Fabrication and characterization of electrospun fibrous nanocomposite scaffolds based on poly(lactide‐co‐glycolide)/poly(vinyl alcohol) blends

Tissue engineering involves the fabrication of three‐dimensional scaffolds to support cellular in‐growth and proliferation. Ideally, the scaffolds should be similar to the native extracellular matrix (ECM). Electrospun polymer nanofibrous scaffolds are appropriate candidates for ECM mimetic materials since they mimic the nanoscale properties of ECM. Electrospun polymer nanocomposites based on poly(lactide‐co‐glycolide) (PLGA)/poly(vinyl alcohol) (PVA) and organically modified montmorillonite (OMMT) were prepared by a solution intercalation technique followed by electrospinning. The morphology of fibrous scaffolds based on these nanocomposites was investigated using scanning electron microscopy. The scaffolds showed highly porous structure within the nanofibres of diameters ranging from 400 to 700 nm. X‐ray diffractometry gave evidence of good dispersion of the OMMT in the blends with exfoliated morphology. Measurements of the water uptake and water contact angle of the fibrous scaffolds indicated significant improvement in the hydrophilicity of the scaffolds. Evaluations of the mechanical properties and unrestricted somatic stem cell culture of the electrospun fibrous nanocomposite scaffolds revealed that the PLGA90/PVA10/1.5% OMMT and PLGA90/PVA10/3% OMMT samples are the most useful from the tissue engineering application viewpoint. Copyright © 2010 Society of Chemical Industry     

In vitro assessment of dual-network electrospun tubes from poly(1,4 cyclohexane dimethylene isosorbide terephthalate)/PVA hydrogel for blood vessel application

The fabrication of artificial blood vessel remains an ongoing challenge for cardiovascular tissue engineering. Full biocompatibility, proper physiological, and immediate availability have emerged as central issues. To address these issues, the dual-network composite scaffolds were fabricated by coating the electrospun nanofibers-based tubes with poly(vinyl alcohol) (PVA) hydrogel, which could increase the cell viability and show the potential for controlling the composition, structure, and mechanical properties of scaffolds. Herein, the tubular scaffolds having an inner diameter of 2 mm, were composed with poly(1,4 cyclohexane dimethylene isosorbide terephthalate)/PVA. The morphology examination showed that tubular structure was dimensionally stable and suitable for an artificial blood vessel. Fourier transform infrared spectra, wetting behavior, stress–strain behavior, and Thiazolyl Blue Tetrazolium Bromide (3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide) analysis also showed that the composite scaffolds have good chemical interactions between poly(1,4 cyclohexane dimethylene isosorbide terephthalate) (PICT) and PVA, blended PICT/PVA tubes showed the appropriate wetting behavior, it achieved the appropriate breaking strength and adequate pliability up to 47.5% and in vitro assessment showed that blended PICT/PVA scaffolds have the appropriate cell viability and nontoxic, respectively. On the basis of characterizations results, it was concluded that resultant scaffolds would be addressed to fulfill the requirements such as biocompatibility, dimensional stability, adequate elongation, breaking strength, immediate availability, and proper for physiologically. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47222.     

Ultraporous poly(lactic acid) scaffolds with improved mechanical performance using high‐pressure molding and salt leaching

A novel processing technique, i.e. high‐pressure compression molding/salt leaching, was developed to fabricate ultraporous poly(lactic acid) (PLA) scaffolds. The optimized composition was studied in relation to the porosity, pore morphology, thermal property, and mechanical performance of the PLA scaffolds. At a porogen (CaCO₃) content of 90 wt %, the scaffolds have an interconnected open pore structure and a porosity above 80%. It was truly interesting that the structural stability of high‐pressure molded scaffolds was remarkably improved based on the fact that its glass transition temperature (83.5°C) increased about 20°C, as compared to that of the conventional compression‐molded PLA (60°C), which is not far from physiological temperature (～37°C) at the risk of structural relaxation or physical aging. More importantly, the mechanical performance of PLA scaffolds was drastically enhanced under optimized processing conditions. At pressure and temperature of 1000 MPa and 190°C, the porous PLA scaffolds attained a storage modulus of 283.7 MPa, comparable to the high‐end value of trabecular bone (250 MPa) ever reported. In addition, our prepared PLA scaffolds showed excellent cellular compatibility and biocompatibility in vitro tests, further suggesting that the high‐pressure molded PLA scaffolds have high potential for bone tissue engineering applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3509–3520, 2013     

