Preparation,characterization, antibacterial properties,and hemostatic evaluation of ibuprofen‐loaded chitosan/gelatin composite films

Ibuprofen‐loaded chitosan/gelatin (CS/GE) composite films were fabricated in this work. The morphology of the composite film was investigated using scanning electron microscopy. The functional groups of the composite film before and after crosslinking were characterized using Fourier transform infrared spectroscopy. Meanwhile, the mechanical properties, antibacterial performance, cytocompatibility, and hemostatic activity of the composite films were investigated. The results show that the amount of CS affected the mechanical properties and liquid uptake capacities of the composite films. The composite film showed better bactericidal activity against Staphylococcus aureus than Escherichia coli. In vitro drug‐release evaluations showed that crosslinking could control the drug‐release rate and period in wound healing. Both types of CS/GE and drug‐loaded CS/GE composite films also showed excellent cytocompatibility in cytotoxicity assays. The hemostatic evaluation indicated that the composite film crosslinked by glutaraldehyde in rabbit livers had a dramatic hemostatic efficacy. Therefore, ibuprofen‐loaded CS/GE composite films are potentially applicable as a wound dressing material. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45441.     

Stabilizing effect of carbodiimide and dehydrothermal treatment crosslinking on the properties of collagen/hydroxyapatite scaffolds

This paper reports the effect of the combined technique of dehydrothermal treatment (DHT) and a mixture of 1‐ethyl‐3(3‐dimethylaminopropyl) carbodiimide (EDC) and N‐hydroxysuccinimide (NHS) crosslinking on the physicochemical properties of collagen/hydroxyapatite materials. Collagen and collagen/hydroxyapatite porous scaffolds containing different amounts of collagen and hydroxyapatite were prepared with use of the freeze‐drying technique. All samples were capable of absorbing a large quantity of phosphate buffered saline. Samples crosslinked by DHT+EDC/NHS presented higher resistance to collagenase degradation (with slightly reduced degradation in DHT+EDC/NHS crosslinked scaffolds prepared from 2% collagen solution), whereas DHT scaffolds exhibited faster degradation. Mechanical testing results suggested that scaffolds crosslinked by DHT+EDC/NHS treatment have an improved compressive modulus compared with EDC/NHS crosslinking. The qualitative analysis of colour intensity resulting from the CellTiter 96 Aqueous One Solution Cell Proliferation Assay (MTS) led to the conclusion that all samples, regardless of the crosslinking method, were well tolerated by cells. However, DHT and EDC/NHS crosslinked scaffolds seem to support better cell viability, in contrast to DHT+EDC/NHS crosslinked scaffolds that support cell differentiation instead. DHT+EDC/NHS crosslinked scaffolds markedly increase the specific alkaline phosphatase activity of cells, which may be of benefit in bone tissue engineering. © 2017 Society of Chemical Industry     

Renewable elastomers based on blends of maleated polypropylene and plasticized starch

Most recent developments in polymers from renewable resources have focused on thermoplastics, whereas there has been no comparable development of plastics with elastomeric properties. Here we evaluate the possibility of developing renewable elastomers based on starch. Potato starch plasticized with glycerol (called plasticized starch, or PLS) was melt‐blended with small quantities (5 wt % or 15 wt%) of maleated polypropylene (MAPP). The maleic anhydride groups of the polypropylene are expected to react with the hydroxy groups of starch under melt blending conditions. The resulting blends of MAPP and PLS were characterized by mechanical testing, SEM, DMA, and DSC. SEM, solubility and adhesion tests indicate that the blends are two‐phase materials, in which the continuous phase PLS is physically crosslinked by polypropylene domains. The materials showed rubbery properties as judged by a low glass transition temperature (～?50°C independent of polypropylene content), and a wide rubbery plateau in DMA experiments that extended from room temperature to as high as 170°C. The tensile properties are also characteristic of elastomers. However, slow aging due to starch crystallization, and extraction of glycerol upon water exposure remain two challenges that must be overcome before the materials can be used as practical elastomers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

PP／PE-LLD／SBS共混交联体系的结构与性能研究

采用两步交联法制备PP/PE-LLD/SBS交联共混物。DSC和WAXR测试结果表明,交联作用对共混物组分的结晶度无明显影响;从维卡软化点和TG、DTG曲线可以看出,交联提高了共混物的耐热温度,热稳定性增强;通过DMA测试发现,交联后共混物组分的玻璃化转变温度Tg无明显变化,交联作用对分子链段的运动影响不大;但交联共混物的内耗角tanδ、存储模量Ε′和损耗模量Ε″都有很大提高,刚、韧性增强。交联使共混物的熔体流动速率减小,流动性下降,但仍保持假塑性流体行为,随剪切速率增大出现剪切变稀;交联作用增大了共混物的活化能,分子链间作用力加强,刚性增大,黏度对温度变化更为敏感。     

