties of SMPUs. DMPA was used to obtain higher recovery and lower residual strain. The morphology, microstructure, mechanical, thermo-mechanical, and shape memory properties of synthesized SMPUs were investigated using Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC), dynamic mechanical thermal analyzer (DMTA) and tensile testing techniques. The results showed that crosslinked SMPUs have better thermal and thermo-mechanical properties, and a good shape memory effect. [Copyright &y& Elsevier]

Abstract: Biodegradable polyurethane elastomers with potential for biomedical application as non-absorbable sutures with improved hydrophobic properties were synthesized by the reaction of poly(ε-caprolactone) (PCL) and 4,4′-diphenylmethane diisocyanate (MDI), extended with different mass ratio of chitin and 1,4-butane diol (BDO). Their molecular engineering and structural transition due to the changes of hydrogen bonding was confirmed by using FT-IR, 1H NMR and 13C NMR. Involvement of chitin was evidenced by the appearance of new signals in both 1H NMR and 13C NMR spectra, and very strong peak at 1724cm−1 in FT-IR spectra. From the results, it was concluded that the reaction of the urethane group occurred mainly at C6of chitin in which strong intermolecular and intersheet hydrogen bonds are involved. Contact angle and surface tension measurement of the synthesized polyurethane as a function of chitin contents were investigated. Optimum hydrophobicity was obtained from elastomer extended with chitin in comparison to elastomers extended with BDO. The surface free energy was also affected by chemical composition of the final PU. Structure–property relationship for prepared elastomers showed that the main determining factors were hydrogen bonding, hydrophobicity and content of chitin in polyurethane backbone. [Copyright &y& Elsevier]

The article describes the synthesis and characterization of novel, biodegradable thermally stable chitin-based polyurethane (PU) elastomers. The researchers synthesized the elastomers with poly(ε-caprolactone), 4,4'-diphenylmethane diisocyanate, chitin and 1,4-butane diol. Results referred to physical effective crosslink density, hydrogen bonding, thermal stability and chitin content in the PU backbone as the determining factors for the observed thermal properties of the elastomers.

Abstract: Chitin based polyurethane bio-nanocomposites (PUBNC) were prepared by emulsion polymerization. The existence of the intercalated clay by polyurethane (PU) in the hybrid was confirmed using X-ray diffraction (XRD), dynamic mechanical measurements and optical microscope (OM) techniques. The values of enthalpies changes (ΔH) associated with different bentonite nanoclay contents are much consistent with the crystalline pattern of the synthesized PUBNC samples. These results revealed that pure silicate disappear in PU/bentonite nanoclay hybrid and a set of new peaks appears corresponding to the basal spacing of PU/bentonite clay bio-nanocomposites. The values of tan δ versus temperature recorded using dynamic mechanical measurements were also in accord with crystalline pattern of the PUBNC samples. [Copyright &y& Elsevier]

Abstract: Chitin based polyurethane elastomers (PUEs) were synthesized by step growth polymerization techniques using poly (ε-caprolactone) (PCL), 4, 4′- diphenylmethane diisocyanate (MDI) and blends of chitin and 1,4-butanne diol (BDO). The conventional spectroscopic characterization of the samples with FT-IR, 1H NMR and 13C NMR were in accordance with proposed PUEs structure. The crystalline behavior of the synthesized polymers were investigated by X-ray diffraction (XRD), differential scanning calorimetery (DSC), optical microscopic technique and loss tangent curves (tan δ peaks). Results showed that crystallinity of the synthesized PUEs samples was affected by varying the chitin contents used as chain extender. The contents of chitin favors the formation of more ordered structure, as higher peak intensities were obtained from the PU extended with chitin than 1,4-butane diol (BDO). X-ray diffraction experiments results correlates with optical microscopy findings. The higher ΔH value; 41.57(Jg−1) was found in the samples extended with chitin than BDO (31.32Jg−1). [Copyright &y& Elsevier]

Abstract: Chitin-based polyurethane elastomers having potential for biomedical applications with tunable mechanical properties were synthesized by step growth polymerization techniques using poly(ɛ-caprolactone) (PCL) with different diisocyanates. The prepolymer was extended using chitin and/or 1,4-butane diol (BDO). The structures of the resulted polymers were determined by Fourier transform infrared (FTIR), 1H NMR and 13C NMR spectroscopic techniques. The effect of structure of diisocyanates and chain extenders on mechanical properties and in vitro biocompatibility were investigated. The results revealed that the final polymers extended with chitin are preferred candidates for surgical threads with on going investigations into their in vitro biocompatibility and non-toxicity. [Copyright &y& Elsevier]