Preparation and degradability of poly(lactic acid)–poly(ethylene glycol)–poly(lactic acid)/SiO2 hybrid material

Poly(lactic acid)–poly(ethylene glycol)–poly(lactic acid) (PLA‐PEG‐PLA)/SiO₂ hybrid material is prepared by sol–gel method using tetraethoxysilane (TEOS) and PLA‐PEG‐PLA as raw material. From Fourier transform infrared spectroscopy (FTIR) and X‐ray photoelectron spectroscopy (XPS) spectra, the hydroxyl groups of the silica sol derived from partially hydrolysis of TEOS and the unhydrolyzed ethoxy groups of TEOS can react with PLA‐PEG‐PLA. Differential scanning calorimetry (DSC) curves imply that the glass transition temperature (T_g) of PLA‐PEG‐PLA/SiO₂ hybrid material is higher than that of PLA‐PEG‐PLA and increases with the increase of silica content. X‐ray diffraction (XRD) analysis results show that PLA‐PEG‐PLA and PLA‐PEG‐PLA/SiO₂ hybrid material are both amorphous. Field scanning electron microscope (FSEM) photographs show that when PLA‐PEG‐PLA/SiO₂ hybrid material has been degraded for 12 weeks in normal saline at 37°C, a three‐dimensional porous scaffold is obtained, which is available for cell growth and metabolism. Moreover, the hydroxyl (? OH) groups on SiO₂ of PLA‐PEG‐PLA/SiO₂ hybrid material could buffer the acidity resulted from the degradation of PLA, which is beneficial to proliferation of cell in tissue repairing. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Benign route for the modification and characterization of poly(lactic acid) (PLA) scaffolds for medicinal application

Scaffolds fabricated from polymers have imprinted its wide applicability in the field of tissue engineering. The surface of electrospun poly(lactic acid) (PLA) nanofibers was modified to improve their compatibility with living medium. PLA film were treated with alkali solution to introduce carboxyl groups on the surface followed by covalent grafting of gelatin using Xtal Fluoro‐E as coupling agent. The gelatin g‐PLA polymer synthesized via ‘graft‐onto’ method exhibit fascinating properties as studied by contact angle measurement, fourier transformed infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, water vapor transmission rate(WVTR), swelling studies and differential scanning calorimetry. The fabricated gelatin g‐PLA scaffolds were further characterized to conduct the study on hydrolytic degradation, and extent of biodegradation at ambient temperature. It was observed from the in‐vitro analysis that the gelatin g‐PLA nanofiber (with hemolytic percentage, 0.56 ± 0.13%) was cytocompatible with fibroblast cell and does not impair cell growth. The WVTR obtained for the electrospun mat around 2900 ± 100 g/m². 24 h signifies the optimal moist environment required for tissue engineering especially wound healing. Notably, many of these strategies resulted in porous hydrophilic scaffolds with human cell growth and proliferation for medical applications of various types. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46056.     

Morphology,biodegradability, mechanical,and thermal properties of nanocomposite films based on PLA and plasticized PLA