Largely improved tensile extensibility of poly(L‐lactic acid) by adding poly(ε‐caprolactone)

Poly(L ‐lactic acid) (PLLA) has good biocompatibility, biodegradability and physical properties. However, one of the drawbacks of PLLA is its brittleness due to the stiff backbone chain. In this work, a largely improved tensile toughness (extensibility) of PLLA was achieved by blending it with poly(ε‐caprolactone) (PCL). To obtain a good dispersion of PCL in the PLLA matrix, blends were prepared via a solution‐coagulation method. An increase in extensibility of PLLA of more than 20 times was observed on adding only 10 wt% of PCL, accompanied by a slight decrease in tensile strength. However, annealing of the samples led to a sharp decrease of extensibility due to phase separation and a change of crystalline structure. To conserve the good mechanical properties of PLLA/PCL blends, the blends were crosslinked via addition of dicumyl peroxide during the preparation process. For the crosslinked blend films, the extensibility was maintained nearly at the original high value even after annealing. Morphological analysis of cryo‐fractured and etched‐smoothed surfaces of the PLLA/PCL blends was carried out using scanning electron microscopy. Differential scanning calorimetry and polarized light microscopy experiments were used to check the possible change of crystallinity, melting point and crystal morphology for both PLLA and PCL after annealing. The results indicated that the combination of solution‐coagulation and crosslinking resulted in a good and stable dispersion of PCL in the PLLA matrix, which is considered as the main reason for the observed improvement of tensile toughness. Copyright © 2010 Society of Chemical Industry     

Dynamic mechanical properties of styrene butadiene rubber and poly (ethylene-co-vinyl acetate) blends

The dynamic mechanical behaviour of uncrosslinked and crosslinked styrene butadiene rubber/poly (ethylene-co-vinyl acetate) (SBR/EVA) blends was studied with reference to the effects of blend ratio, crosslinking systems, a compatibilizer viz. maleic-anhydride grafted poly [styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS-g-MA), frequency and temperature. The two separate tan δ peaks, obtained during DMA, indicated the immiscibility of SBR/EVA system. The damping properties increased with SBR content for uncrosslinked and crosslinked blends. In the case of crosslinked systems, depending upon the type of crosslinking agent used, the glass transition temperature (T _g) of SBR phase has been found to be shifted to higher temperatures. The damping characteristics of the blends were observed to be affected by the variations in frequency. The addition of the compatibilizer improved the storage modulus and reduced the damping properties. These results have been correlated with the morphology of the blends, attested by scanning electron micrographs. The activation energy for glass transition has been computed. The experimental data on storage modulus were compared with theoretical predictions.     

Development of new poly(ϵ‐caprolactone)/chitosan films

This study reports for the first time the production of poly(?‐caprolactone)/chitosan (PCL/CHT) films by solvent casting using a mixture of formic acid/acetone (70:30 vol%). Both uncrosslinked and crosslinked films with the natural crosslinker genipin were developed. The mechanical properties of the samples were analyzed by dynamical mechanical analysis (DMA) in the hydrated state. DMA was also successfully used for the first time to monitor in situ the crosslinking process as a function of time and crosslinker concentration. The compatibility between the polymers in the blended films was analyzed by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). It was found that phase distribution is highly dependent on the blend composition. The developed films could potentially be used in different applications, such as tissue engineering scaffolds. © 2013 Society of Chemical Industry     

Preparation and characterization of films based on crosslinked blends of gum acacia,polyvinylalcohol, and polyvinylpyrrolidone-iodine complex

In an attempt to develop iodine-release systems based on polymeric blend for biomedical applications, our research group prepared blends of gum acacia (GA), polyvinylalcohol (PVA), and polyvinylpyrrolidone-iodine (PVP-I) complex. The blends of GA/PVA and GA/PVA/PVP-I prepared from the aqueous solutions of the polymers were crosslinked with glutaraldehyde to increase the water resistance of the films and to improve their thermal and mechanical properties. The crosslinked GA/PVA and GA/PVA/PVP-I blend films were characterized by FTIR spectroscopy, DSC, and TGA. The swelling behavior of the prepared blends was investigated and crosslinked GA/PVA blend films were found to be pH sensitive. The properties of PVP-I containing blends differed from those prepared without it probably due to the formation of an intermolecular interaction between PVP-I and the hydroxy-polymers. The results indicated that after crosslinking the blends showed improvement in water resistance, thermal, and mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

