Synthesis and characterization of polyurethane-g-chitosan

Polyols and Polyurethane Foams Based on Water-Soluble Chitosan

At present, majority of polyols used in the synthesis of polyurethane foams are of petrochemical origin. The decreasing availability of crude oil imposes the necessity to convert other naturally existing resources, such as plant oils, carbohydrates, starch, or cellulose, as substrates for polyols. Within these natural resources, chitosan is a promising candidate. In this paper, we have attempted to use biopolymeric chitosan to obtain polyols and rigid polyurethane foams. Four methods of polyol synthesis from water-soluble chitosan functionalized by reactions of hydroxyalkylation with glycidol and ethylene carbonate with variable environment were elaborated. The chitosan-derived polyols can be obtained in water in the presence of glycerol or in no-solvent conditions. The products were characterized by IR, 1H-NMR, and MALDI-TOF methods. Their properties, such as density, viscosity, surface tension, and hydroxyl numbers, were determined. Polyurethane foams were obtained from hydroxyalkylated chitosan. The foaming of hydroxyalkylated chitosan with 4,4′-diphenylmethane diisocyanate, water, and triethylamine as catalysts was optimized. The four types of foams obtained were characterized by physical parameters such as apparent density, water uptake, dimension stability, thermal conductivity coefficient, compressive strength, and heat resistance at 150 and 175 °C. It has been found that the obtained materials had most of the properties similar to those of classic rigid polyurethane foams, except for an increased thermal resistance up to 175 °C. The chitosan-based polyols and polyurethane foams obtained from them are biodegradable: the polyol is completely biodegraded, while the PUF obtained thereof is 52% biodegradable within 28 days in the soil biodegradation oxygen demand test.

Synthesis and Characterization of Biopolyol-Based Waterborne Polyurethane Modified through Complexation with Chitosan

In this study, a series of castor oil-based anionic waterborne polyurethane (CWPU) systems, which it has been suggested may be suitable for use as green elastomers with diverse applications in films and coatings, was prepared by modified with O-carboxymethyl chitosan (CS) as not only a reinforcing filler, but a chain-extender of polyurethane prepolymer to enhance the properties of polyurethanes. Moreover, not only was the system obtained with castor oil-based polyol in the absence of a catalyst, but it was maintained with low viscosity by using acetone instead of toxic methyl ethyl ketone (MEK) during the synthesis process. The sizes, zeta potential, chemical formation, and morphology of the CWPU-CS composites had been investigated by dynamic light scattering (DLS), infrared spectroscopy (IR), and scanning electron microscopy (SEM). Moreover, the results show that the modification allows to enhance storage/loss modulus, tensile properties, thermal stability at high temperature, and biocompatibility of CWPU and CWPU/CS nanocomposites according to various contents of CS.

The Effect of Chitosan on the Chemical Structure, Morphology, and Selected Properties of Polyurethane/Chitosan Composites

Materials science is an interdisciplinary area of studies. This science focuses on the influence of the physico-chemical properties of materials on their application in human everyday lives. The materials’ synthesis should be developed in accordance with sustainable development. Polyurethanes (PUR) represent a significant consumption of plastic in the world. Modification of PUR, e.g., with polysaccharide of natural origin (chitosan, Chit), should have a positive effect on their functional properties and degradability in the natural environment. The basic parameters affecting the scope and direction of changes are the size and quantity of the chitosan particles. The impact assessment of chitosan on the chemical structure, morphology, thermal properties, crystallinity, mechanical properties, flammability, water sorption, adsorption properties, degradability, and biological activity of PUR/Chit composites (without other additives) is discussed in this article. To the best of our knowledge, recent literature does not contain a study discussing the direct impact of the presence of chitosan in the structure of PUR/Chit composite on its properties, regardless of the intended uses. This paper provides an overview of publications, which presents the results of a study on the effect of adding chitosan in polyurethane/chitosan composites without other additives on the properties of polyurethane.

