聚乙烯醇/聚乙烯基吡咯烷酮共混体系的结晶行为

用DSC、WAXD和SAXS研究了聚乙烯醇(PVAl)/聚乙烯基吡咯烷酮(PVP)共混体系的结晶行为.PVAl的结晶度随PVP含量增加而减少,并存在结晶度为零的组成(PVAl)的重量分数约为50％.与纯PVAl相比,共混物的温度区间T_m-T_g减小,表明PVP对PVAl的结晶起抑制作用.共混物中PVAl的结晶速度下降,具体表现为PVAl过冷区随PVP含量增加而扩大,动力学速度常数减小,球晶增长速度下降.纯PVAl和共混体系的等温结晶速率均遵循Avrami方程.退火样品的长周期、片晶厚度和过渡层厚度大于相同组成未退火样品.两者长周期随PVP含量增长加显著增大,片晶厚度增长次之,过渡层厚度变化不大.     

细菌纤维素(BC)增强PVA/PVP复合水凝胶的制备及性能表征

通过冷冻-熔融法制备了细菌纤维素/聚乙烯醇/聚乙烯吡咯烷酮(BC/PVA/PVP)双网络复合水凝胶,并采用X射线衍射,红外光谱,扫描电镜,力学性能测试等手段对凝胶的结构和性能进行表征.研究发现PVA、PVP通过氢键作用均匀地吸附于纤维微丝周围,将BC纤维有效地分开,因而干燥后的复合凝胶在热水中浸泡后仍可恢复原状;X射线...     

与基板间相互作用对聚乙烯醇水凝胶摩擦行为的影响

选择分别与聚乙烯醇(PVA)水凝胶具有较强和较弱相互作用的基板, 研究水介质中PVA水凝胶在其表面的摩擦行为. 结果表明, 与具有弱相互作用的凝胶-玻璃板体系相比, 具有强相互作用的凝胶-铝板体系的摩擦力(f)较高, 且其粘弹-流体润滑转变速率(vf)较大, 用吸附-排斥模型对其进行了分析. 当滑动速率v相似文献   

Interaction of collagen and poly(vinyl pyrrolidone) in blends

The interaction between collagen and poly(vinyl pyrrolidone) (PVP) in blends has been studied by viscometry, differential scanning calorimetry (DSC) and by Fourier transform infrared spectroscopy (FTIR). It was found that the amide A and amide I bands position in FTIR spectra of collagen were shifted after blending with PVP to higher wavenumbers. DSC measurements showed different melting temperature, glass transition temperature and enthalpy for the blends and for the single components. Viscosity measurements showed interaction between collagen and PVP also in a dilute water solution.The results have shown, that the interactions between collagen and PVP exist due to the strong interactions between the synthetic and biological component, mainly by hydrogen bonds. These interactions caused that collagen and PVP are miscible at molecular level. The blending of collagen with PVP may give the possibility of producing new materials for potential biomedical applications.     

Oxo-biodegradable polymers - Effect of hydrolysis degree on biodegradation behaviour of poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) is considered to be one of the very few vinyl polymers soluble in water and susceptible to biodegradation in aqueous media by specific microorganisms, implying oxidation of the carbon backbone followed by a random endocleavage of the polymer chains. The overall process does not appear to be appreciably affected by either degree of polymerization (DPn) or degree of hydrolysis (HD) of PVA at least in the 100-1000 and 80-100% ranges, respectively.In order to assess the effect of HD on the biodegradation propensity of PVA, different PVA samples having similar DPn and noticeably different HD values were synthesized by controlled acetylation of commercial PVA (HD = 99%) and submitted to biodegradation tests in aqueous medium, mature compost and soil by using respirometric procedures. Re-acetylated PVA samples characterized by HD of between 25 and 75% underwent extensive mineralization when buried in solid media, whilst PVA (HD = 99%) showed recalcitrance to biodegradation under those conditions. An opposite trend was indeed observed in aqueous solution, thus suggesting that biodegradation is not an absolute attribute directly related to structural features of the substrate under investigation. Boundary conditions related to the framework under which the biodegradation assessment is undertaken have to be taken into account and specifically well defined.     

