Crystallinity Of PVA Research Articles

Structure and properties of hydrophobic cationic poly(vinyl alcohol)

AbstractA new class of derivatives of poly(vinyl alcohol) (PVA) was prepared through hydrophobic cationic modification. The structure and composition of PVA grafted with glycidyl‐N‐alkyl‐N,N‐dimethyl‐ammonium chloride (DA) (PVA‐graft‐DA) was confirmed with Fourier transform infrared spectral analysis and 1H NMR spectral analysis. The stress‐strain curves of PVA‐graft‐DA samples all exhibited an elastic deformation stress plateau, and strain hardening behavior can be observed, indicating the transition of PVA from brittle fracture to ductile fracture. Compared with virgin PVA, the relaxation peak (Tg) of PVA‐graft‐DA shifted to a lower temperature. With increasing alkyl chain length and grafting ratio of DA, Tg decreased, and PVA‐graft‐DA exhibited a gradually decreasing storage modulus over the whole temperature range of testing due to the relatively weak intermolecular hydrogen bonding and increasing flexibility of molecular chains by introduction of long alkyl chains. PVA crystallites were not affected by grafting with DA, while the crystallization temperature and crystallinity of PVA were improved and the grain size decreased. On grafting with DA, the fracture surface of PVA changed from a smooth surface to regularly distanced striations, displaying much obvious character of tough fracture, indicating that appropriate intermolecular association of the hydrophobic groups facilitated the formation of physical entanglement of molecular chains to strengthen and toughen the PVA matrix. PVA‐graft‐DA showed a significant decreasing surface tension with polymer concentration, while the surface tension of PVA‐graft‐DA12 dropped most dramatically and declined with increasing grafting ratio of DA12, indicating improvement of the surface activity of PVA by introduction of hydrophobic alkyl chains and hydrophilic cationic groups. Copyright © 2011 Society of Chemical Industry

Outstanding reinforcing effect of highly oriented chitin whiskers in PVA nanocomposites.

To utilize the extreme reinforcing performance of chitin whiskers (ChWs), the current work was undertaken to fabricate nanocomposites embedded with highly uniaxial oriented ChWs into the matrix polymer. Fibers of poly(vinyl alcohol) (PVA)/ChWs were prepared by gel spinning and the fibers were subjected to a hot drawing to their maximal draw ratio. WAXD analysis revealed the very high orientation of ChWs in the PVA matrix. DSC measurements showed that, upon ChWs loadings, crystallinity of PVA increased and non-isothermal cooling crystallization peak of PVA shifted towards lower temperature, indicating the interaction of PVA with ChWs. Measurement of infrared dichroism suggested that the orientation of overall PVA chains increased with the increase in ChWs loading due to the possible dragging of PVA chains attached with ChWs during drawing, which resulted higher PVA crystallinity in the composites. The stress transfer in PVA/ChWs interface quantified by X-ray diffraction evidenced the strong adherence between the two. The stress transfer between PVA and ChWs interface, and higher PVA crystallinity induced by ChWs were reflected to the outstanding enhancement in mechanical- and anti-creep properties of nanocomposite fibers.

Structural changes of starch/polyvinyl alcohol biocomposite films reinforced with microcrystalline cellulose due to biodegradation in simulated aerobic compost environment

AbstractStarch/Polyvinyl alcohol (PVA) based biocomposite films reinforced with micro crystalline cellulose (MCC) (10 wt %) particles were prepared by solution casting method, incorporating glycerol as plasticizer. These biocomposite films were subjected to biodegradation at ambient temperature in a simulated aerobic compost pit. The extent of biodegradation of these films was studied in terms of weight loss. The corresponding changes in the structure of the films were observed using scanning electron microscopy, X‐Ray diffraction study, and differential scanning calorimetry. The melting point of PVA component of the biocomposite film shifted from 204 to 223°C with increase in biodegradation time and a remarkable difference was observed in their melt crystallization behavior. The unreinforced films also showed a similar trend, but the increase in the crystallinity of PVA was more pronounced in MCC reinforced films than that observed in the unreinforced ones. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