In this study, melt intercalation method is applied to prepare poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG)‐plasticized PLA nanocomposite films including 0, 3, and 5% organoclay (Cloisite 30B) using a laboratory scale compounder, which is connected to a microcast film device. To evaluate the nanomorphology and the dispersion state of the clays, X‐ray diffraction (XRD) and transmission electron microscopy (TEM) are conducted. Tensile tests are performed to characterize the mechanical behavior of the films. Biodegradation rate is determined by degradation tests in composting medium. Differential scanning calorimeter (DSC) is applied to observe the thermal behavior of the films. XRD and TEM show that the exfoliation predominantly occurrs in plasticized PLA nanocomposites, whereas unexfoliated agglomerates together with exfoliated clays are observed in the nonplasticized PLA. Tensile tests indicate that the addition of 3% clay to the neat‐PLA does not affect the strength; however, it enhances the modulus of the nanocomposites in comparison to neat‐PLA. Incorporation of 3% clay to the plasticized PLA improves the modulus with respect to PLA/PEG; on the other hand, the strain at break value is lowered ～ 40%. The increase in the rate of biodegradation in composting medium is found as in the order of PLA > PLA/PEG > 3% Clay/PLA/PEG > 5% Clay/PLA/PEG > 3% Clay/PLA. DSC analysis shows that the addition of 3% clay to the neat PLA results in an increase in T_g. The addition of 20% PEG as a plasticizer to the neat‐PLA decreases T_g about 30°C, however incorporation of clays increases T_g by 4°C for the plasticized PLA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Compressive properties and creep resistance of a novel,porous, semidegradable poly(vinyl alcohol)/poly(lactic‐co‐glycolic acid) scaffold for articular cartilage repair

Tissue engineering for articular cartilage repair has shown success in ensuring the integration of neocartilage with surrounding natural tissue, but the rapid restoration of biomechanical functions remains a significant challenge. The poly(vinyl alcohol) (PVA) hydrogel is regarded as a potential articular cartilage replacement for its fair mechanical strength, whereas its lack of bioactivity limits its utility. To obtain a scaffold possessing expected bioactivity and initial mechanical properties, we herein report a novel salt‐leaching technique to fabricate a porous PVA hydrogel simultaneously embedded with poly(lactic‐co‐glycolic acid) (PLGA) microspheres. Through the investigation of environmental scanning electron microscopy, we found that the porous PVA/PLGA scaffold was successfully manufactured. The compression and creep properties were also comprehensively studied before and after cell culturing. The relationship between the compressive modulus and strain ratio of the porous PVA/PLGA scaffold showed significant nonlinear behavior. The elastic compressive modulus was influenced a little by the porogen content, whereas it went higher with a higher PLGA microsphere content. The cell‐cultured scaffolds presented higher compressive moduli than the initial ones. The creep resistance of the cell‐cultured scaffolds was much better than that of the initial ones. In all, this new scaffold is a promising material for articular cartilage repair. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40311.     

The odontogenic differentiation of human dental pulp stem cells on hydroxyapatite-coated biodegradable nanofibrous scaffolds

The authors aimed to design nanofibrous (NF) scaffolds that facilitate odontogenic and osteogenic differentiation of human dental pulp-derived mesenchymal stem cells (DPSCs) in vitro. For this purpose, hydroxyapatite (HA)–loaded poly (L-lactic acid)/poly (?-caprolactone) (PLLA:PCL 2;1) blend NFs were prepared using the electrospinning method. Alizarin red activity and cell viability were evaluated by MTT assay, and SEM revealed the proliferation properties of NF scaffolds. QRT-PCR results demonstrated that HA-loaded PLLA/PCL can lead to osteoblast/odontoblast differentiation in DPSCs through the up-regulation of related genes, thus indicating that electrospun biodegradable PCL/PLA/HA has remarkable prospects as scaffolds for bone and tooth tissue engineering.     

Synthesis of poly(vinyl alcohol)‐graft‐poly(ε‐caprolactone) and poly(vinyl alcohol)‐graft‐poly(lactide) in melt with magnesium hydride as catalyst

