低聚肽对PVA/PEG复合薄膜相容性的影响

以α-氨基酸为起始材料合成了低聚肽(TEA),通过溶液共混法将其引入聚乙二醇与PVA的复合体系中,使用不同分子量的PEG,制备了一系列PEG/TEA/PVA共混膜。试验了不同分子量PEG与TEA和PVA的相互作用,并分析了TEA对PEG/PVA复合体系相容性的影响。结果表明,TEA改变了PEG与PVA的相互作用模式,当PEG分子量较低时,PEG优先与TEA通过分子间作用力形成自组装微区,均匀分布于PVA连续相中,随着PEG的分子量增大,自组装微区的体积逐渐增大,PEG与TEA的相互作用随着距离的增加而减弱。当PEG分子量达到4 000时,PEG与PVA的链段缠结作用远大于TEA与PEG的相互作用,TEA分子分散在PEG/PVA体系中,在分子间的芳基堆砌作用驱动下,TEA自组装成纤丝。     

聚乙烯醇/壳聚糖共混纤维毡的制备与表征

将不同质量比的聚乙烯醇(PVA)和壳聚糖(CS)溶于甲酸中配制成共混溶液进行静电纺丝,得到PVA/CS共混纤维毡。对纤维毡进行原子力显微镜(AFM)表征、红外光谱分析和吸水性能测试。结果表明:共混溶液中PVA质量分数为8%,CS质量分数为4%时,静电纺丝效果较好,纤维光滑平直,平均直径为307 nm,;红外光谱分析表明,PVA和CS共混时,大分子之间产生了较强的氢键作用,CS原有的结晶结构在一定程度上被破坏;PVA/CS共混纤维毡的吸水量和吸水速率都小于PVA纤维毡。     

PVA/PTMG共混膜制备及性能研究

采用流延成膜的方法制备了聚乙烯醇(PVA)/聚四氢呋喃(PTMG)共混薄膜,当PTMG摩尔分数小于8%时,可以得到均一连续的共混膜。通过拉伸测试和示差扫描量热仪(DSC)等手段对PVA/PTMG共混膜的性能进行了研究。实验结果表明,PTMG可以与PVA形成分子间氢键,破坏了PVA分子内及分子间氢键,进而改善了PVA薄膜的性能。     

聚乙二醇／聚乙烯醇固一固相变材料等温结晶动力学及熔融行为研究

采用接枝共聚法将聚乙二醇（PEG）接枝到聚乙烯醇（PVA）主链上,得到了系列性能稳定的PEG／PVA高分子固固相转变材料,利用DSC法对PEG在受限状态下等温结晶及结晶后的熔融行为进行了研究。结果表明：PEG和共聚体系的Avrami指数n在2左右,说明结晶生长方式是二维生长,速率常数Z随温度升高而减小,样品的成核属非均相依热成核方式。结晶后的等温熔融行为表明PEG出现熔融双峰,共聚体系只显示一个与PEG低温峰相对应的吸收峰,该峰的高温侧出现肩峰,且随T0升高而变得明显。     

柚皮素分子印迹膜的制备及评价

以壳聚糖(CS)为功能聚合物,聚乙烯醇(PVA)为添加剂,聚乙二醇(PEG)为致孔剂,水相共混,流延法制备了CS/PVA共混膜作为制备CS分子印迹膜的基本实验条件。实验优化了分子印迹膜的基础制备条件和工艺。在选定的膜配比下,以柚皮素(NG)为印迹分子,乙醇为洗脱剂,水相共混包埋制备了以NG为模板分子的壳聚糖分子印迹膜。结果表明,当m(NG)∶m(CS)=1/15时,印迹膜的容量最大。印迹膜较之非印迹膜,对NG有较大的透过量,NG分子的渗透量与印迹容量成正比,非印迹分子槲皮素在印迹膜上的渗透速率较低。相同浓度下,基膜组成为PVA/CS=0.6/1.4时印迹分子NG与竞争物桷皮素的分离因子为10.09,组成为PVA/CS=1.4/0.6时印迹分子NG与竞争物槲皮素的分离因子为8.40。     

柚皮素分子印迹膜的制备及评价

以壳聚糖(CS)为功能聚合物,聚乙烯醇(PVA)为添加剂,聚乙二醇(PEG)为致孔剂,水相共混,流延法制备了CS/PVA共混膜作为制备CS分子印迹膜的基本实验条件。实验优化了分子印迹膜的基础制备条件和工艺。在选定的膜配比下,以柚皮素(NG)为印迹分子,乙醇为洗脱剂,水相共混包埋制备了以NG为模板分子的壳聚糖分子印迹膜。结果表明,当m(NG)∶m(CS)=1/15时,印迹膜的容量最大。印迹膜较之非印迹膜,对NG有较大的透过量,NG分子的渗透量与印迹容量成正比,非印迹分子槲皮素在印迹膜上的渗透速率较低。相同浓度下,基膜组成为PVA/CS=0.6/1.4时印迹分子NG与竞争物桷皮素的分离因子为10.09,组成为PVA/CS=1.4/0.6时印迹分子NG与竞争物槲皮素的分离因子为8.40。     