천연 염료에 의한 폴리(비닐 알코올)의 가교 특성

폴리(비닐 알코올)(PVA)의 수분 팽윤성 조절을 위하여 천연 색소 가교제로 PVA를 가교한 후, 이들의 물성을 화학 가교된 PVA와 함께 비교하였다. 천연 가교제로 사용된 안토시아닌 그리고 크로신에 함유된 하이드록시기는 NaCl 촉매 하에서 PVA의 하이드록시기와 수소 결합하여 PVA를 물리적으로 가교시킴을 알 수 있었다. 화학 가교제인 Polycup 172에 의하여 가교된 PVA와 비교하여 수분 팽윤성이 현저히 감소하며 또한 가교에 의한 결정화도가 감소함을 확인하였다. 천연 가교제로 가교된 PVA는 화학 가교된 PVA에 비하여 상대적으로 열안정성이 떨어지나 함유된 다당류에도 불구하고 순수 PVA보다는 높은 열안정성을 가짐을 알 수 있었다.

Preparation and characterization of poly(vinyl alcohol) nanofiber mats crosslinked with blocked isocyanate prepolymer

AbstractPoly(vinyl alcohol) (PVA) nanofibers crosslinked with blocked isocyanate prepolymer (BIP) were successfully prepared using the electrospinning process and subsequent thermal treatment. Fourier transform infrared spectroscopy and solid‐state 13C NMR spectroscopy demonstrated that chemical crosslinks between the hydroxyl group of PVA and the isocyanate group of BIP were formed. Thermogravimetric analysis and differential scanning calorimetry results indicated that when the BIP content was increased, the thermal stability of PVA/BIP nanofibers increased, and the crystallinity of PVA decreased. Field emission scanning electron microscopy was used to measure the average diameter (200–300 nm) of the electrospun PVA/BIP nanofibers. The water contact angles were 10.2° and 113° for the pristine PVA nanofibers and PVA nanofibers crosslinked with 8 wt% BIP, respectively. The tensile strength of the crosslinked PVA nanofibers was 53.7 MPa, which was seven times higher than that of pristine PVA. The improved tensile strength and water resistance of the crosslinked PVA/BIP nanofibers were due to a combination of increased crosslinking density and decrease in the number of hydroxyl groups on the surface of the PVA/BIP nanofibers. Copyright © 2010 Society of Chemical Industry

The influence of vanadium pentoxide on the structure and dielectric properties of poly(vinyl alcohol)

AbstractPolymers containing metal oxides of nanoscale dimensions have attracted attention because of their unique properties and new findings concerning technological applications. Polymers containing vanadium pentoxide (V2O5) have attracted our interest in respect of their potential applications in memory and switching devices. Poly(vinyl alcohol) (PVA) containing different concentrations of V2O5 ranging from 0 to 0.5 wt% were prepared. The synthesized PVA/V2O5 composites were cast as self‐standing flexible films. The composites were characterized using X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. An attempt was made to study the relaxation characteristics of PVA/V2O5 samples. The permittivity and dielectric loss were determined as a function of V2O5 concentration. The results show that the optimum concentration is 0.3 wt%. The electrical conductivity and dielectric modulus in the temperature range 303–433 K at various frequencies (10–100 kHz) for the optimum concentration were investigated. XRD and FTIR results show that the addition of V2O5 reduces the crystallinity of PVA due to the interaction of vanadium ions with the OH groups of PVA. The application of the dielectric modulus formulism gives a simple method for evaluating the activation energy of the dielectric relaxation. The frequency dependence of the electrical conductivity follows the Jonscher universal dynamic law. The conductivity in the direct regime is described by the small polaron model. The electrical conductivity and dielectric properties show that Hunt's model is well adapted to PVA/V2O5 films. Copyright © 2010 Society of Chemical Industry

Preparation and characterization of graphene/poly(vinyl alcohol) nanocomposites

AbstractGraphene (GE)‐based nanocomposites are emerging as a new class of materials that hold promise for many applications. In this article, we present a general approach for the preparation of GE/poly(vinyl alcohol) (PVA) nanocomposites. The basic strategy involved the preparation of graphite oxide from graphite, complete exfoliation of graphite oxide into graphene oxide sheets, followed by reduction to GE nanosheets, and finally, the preparation of the GE/PVA nanocomposites by a simple solution‐mixing method. The synthesized products were characterized by X‐ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, and differential scanning calorimetry analysis. The GE nanosheets were well dispersed in the PVA matrix, and the restacking of the GE sheets was effectively prevented. Because of the strong interfacial interaction between PVA and GE, which mainly resulted from the hydrogen‐bond interaction, together with the improvement in the PVA crystallinity, the mechanical properties and thermal stability of the nanocomposites were obviously improved. The tensile strength was increased from 23 MPa for PVA to 49.5 MPa for the nanocomposite with a 3.25 wt % GE loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Characterization of Poly (Vinyl Alcohol) /Silver Nanocomposites Prepared by Heat Treatment Method

