结晶-非晶共混体系的结晶行为研究——PEO/PMMA与PEO/PVA共混物

用DSC和傅里叶红外(FTIR)光谱表征PEO/PMMA和PEO/PVA共混体系的结晶行为。发现PEO/PVA体系的结晶度与其组成的变化是一致的;而PEO/PMMA体系的结晶度随非晶组分增加而下降的速度,从与组成变化一致到比后者快,但又随时间而改变。对此结晶/非晶共混体系的结晶度随组成和时间而变化的现象,可用体系的玻璃化转变温度(T_g)来解释。     

PVA/PVP共混物的SAXS研究

聚乙烯醇(PVA)/聚吡咯烷酮(PVP)共混物的小角X-射线散射(SAXS)研究表明,PVA/PVP共混物的结构参数与共混物组分比及热历史密切相关。按Vonk一维电子密度相关函数法,得到PVA/PVP共混物的长周期,过渡层厚随PVP组分含量增加而增加;结晶片层厚和比内表面积却随PVP含量增加而降低。热处理可提高共混物的结晶性。     

聚乙烯醇/聚乙烯基吡咯烷酮共混体系相容性研究

用DSC、FTIR、SAXS和测定Flory-Huggins相互作用参数等方法对聚乙二醇(PVA1)/聚乙烯基吡咯烷酮(PVP)共混体系的研究。结果表明,该体系具有完全互容的性质。共混物只有一个玻璃化转变温度。用DMSO作溶剂浇铸的膜光学透明。PVA1的长周期和片晶厚度均随PVP含量增加而增大,但后者增大的幅度比前者小得多,表明PVP和PVA1的非晶部分形成均相并夹入到球晶内部。共混物中PVP羰基吸收峰和PVA1的羟基吸收峰与相应均聚物相比,在红外光谱图中皆向低频方向迁移,迁移波数随第二组分含量的增加而增大。表明二者间有氢键生成。用平衡熔点计算的Flory-Huggins相互作用参数为-0.88。     

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.     

PEO／PVP共混体系结晶行为

本文用WAXD、PLM、DSC方法研究了聚氧化乙烯(PEO)/聚乙烯基吡咯烷酮(PVP)共混体系的结晶行为,探索了两组分聚合物间相互作用及体系结晶度与非晶组分含量的关系。DSC研究表明PEO/PVP共混体系具有两个玻璃化转变温度,分别是纯组分的T_g,无相容性。应用Avrami和LH方程对其动力学参数进行了研究。偏光显微镜观察了共混物结构形态。     

聚环氧乙烷(PEO)与聚醋酸乙烯酯(PVA)的共混研究

动态力学谱研究表明熔融共混PVA/PEO体系的无定形态中存在着纯PEO及PVA/PEO的相容或部分相容相。相容或部分相容相的T_g随共混物组成的变化远高于按照FOX方程的计算值。用结晶和分子间相互作用解释了这种对FOX方程的偏离。应用FTIR差示光谱技术对PVA/PEO共混物和PVA/DGDE浓溶液的研究证实了PVA分子链上酯基和PEO分子链存在着强的相互作用。     

热塑性聚酰亚胺与聚醚醚酮共混物的等温结晶动力学

采用熔融共混方法制备了热塑性聚酰亚胺(TPI)与聚醚醚酮(PEEK)的共混物; 用示差扫描量热分析(DSC)研究了共混物的等温结晶动力学. 分别采用Avrami方程和Hoffman-Lauritzen方程分析共混物的等温结晶动力学、端表面自由能(σe)和分子链折叠功(q). 结果表明, 加入TPI后PEEK的结晶速率降低, 结晶活化能、σe和q均增加. 但这些数值的变化与TPI含量不呈线性关系, 并从共混物的相容性和表面形貌给出了可能的解释.     

PVA／PVP共混物的聚集态结构

热处理前后不同组份比二元共混物聚乙烯醇(PVA)和聚乙烯吡咯烷酮(PVP)的聚集态结构研究表明,热处理可明显提高共混物的结晶性。热处理前样品仅观察到(101)晶面衍射,热处理后可观察到4个以上衍射晶面。结晶度和微晶大小随共混物中PVP含量增加而降低。第二类晶格畸变则随PVP含量增加而增大。     