Grafting of poly(ε‐caprolactone) (PCL) and poly(lactide) (PLA) chains on poly(vinyl alcohol) backbone (PVA degree of hydrolysis 99%) was investigated using MgH₂ environmental catalyst and melt‐grown ring‐opening polymerization (ROP) of ε‐caprolactone (CL) and L ‐lactide (LA), that avoiding undesirable toxic catalyst and solvent. The ability of MgH₂ as catalyst as well as yield of reaction were discussed according to various PVA/CL/MgH₂ and PVA/LA/MgH₂ ratio. PVA‐g‐PCL and PVA‐g‐PLA were characterized by ¹H‐ and ¹³C‐NMR, DSC, SEC, IR. For graft copolymers easily soluble in tetrahydrofuran (THF) or chloroform, wettability and surface energy of cast film varied in relation with the length and number of hydrophobic chains. Aqueous solution of micelle‐like particles was realized by dissolution in THF then addition of water. Critical micelle concentration (CMC) decreased with hydrophobic chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(acrylamide‐co‐vinyl alcohol)—Superabsorbent materials reinforced by modified clay

A series of copolymeric superabsorbent materials comprising polyacrylamide (PAM), polyvinyl alcohol (PVA) reinforced with variable wt% of modified clay were prepared. The copolymer/clay composite was characterized by Fourier transformed infrared, transmission electron microscopy, and scanning electron microscopy. The water absorbencies of poly(acrylamide‐co‐vinyl alcohol)/clay composites were measured by calculating their percentage swelling ratio. The effects of copolymerization, type of clay, and clay content on the water absorbencies were studied. The swelling was measured in acidic, alkaline, and saline condition to ensure its versatility. The results indicated a remarkable increase in swelling ratio by incorporation of modified clay having higher hydrophilicity and optimum clay loading. The poly(acrylamide‐co‐vinyl alcohol)/clay composite hydrogel was found to have better re‐swelling ability and water retention capacity compared to the virgin copolymer. The substantial enhancement of swelling properties enables the superabsorbent poly(acrylamide‐co‐vinyl alcohol)/clay suitable for agricultural and horticultural application. POLYM. COMPOS., 34:1794–1800, 2013. © 2013 Society of Plastics Engineers     

Preparation of poly(lactic acid)/poly(ethylene glycol)/organoclay nanocomposites by melt compounding

Poly(lactic acid) (PLA)/organoclay nanocomposites were prepared by melt compounding in a co‐rotating twin screw extruder. Two types of commercialized organoclay (dimethyl benzyl stearyl ammonium ion and dimethyl distearyl ammonium ion intercalated between clay platelets named as Clay A and Clay B, respectively) and two grades of poly(ethylene glycol) (PEG) with different molecular weight (M_w = 2,000 and 300,000–500,000 named as PEG2k and PEG500k, respectively) were used in this study. The Young's modulus improved by the addition of organoclay to PLA matrix. The Young's modulus decreased with the addition of PEG to PLA/organoclay nanocomposites. The tensile strength and elongation of PLA/Clay B nanocomposites increased with the addition of PEG2k. The effect of the addition of PEG on d‐spacing of PLA/organoclay nanocomposites is dependent upon the kind of organoclay. The sizes of clay agglomerations in PLA/PEG/organoclay nanocomposites are larger than those of PLA/organoclay ones in the same organoclay. Addition of PEG to PLA/organoclay nanocomposites during melt compounding will not be useful for the preparation of PLA/organoclay having fully exfoliated clay platelets. The shear thinning properties of the nanocomposites are independent of the addition of PEG. On the whole, PEG2k is good plasticizer for PLA/organoclay nanocomposites. POLYM. COMPOS. 27:256–263, 2006. © 2006 Society of Plastics Engineers     

Thermal and mechanical properties of plasticized poly(L‐lactide) nanocomposites with organo‐modified montmorillonites