Poly (vinyl alcohol) (PVA)/silver (Ag) nanoparticle composites were prepared via heat treatment of a mixture solution of silver nitrate (AgNO3) and PVA. The resultant composites were characterized by infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). XRD results showed that pure phase Ag was obtained in the prepared nanocomposites. They also showed that crystallinity of PVA was largely decreased after the composition with nano-sized Ag. TEM results showed that the Ag particles were in sphere shape with 10-40nm diameter in the as-prepared nanocomposites. DSC results showed that the glass transition temperature of the nanocomposites was enhanced by the incorporation of Ag.

STRUCTURE AND RHEOLOGICAL PROPERTIES OF POLY(VINYL ALCOHOL) HYDROGELS OBTAINED BY FREEZING/THAWING CYCLES

The relationships between the structure and the rheological behavior of poly(vinyl alcohol) (PVA) hydrogels prepared by freeze /thaw cycles were investigated as a function of polymer concentration (5 wt% ～ 25 wt% ). The degree of crystallinity and apparent dimensions of crystallite were determined by XRD. Rheological properties of PVA solutions including modulus and creep properties were characterized by controlled stress rheometer. Measurements of the shear storage and loss modulus were performed at a fixed frequency of 1 Hz and a low stress,under conditions where the deformation imposed on the gel structure is entirely reversible. The storage modulus at low frequency and low strain amplitude increases as the concentration increases,but the increase rate becomes clearly slow when the concentration is higher than 20 wt%. The storage modulus at 1 Hz was determined and related to the degree of crystallinity and concentration. Based on these measurements it was concluded that a minimum crystallinity and concentration were required for these PVA samples to exhibit gel behaviour. A more detailed comparison of XRD and rheological data led to the conclusion that the storage modulus was mainly controlled by the PVA crystallinity while the hydrogen bond interactions had a much smaller contribution,when the concentration was lower than 15 wt%. A structural parameter related to the network mesh size is derived from measurements of the dynamic storage moduli at low values of strain frequency and amplitude. The storage modulus of PVA hydrogels at different temperatures was analyzed on the basis of a theoretical model based on the scaling approach. The creep response of PVA hydrogels was investigated. With increase in concentration,these hydrogels exhibited an evolution from a linear viscoelastic response to a nonlinear viscoelastic response.

Effect of annealing on aqueous stability and elastic modulus of electrospun poly(vinyl alcohol) fibers

Electrospun poly(vinyl alcohol) (PVA) fibers rapidly dissolve in water. Their aqueous stability can be improved by annealing using a combination of controlled temperature and treatment time. The increase in aqueous stability of the PVA fibers is associated with an increase in PVA crystallinity and is defined by X-ray diffraction and the ratio of the Fourier transform infrared spectroscopy band intensities at 1141 and 1425 cm−1. A ratio of intensity of these two infrared bands ≥2.5 or ~75% and above in the degree of crystallinity as determined by X-ray diffraction indicates fiber stability in water. Annealing treatment also results in an increase in the stiffness of the fibers. At a treatment temperature of 135 °C for 4 h, the elastic modulus of the fiber increased by 80%. This information is useful when these fibers are being considered for applications in an aqueous environment such as membrane filter or tissue scaffold.

X‐ray diffraction and dynamic mechanical analyses of α‐chitin whisker‐reinforced poly(vinyl alcohol) nanocomposite nanofibers