聚(L-丙交酯)/聚(DL-丙交酯)的结晶性能及相溶性

用共溶液沉淀法制备了聚 (L 丙交酯 ) 聚 (DL 丙交酯 )共混物 (PLLA PDLLA) ,然后用成纤模压法压制成3 2mm的棒材 .用差示扫描量热法研究了共混物的结晶性能和相溶性 .结果表明 ,PLLA组分在共溶液沉淀过程中可生成结晶 ,共混物中PDLLA含量直到 30 %时 ,PLLA组分的结晶熔融温度和结晶度与纯PLLA相同 ,但PDLLA含量为 5 0 %时 ,PLLA组分的结晶熔融温度和结晶度明显下降 .由于加工成型条件的不一致性 ,共混物棒材中的PLLA组分的结晶熔融温度和结晶度呈较大的分散性 .共混物从熔体降温 ,在其后的升温DSC扫描中出现分别相应于PDLLA和PLLA的玻璃化转变 ,表明PDLLA与未结晶的PLLA形成的非晶相是不相溶的     

PC/PET/EPDM共混体系的结晶与熔融行为

本文用解偏振光法与DSC法分别测定并研究了PC/PET/EPDM共混体系的结晶速度、结晶度、Avrami指数(n)和熔融温度及其影响因素,共混物中PET的结晶速度、结晶度均随PC含量增加而下降;EPDM用量不超过10%时,可提高PET的结晶速度,但不影响结晶度和成核与增长方式,n值不变。当EPDM为5%时,结晶速度呈现极大值。经退火处理的共混物呈现熔融双峰,PC量增加,高温熔融峰略移向高温方向;热处理温度升高或时间延长,则低温熔融峰移向高温方向。     

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.     

Acrylonitrile–maleic anhydride copolymer membrane (I): effects of casting conditions

The effects of casting conditions, including casting solution (composition and temperature) and coagulation conditions (pre‐evaporation time, temperature and concentration of coagulation bath) on the structure and performance of acrylonitrile–maleic anhydride copolymer membrane have been investigated. The results showed that the water flux decreased gradually while the rejection of bovine serum albumin (BSA) decreased as the concentration of copolymer increased. When the total solid concentration was kept unchanged, the water flux increased with additive polyvinylpyrrolidone (PVP), the rejection did not decrease until the ratio of PVP/copolymer was 60%. When the content of copolymer in the casting solution was kept constant, the water flux decreased rapidly while the rejection increased a little (compared with the case of no additive) as the ratio of PVP/copolymer increased. As to the temperature of casting solution, the water flux had a maximum at 45 °C and the rejection had a maximum and a minimum at 45 and 55 °C, respectively. The water flux had a maximum value when the pre‐evaporation time was 40 sec. The rejection of BSA was almost unchanged when the pre‐evaporation time was less than 40 sec. and then decreased and reached a minimum value at 60 sec. As the temperature of coagulation bath increased, the water flux reached a maximum at 35 °C while the rejection increased uniformly. With increasing the concentration of DMSO in the coagulation bath, the water flux decreased gradually and got to a minimum at 50 wt% as the concentration of dimethylsulfoxide in the coagulation bath increased, but no apparent effect on the rejection was observed. Copyright © 2000 John Wiley & Sons, Ltd.     

Preparation of Polyvinyl Pyrrolidone-Based Hydrogels by Radiation-Induced Crosslinking with Potential Application as Wound Dressing

Polyvinyl pyrrolidone/polyethylene glycol hydrogels (PVP/PEG) and PVP/PEG/Starch were prepared by irradiating the mixtures of aqueous solutions of PVP, PEG and starch with electron beam at different doses. Their properties were evaluated to identify their usability in wound dressing applications. The physical properties of the prepared hydrogels, such as gel content, swelling, water content and degree of water evaporation with varying composition and irradiation dose were examined to evaluate the usefulness of the hydrogels for wound dressing. The gel content increases with increasing PVP concentration due to increased crosslink density, and decreases with increasing the PEG concentration. PEG seems to act not only as plasticizer but also to modify the gel properties as gelation% and maximum swelling. Mechanical experiments were conducted for both PVP/PEG and PVP/PEG/Starch. The adding of PEG and starch to PVP significantly improves elongation and tensile strength of prepared hydrogels, respectively. The crystallinity of both prepared hydrogels was investigated with varying their components, XRD studies indicated that the crystallinity in the gel was mainly due to PVP and mainly decreased with enhanced starch content. The prepared hydrogels had sufficient strength to be used as wound dressing and could be considered as a good barrier against microbes.     