DSC and DMA studies on silane‐grafted and water‐crosslinked LDPE/LLDPE blends

Effects of silane grafting and water crosslinking reactions on crystallizations, melting behaviors, and dynamic mechanical properties of the LDPE/LLDPE blends are investigated using DSC and DMA. From DSC data, cocrystallization of LDPE and LLDPE does not occur, but cocrosslinking of these two polymers is evidenced at the experimental temperature of 100°C, a temperature lower than melting temperatures of both polymers. The water crosslinking reactions of the LLDPE‐rich blends enable development of a new phase having a melting endotherm in between that of LDPE and LLDPE. From the thermal fractionation data, interaction between LDPE and LLDPE is observed, and compatibilization of the blends can be achieved by the crosslinking reactions. From DMA data, the storage moduli of the blends are not found to be consistent with their degrees of crosslinking. The storage moduli of the blends are not simply determined by the degree of crosslinking but determined by very complicated but unclear factors. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1808–1816, 2001     

Properties of crosslinked blends of pellethene and multiblock polyurethane containing poly(ethylene oxide) for biomaterials

A series of multiblock polyurethanes, containing various poly(ethylene oxide) (PEO; number‐average molecular weight = 400–3400) contents (0–80 wt %) and prepared from hexamethylene diisocyanate/PEO/poly(dimethylsiloxane) diol/polybutadiene diol/1,4‐butanediol, were used as modifying additives (30 wt %) to improve the properties of biomedical‐grade Pellethene. Different molecular weights of PEO were used to keep poly(ethylene glycol) at a fixed molar content, if possible, although the PEO content, related to the PEO block length in the multiblock polyurethanes, was varied from 0 to 80 wt %. The hydrophilic PEO component was introduced through the addition of PEO‐containing polyurethanes and dicumyl peroxide as a crosslinking agent in a Pellethene matrix. As the PEO content (PEO block length) increased, the hydrogen‐bonding fraction of the crosslinked Pellethene/multiblock polyurethane blends increased, and this indicated an increase in the phase separation with an increase in the PEO content in the crosslinked Pellethene/multiblock polyurethane blends. According to electron spectroscopy for chemical analysis, the ratio of ether carbon to alkyl carbon in the crosslinked Pellethene/multiblock polyurethane blends increased remarkably with increasing PEO content. The water contact angle of the crosslinked Pellethene/multiblock polyurethane blend film surfaces decreased with increasing PEO content. The water absorption and mechanical properties (tensile modulus, strength, and elongation at break) of the crosslinked Pellethene/multiblock polyurethane blend films increased with increasing PEO content. The platelet adhesion on the crosslinked Pellethene/multiblock polyurethane blend film surfaces decreased significantly with increasing PEO content. These results suggest that crosslinked Pellethene/multiblock polyurethane blends containing the hydrophilic component PEO may have potential for biomaterials that come into direct contact with blood. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2348–2357, 2004     

Effect of dynamic vulcanization on the microstructure and performance of polyethylene terephthalate/elastomer blends

Blends of polyethylene terephthalate (PET) and ethylene‐ethyl acrylate‐maleic anhydride terpolymer (E‐EA‐MAH) were dynamically crosslinked in a one‐step extrusion process. An amine‐terminated glycol reacting with MAH moieties was used as the crosslinking agent. The effect of blend composition and dynamic crosslinking on the microstructure and mechanical properties were investigated. Blend ratios ranging from 80:20 to 20:80 PET/E‐EA‐MAH were studied. The region of phase inversion was located for uncrosslinked and dynamically crosslinked blends. The rheological characterization was also carried out for these blends in comparison with the neat materials. After dynamic crosslinking, the phase inversion is shifted from the 30–40% range to the 70–80% range of elastomer content. This shift is induced by the increase of viscosity and elasticity of the network formed. Dynamically crosslinked blends show significant improvements in impact strength but also exhibit a decrease in elongation at break.     