自组装法制备CMCS/PEG纳米粒子及其pH值响应性研究

以壳聚糖(CS)为原料与氯乙酸反应制备羧甲基壳聚糖(CMCS),再将聚乙二醇(PEG)和CMCS以不同的质量比溶解在不同pH值的溶液中,通过氢键相互作用自组装形成CMCS/PEG纳米粒子,并研究其粒径大小与二者配比和溶液pH值之间的关系。结果表明,不同配比下的粒子粒径均随pH值的增大先增大后减小;当pH5时,在相同pH值溶液中,随着PEG比例的增加,粒子的粒径先减小后增大,在pH=1.22、PEG∶CMCS=4∶1时粒径最小,约为160nm;当pH≥5时,在相同pH值溶液中,粒径随PEG用量的增加而增大;通过自组装法制备的CMCS/PEG纳米粒子粒径大小具有pH值响应性。     

木质素与合成高分子共混的研究进展

根据文献资料,对木质素与不同合成高分子共混体系的性能、相容性和共混物分子间的氢键作用以及对相容性的影响进行了综述。根据木质素本身的特点,分析了木质素/合成高分子共混体系中的结晶性能、热稳定和光稳定性能以及抗氧化性能的变化。通过对文献的理解和数据的比较,对不同官能团、不同化学环境对木质素/高分子共混体系相容性的影响以及木质素在其晶区所起的作用作了深入的分析,并且对相容性较差体系中木质素种类、分子量和分子量分布对相容性及其它性能的影响进行了评述。     

TLCPa对PA 6/PA 66相容性及结晶行为的影响

采用溶液共混法制备了聚酰胺6(PA 6)／聚酰胺66(PA 66)/热致聚酰胺液晶(TLCPa)共混物,分析了TLCPa对PA 6／PA 66相容性及结晶行为的影响。差示扫描量热法分析表明,TLCPa的加入改善了PA 6和PA 66之间的相容性,PA 6／PA 66共混物结晶受到抑制;傅里叶变换红外光谱研究表明,TLCPa和PA 6、PA 66分子间形成了大量的分子间氢键,是TLCPa改善共混物相容性的主要原因;广角X射线衍射分析表明,TLCPa的加入没有影响共混物的晶型结构,当w(TLCPa)大于10％时,共混物的结晶度明显下降。     

复合纺丝法制备PEG/PVA相变储能初生纤维

采用不同相对分子质量的聚乙二醇(PEG)与聚乙烯醇(PVA)进行湿法复合纺丝制备PEG/PVA相变储能初生纤维,对PEG与PVA溶液的相容性、PEG的凝固性能、PEG/PVA纤维的相变潜热及纤维形貌进行了研究。结果表明:PEG 2000与PVA复合纺丝得到的相变储能初生纤维具有较高的相变潜热,PEG 2000与PVA的质量比小于3:10时,PEG 2000在纺丝过程中流失量较小,纤维截面随着PEG 2000含量的增加而由肾形向圆形变化。     

Molecular modeling simulations and thermodynamic approaches to investigate compatibility/incompatibility of poly(l-lactide) and poly(vinyl alcohol) blends

This paper investigates the molecular modeling simulation approaches for understanding the blend compatibility/incompatibility of poly(l-lactide), PLL and poly(vinyl alcohol), PVA. Blends of PLL/PVA have been widely used in biotechnology as well as membranes in separation science. Realizing their importance, we thought of investigating to verify experimental observations on their compatibility/incompatibility aspects by calculating thermodynamic interactions between PLL and PVA over the entire range of blend compositions. In doing so, Flory-Huggins interaction parameter, χ, was computed for different blends using atomistic simulations to predict blend miscibility. It was found that at 1:9 blend composition of PLL/PVA, miscibility was observed, but increasing immiscibility was prevalent at higher compositions of PLL component. Computed results confirmed the literature findings on differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) and mechanical property studies, suggesting the validity of modeling strategies. Plots of Hildebrand solubility parameter, δ, and cohesive energy density, CED, supported these findings. Miscibility of PLL and PVA polymers is attributed to hydrogen-bonding effect. Literature findings have been validated to understand the nature of interactions between different groups of the polymers by computing radial distribution function, RDF, for groups that are tentatively involved in such interactions, leading to miscibility or immiscibility. RDF plot was constructed to identify the exact contribution of particular atoms of polymers to confirm miscibility/immiscibility of blends. Results of this study are correlated well with the reported data. Kinetics of phase separation was examined using density profiles calculated from the MesoDyn approach to examine miscibility/immiscibility aspects of the blends. Computed free energy from the mesoscopic simulation of blends reached equilibrium, particularly when simulation was performed at higher time step, indicating the stability of the blend at certain compositions. X-ray diffraction profiles have been constructed for individual polymers as well as for their blends, which agreed well with the reported data.     