Effect of γ irradiation on the surface properties of wet polysulfone films containing poly(vinylpyrrolidone)

In Japan, hemodialyzers are usually sterilized by γ irradiation. However, the polymer materials used in the dialysis membrane, such as polysulfone (PSf) and poly(vinylpyrrolidone) (PVP), undergo crosslinking or degradation on exposure to γ radiation. In the present study, we prepared PSf/PVP films (PVP content, 0–50 wt%) and used atomic force microscopy (AFM) to perform nanoscale evaluations of the effect of γ irradiation (25 and 50 kGy) on the surface properties of wet PSf/PVP surfaces. Force‐curve measurements were used to evaluate the hardness of and fibrinogen adsorbability on the wet PSf/PVP surface; fibrinogen adsorbability on the wet PSf/PVP surface was evaluated using AFM probes with fibrinogen immobilized on the tips of the probes. At PVP levels greater than 5 wt%, the wet PSf/PVP film surface was completely covered with hydrated and swollen PVP particles. The surface hardness of the wet PSf/PVP films exposed to 25‐kGy γ irradiation greatly decreased with increasing PVP content, whereas the surface hardness of the wet PSf/PVP films exposed to 50‐kGy γ irradiation did not decrease significantly. At higher PVP levels, the reduction in the fibrinogen adsorbability on a wet PSf/PVP film exposed to 25‐kGy γ irradiation was more significant than that on a wet PSf/PVP film exposed to 50‐kGy γ irradiation. PVP particles on the wet PSf/PVP film surface exposed to 50‐kGy γ irradiation did not show significant hydration and swelling because the polymer materials PVP–PSf and PVP‐PVP in these membranes has undergone excessive crosslinking due to γ irradiation. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of highly monodisperse polystyrene microspheres via dispersion polymerization using an amphoteric initiator

The highly monodisperse polystyrene (PS) microspheres were produced by dispersion polymerization using an amphoteric initiator, 2,2'-azobis [N-(2-carboxyethyl)-2-2-methylpropionamidine] (VA-057). The polymerization characteristics were investigated and compared with conventional initiators, 2,2-azobis(isobutyronitrile) (AIBN) and benzoyl peroxide (BPO). The monodisperse PS microspheres having the coefficient of variation (C(v)) of diameter all less than 4% are obtained at very low stabilizer, poly(vinyl pyrrolidone) (PVP) concentrations of 1 and 2 wt%. It is found that the size dependence of the VA-057 system, D(n) proportional, variant [VA-057](0.267), is less sensitive than a conventional initiator system. When the same amount, 2 wt%, of AIBN, BPO, and VA-057 is used under the identical PVP concentration of 2 wt%, the D(n)/C(v)'s are 1.95/11.57, 1.47/22.44, and 2.08 microm/2.50%, respectively. The uniformity of particles was characterized employing an optical analyzer, Turbiscan. For the VA-057 system, the back scattering intensity is linearly reduced with time having a constant sedimentation rate of 48.98 microm/min throughout the settling process. The uniformity of PS particles in the VA-057 system stems from (1) the higher rate of polymerization in early stage of polymerization, followed by significantly faster reduction of the rate, and (2) good dispersion stability of primary particles. Therefore, it is found that the use of an amphoteric initiator, VA-057, is promising for producing monodisperse particles in dispersion polymerization.     

The Effect of the Molecular Weight of Polyvinylpyrrolidone and the Model Drug on Laser-Induced In Situ Amorphization

Laser radiation has been shown to be a promising approach for in situ amorphization, i.e., drug amorphization inside the final dosage form. Upon exposure to laser radiation, elevated temperatures in the compacts are obtained. At temperatures above the glass transition temperature (T_g) of the polymer, the drug dissolves into the mobile polymer. Hence, the dissolution kinetics are dependent on the viscosity of the polymer, indirectly determined by the molecular weight (M_w) of the polymer, the solubility of the drug in the polymer, the particle size of the drug and the molecular size of the drug. Using compacts containing 30 wt% of the drug celecoxib (CCX), 69.25 wt% of three different M_w of polyvinylpyrrolidone (PVP: PVP12, PVP17 or PVP25), 0.25 wt% plasmonic nanoaggregates (PNs) and 0.5 wt% lubricant, the effect of the polymer M_w on the dissolution kinetics upon exposure to laser radiation was investigated. Furthermore, the effect of the model drug on the dissolution kinetics was investigated using compacts containing 30 wt% of three different drugs (CCX, indomethacin (IND) and naproxen (NAP)), 69.25 wt% PVP12, 0.25 wt% PN and 0.5 wt% lubricant. In perfect correlation to the Noyes–Whitney equation, this study showed that the use of PVP with the lowest viscosity, i.e., the lowest M_w (here PVP12), led to the fastest rate of amorphization compared to PVP17 and PVP25. Furthermore, NAP showed the fastest rate of amorphization, followed by IND and CCX in PVP12 due to its high solubility and small molecular size.     

