Biocompatible Polymer Blends of Poly(D,L-lactic acid-co-glycolic acid) and Triblock PCL-PDMS-PCL Copolymers: Their Characterizations and Degradations

Polymer blends of poly(D,L-lactic-co-glycolic acid), PDLLGA, and triblock polycaprolactonepoly(dimethylsiloxane)-polycaprolactone (PCL-PDMS-PCL) copolymer, TEGOMER, were obtained by coprecipitation from their chloroform mixed solutions into methanol and were characterized by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), degradation tests and scanning electron microscopy (SEM). Binary blends of PDLLGA/TEGOMER were found to be partially miscible according to DSC measurements and FTIR analysis. Stressstrain results showed that addition of TEGOMER improved significantly the overall toughness of PDLLGA. Degradation of PDLLGA/TEGOMER blends was investigated in phosphate buffered saline at pH = 7.4 and 37 °C, and the morphology of the blends during degradation was examined by scanning electron microscopy

Biocompatible Polymer Blends of Poly(D,L-lactic acid-co-glycolic acid) and Triblock PCL-PDMS-PCL Copolymers: Their Characterizations and Degradations

Polymer blends of poly(D,L-lactic-co-glycolic acid), PDLLGA, and triblock polycaprolactonepoly(dimethylsiloxane)-polycaprolactone (PCL-PDMS-PCL) copolymer, TEGOMER, were obtained by coprecipitation from their chloroform mixed solutions into methanol and were characterized by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), degradation tests and scanning electron microscopy (SEM). Binary blends of PDLLGA/TEGOMER were found to be partially miscible according to DSC measurements and FTIR analysis. Stressstrain results showed that addition of TEGOMER improved significantly the overall toughness of PDLLGA. Degradation of PDLLGA/TEGOMER blends was investigated in phosphate buffered saline at pH = 7.4 and 37 °C, and the morphology of the blends during degradation was examined by scanning electron microscopy

ESR study and copolymer analysis of acrylamide-methacrylamide solid solutions

When acrylamide‐methacrylamide mixed crystals are irradiated by ultraviolet (UV) rays, a copolymeric sample is obtained containing both monomeric constituents. For identification and quantitative analysis of these copolymers, a modified form of UV spectroscopy was used. The greatest advantage of UV spectroscopy for copolymer analysis lies in its rapid application. A comparison of the spectrum of the unknown compositions with spectra of known systems by using a calibration curve and the shifts in absorption maxima in different concentrations are valuable aids in establishing the composition. Electron spin resonance (ESR) provides a correlation between the obtained copolymer composition and the shape of the signal of the responsible radical. ESR spectra obtained for UV‐irradiated acrylamide‐methacrylamide mixed crystals reveal that during polymerization both radicals are present. As methacrylamide percentage increases in the mixture, the signal becomes similar to the 9‐line spectrum of pure methacrylamide. When there is 90% methacrylamide present in the original mixture, a 5‐line signal is observed, with even‐numbered peaks in the methacrylamide signal appearing now as shoulders. When the methacrylamide percentage is about 16%, a characteristic 3‐line signal of acrylamide is dominant. As the methacrylamide percentage increases in the original mixture of the copolymers, ESR signals indicate a decrease in the rate constant values for second‐order decay at 60°C. The stability of the formed radicals was studied by admitting oxygen to the copolymeric samples as well as to the homopolymeric systems. Since the peroxidic radicals are more active in the hydrogen abstraction process, they decay more rapidly than the macro radical itself by a bimolecular termination reaction. As the methacrylamide percentage increases in the copolymeric mixtures, the peroxide radical formation becomes more difficult. This indicates that polymethacrylamide brings more stability in copolymerization reactions with acrylamide. The polymerization rate of both monomers and their mixed crystals were enhanced by adding chlorine gas before irradiation. Chlorine acts as an agent for slowing down the radical decay as well as accelerating the radical initiation reactions

Preparation and Characterization of Hydrogels of Several Polysaccarides for Biomaterials Applications Hydrogels for Biomaterials Applications

The advantages of hydrogels as biomedical materials and their performance in applications depend on their molecular structures. Two hydrogels derived from biopolymers such as alginate and chitosan obtained from natural sources were prepared and characterized for biomaterials applications. Morphology of the crosslinked material was investigated by using SEM. Swelling behavior of chitosan/polycaprolactone and chitosan/alginate hydrogels in different compositions was studied. The biopolymer hydrogels thus prepared were used for cell growth experiments. To measure the degree of cell proliferation, the gels were seeded with L929 mouse fibroblasts. The cell growth properties were followed by SEM photographs. It was found that the population of cells in the cross-linked polymer gels increased

Copolymer analysis by UV spectroscopy

An extensive and detailed analysis of copolymers was made by developing a rapid spectrophotometric method. Successful analysis of composition in styrene‐p‐methoxystyrene, styrene‐p‐chlorostyrene, and styrene‐p‐fluorostyrene copolymers were performed by UV spectrometry. Their absorption bands were investigated either with respect to pure polystyrene or with respect to the homopolymer of the other constituent at the same wavelength. Attempts to analyze copolymers of styrene‐4‐vinylpyridine and styrene‐N‐vinylcarbazole by similar methods were unsuccessful.Publisher's Versio

Chitosan/alginate crosslinked hydrogels: Preparation, characterization and application for cell growth purposes

Chitosan hydrogels may be formed by various mechanisms. In this study, we aimed to form hybrid polymer networks of chitosan with alginate using a crosslinker which enabled the covalent binding of the two macromolecules. The structural and thermal characterization of these hydrogels was performed by using Fourier transform infrared (FTIR) and differential scanning calorimeter (DSC). The morphological analysis of the crosslinked material was investigated by scanning electron microscopy (SEM) and a scanning probe microscope with atomic force microscope (AFM) attachment. The swelling properties of these gels were analyzed in water and in phosphate buffered saline (PBS) solution. The presence of alginate in a chitosan/alginate hydrogel was shown to support the hydrogel stability. Compared to chitosan/alginate (1/2) hydrogel prepared with 1 wt% DCC, the swelling of chitosan/alginate (1/2) hydrogels prepared with 3 wt% DCC was limited. To measure the degree of cell proliferation, the hydrogels were seeded with L929 mouse fibroblasts and cell numbers measured by neutral red uptake assay. The cell attachment was also followed by (SEM) photography. It was observed that chitosan/alginate (1/2) hydrogels with 1 wt% (DCC) provides a better environment for cell attachment and proliferation. This study presents functional hydrogel formation by crosslinked chitosan and alginate, a novel biomaterial which also supports cell growth. (C) 2013 Published by Elsevier B.V