Polyurethane-Based Composites: Effects of Antibacterial Fillers on the Physical-Mechanical Behavior of Thermoplastic Polyurethanes

The challenge to manufacture medical devices with specific antibacterial functions, and the growing demand for systems able to limit bacterial resistance growth, necessitates the development of new technologies which can be easily produced at an industrial level. The object of this work was the study and the development of silver, titanium dioxide, and chitosan composites for the realization and/or implementation of biomedical devices. Thermoplastic elastomeric polyurethane was selected and used as matrix for the various antibacterial functions introduced during the processing phase (melt compounding). This strategy was employed to directly incorporate antimicrobial agents into the main constituent material of the devices themselves. With the exception of the composite filled with titanium dioxide, all of the other tested composites were shown to possess satisfactory mechanical properties. The best antibacterial effects were obtained with all the composites against Staphylococcus aureus: viability was efficiently inhibited by the prepared materials in four different bacterial culture concentrations.

Preparation, Physicochemical Properties and Hemocompatibility of Biodegradable Chitooligosaccharide-Based Polyurethane

The purpose of this study was to develop a process to achieve biodegradable chitooligosaccharide-based polyurethane (CPU) with improved hemocompatibility and mechanical properties. A series of CPUs with varying chitooligosaccharide (COS) content were prepared according to the conventional two-step method. First, the prepolymer was synthesized from poly(ε-caprolactone) (PCL) and uniform-size diurethane diisocyanates (HBH). Then, the prepolymer was chain-extended by COS in N,N-dimethylformamide (DMF) to obtain the weak-crosslinked CPU, and the corresponding films were obtained from the DMF solution by the solvent evaporation method. The uniform-size hard segments and slight crosslinking of CPU were beneficial for enhancing the mechanical properties, which were one of the essential requirements for long-term implant biomaterials. The chemical structure was characterized by FT-IR, and the influence of COS content in CPU on the physicochemical properties and hemocompatibility was extensively researched. The thermal stability studies indicated that the CPU films had lower initial decomposition temperature and higher maximum decomposition temperature than pure polyurethane (CPU-1.0) film. The ultimate stress, initial modulus, and surface hydrophilicity increased with the increment of COS content, while the strain at break and water absorption decreased, which was due to the increment of crosslinking density. The results of in vitro degradation signified that the degradation rate increased with the increasing content of COS in CPU, demonstrating that the degradation rate could be controlled by adjusting COS content. The surface hemocompatibility was examined by protein adsorption and platelet adhesion tests. It was found that the CPU films had improved resistance to protein adsorption and possessed good resistance to platelet adhesion. The slow degradation rate and good hemocompatibility of the CPUs showed great potential in blood-contacting devices. In addition, many active amino and hydroxyl groups contained in the structure of CPU could carry out further modification, which made it an excellent candidate for wide application in biomedical field.

Novel triphosphorylation polyurethane nanoparticles for blood-contacting biomaterials' coating

Improving hemocompatibility of biomaterials and devices contacting the human blood has been the subject of intensive research. In this study, we synthesized a novel excellent blood compatible polyurethane/sodium triphosphate nanoparticle (PU/STPP). Characterization of polyurethane/sodium triphosphate (PU/STPP) nanoparticles was carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS), nuclear magnetic resonance (NMR), and energy dispersive spectroscopy (EDS). Blood compatibility assessment of PU/STPP nanoparticles was performed by in vitro coagulation time, plasma clotting time, hemolysis rate, and red blood cell morphology tests. Cell compatibility evaluations of PU/STPP nanoparticles were obtained by MTT cell viability tests. The PU/STPP nanoparticles also were used to modify vascular prostheses with cosedimentation. Platelet adhesion tests showed that blood compatibility of vascular prostheses coated with PU/STPP nanoparticles is better than that of pure vascular prostheses.

The amine content of PEGylated chitosan Bombyx mori nanoparticles acts as a trigger for protein delivery

In modern medicine, effective protein therapy is a major challenge to which a significant contribution can be expected from nanoscience through the development of novel delivery systems. Here we present the effect of the amine content of nanoparticles based on PEGylated chitosan Bombyx mori (PEG-O-ChsBm) copolymers on the entrapment of molecules in a search for highly efficient nanocarriers. PEG-O-ChsBm copolymers were synthesized with amine contents from 1.12% to 0.70%, and nanoparticles were generated by self-assembly in dilute aqueous solutions. These nanoparticles successfully entrapped molecules with a wide range of sizes, the efficiency of which was dependent on their amine contents. While hydrophobic molecules were entrapped with high efficiency in all types of nanoparticle, hydrophilic molecules were entrapped only in those with low amine content. Bovine serum albumin, selected as a model protein, was entrapped in nanoparticles and efficiently released in acidic conditions. The triggered entrapment of molecules in PEG-O-ChsBm nanoparticles by selection of the appropriate amine content represents a straightforward way to modulate their delivery by fine changes in the properties of nanocarriers.