AbstractElectrospinning is a facile method for preparing nanocomposite materials in fiber form. Nanomaterials that have been incorporated within such fibers are usually inorganic in nature. Recently, nanocomposite nanofibers based on poly(vinyl alcohol) (PVA) as the matrix and nanocrystals of α‐chitin (i.e. chitin whiskers; ca 31 nm in width and ca 549 nm in length on average) as the nanofiller have been successfully prepared. In the study reported here, the fibers were further investigated using X‐ray diffraction (XRD) and dynamic mechanical analyses in comparison with the corresponding solvent‐cast films. The average diameters of the PVA/chitin whiskers fibers ranged between 175 and 218 nm. Careful analysis of the wide‐angle XRD patterns of the fiber mats and the films showed that PVA was partially crystalline, and the incorporation of the whiskers within the fibers was confirmed by peaks characteristic to α‐chitin crystals. Dynamic mechanical analysis showed that the fiber mats were weaker than the films and that the relaxation temperatures associated with the glass transition (Tg) of the fiber mats were greater than those of the films. The addition and increasing the amount of the whiskers caused the crystallinity of PVA within the nanocomposite materials to decrease and Tg to increase. The present study shows that the geometry of nanocomposite materials plays a major role in determining their properties. Copyright © 2009 Society of Chemical Industry

Poly(vinyl alcohol) and poly(sodium styrene sulfonate) compatibility by differential scanning calorimetry, Fourier transform infrared and scanning electron microscopy

AbstractTo prepare ion‐exchange membrane from poly(vinyl alcohol) (PVA) and poly (sodium‐4‐styrene sulfonate) (PSSNa), the polymer compatibility was investigated by means of differential scanning calorimetry, attenuated total reflection Fourier Transform Infrared spectroscopy, and scanning electron microscopy. Using the strong–fragile concept to interpret the differential scanning calorimetric results, we show that the interactions between the segments of both polymers increase with decrease in PVA fraction. Because of these intermolecular interactions, the PVA crystallinity degree decreased with the decrease in PVA fraction, and a single‐transition temperature was observed for the polymer blend in the amorphous phase. At the nanoscopic scale, the Fourier Transform Infrared results show that the PVA/PSSNa compatibility is mainly promoted by hydrogen bonds and dipole–ion interactions between PVA and PSSNa segments, whereas at microscopic scale, the morphology obtained by scanning electron microscopy technique shows that PVA and PSSNa form one homogeneous phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The effect of copper(II) on the thermal and mechanical properties of poly(vinyl alcohol)/silica hybrid

AbstractA novel copper‐poly(vinyl alcohol) (PVA)/silica complex was prepared and its chemical structure, thermal, and mechanical properties were studied. The results showed that the crystallinity of PVA first increased and then decreased by the addition of copper chloride, whereas, the thermal decomposition temperature increased dramatically. For PVA/silica hybrid, the decomposition temperature associated with the removal of water molecules in PVA chains was 262°C. But the temperature increased to 361°C when the content of copper chloride was 2 wt%. The intelligent electronic tensile tester was used to investigate the mechanical properties of these complexes. The results suggested that the tensile strength of the complexes is improved with negligible decrease in the plasticity. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Biodegradable bioartificial materials made with chitosan and poly(vinyl alcohol). Part I: Physicochemical characterization.

Polymers have widespread applications in therapeutics, and their use can play important structural and functional roles in different disease conditions. Bioartificial biodegradable materials, to be used as biomaterials and, in particular, as localized drug carriers, were prepared mixing chitosan (CHI) and poly(vinyl alcohol) (PVA), then manufactured as films, and finally cross-linked with glutaraldehyde (GTA), both in the absence and in the presence of the edible plasticizer sorbitol (SOR). The materials were characterized by Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), ther-mogravimetric analysis (TGA), X-ray diffraction, scanning electron microscopy (SEM), and tensile test. The FTIR spectroscopy and the X-ray diffraction indicated that the presence of CHI lowers the crystallinity of PVA, and that the cross-linking with GTA does not modify the interactions between the two polymers, but only forms bridges between the different chains. In addition, the thermodynamic parameters for PVA, evaluated from the DSC measurements, confirmed that the PVA structure was less crystalline in the blends than in the pure state. The addition of SOR as a plasticizer to the CHI/PVA blends generally improved the characteristics of the films, making the cross-linked films less brittle, as confirmed by the SEM measurements and by the mechanical test. The TGA measurements confirmed the presence of chemical interactions between the polymers, as indicated by the DSC measurements. On the whole, the physicochemical properties of the blends showed the strong interactions existing between the component materials.