Nanocomposites of poly(lactide) (PLA) and the PLA plasticized with diglycerine tetraacetate (PL‐710) and ethylene glycol oligomer containing organo‐modified montmorillonites (ODA‐M and PGS‐M) by the protonated ammonium cations of octadecylamine and poly(ethylene glycol) stearylamine were prepared by melt intercalation method. In the X‐ray diffraction analysis, the PLA/ODA‐M and plasticized PLA/ODA‐M composites showed a clear enlargement of the difference of interlayer spacing between the composite and clay itself, indicating the formation of intercalated nanocomposite. However, a little enlargement of the interlayer spacing was observed for the PLA/PGS‐M and plasticized PLA/PGS‐M composites. From morphological studies using transmission electron microscopy, a finer dispersion of clay was observed for PLA/ODA‐M composite than PLA/PGS‐M composite and all the composites using the plasticized PLA. The PLA and PLA/PL‐710 composites containing ODA‐M showed a higher tensile strength and modulus than the corresponding composites with PGS‐M. The PLA/PL‐710 (10 wt %) composite containing ODA‐M showed considerably higher elongation at break than the pristine plasticized PLA, and had a comparable tensile modulus to pure PLA. The glass transition temperature (T_g) of the composites decreased with increasing plasticizer. The addition of the clays did not cause a significant increase of T_g. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Supercritical CO2 deposition and foaming process for fabrication of biopolyester–ZnO bone scaffolds

Subsequent supercritical CO₂‐assisted deposition and foaming process followed by in situ synthesis was used to fabricate functional polylactide (PLA) and polylactide–poly(?‐caprolactone) (PLA–PCL) bone scaffolds. Deposition of zinc bis(2‐thenoyltrifluoroacetonate) as a ZnO precursor onto biopolyester substrates (30 MPa; 110 °C) was followed by fast depressurization to create cellular structure. Contact time was optimized regarding the deposition yield (2 h), while PCL content in PLA was varied (1–10 wt %). Scaffolds impregnated with the precursor were treated with hydrazine alcoholic solution to obtain biopolyester–ZnO composites. Precursor synthesis and deposition onto the scaffolds was confirmed by Fourier‐transform infrared. Processed scaffolds had micron‐sized pores (d₅₀ ～ 20 μm). High open porosity (69–77%) and compressive strength values (2.8–8.3 MPa) corresponded to those reported for trabecular bone. PLA blending with PCL positively affected precursor deposition, crystallization rate, and compressive strength of the scaffolds. It also improved PLA surface roughness and wettability which are relevant for cell adhesion. ZnO improved compressive strength of the PLA scaffolds without significant effect on thermal stability. Analysis of structural, thermal, and mechanical properties of biopolyester–ZnO scaffolds testified a great potential of the obtained platforms as bone scaffolds. Proposed processing route is straightforward and ecofriendly, fast, easy to control, and suitable for processing of thermosensitive polymers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45824.     

Evaluation of the chondrogenic differentiation of mesenchymal stem cells on hybrid biomimetic scaffolds

Hybrid materials are widely and promisingly used as scaffolds in cartilage tissue remodeling. In this study, hybrid scaffolds consist of polycaprolactone (PCL), poly(vinyl alcohol) (PVA) with/without gelatin (GEL) to mimic natural cartilage extracellular matrix (ECM) were investigated. Scaffolds were prepared by freeze drying and characterized by scanning electron microscopy and compressive mechanical testing. Biological assays of mesenchymal stem cell (MSC) cultures, 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide, and dimethyl methylene blue were performed, and real‐time polymerization chain reaction analysis of the cartilage‐specific ECM gene marker expression was done. The results show an open interconnected porous structure with a compression modulus of 1.27 ± 0.04 MPa. The surface of the scaffolds showed an excellent efficiency in the adhesion and proliferation of MSCs. A significant increase in the proteoglycan content from 3.70 ± 0.96 to 5.4 ± 1.13 μg/mL was observed after 14 days in the PCL–PVA–GEL scaffolds. The expression amount of the sex‐determining region Y–Box 9 (SOX9) and collagen II (COL2) mRNA levels of the MSCs showed significant increases in SOX9 and COL2, respectively in comparison with PCL–PVA scaffold. The study revealed that the aforementioned scaffold as a blend of natural and synthetic polymers may be a promising substrate in tissue engineering for cartilage repair with MSC transplantation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40635.     

