Phase separation in poly(vinyl alcohol)/gelatin blend systems

Blends of a commercial poly(vinyl alcohol) (a-PVA) derived from vinyl acetate and gelatin obtained from collagen were prepared by mixing aqueous solutions of both samples under various conditions. For the blend hydrogels, the depression of melting temperatures was observed at high PVA content. Similarly to the a-PVA/silk fibroin (SF) system, when the degrees of polymerization of PVA increased, the microphase separation region in a phase diagram of the blend films increased for the a-PVA/gelatin system. In the IR spectra of the blend films, no absorption bands corresponding to a conformational change of gelatin appeared. Comparison of the mechanical properties of the a-PVA/gelatin and a-PVA/SF systems, showed the interaction between PVA and gelatin molecules to be smaller than that between PVA and SF molecules. © 1999 Society of Chemical Industry     

Complexation of chitosan and gelatin: From soluble complexes to colloidal gel

The formation of soluble and insoluble complexes between chitosan (CH) and gelatin type B (GB) was investigated as a function of pH (3.0–6.5), sodium chloride (NaCl) concentration (0–100 mM), and storage time (up to 40 days). The turbidity of the CH/GB complexes achieved a maximum value at pH 5.5 and increased with time. The increase of ionic strength first intensified the complex formation but then decreased it at higher salt content. After phase separation, the main component of the separated dense phase was water, from 95.5 to 97.8 wt%, depending on NaCl concentration. With increasing storage time, the insoluble phase changed from a liquid-like system to a thermoreversible colloidal gel, as supported by confocal laser scanning microscopy as well as rheological data. The formation of this colloidal gel is explained in terms of electrostatic complexation and hydrogen bonding.     

Grafting of butyl acrylate onto gelatin in a water-isopropanol medium

Graft copolymerization of butyl acrylate onto gelatin using potassium persulphate initiator was studied in a water-isopropanol medium. The crude graft copolymers were soxhlet extracted with acetone to remove the loosely bound ungrafted homopolymer. The influence of a number of experimental factors such as effect of time, monomer concentration, initiator concentration, backbone concentration and temperature on the graft copolymerization of gelatin were investigated.     

DSC and TGA studies of the behavior of water in native and crosslinked gelatin

Water molecules absorbed into gelatin are found to be only partially crystallizable. The fraction of noncrystallizable water depends on whether the gelatin is native or crosslinked, and on the crosslinking conditions as well. This dependence is explained by the T_g‐regulation effect newly proposed by Rault and coworkers for water‐swollen gelatin cooled below 0°C. According to this effect, a part of the frozen water cannot crystallize because during the cooling the amorphous gelatin–water phase becomes glassy before the water crystallization temperature is reached. During the heating of water‐plasticized gelatin samples in a TGA cell, the crystallizable water separates from the gelatin, mainly in the temperature interval 50–100°C, whereas the noncrystallizable water leaves the gelatin gradually over the entire temperature interval investigated, up to 300°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 465–470, 1999     

热致相分离法制备明胶多孔支架及其性能研究

本文对热致相分离法制备明胶多孔支架及其性能进行了系统的研究。采用冷冻致孔真空干燥法制备了明胶基组织工程多孔支架,并对影响其结构与性能的因素(如明胶溶液浓度、交联剂用量、体系pH值等)进行了考察。实验结果表明:真空冷冻干燥法制备的明胶基多孔组织工程支架都具有三维孔洞结构;所制备的支架平均孔径可达100μm。     

Graft copolymerization of methyl methacrylate upon gelatin initiated by benzoyl peroxide in aqueous medium

The graft copolymerization of methyl methacrylate upon gelatin was studied using benzoyl peroxide as an organic initiator in aqueous medium. The grafting reactions were carried out within the 65–90°C temperature range, and the effect of monomer and initiator concentrations on the graft yield were also investigated. The maximum graft yield was obtained at a benzoyl peroxide concentration of 0.20 × 10⁻² mol/L and the optimum temperature was 80°C. Thermogravimetric analysis showed that the thermal stability of gelatin increased as a result of grafting. Further, such changes in the properties of methyl methacrylate‐grafted gelatin as density, moisture regain, and water uptake were also determined. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1547–1556, 1999     

Phase separation behavior of cyanate ester resin/polysulfone blends

The composition of the blends and the curing temperature affect the morphology of the blends and the phase separation mechanism. The phase separation mechanism depends on the viscosity of medium at the initial stage of phase separation determined by the amount of thermoplastics and the curing temperature, and is closely related with the final morphology. When the homogeneous bisphenol A dicyanate (BADCy)/polysulfone (PSF) blends with low content of PSF (less than 10 wt %) were cured isothermally, the blends were phase separated by nucleation and growth (NG) mechanism to form the PSF particle structure. On the other hand, with more than 20 wt % of PSF content, the BADCy/PSF blends were phase separated by spinodal decomposition (SD) to form the BADCy particle structure. With about 15 wt % of PSF content, the blends were phase separated by SD and then NG to form a combined structure having both the PSF particle structure and the BADCy particle structure. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 33–45, 1999     