Relationships between nanostructure and thermomechanical properties in poly(vinyl alcohol)/montmorillonite nanocomposite with an entrapped polyelectrolyte

AbstractPoly(vinyl alcohol)/montmorillonite (PVA/MOM) hydrogels containing coacervated microparticles of sulfonated polyester (PES) were prepared by direct mixture of the components in water. The system was characterized by using differential scanning calorimetry (DSC), small‐angle X‐ray scattering (SAXS), and dynamical mechanical analysis (DMA). The influence of PES and MOM on the microstructure of the nanocomposite hydrogels was established. The presence of PES causes a significant change on the crystallinity of PVA. Furthermore, the presence of MOM leads to a hierarchical nanostructure that also contributes to change the crystallinity of PVA. The results of structural investigation are correlated with the mechanical properties of the composites obtained by DMA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2618–2629, 2008

Design of a Physical and Nontoxic Crosslinked Poly(Vinyl Alcohol) Hydrogel

Controlled delivery matrices are an alternative available to provide a better administration of drugs. Hydrogels have been used to produce these matrices due to the control of absorption and desorption rates of water into their molecular structure, which allows us to obtain various delivery profiles. Poly(vinyl alcohol) (PVA), a candidate matrix material, was physically modified through a solvation-desolvation process with acetone to change its crystallinity. Tolbutamide is a poorly water-soluble drug with a dissolution-rate-limited bioavailability. Thus, it was used as a model for this methodology. This physical method introduces crosslinks, which decrease the crystallinity of PVA in the order of 8% and has the advantage that there is no residual toxic chemical present in the hydrogel. Dissolution studies, carried out with the PVA-hydrogel (H) loaded with tolbutamide, allow us to state that 78% of drug release takes place in about 24 h which contrasts with the dissolution curves of tablets of tolbutamide and tolbutamide mixed with the PVA as powder both of which were used as comparative preparations.

Diffusivity enhancement of water vapor in poly(vinyl alcohol)–fumed silica nano-composite membranes: Correlation with polymer crystallinity and free-volume properties

The diffusion coefficients of water vapor in poly(vinyl alcohol)–fumed silica (PVA–FS) nano-composite membranes were determined using the gravimetric method. Water vapor was observed to diffuse more rapidly in membranes with increased FS content. The vapor diffusion coefficient was determined as 1.2 × 10 −13 m 2/s in pure PVA and was observed to increase to 3.0 × 10 −13 m 2/s in PVA composites containing 30% FS nano-particles. The free-volumes of PVA–FS membranes were characterized using positron annihilation lifetime (PAL) spectroscopy. PAL results showed that both the ortho-positronium (o-Ps) lifetime and intensity increased with the addition of FS. The intensity ( I 3) was found to be higher than the estimated value determined from the linear combination of the data from pristine PVA and FS, and correlated excellently with the polymer amorphous content. The PAL results indicate that a higher FS content in PVA increases the free-volume hole size (a volume increase from 40 to 55 Å 3) and free-volume hole density (an I 3 increase from 23 to 28%), resulting in a higher fractional free-volume in the nano-composites. The increase in the relative polymer free-volume with higher FS content was associated with a decrease in the PVA crystallinity, as determined from differential scanning calorimetry measurements. It is postulated that the incorporated FS nano-particles interrupt polymeric chain packing and retard crystallization during membrane formation. More crystalline segments were transformed into amorphous regimes in the nano-composites containing more FS. A correlation between water diffusivity and the fractional free-volume was obtained, and the water diffusivity was successfully expressed by the free-volume theory.

Thermal and rheological properties of poly(vinyl alcohol) and water‐soluble chitosan hydrogels prepared by a combination of γ‐ray irradiation and freeze thawing

AbstractPoly(vinyl alcohol) (PVA)/water‐soluble chitosan (ws‐chitosan) hydrogels were prepared by a combination of γ‐irradiation and freeze thawing. The thermal and rheological properties of these hydrogels were compared with those of hydrogels prepared by pure irradiation and pure freeze thawing. Irradiation reduced the crystallinity of PVA, whereas freeze thawing increased it. Hydrogels made by freeze thawing followed by irradiation had higher degrees of crystallinity and higher melting temperatures than those made by irradiation followed by freeze thawing. ws‐Chitosan disrupted the ordered association of PVA molecules and decreased the thermal stability of both physical blends and hydrogels. All the hydrogels showed shear‐thinning behavior in the frequency range of 0.2–100 rad/s. Hydrogels made by freeze thawing dissolved into sol solutions at about 80°C, whereas those made by irradiation showed no temperature dependence up to 100°C. The chemical crosslinking density of the hydrogels made by irradiation followed by freeze thawing was much greater than that of hydrogels made by freeze thawing followed by irradiation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Electrical response characterization of PVA–P(AA/AMPS) IPN hydrogels in aqueous Na2SO4 solution