Ultrasonication‐Induced Modification of Hydroxyapatite Nanoparticles onto a 3D Porous Poly(lactic acid) Scaffold with Improved Mechanical Properties and Biocompatibility

A 3D porous poly(lactic acid) (PLA) scaffold with high porosity and well‐connected pores is fabricated using a vacuum‐assisted solvent casting technique. Its surface is modified with hydroxyapatite (HA) nanoparticles using ultrasonication to prepare an HA‐modified PLA/HA scaffold. For reference, an HA‐blended (b‐PLA‐HA) scaffold is fabricated via the solution blending method. The morphology, porosity, hydrophilicity, swelling ratio, mechanical properties, and cell viability of the PLA, b‐PLA‐HA, and PLA/HA scaffolds are systematically studied. The results show that HA nanoparticles are successfully introduced onto the surface of the PLA/HA scaffold, and strong interactions occur between the HA nanoparticles and the PLA matrix. The PLA/HA scaffold still has a high porosity of more than 85% after ultrasonication. The hydrophilicity and mechanical properties of the PLA/HA scaffold are significantly higher than those of the PLA and b‐PLA‐HA scaffolds. Compared with the PLA and b‐PLA‐HA scaffolds, the attachment and growth of mouse embryonic osteoblasts cells (MC3T3‐E1) cultured on the PLA/HA scaffold significantly improve, due to most HA nanoparticles on the surface, resulting in a good and direct interaction between the cells and the scaffold. Therefore, the PLA/HA scaffold possesses great potential to be used as a tissue engineering scaffold.     

Controlling micro‐ and nanofibrillar morphology of polymer blends in low‐speed melt spinning process. Part II: Influences of extrusion rate on morphological changes of a PLA/PVA blend through a capillary die

The effects of the extrusion rate on the morphological changes of poly(lactic acid) (PLA)/poly(vinyl alcohol) (PVA) blend through a capillary die were investigated. In this study, the extrusion rate or mass flow rate is altered from 0.5 g min^?1 to 2 g min^?1 with an increment of 0.5 g min^?1. The PLA/PVA blend with a composition of 30/70 (wt %) exhibits a particle matrix morphology with dispersed PLA droplets within the PVA matrix. It is found that, the spherical or ellipsoidal dispersed PLA droplets are elongated and coalesced into rod‐like or longer ellipsoidal droplets when they pass through the capillary die. When the extrusion rate increases, the coalescence between the large PLA droplets occurs more intense. However, the changes of the extrusion rate have no strong effect on the coalescence of small droplets having diameter less than about 150 nm. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44257.     

Poly(vinyl alcohol) nanocomposites with different clays: Pristine clays and organoclays

Poly(vinyl alcohol) (PVA)/clay nanocomposites were synthesized using the solution intercalation method. Na ion‐exchanged clays [Na⁺–saponite (SPT) and Na⁺–montmorillonite (MMT)] and alkyl ammonium ion‐exchanged clays (C₁₂–MMT and C₁₂OOH–MMT) were used for the PVA nanocomposites. From the morphological studies, the Na ion‐exchanged clay is more easily dispersed in a PVA matrix than is the alkyl ammonium ion‐exchanged clay. Attempts were also made to improve both the thermal stabilities and the tensile properties of PVA/clay nanocomposite films, and it was found that the addition of only a small amount of clay was sufficient for that purpose. Both the ultimate tensile strength and the initial modulus for the nanocomposites increased gradually with clay loading up to 8 wt %. In C₁₂OOH–MMT, the maximum enhancement of the ultimate tensile strength and the initial modulus for the nanocomposites was observed for blends containing 6 wt % organoclay. Na ion‐exchanged clays have higher tensile strengths than those of organic alkyl‐exchanged clays in PVA nanocomposites films. On the other hand, organic alkyl‐exchanged clays have initial moduli that are better than those of Na ion‐exchanged clays. Overall, the content of clay particles in the polymer matrix affect both the thermal stability and the tensile properties of the polymer/clay nanocomposites. However, a change in thermal stability with clay was not significant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3208–3214, 2003     

Rheological properties of high molecular weight (HMW) syndiotactic poly(vinyl alcohol) (PVA)/HMW atactic PVA blend solutions