聚乙烯醇系高分子表面活性剂

聚乙烯醇(PVA)系高分子表面活性剂,可用作乙烯基单体乳液均聚或共聚的乳化剂和氯乙烯(VC)悬浮聚合的分散稳定剂。本文主要介绍它的分类、性能、应用和乳化分散作用机理。     

The miscibility of poly(vinyl alcohol)/poly(N-vinylpyrrolidone) blends investigated in dilute solutions and solids

Poly(vinyl alcohol) (PVA) (polymer A) and poly(N-vinylpyrrolidone) (PVP) (polymer B) are known to form a thermodynamically miscible pair. In the present study the conclusion on miscibility of PVA/PVP solid blends, confirmed qualitatively (DMTA, FTIR) and quantitatively (DSC, χ_AB = − 0.69 at 503 K) is compared with the miscibility investigations of PVA/PVP solution blends by the technique of dilute solution viscometry. The miscibility of the ternary (polymer A/ polymer B/ solvent) system is estimated on the basis of experimental and ideal values of the viscosity parameters k, b and [η]. It is found that the conclusions on miscibility or nonmiscibility drawn from viscosity measurements in dilute solution blends depend: (i) on the applied extrapolation method used for the determination of the viscosity interaction parameters, (ii) on the assumed definition of the ideal values and (iii) on the thermodynamic quality of the solvent, which in the case of PVA depends on its degree of hydrolysis. Hence, viscometric investigations of dilute PVA/PVP solution blends have revealed that viscometry, widely used in the literature for estimation of polymer-polymer miscibility can not be recommended as a sole method to presume the miscibility of a polymer pair.     

Effects of the Molecular Weight of PLGA on Degradation and Drug Release In vitro from an mPEG-PLGA Nanocarrier

We successfully synthesized four kinds of copolymers with varying molecular weights of poly(lactide-co-glycolide)(PLGA) to yield methoxy-poly(ethylene glycol)-block-poly(lactide-co-glycolide)(mPEG-PLGA) nanocarriers:mPEG-PLGA(3k), mPEG-PLGA(9k), mPEG-PLGA(11k) and mPEG-PLGA(16k). An antitumor drug, 10-hydroxycamptothecin(HCPT), was encapsulated into the mPEG-PLGA nanocarrier cores by self-assembly in dialysis. The lower molecular weight nanocarriers degraded more quickly, resulting in mass loss, pH decline, and a rapid HCPT release rate in vitro. The degradation and drug release of the nanocarriers were dependent on the PLGA molecular weight. However, the larger molecular weight nanocarriers could not increase the loading content and encapsulation efficiency. Considering the antitumor effect of these nanocarriers, the mPEG-PLGA(9k) nanocarrier, which had the highest drug loading content[(7.72±0.57)%] and a relatively high encapsulation efficiency[(22.71±5.53)%], is an optimum agent for drug delivery.     

Photochemical stability of poly(vinyl pyrrolidone) in the presence of collagen

The photochemical stability of poly(vinyl pyrrolidone) (PVP) in the presence of 1%, 3% and 5% of collagen has been studied by UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), thermogravimetry analysis (TG) and derivative thermogravimetry (DTG). Surface properties have been studied by contact angle measurements. PVP samples and samples containing 1%, 3% and 5% of collagen were irradiated with UV light of wavelength λ = 254 nm in air for up to 24 h. The amount of gel created during UV irradiation was estimated.PVP in the presence of 1%, 3% and 5% of collagen is less stable both thermally and photochemically. Collagen enhances photochemical processes leading to crosslinking of PVP. The contact angle measurements and values of surface free energy showed that the wettability of PVP films was changed by the addition of collagen and by UV irradiation. The increase of polarity of samples indicates an efficient photooxidation on the surface upon UV irradiation.     