Application of spectroscopic methods for structural analysis of chitin and chitosan

Chitin, the second most important natural polymer in the world, and its N-deacetylated derivative chitosan, have been identified as versatile biopolymers for a broad range of applications in medicine, agriculture and the food industry. Two of the main reasons for this are firstly the unique chemical, physicochemical and biological properties of chitin and chitosan, and secondly the unlimited supply of raw materials for their production. These polymers exhibit widely differing physicochemical properties depending on the chitin source and the conditions of chitosan production. The presence of reactive functional groups as well as the polysaccharide nature of these biopolymers enables them to undergo diverse chemical modifications. A complete chemical and physicochemical characterization of chitin, chitosan and their derivatives is not possible without using spectroscopic techniques. This review focuses on the application of spectroscopic methods for the structural analysis of these compounds.

Synthesis and Characterization of Porous Polyurethane-Chitosan Blends

In this work the synthesis and characterization of polyurethane (PU)-chitosan(CH) porous prepared by thermal induced phase separation (TIPS) is described, the obtained products were characterized by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC), evidence of the interaction between both polymers was acquired from infrared spectroscopy. The morphology of the scaffolds was studied by scanning electron microscopy also the mechanical properties were acquired. The results showed that the TIPS technique is appropriate for the production of PU-CH porous materials.

Self-aggregated nanoparticles from methoxy poly(ethylene glycol)-modified chitosan: Synthesis; characterization; aggregation and methotrexate release in vitro

Methoxy poly(ethylene glycol)-grafted-chitosan (mPEG-g-CS) conjugates were synthesized by formaldehyde linking method and characterized by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance ((1)H-NMR). The degree of substitution (DS) of methoxy poly (ethylene glycol) (mPEG) in the mPEG-g-CS molecules determined by (1)H-NMR ranged from 19% to 42%. The critical aggregation concentration (CAC) was determined by fluorescence spectroscopy using pyrene as fluorescence probe and its value was 0.07 mg/mL in water. mPEG-g-CS formed monodisperse self-aggregated nanoparticles with a roughly spherical shape and a mean diameter of 261.9 nm were prepared by the dialysis method. mPEG-g-CS self-aggregated nanoparticles were used as carriers of poorly water-soluble anticancer drug methotrexate (MTX). MTX was physically entrapped inside mPEG-g-CS self-aggregated nanoparticles by dialysis method and the characteristics of MTX-loaded mPEG-g-CS self-aggregated nanoparticles were analyzed using dynamic laser light scattering (DLLS), transmission electron microscopy (TEM). Moreover, in vitro release behavior of MTX was also investigated and the results showed that MTX was continuously released more than 50% in 48 h.

Improved Performances of Intraocular Lenses by Poly(ethylene glycol) Chemical Coatings

Cataract surgery is a routine ophthalmologic intervention resulting in replacement of the opacified natural lens by a polymeric intraocular lens (IOL). A main postoperative complication, as a result of protein adsorption and lens epithelial cell (LEC) adhesion, growth, and proliferation, is the secondary cataract, referred to as posterior capsular opacification (PCO). To avoid PCO formation, a poly(ethylene glycol) (PEG) chemical coating was created on the surface of hydrogel IOLs. Attenuated total reflectance Fourier transform infrared spectroscopy, "captive bubble" and "water droplet" contact angle measurements, and atomic force microscopy analyses proved the covalent grafting of the PEG chains on the IOL surface while keeping unchanged the optical properties of the initial material. A strong decrease of protein adsorption and cell adhesion depending on the molar mass of the grafted PEG (1100, 2000, and 5000 g/mol) was observed by performing the relevant in vitro tests with green fluorescent protein and LECs, respectively. Thus, the study provides a facile method for developing materials with nonfouling properties, particularly IOLs.