To identify the effect of blend ratios of syndiotacticity‐rich poly(vinyl alcohol) (s‐PVA)/atactic PVA (a‐PVA) having similar number‐average degrees of polymerization (P_n)s of 4000 and degrees of saponification (DS)s of 99.9% on the rheological properties of s‐PVA/a‐PVA/water solutions, water‐soluble s‐PVA and a‐PVA with different syndiotactic diad contents of 58.5 and 54.0%, respectively, were prepared by bulk copolymerization of vinyl pivalate and vinyl acetate (VAc) and solution polymerization of VAc, followed by saponifying the corresponding copoly(vinyl pivalate/vinyl acetate) and poly(vinyl acetate). The blend ratios played a significant role in rheological behavior. Over the frequency range of 10^?1–10² rad/s, s‐PVA/a‐PVA blend solutions with larger s‐PVA content show more shear thinning at similar (P_n)s and (DS)s of polymer, suggesting that PVA molecules are more readily oriented as s‐PVA content increases. Yield stress is higher for s‐PVA/a‐PVA blend solutions with larger s‐PVA content at similar (P_n)s and (DS)s of polymer. This indicates that more domains with internal order are produced at larger s‐PVA content in s‐PVA/a‐PVA blend solutions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3934–3939, 2006     

Nanofibrous scaffold prepared by electrospinning of poly(vinyl alcohol)/gelatin aqueous solutions

A series of nanofibrous scaffolds were prepared by electrospinning of poly(vinyl alcohol) (PVA)/gelatin aqueous solution. PVA and gelatin was dissolved in pure water and blended in full range, then being electrospun to prepared nanofibers, followed by being crosslinked with glutaraldehyde vapor and heat treatment to form nanofibrous scaffold. Field emission scanning electron microscope (FESEM) images of the nanofibers manifested that the fiber average diameters decreased from 290 to 90 nm with the increasing of gelatin. In vitro degradation rates of the nanofibers were also correlated with the composition and physical properties of electrospinning solutions. Cytocompatibility of the scaffolds was evaluated by cells morphology and MTT assay. The FESEM images revealed that NIH 3T3 fibroblasts spread and elongated actively on the scaffolds with spindle‐like and star‐type shape. The results of cell attachment and proliferation on the nanofibrous scaffolds suggested that the cytotoxicity of all samples are grade 1 or grade 0, indicating that the material had sound biosafety as biomaterials. Compared with pure PVA and gelatin scaffolds, the hybrid ones possess improved biocompatibility and controllability. These results indicate that the PVA/gelatin nanofibrous have potential as skin scaffolds or wound dressing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structural characterization of hydrophilic polymer blends/montmorillonite clay nanocomposites

The nanocomposite films comprising polymer blends of poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), poly(ethylene oxide) (PEO), and poly(ethylene glycol) (PEG) with montmorillonite (MMT) clay as nanofiller were prepared by aqueous solution casting method. The X‐ray diffraction studies of the PVA–x wt % MMT, (PVA–PVP)–x wt % MMT, (PVA–PEO)–x wt % MMT and (PVA–PEG)–x wt % MMT nanocomposites containing MMT concentrations x = 1, 2, 3, 5 and 10 wt % of the polymer weight were carried out in the angular range (2θ) of 3.8–30°. The values of MMT basal spacing d₀₀₁, expansion of clay gallery width W_cg, d‐spacing of polymer spherulite, crystallite size L and diffraction peak intensity I were determined for these nanocomposites. The values of structural parameters reveal that the linear chain PEO and PEG in the PVA blend based nanocomposites promote the amount of MMT intercalated structures, and these structures are found relatively higher for the (PVA–PEO)–x wt % MMT nanocomposites. It is observed that the presence of bulky ester‐side group in PVP backbone restricts its intercalation, whereas the adsorption behavior of PVP on the MMT nanosheets mainly results the MMT exfoliated structures in the (PVA–PVP)–x wt % MMT nanocomposites. The crystallinities of the PEO and PEG were found low due to their blending with PVA, which further decreased anomalously with the increase of MMT concentration in the nanocomposites. The decrease of polymer crystalline phase of these materials confirmed their suitability in preparation of novel solid polymer nanocomposite electrolytes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40617.