Feasibility of Polyvinyl Alcohol as a Transdermal Drug Delivery System for Terbutaline Sulphate

A series of terbutaline sulphate drug incorporated polyvinyl alcohol (PVA) matrix films were produced by the solvent evaporation method. The effect of xanthan gum and plasticizers (propylene glycol and dibutyl phthalate) on the rate and amount of drug diffusion from PVA membrane across the hydrated cellophane membrane has been evaluated, using an open glass diffusion‐tube. The obtained films were clear, smooth and flexible having sufficient mechanical strength. The mechanical performance of the dry PVA films with xanthan gum and plasticizers were also ascertained. Polyvinyl alcohol‐xanthan gum blends showed a high rate of drug release compared to that of polyvinyl alcohol film alone. Among the two plasticizers employed, propylene glycol showed better permeability. Among different formulations studied, the formulation PVA/xanthan gum/propylene glycol (F7) was found to be an optimized composition for efficient transdermal delivery of the model drug, terbutaline sulphate. The mechanism of drug diffusion has been evaluated using the Peppas model. Stability studies carried out on polymer‐drug formulations revealed that the drug is stable at 40°C and 75% RH for a period of 6 weeks.     

聚乙烯醇/聚乙烯吡咯烷酮碱性复合膜的制备及其性能

通过在不同浓度KOH溶液中进行掺杂,制备出了聚乙烯醇/聚乙烯吡咯烷酮(PVA/PVP)碱性聚合物电解质膜.详尽考察了膜的组成、微观结构、热稳定性、离子电导率和甲醇吸收率.结果表明,PVA与PVP两者具有较好的相容性,当m(PVA)∶m(PVP)=1∶0.5时,膜断面致密、均匀,未发生大尺度相分离.PVP的混入可以极大提高复合膜的电导率和热稳定性.当m(PVA)∶m(PVP)=1∶1时,复合膜的电导率可达2.01×10-3 S.cm-1.PVA/PVP/KOH膜的甲醇吸收率随温度的升高没有明显变化,100℃时其甲醇吸收率仅为同条件下Nafion 115膜的1/4.这表明该复合膜有望作为一种新型的碱性直接甲醇燃料电池用固体电解质膜且可提高膜的使用温度.     

聚环氧乙烷-g-聚己内酯两亲性接枝共聚物的合成及药物释放行为

通过环氧丙醇(GL)与环氧乙烷(EO)的阴离子顺序开环聚合制备了水溶性嵌段共聚物PEO-b-PGL, 以PGL嵌段每个重复单元的侧羟基为引发点进一步引发ε-己内酯(CL)的开环聚合, 合成了结构规整的以聚环氧乙烷(PEO)为主链的两亲性接枝共聚物(PEO-b-PGL-g-PCL). 研究了PEO-b-PGL-g-PCL在水相中的自组装行为, 采用稳态荧光探针法测定了胶束的临界胶束浓度(cmc). 以疏水性药物阿霉素(DOX)为模型药物, 研究了两亲性接枝共聚物的化学组成对药物的扩散释放以及降解释放行为的影响.     