Enhancement of water barrier properties of cassava starch-based biodegradable films using silica particles

Biodegradable films are used in a variety of applications, including packaging. However, their use is limited due to their high moisture and water sensitivity. In this work, cassava starch (CS) was blended with poly(vinyl alcohol) (PVA). Silica particles (SiO₂) were incorporated to increase the hydrophobicity of the blend by intermolecular interaction through hydrogen bonding between the three components. Instead of a plasticizer or crosslinker, a small amount of triethylamine was added to eliminate residual acetate groups in PVA. The miscibility of CS and PVA phases was confirmed by smooth fracture surfaces and a single glass transition temperature. When SiO₂ content was below 5% (wt), the particles were well dispersed in a continuous phase of polymer matrix. At this loading of SiO₂, the increase in tensile strength was as high as 170% and in elongation-at-break, 250%. All loadings of SiO₂ increased thermal stability of the blend films because silanol groups on the surface of SiO₂ particles formed effective interfacial interactions with hydroxyl groups of the polymers. These interactions also prevented the ingress of water molecules, significantly increasing the hydrophobicity of the films. The water contact angle increased as high as 113° and moisture absorbency and water solubility were low. These highly hydrophobic, photodegradable, biodegradable CS/PVA/SiO₂ films show great potential as a low-cost, eco-friendly material.

     

Diazotization-bromination of aromatic amines using polymer-supported bromide via Sandmeyer-type reaction

Polyethylene glycol (PEG) as a promoting material for CO₂ separation performance of a composite membrane is introduced into the polytrifluoropropylmethylsiloxane (PTFPMS) network to form a blend selective layer coated on a porous polyetherimide (PEI) support membrane. The maximum blend ratio of PEG to PTFMS in mass is determined for PEG-400, PEG-600, and PEG-1000 at 0.5, 0.2 and 0.2 from the blend solution status observed by an optical microscope. The miscibility of PEG and PTFPMS is verified from one peak of the blend film in DSC characterization. Furthermore, the interaction between PEG and PTFPMS is van der Waals force from the decreasing strength of ether group in ATR-FTIR analysis. The stability of the PEG/PTFPMS blend composite membrane is investigated with pure N₂, O₂, and CO₂ permeation experiments under the transmembrane pressure difference up to 1.0 MPa. The N₂ permeation rate of the PEG400/PTFPMS blend composite membrane with a blend ratio of 0.2 is 2.11 GPU, while the O₂/N₂ and CO₂/N₂ selectivities are improved to 2.67 and 26.67, respectively, which are higher than those of pure PTFPMS composite membrane that is 2.2 and 13.79, respectively.     

Water vapor/propylene sorption and diffusion behavior in PVA-P(AA-AMPS) blend membranes by GCMC and MD simulation

Detailed atomistic structures of blend membranes (poly vinyl alcohol (PVA)/(acrylic acid-co-2-acrylamido-2-methylpropylsulfonic acid) (P(AA-AMPS)) were constructed to investigate the sorption and diffusion behavior of gas molecules (water and propylene) in the membranes. Interaction and miscibility between PVA and P(AA-AMPS) were calculated, and it was found that strong intermolecular interaction resulted in good miscibility of PVA and P(AA-AMPS) in the blend. The polymer chains mobility and free volume properties of the blend membranes were characterized. The sorption quantities and sorption sites of water and propylene in the blend membranes were calculated using Grand Canonical Monte Carlo (GCMC) method. The diffusion coefficients of water in the blend membranes were calculated by molecular dynamics (MD) simulation. The simulated results of the membrane structure (chain mobility, free volume properties), the sorption quantities and diffusion coefficients of water/propylene in the blend membranes showed the identical changing trends as the experimental results. Hopefully, this study could offer qualitative insight into the mass transport phenomena within the blend membranes.     