Abstract Interpenetrating polymer networks (IPN) hydrogels composed of poly(vinyl acohol) (PVA) and poly(acrylic acid-co-2-acrylamido-2-methyl propyl sulfonic acid) (P(AA/AMPS)) were synthesized by solution polymerization. The IPN hydrogels were characterized using Fourier-transform infrared (FT-IR) and X-ray diffraction (XRD). The results indicated that strong hydrogen bond was formed between PVA and P(AA/AMPS), and the crystallinity of PVA in IPN hydrogels was declined significantly. The swelling/deswelling properties of IPN hydrogel in aqueous Na 2 SO 4 solution were studied. When a sheet of water swollen IPN hydrogel (all the samples were swollen in deionized water) was placed in aqueous Na 2 SO 4 solution, the IPN hydrogel shrunk. However, if a voltage was applied, the IPN hydrogel shrunk at high concentration of Na 2 SO 4 solution, but swelled at low concentration. The results show that the critical concentration of Na 2 SO 4 solution is about 0.005 mol/L. The stimuli response of the IPN hydrogel in electric field was also investigated. When water swollen samples were placed between a pair of electrodes in aqueous Na 2 SO 4 solution, the IPN hydrogel showed significant bending behavior upon the application of an electric field. The bending direction of the IPN hydrogel depends on the concentration of Na 2 SO 4 solution. At high concentration the IPN hydrogel bended toward anode, contrarily, at low concentration the IPN hydrogel bended toward cathode. The critical concentration of Na 2 SO 4 solution is also about 0.005 mol/L. Further investigation showed that the gel component, concentration of aqueous Na 2 SO 4 solution and the applied voltage influenced the bending speed of IPN hydrogel.

Gas transport property of polyallylamine–poly(vinyl alcohol)/polysulfone composite membranes

Polyallylamine (PAAm) was synthesized by free radical polymerization and characterized by Fourier transform infrared resonance (FT-IR) spectroscopy, hydrogen nuclear magnetic resonance ( 1H NMR) spectroscopy and differential scanning calorimetry (DSC). The composite membranes were prepared by using PAAm–poly(vinyl alcohol) (PVA) blend polymer as the separation layer and polysulfone (PSF) ultrafiltration membranes as the support layer. The surface and cross-section morphology of the membrane was inspected by environmental scanning electron microscopy (ESEM). The gas transport property of the membranes, including gas permeance, flux and selectivity, were investigated by using pure CO 2, N 2, CH 4 gases and CO 2/N 2 gas mixture (20 vol% CO 2 and 80 vol% N 2) and CO 2/CH 4 gas mixture (10 vol% CO 2 and 90 vol% CH 4). The plots of gas permeance or flux versus feed gas pressure imply that CO 2 permeation through the membranes follows facilitated transport mechanism whereas N 2 and CH 4 permeation follows solution–diffusion mechanism. Effect of PAAm content in the separation layer on gas transport property was investigated by measuring the membranes with 0–50 wt% PAAm content. With increasing PAAm content, gas permeance increases initially, reaches a maximum, and then decreases gradually. For CO 2/N 2 gas mixture, the membranes with 10 wt% PAAm content show the highest CO 2 permeance of about 1.80 × 10 −5 cm 3 (STP) cm −2 s −1 KPa −1 and CO 2/N 2 selectivity of 80 at 0.1 MPa feed gas pressure. For CO 2/CH 4 gas mixture, the membranes with 20 wt% PAAm content display the highest CO 2 permeance of about 1.95 × 10 −5 cm 3 (STP) cm −2 s −1 KPa −1 and CO 2/CH 4 selectivity of 58 at 0.1 MPa feed gas pressure. In order to explore the possible reason of gas permeance varying with PAAm content, the crystallinity of PVA and PAAm–PVA blend polymers was measured by X-ray diffraction (XRD) spectra. The experimental results show an inverse relationship between crystallinity and gas permeance, e.g., a minimum crystallinity and a maximum CO 2 permeance are obtained at 20 wt% PAAm content, indicating that the possibility of increasing CO 2 permeance with PAAm content due to the increase of carrier concentration could be weakened by the increase of crystallinity.