Properties of polyelectrolyte complex films of chitosan and gelatin

A series of chitosan–gelatin complexes was prepared by varying the ratio of constituents. Differential scanning calorimetry was used to determine the amount of the different states of water. The interaction between chitosan and gelatin was checked by IR and X-ray analysis and was related to mechanical strength. The results indicate that the water take-up of a chitosan–gelatin complex is depressed by strong interactions within networks. Chitosan can improve the tensile strength of complex films, and even with high water content these can keep appropriate tensile strength and higher elongation. © 1999 Society of Chemical Industry     

Phase separation in blends of linear polymers formed in situ according to different mechanisms

The in situ formation of blends of two incompatible polymers was studied. The kinetics of simultaneously proceeding reactions of radical polymerization of methyl methacrylate and polyaddition reaction of polyurethane formation was investigated for various ratios of monomeric compounds in the reaction mixture. It was established that the kinetics of formation of each polymer in the mixture depends on the presence of the other and on the kinetics of its formation. These parallel reactions are accompanied by phase separation at a definite conversion degree of each monomer. The onset of phase separation does not affect the course of the kinetic curves. The regularities of phase separation in connection with reaction kinetics were investigated by light scattering. It was found that because of the difference in the rates of the two reactions, the ratio of the polymers formed in the reaction mixture continually changes in time. In spite of this, initial stages of the phase separation may be considered as proceeding according to the spinodal mechanism. Values of amplification factors were calculated which depend on the component ratio and reaction rates. It was established that reaction‐induced phase separation determines the formation of the interconnected morphology immediately after the onset of phase separation, when the composition of the polymer blends has not yet reached its equilibrium value. © 2002 Society of Chemical Industry     

Phase separation structure in poly(vinyl alcohol)/silk fibroin blend films

Blend films of a commercial poly(vinyl alcohol) (a-PVA) derived from vinyl acetate and silk fibroin (SF) obtained from degummed silk were prepared by mixing the aqueous solutions of both samples. A plain weave structure was recognized only in the blend films, whereas no structure was found for the superimposed films of both samples. The phase separation structure of the blend films was examined by microscopic observations elongation, tensile tests, and IR measurements. The microphase separation region increased with increase in the degree of polymerization of the PVA. In the IR spectra of the blend films with high PVA contents cast under certain conditions, the absorption peak attributed to the cross-β-form conformation of SF appeared strongly. Gelatin, a water-soluble and natural polymer, was also used for comparison with SF. The ternary phase diagram in an a-PVA/gelatin/H₂O system was obtained experimentally and the critical point was used to estimate the interaction parameter between PVA and gelatin molecules. The phase separation structure and the interaction between PVA and SF molecules were also discussed taking into consideration the results of the a-PVA/gelatin system. © 1998 SCI.     

Nanoencapsulation of capsaicin by complex coacervation of gelatin,acacia, and tannins

Using gelatin and acacia as wall and capsaicin as core substance, nanocapsules were prepared by mixing two solutions of oppositely charged polymers, and then treated by hydrolysable tannins. The morphology and size distribution of the nanocapsules were analyzed by transmission electron microscope and laser particle size analyzer, respectively. The nanocapsules had a mean diameter of 300–600 nm, with mean drug loading content (20.81%) and encapsulation efficiency (81.17%) with good dispersion and spherical morphology. The interaction between gelatin and tannins is discussed in the article. Moreover, the addition of hydrolysable tannins in the system had an important influence on the morphology and particle distribution of the nanocapsules because of the synergistic actions of hydrogen bonding and hydrophobic effects. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2225–2229, 2005     

Carbon fiber‐reinforced gelatin composites. II. Swelling behavior

Carbon fiber‐reinforced gelatin composites have been prepared in our laboratory to obtain a novel biomaterial of improved mechanical properties. The swelling behavior (swelling rate, swelling kinetics, maximum solvent uptake, etc.) for both continuous carbon fiber‐reinforced gelatin composite (C_L/Gel) and short carbon fiber‐reinforced gelatin composite (C_S/Gel) are investigated. Experimental data show that the swelling process of the original gelatin and gelatin matrixes in both composites follows a second‐order kinetics. The swelling of the gelatin matrixes in both composites proceeds slower than that of the pristine gelatin, and depends on fiber form and fiber volume fraction (Vf). Results indicate that the presence of carbon fibers suppresses the swelling of the gelatin matrixes in both composites. It is found that the gelatin matrix in C_S/Gel possesses a smaller swelling rate and maximum solvent uptake than that in C_L/Gel. A mechanism governing these phenomena is discussed in this article. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 994–998, 2000     

明胶类血浆代用品

随着对血源性传染病的了解及自身输血技术的发展,血浆代用品应用越来越广泛。本文回顾了血浆代用品的历史,介绍了常用的几种血浆代用品,并详细地介绍了明胶类血浆代用品的历史、制剂种类、药理作用及其应用发展情况。     

明胶在生物医用材料中的应用

明胶由于其优异的生物学性能,近几十年来被广泛的应用于食品、保健品、化妆品、生物医药材料等行业。本文简要综述了明胶应用于医用材料的特性,列举了明胶在医用材料中的应用,展望了明胶应用于医用材料的前景。     