Novel amphiphilic ternary polysaccharide derivates chitosan-g- PCL-b-MPEG: Synthesis, characterization, and aggregation in aqueous solution

Chitosan-g-PCL-b-MPEG copolymers of various compositions were successful synthesized via a protection-graft-deprotection procedure, by the esterification of phthaloyl-protected chitosan (PHCS) with MPEG-b-PCL-COOH, which was synthesized from MPEG and epsilon-caprolactone and carboxylated by maleic anhydride. The chemical structure of the chitosan-g-PCL-b-MPEG was characterized by Fourier transform infrared and NMR spectroscopy. The chitosan-g-PCL-b-MPEG was obtained as amphoteric hybrid with amino polysaccharide backbone and amphiphilic MPEG-b-PCL side chain. Their crystallinity and aggregation behavior in aqueous solution were also investigated.

Regioselective Grafting of Poly(ethylene glycol) onto Chitosan and the Properties of the Resulting Copolymers

PEG was grafted onto chitosan regioselectively at the hydroxyl groups with phthaloylchitosan as an intermediate. After the graft reaction, the phthaloyl groups were deprotected to give chitosan-g-PEG copolymers with free amino groups. The chemical structure of the graft copolymers was confirmed by FT-IR, (1)H and (13)C NMR spectroscopy. The resulting graft copolymers showed improved thermal stability compared to the original chitosan, and showed a lower thermal transition temperature at around 185 degrees C. Chitosan-g-PEG exhibited a high affinity not only for aqueous acid but also for some organic solvents because of the presence of abundant free amino groups and PEG branches, and it exhibited higher hygroscopicity and moisture retention ability than chitosan. [structure: see text]

Preparation, characterization, and properties of chitosan-g-poly(vinyl alcohol) copolymer

The graft copolymer chitosan-g-poly(vinyl alcohol), with nontoxicity, biodegradability, and biocompatibility, was prepared by a novel method. The copolymer with porous net structure was observed by scanning electron microscopy (SEM). It is a potential method to combine chitosan with the synthetic polymers. The grafting reactions were conducted with various poly(vinyl alcohol) (PVA)/6-O-succinate-N-phthaloyl-chitosan (PHCSSA) feed ratios to obtain chitosan-g-poly(vinyl alcohol) copolymers with various PVA contents. The chemical structure of the chitosan-g-poly(vinyl alcohol) was characterized by Fourier transform infrared and nuclear magnetic resonance (NMR) spectroscopy. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and SEM were also detected to characterize the copolymer.

Facile preparation of biodegradable chitosan derivative having poly(butylene glycol adipate) side chains

Various modes are being explored for the construction of functional materials from nanoparticles. Despite these efforts, the assembly of nanoparticles remains challenging with respect to the requirement of multiple component organization on varying dimensions and length scales. The graft copolymers of chitosan with poly(butylene glycol adipate) (PBGA) were prepared due to the esterification reaction between PBGA and 6-O-succinate-N-phthaloyl-chitosan (PHCSSA) in the presence of toluene as a swelling agent. The graft copolymers are nanoparticles with the size of few hundred nanometers as observed from TEM. It is a potential method to combine chitosan with the hydrophobic synthetic polymers. The grafting reactions were conducted with various PBGA/PHCSSA feed ratios to obtain chitosan-g-PBGA copolymers with various PBGA contents. FT-IR, NMR, XRD, spectrofluorophotometer, and TEM were detected to characterize the copolymers.

Fabrication and properties of a porous chitin/chitosan conduit for nerve regeneration

A porous, biodegradable, natural chitin/chitosan nerve conduit was constructed. Scanning electron microscopy confirmed that it was homogeneous and highly porous. FT-IR spectra showed that there were no residues arising from the preparation process in the conduit. Addition of chitin to the chitosan solution increased the mechanical strength and maximum tensile strength from 7.2 to 9.6 MPa. Preliminary animal tests indicated that porous chitin/chitosan conduits did not swell in vivo and were compatible with surrounding tissue.