Preparation and characterization of ultrahigh molecular weight polyethylene and polyisoprene solvent-cast blend films

This study covers the preparation of noncrosslinked and crosslinked solvent-cast blend films of ultrahigh molecular weight polyethylene (UHMWPE) and polyisoprene rubber (PIR) and their mechanical, thermal, IR spectroscopic, and morphological characterizations. Solvent-cast films of polymer blends with 0, 10, 20, 35, 50, and 65% PIR composition were prepared by vigorous stirring from a hot decalin solution. The films were crosslinked chemically by using acetophenone as a crosslinking agent under UV radiation. The mechanical properties, measured as ultimate properties and tensile modulus, were found to decrease with PIR content but crosslinking was found to enhance the ultimate strength and tensile modulus. DSC results revealed that melting point of UHMWPE remains almost constant in blends. However, upon crosslinking, the melting point of UHMWPE is depressed almost 5°C. We observed a similar trend in the enthalpy change of the melting of UHMWPE and the variation of percent crystallinity in UHMWPE. Scanning electron microscopy (SEM) studies on the fractured surfaces of the blends showed that the fibrillar texture is present in both crosslinked and noncrosslinked blends. The crosslinking appeared to be through oxygen linkages, which are preferentially conjugated to double bonds, in addition to the possible carbon–carbon crosslinks. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1619–1630, 1998     

SBS/PE-LD共混物的强化辐射交联研究

研究了多官能团单体的用量、官能团数目以及辐射剂量对苯乙烯丁二烯共聚物（SBS）与低密度聚乙烯（PE-LD）共混物的强化辐射交联效应,测试了共混物的辐射交联程度、力学性能与形状记忆性能。结果表明,随辐射剂量的增加,SBS/PE-LD共混物的交联程度增加;多官能团单体的加入能够提高共混物的交联程度;相同辐射剂量时,官能团数目越多,交联程度越高;辐射剂量高于150 kGy时,多官能团单体的加入可以提高SBS/PE-LD共混物的拉伸强度;强化辐射交联SBS/PE LD共混物具有优异的形状记忆性能。     

SBS/PE-LD的强化交联与形状记忆效应研究

用苯乙烯丁二烯共聚物（SBS）与低密度聚乙烯（PE-LD）共混,采用过氧化二异丙苯（DCP）作为引发剂,3种不同的多官能团单体作为强化交联剂,使共混物发生强化交联形成网状结构,对多官能团单体的强化交联作用进行了分析,测试了交联共混物的拉伸强度与断裂伸长率,探讨了交联共混物的形状记忆效应。结果表明,多官能团单体的加入能够显著提高SBS/PE-LD交联共混物的交联程度,交联SBS/PE-LD共混物具有优异的形状记忆性能,形状固定率和形状回复率均可达100 %。     

Structure and properties of new reversibly crosslinked iPP/LDPE blends

Reversibly crosslinked blends of isotactic polypropylene and low density polyethylene (iPP/LDPE) were prepared in the presence of crosslinking agents using reactive extrusion. The structure and properties of the modified blends were investigated by means of wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and macro- and micro-mechanical measurements. The crystallinity of the modified samples (LDPE, iPP, and their blends) does not seem to be so much affected by the crosslinking process. Results show that the microhardness of the iPP/LDPE blends notably increases with the iPP content. The micromechanical properties of the modified blends only improve slightly as a consequence of the crosslinking process. In the iPP samples, and also in the iPP/LDPE blends, this process gives rise to the appearance of new, crystalline ethylenic chains, as evidenced by the calorimetric measurements. Furthermore, the impact strength of the modified materials is improved as compared with that of the original ones, while some of the crosslinked blends show a ductile fracture behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Comprehensively improved mechanical properties of silane crosslinked polypropylene/ethylene propylene diene monomer elastomer blends

The properties and structure of silane crosslinked polypropylene (PP)/ethylene propylene diene monomer (EPDM) elastomer blends had been carried out. Fourier transform infrared spectroscopy and gel content tests were employed to evaluate the crosslinking reaction of PP/EPDM blends. Crosslinking efficiency of PP/EPDM blends was investigated using thermogravimetric analysis, differential scanning calorimeter, dynamic mechanical analysis, dynamic rheology, and tensile testing. Tanδ curves of silane crosslinked PP/EPDM blends exhibited an obvious “gel point” originated from the formation of dynamic crosslinking network. The blend corresponding to the “gel point” presented comprehensively improved mechanical properties. These results demonstrated that characteristic rheological parameters showed close correlations with key mechanical properties of silane crosslinked PP/EPDM blends. Scanning electron microscopy images illustrated that crosslinking had remarkably changed the morphologies of PP/EPDM blends. The large deformation mechanism of these blends had been suggested.     