高稳定性化学交联聚乙烯醇/聚乙烯吡咯烷酮碱性固体电解质膜

碱性固体电解质膜的稳定性是影响其在电化学领域应用的一个重要因素.本文在前期研究工作的基础上,通过直接共混和化学交联修饰制备出了聚乙烯醇/聚乙烯吡咯烷酮(PVA/PVP)碱性聚合物电解质膜.采用傅里叶变换红外(FTIR)光谱、热重分析(TGA)、扫描电镜(SEM)和交流阻抗等方法详细考察了复合膜的分子结构、热稳定性、化学稳定性、氧化稳定性和尺寸稳定性.红外光谱结果表明,PVP成功地混入聚合物基体中,在1672cm-1处表现出来自于PVP第I带C襒O的强吸收峰.TGA结果表明,提高掺杂的KOH溶液浓度对PVA/PVP碱性膜的热稳定性没有明显影响.SEM分析结果表明,复合膜经高温、高浓度碱(80℃,10mol·L-1)处理后,其断面结构仍致密均匀,未出现类似小孔等膜降解情况,此时膜电导率(1.58×10-3S·cm-1)相比室温相同碱液时提高91.5%,表明PVA/PVP膜具有很好的耐碱化学稳定性.同时,PVA/PVP碱性膜表现出良好的抗氧化性,在60℃的3%和10%H2O2溶液中处理均没有观察到明显的质量损失,150h后仍能保持原膜质量的89%和85%.此外,由于膜内形成致密的内互交联网络结构,复合膜在水中800h之后也表现出很好的同向性和电导率稳定性.     

Preparation of Colloidal Transition Metals in Polymers by Reduction with Alcohols or Ethers

Colloidal dispersions of rhodium, palladium, osmium, iridium, and platinum are prepared by refluxing the methanol-water solutions of rhodium(III) chloride, palladium(II) chloride, osmium(VIII) oxide, sodium chloroiridate, and chloroplatinic acid, respectively, in the presence of poly(vinyl alcohol) as a protective colloid. The preparations of colloidal dispersions of rhodium are successful in the presence of vinyl polymer with polar group such as poly(vinyl alcohol), polyvinylpyrrolidone, or poly(methyl vinyl ether). Polyethyleneimine, gelatin, polyethylene glycol), and dextran are ineffective as the protective colloid. Water-soluble primary alcohols such as methanol and ethanol, water-soluble secondary alcohols such as 2-propanol, and water-soluble diethers such as 1,4-dioxane are available as reductants for preparation of the colloidal dispersion of rhodium. The average diameters of metal particles in the colloidal dispersions of palladium, rhodium, platinum, iridium, and osmium in poly(vinyl alcohol) are determined by electron microscopy to be 53, 40, 27, 14, and < 10 Å, respectively. The particle size distribution in each colloidal dispersion is sharp within 50 Å wide. The particles in the colloidal dispersions of both iridium and osmium are highly dispersed with no aggregation, while in the colloidal dispersions of rhodium, palladium, and platinum, there exist aggregates of 5-15, 5-30, and 100-200 particles, respectively. Colloidal dispersions of rhodium, palladium, osmium, and platinum are effective as catalysts for hydrogenation of cyclohexene at 30.0°C under atmospheric hydrogen pressure.     

燃料电池用聚乙烯醇基碱性聚合物电解质膜的制备及其性能

通过在不同浓度KOH溶液中进行掺杂,制备出了聚乙烯醇(PVA)、聚乙烯醇/聚乙烯吡咯烷酮(PVA/PVP)和聚乙烯醇/聚乙二醇二甲醚(PVA/PEGDE)碱性聚合物电解质膜详细考察了膜的外观形貌、微观结构、热稳定性、离子电导率和化学稳定性等.结果表明,PVA与PVP以及PEGDE具有很好的相容性,所制备的复合膜断面致密...     

Effect of temperature on the intrinsic viscosity of poly(ethylene glycol)/poly(vinyl pyrrolidone) blends in aqueous solutions

In this work the intrinsic viscosity of poly(ethylene glycol)/poly(vinyl pyrrolidone) blends in aqueous solutions were measured at 283.1–313.1 K. The expansion factor of polymer chain was calculated by use of the intrinsic viscosities data. The thermodynamic parameters of polymer solution (the entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer–solvent interaction parameter and second osmotic virial coefficient) were evaluated by temperature dependence of polymer chain expansion factor. The obtained thermodynamic parameters indicate that quality of water was decreased for solutions of poly(ethylene oxide), poly(vinyl pyrrolidone) and poly(ethylene oxide)/poly(vinyl pyrrolidone) blends by increasing temperature. Compatibility of poly(ethylene oxide)/poly(vinyl pyrrolidone) blends were explained in terms of difference between experimental and ideal intrinsic viscosity and solvent–polymer interaction parameter. The results indicate that the poly(ethylene glycol)/poly(vinyl pyrrolidone) blends were incompatible.     