热致液晶聚酯酰亚胺的非等温相转变动力学研究

以差示扫描量热法对热致液晶聚酯酰亚胺的结晶过程和液晶化过程的非等温相转变动力学行为进行了初步研究，根据Ｊｅｚｉｏｒｎｙ方法处理数据得到了表征聚合物非等温相转变动力参数Ｚｃ，Ｇｃ并对其进行了讨论，结果表明，在所研究的条件下聚合物的相转变过程基本上符事Ｊｅｚｉｏｒｎｙ结论，但两种相转变的成核与生长方式是不同的。     

ATRP-template dispersion polymerization of methacrylic Acid/PVP

ATRP-template dispersion polymerization of methacrylic acid （MAA） on the template of polyvinyl pyrrolidone （PVP K-30） was carried out in the aqueous solution by using methyl 2-bromopropionate （MBP）/CuC1/2,2＇-bipyridine （bpy） as the initiation system. The scanning electron microscopy （SEM）, dynamic light scattering （DLS） and gel permeation chromatography （GPC） were employed for evaluating the results of polymerization. As a result, the minimonomer droplets formed due to the H-bond interaction of PVP-MAA. The stability of droplets was dependent on pH and the concentrations of both PVP and MAA. When pH 〈 2, the coagulum of PVP-MAA formed, whereas when pH 〉 4.5, the droplets were not observable by DLS. In order to prepare the stable latex, the concentration of PVP should be lower than 9 wt%, whilst the concentration of MAA should be lower than 5.5 wt%. The optimum condition was pH 2.4, PVP 4.76 wt% and MAA 5 wt%, by which the stable latex of ca. 50 nm nanoparticles of PMAA/PVP was prepared by ATRP polymerization and simultaneously the molar mass of PVP was duplicated by PMAA according to GPC diagrams. In contrast, by using AIBN, KPS and KPS-Na2SO3 redox initiation system, the coagulum accompanying with the larger molar mass of PMAA was obtained, irrespective of pH and concentrations of PVP and MAA.     

Effect of water-soluble polymers, polyethylene glycol and poly(vinylpyrrolidone), on the gelation of aqueous micellar solutions of Pluronic copolymer F127

The micellization of F127 (E(98)P(67)E(98)) in dilute aqueous solutions of polyethylene glycol (PEG6000 and PEG35000) and poly(vinylpyrrolidone) (PVP K30 and PVP K90) is studied. The average hydrodynamic radius (r(h,app)) obtained from the dynamic light scattering technique increased with increase in PEG concentration but decreased on addition of PVP, results which are consistent with interaction of the micelles with PEG and the formation of micelles clusters, but no such interaction occurs with PVP. Tube inversion was used to determine the onset of gelation. The critical concentration of F127 for gelation increased on addition of PEG and of PVP K30 but decreased on addition of PVP K90. Small-angle X-ray scattering (SAXS) was used to show that the 30 wt% F127 gel structure (fcc) was independent of polymer type and concentration, as was the d-spacing and so the micelle hard-sphere radius. The maximum elastic modulus (G(max)(')) of 30 wt% F127 decreased from its value for water alone as PEG was added, but was little changed by adding PVP. These results are consistent with the packed-micelles in the 30 wt% F127 gel being effectively isolated from the polymer solution on the microscale while, especially for the PEG, being mixed on the macroscale.     

Nanotechnological evaluation of protein adsorption on dialysis membrane surface hydrophilized with polyvinylpyrrolidone

Hydrophilizing synthetic polymer dialysis membranes with polyvinylpyrrolidone (PVP) play an important role for inhibition of protein adsorption on membrane surface. In the present study, the effect of PVP on protein adsorption was evaluated from a nano-scale perspective. Swelling behavior of PVP present on wet polysulfone (PS)/PVP film surfaces was observed by atomic force microscopy (AFM). Fibrinogen and human serum albumin (HSA) were immobilized on the tip of AFM probes, with which a force-curve between protein and wet PS/PVP film surface was measured by AFM while scanning in order to visualize two-dimensional protein adsorbability on film surfaces. Furthermore, HSA adsorbability on non-PVP containing PEPA dialysis membrane (FLX-15GW) and PVP containing PEPA dialysis membrane (FDX-150GW) was evaluated by the AFM force-curve method. As a result, PS/PVP film surface was completely covered with hydrated and swollen PVP at 5 wt% or more PVP content. Protein adsorbability on PS/PVP film surfaces decreased greatly with increasing content of PVP. The adsorption of HSA was inhibited by the presence of PVP on film surfaces more significantly than that of more hydrophobic fibrinogen. HSA adsorbability on wet FLX-15GW dialysis membrane surface was 428 ± 174 pN whereas that on wet FDX-150GW dialysis membrane surface was 42 ± 29 pN.