Polyurethanes from benzene polyols synthesized from vegetable oils: Dependence of physical properties on structure

Asymmetric and symmetric aromatic triol isomers were synthesized from erucic acid. The pure asymmetric and symmetric triols were crosslinked with MDI into their corresponding polyurethane sheets. The physico‐chemical properties of these polyurethanes were studied by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis coupled with Fourier transform infrared (TGA‐FTIR) spectroscopy, and tensile analysis. The A‐PU and S‐PU demonstrated differences in their glass transition temperatures (T_g) and crosslinking densities. The difference in T_g of these polyurethanes could be explained by the differences in crosslinking densities, which could be related to the increase in steric hindrance, to the crosslinking MDI molecules, between adjacent hydroxyl groups of the asymmetric triol monomers. Overall, it was found that both polyurethanes had similar mechanical and thermal properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly(vinylidene fluoride)–acrylic rubber partially miscible blends: Phase behavior and its effects on the mechanical properties

A phase diagram of poly(vinylidene fluoride) (PVDF) and acrylic rubber (ACM) was plotted, and the effects of the extent of miscibility on the mechanical properties of the polymer blends were examined. A compressible, regular solution model was used to forecast the phase diagram of this blend. The model prediction, the lower critical solution temperature (LCST) over the upper critical solution temperature (UCST), was done qualitatively according to the experimentally determined phase diagram by differential scanning calorimetry (DSC), optical microscopy, and rheological analysis. These experimental methods showed that this system was miscible in ACM‐rich blends (>50% ACM) and partially miscible in PVDF‐rich blends. A wide‐angle X‐ray diffraction study revealed that PVDF/ACM blends such as neat PVDF had a characteristic α‐crystalline peak. The partially miscible blends displayed up to 350% elongation at break; this was a significant increment of this parameter compared to that of neat PVDF(20%). However, the miscible blends showed elongation of up to 1000% [again, a remarkable increase compared to chemically crosslinked ACM (220%)] and displayed excellent mechanical properties and tensile strength and a large elongation at break. For the miscible and partially miscible blends, two different mechanisms were responsible for this improvement in the mechanical properties. It was suggested that in the partially miscible blends, the rubbery depletion layer between the spherulite and the conventional rubber cavitations mechanism were responsible for the increase in the elongation at break, whereas for the miscible blends, the PVDF spherulite acted as a crosslinking junction. The stretched part of the tensile samples in the partially miscible blends showed characteristic β‐crystalline peaks in the Fourier transform infrared spectra, whereas that in the miscible blends showed α‐crystalline peaks. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1247‐1258, 2013     

Influence of crosslinking on crystallization,rheological, and mechanical behaviors of high density polyethylene/ethylene‐vinyl acetate copolymer blends

High density polyethylene (HDPE)/ethylene‐vinyl acetate copolymer (EVA) blends with selective crosslinking the EVA phase were prepared and the crystallization, rheological, and mechanical behaviors were studied. Selective crosslinking of EVA component could greatly improve both tensile and impact strengths of the HDPE‐rich blends and influence melting enthalpy at different annealing temperature in successive self‐nucleation and annealing procedure. Dynamic mechanical analysis reveals that glass transition temperatures of both the HDPE and EVA components are lowered upon blending and are raised upon crosslinking. The uncrosslinked HDPE/EVA blends are unstable in the melt and show increment in storage modulus (G′) and decay in loss tangent (tanδ) with annealing time associated with phase coarsening. However, morphology of selectively crosslinked blends in the melt state is highly unstable, characterized by a fast migration of uncrosslinked HDPE component out of the crosslinked EVA phase to the surface resulting in a rapid decay in G′ and an increment in tanδ at the early stage of annealing. POLYM. ENG. SCI., 54:2848–2858, 2014. © 2014 Society of Plastics Engineers     

Preparation and characterization of novel hyperbranched poly(amine‐ester) films crosslinked by glutaraldehyde

Novel films based on hydroxyl terminated hyperbranched poly (amine‐ester) (HPAE‐OH) of different generation were prepared by crosslinking the terminal hydroxyl groups of HPAE with glutaraldehyde (GA). The progress of crosslinking reaction was characterized by Fourier transform infrared (FTIR) and viscosity measurement. The surface morphology of the crosslinked HPAE films was characterized by field emission scanning electron microscope (FE‐SEM) and atomic force microscopy. The results suggested that the films have homogenously dense interior matrices and smooth surface. The hydrophilicity/hydrophobicity of the crosslinked HPAE films was characterized by the water contact angle measurement. Variable swelling behavior in different solvents was also studied. The in vitro biocompatibility of the film was investigated by the bovine hemoglobin (Hb) adsorption measurement. And these results showed that these crosslinked HPAE films had excellent hydrophilicity, variable swelling behavior in different solvents, and relative low protein absorption. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008