A novel route to substituted poly(vinyl pyrrolidone)s via simple functionalization of 1-vinyl-2-pyrrolidone in the 3-position by ring-opening reactions

A general synthetic approach is described that allows to obtain novel 1-vinyl-2-pyrrolidone (VP) derivatives with different kinds of functional groups in its 3-position in a one-pot reaction. The strategy used to achieve this goal is the reaction of the carboxamide anion of 1-vinyl-2-pyrrolidone with cyclic precursors of these functionalities. While the driving force for the reactions of three-membered rings is their high annular tension, it is shown here that larger heterocycles can be opened with good yield when additional electron-withdrawing groups are present in the ring. This leads to VP with longer spacer groups between the functionality and the future polymeric main chain. Furthermore, the high versatility of this procedure is demonstrated by the preparation, for the first time, of VP modified with amine or sulfonic functionalities that allow to prepare the corresponding aminated and sulfonated PVPs.     

Synthesis and Drug Release Properties of Thermosensitive Poly(N-vinylacetamide-co-vinylacetate) Hydrogels

Thermosensitive poly[N-vinylacetamide-co-vinylacetate][P(NVA-co-VAc)] hydrogels were prepared via free radical copolymerization from hydrophilic NVA and hydrophobic VAc in the presence of butylenes-bis (N-vinylacetamide)(Bis-NVA) as crosslinker. Scanning electron microscopy(SEM) images reveal that the as-prepared hydrogels were of three-dimensional network with irregular cave structure. The prepared hydrogels with more NVA in the feed swelled faster and the swelling ratio of the hydrogels gradually decrease...     

High-performances membranes for pervaporation I. Poly(vinyl alcohol)–poly(N-vinyl pyrrolidone) blends

Dense membranes were prepared from poly(vinyl alcohol)–poly(N-vinyl pyrrolidone) (PVA–PVP) blends of different compositions and studied in swelling and dehydration by pervaporation of three organic solvents contaminated by 5 wt% water. The swelling generally increases with the PVP content. No extraction occurs in water–tetrahydrofuran (THF) and water–methyl ethyl ketone (MEK) mixtures. In ethanol containing 10 wt% of water, there is no extraction for blends containing less than 40 wt% PVP and an increasing extraction beyond this PVP content. The pervaporation flux of the water–ethanol mixture increases drastically at the same threshold whereas the water permselectivity falls to a low level. The values of the diffusion and permeability coefficients determined from transient permeation of the test water–ethanol mixture exhibit a similar sudden increase at the same PVP content threshold. This singular behavior of the blend membranes is interpreted by a strong affinity of the PVP component to ethanol, combined with a disappearance of crystallites in the blend at this threshold. Consequently the amorphous membrane can swell freely according to the affinity of the PVP component, leading to the observed behavior.     

Synthesis and characterization of poly(vinyl pyrrolidone)-capped bismuth nanospheres

Poly(vinyl pyrrolidone)-capped bismuth nanospheres were synthesized by a simple and convenient wet chemical method. In the process, bismuth nitrate was reduced by ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP) at 185 °C in air. PVP was used as a protecting agent to prevent oxidation of the sperical bismuth particles. PVP molecules were absorbed on the surface of bismuth nanospheres through the interaction of O–Bi bond which was confirmed by Fourier transform infrared (FT-IR) measurement. The thermal analysis shows the samples contained about 73 wt.% metallic bismuth. The optical absorption spectrum of poly(vinyl pyrrolidone)-capped bismuth nanosphere shows a strong absorption band at 275 nm.