Characterization of polyvinyl alcohol/gelatin blend hydrogel films for biomedical applications

In the present investigation, attempt was made to prepare blend hydrogel by esterification of polyvinyl alcohol with gelatin. The blend hydrogel was further converted into films by the conventional solution‐casting method. These films were characterized by FTIR, DSC, and X‐ray diffraction studies. The refractive index and viscosity of different composition of the blends were measured in the solution phase of the material. The mechanical properties of the blend films were measured by tensile test. Swelling behavior of the blend hydrogel was also studied. The FTIR spectrum of the blend film indicated complete esterification of the free carboxylic group of gelatin. The DSC results indicate that the addition of gelatin with PVA changes the thermal behavior like melting temperature of PVA, which may be due to the miscibility of PVA with gelatin. The interaction of gelatin with PVA molecule changes the crystallite parameters and the degree of crystallinity. The crystallinity of the blend film was mainly due to gelatin. The comparison of viscosity indicated an increase in the segment density within the molecular coil. The results revealed the changes observed in the properties of the gel, and it enhances the gel formation at viscoelastic phase of the material. The blend film had sufficient strength and water‐holding capacity. The results obtained indicated that the blend film could be used for various biomedical applications such as wound dressing and drug‐delivery systems. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies of chitosan. I. Preparation and characterization of chitosan/poly(vinyl alcohol) blend films

Various blending ratios of chitosan/poly (vinyl alcohol) (CS/PVA) blend films were prepared by solution blend method in this study. The thermal properties and chemical structure characterization of the CS/PVA blend films were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and Fourier transform infrared (FTIR). Based upon the observation on the DSC thermal analysis, the melting point of PVA is decreased when the amount of CS in the blend film is increased. The FTIR absorption characteristic is changed when the amount of CS in the blend film is varied. Results of X‐ray diffraction (XRD) analysis indicate that the intensity of diffraction peak at 19° of PVA becomes lower and broader with increasing the amount of CS in the CS/PVA blend film. This trend illustrates that the existence of CS decreases the crystallinity of PVA. Although both PVA and CS are hydrophilic biodegradable polymers, the results of water contact angle measurement are still shown as high as 68° and 83° for PVA and for CS films, respectively. A minimum water contact angle (56°) was observed when the blend film contains 50 wt % CS. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

A dynamic mechanical and thermal analysis of unplasticized and plasticized poly(vinyl alcohol)/methylcellulose blends

The miscibility of poly(vinyl alcohol) (PVA)/methylcellulose (MC) blends was investigated over the entire composition range using the dynamic mechanical analyzer (DMA) and the differential scanning calorimeter (DSC). On the basis of the glass transition temperature, determined by DMA, one could conclude that the blends exhibited some miscibility below 80 wt % of MC and a good miscibility above 80 wt % of MC. The highest depressions of the melting and crystallization temperatures of the blends compared to those of PVA, determined via DSC analysis, were observed for MC contents greater than 80 wt %. The miscibility between PVA and MC can be attributed to the hydrogen bonds formed between the two components. The DMA studies showed that water is a good plasticizer for PVA and poly(ethylene glycol) 400 (PEG 400), a good plasticizer for MC. The inclusion of both water and PEG 400 in the blends revealed a synergistic plasticizing effect, which resulted in an increased miscibility between PVA and MC over a greater range of MC compositions (>60 wt %). The elongations of PVA, MC, and their blends were found to increase with the addition of PEG 400, but the tensile strengths to decrease. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1825–1834, 2001     

Physicochemical and morphological evaluation of chitosan/poly(vinyl alcohol)/methylcellulose chemically cross-linked ternary blends

Chitosan/poly(vinyl alcohol)/methylcellulose (CS/PVA/MC) ternary blend was prepared and chemically cross-linked with glutaraldehyde. The prepared ternary blends were characterized by Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The FTIR results showed that the strong intermolecular hydrogen bonds took place between CS and PVA. TGA showed the thermostability of the blend is enhanced by glutaraldehyde as crosslink agent. Results of XRD indicated that the relative crystalline of pure CS film was reduced when the polymeric network was reticulated by glutaraldehyde. Finally, the results of scanning electron microscopy (SEM) indicated that the morphology of the blend is rough and heterogenous, further it confirms the interaction between the functional groups of the blend components.     

Miscibility of polymethylmethacrylate and polyethyleneglycol blends in tetrahydrofuran

The miscibility of polymethylmethacrylate (PMMA) and polyethyleneglycol (PEG) blends in tetrahydrofuran (THF) has been investigated by viscosity, density, refractive index, and ultrasonic velocity studies. Various interaction parameters such as polymer–solvent and blend–solvent interaction parameters and heat of mixing have been calculated using the viscosity, density, and ultrasonic velocity data. The results indicated the existence of positive interactions in the blend polymer solutions and that they are miscible in THF in the entire composition range. The study also revealed that variation in the temperature does not affect the miscibility of PMMA and PEG blends in THF significantly. The presence of hydrogen bonding in the blends in the solid state has also been indicated by FTIR studies. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009