Thermal and NMR investigation of the change in the states of water caused by volume phase transition of gelatin gel

The occurrence of volume phase transition (VPT) of a polymer gel is often accompanied by the loss of water. In view of the fact that few studies have been made on the change in different states of water during VPT, in this paper, DSC and NMR are used to check the variation in states of water during VPT of glutaraldehyde crosslinked gelatin gel caused by the variation in composition of water–acetone mixture. The results indicate that the volume of gel collapses at 50 % acetone concentration. The contents of free, intermediate and bound water absorbed by gelatin gel decrease with an increase in the amount of acetone. At 50 % and 60 % acetone content, free water disappears; because acetone accounts for 70 % and 85 %, there remains only bound water. Near VPT the relative content of bound water to total water increases sharply. The spin–lattice relaxation times (T₁) determined by NMR show that the T₁ values of intermediate and bound water, respectively, decrease by approximately four and ten times compared with that of free water. Before VPT, most of the water is freezable and highly mobile. After VPT, bound water gradually plays a dominant role in the mobility of water in the gel. The findings are helpful in understanding the dehydration process of protein induced by poor solvent. © 2000 Society of Chemical Industry     

Phase dynamics and wetting layer formation mechanisms of pattern-directed phase separation in binary polymer mixture films with asymmetry compositions

Focusing on the binary polymer mixture films under the off-critical condition, the phase dynamics and wetting layer formation mechanisms of pattern-directed phase separation are numerically investigated. The simulated results demonstrate that, for different compositions, the polymer mixtures on the strip patterned surface can exhibit various phase morphologies in the strips of the bulk, which can be used to tailor the microscopic structures of films. The evolutions of these phase structures in the strips of the bulk obey almost the same power law with an exponent of 1/3, i.e., the Lifshitz-Slyozov growth law for the films with various off-critical degrees. It is found that the wetting layer thickness near the patterned surface grows logarithmically at the initial stages, just like the wetting layer formation mechanism of the polymer mixture near the surface with an isotropic potential. This revels that only patterning the surface potential may not change the growth law of the wetting layer. The simulated results also indicate that the diffusion of the component in the direction parallel to the surface originates from the edge of the strips.     

Phase behavior and morphological studies of polyimide/PVP/solvent/water systems by phase inversion

The solubility gaps for poly(vinyl pyrrolidone) (PVP) in four polyimide solutions (NMP, DMF, GBL, DMSO) were determined by cloud point measurement and correlated with χ_PI/Solvent and Δδ_PVP/Solvent. Membranes prepared with NMP and DMF systems showed a tendency of suppressing fingerlike structure with addition of PVP. On the other hand, membranes prepared with GBL and DMSO systems showed an inclination toward inducing macrovoid formation. These effects of PVP on the membrane morphology were explained by means of miscibility gap, viscosity of the polymer solution, polymer–polymer phase separation, and overall porosity. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3481–3488, 2001     

Controlling absorbency in gelatin networks: Preparation and characterization of alkylated,crosslinked gelatin

Gelatin is a highly abundant and relatively inexpensive protein which is used in a variety of gel applications including photography, drug delivery, microencapsulation, and food preparation. Control of network formation in gelatin may therefore provide methods of preparing protein gels tailored for specific applications. In this study, circular dichroism (CD), Raman, and nuclear magnetic resonance (NMR) spectroscopies were used to characterize ordering processes which occur in gelatin and their relationship to absorbency. Ordering of the unmodified protein, studied as a function of concentration, temperature, and time after initial preparation, correlates inversely with absorbency. Chemical modification was used to control the absorbency and solubility of the protein gels. Alkylation of gelatin using glycidyltrimethylammonium chloride causes substantial increases in water absorbency with degrees of substitution as low as 0.5%. Increases in saline swelling were observed only after additional modification of the alkylated gelatin with a nonionic polyoxyalkyleneamine crosslinking agent (Jeffamine®). Limiting the initial degree of substitution prior to crosslinking (to just below 1%) plays a key role in optimizing the absorbency and minimizing the dissolution of the gel in saline. The methods and principles used to manipulate the absorbency of gelatin may also find use for other natural protein systems. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:281–292, 1998     

LDPE生产工艺中的相平衡

运用相平衡理论分析了低密度聚乙烯(LDPE)工艺流程及LDPE在不同压力、温度、相对分子质量状态下的相分离特性,优化了工艺操作方案,使LDPE熔融产品在分离系统中能够有效地分离,降低了聚合物在装置设备上的结垢速度,避免了因聚合物结垢带来的安全隐患。     

Phase‐separation phenomena in the polymerization of styrene in the presence of polyethylene wax

The demixing processes that occur during the polymerization of styrene in the presence of a low molar mass polyethylene wax were investigated. Quantitative information on the phase behavior of such a three‐component system was obtained through the investigation of the temperature‐induced phase separation and the observation of the phase separation during polymerization. Both techniques allow the construction of the same ternary phase diagram. Such phase behavior can be understood through the discussion of the interference of a liquid–liquid phase‐separation process and crystallization. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2234–2243, 2004