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1.
Polyvinyl alcohol (PVA)-based proton conducting polymer electrolytes have been prepared by the solution cast technique. The
conductivity is observed to increase from 10−9 to 10−4 S cm−1 as a result of orthophosphoric acid (H3PO4) addition. The plot of conductivity vs temperature shows that a phase transition occurred at 343 K in the sample PVA-33 wt%
H3PO4. The β-relaxation peak is observed at 313 K. The glass transition temperature of PVA-33 wt% H3PO4 is 343 K. Orthophosphoric acid seems to play a dual role, i.e., as a proton source and as a plasticizer. The ac conductivity
σ
ac = Aω
s was also calculated in the temperature range from 303 to 353 K. The conduction mechanism was inferred by plotting the graph
of s vs T from which the conduction mechanism for sample PVA-17 wt% H3PO4 was inferred to occur by way of the overlapping large polaron tunneling (OLPT) model and the conduction mechanism for the
sample PVA-33 wt% H3PO4 by way of the correlated barrier height (CBH) model. 相似文献
2.
3.
4.
聚乙烯醇高含水胶固定化脲酶的研究 总被引:2,自引:0,他引:2
冷冻-部分脱水法制成的聚乙烯醇高含水胶固定化脲酶活力收率及对脲素的分解能力明显高于聚丙烯酰胺囱定化脲酶,稳定性相近;用低浓度的戊二醛后处理,提高了固定化酶的稳定性。 相似文献
5.
Yongcheng Liu Xin Chen Jianghong Qian Haiying Liu Zhengzhong Shao Jiaqi Deng Tongyin Yu 《Applied biochemistry and biotechnology》1997,62(2-3):105-117
The structure and properties of the blend of regenerated silk fibroin (RSF) and poly(vinyl alcohol) (PVA) were investigated.
The two polymers in the blend are in the state of phase segregation. Infrared (IR) spectra indicate that the RSF in the blend
maintains its intrinsic properties, thus, ethanol treatment can transfer silk I structure of RSF to silk II structure. The
water absorption property and mechanical property of the blend are improved in comparison with those of RSF. The blend maintains
the major merit of RSF, that is, it can immobilize glucose oxidase on the basis of the conformational transition from silk
I structure to silk II structure. The properties of the immobilized enzyme are examined. Moreover, the second generation of
glucose sensor based on the immobilized enzyme is fabricated and it has a variety of advantages including easy maintenance
of enzyme, simplicity of construction, fast response time and high stability. 相似文献
6.
ChangLuSHAO HongYuGUAN ShangBinWEN BinCHEN XingHuaYANG JianGONG YiChunLIU 《中国化学快报》2004,15(4):492-494
Thin PVA/cobalt acetate composite fibers were prepared by using sol-gel processing and electrospinning technique.After calcination of the above precursor fibers,Co3O4 nanofibers with a diameter of 50-150 nm could be successfully obtained.The fibers were characterized by SEM,FT-IR,WAXD,respectively. 相似文献
7.
Ok Hyung Kim Kangseok Lee Kijung Kim Byung H. Lee Soonja Choe 《Colloid and polymer science》2006,284(8):909-915
The optimum conditions for preparing micron-sized monodisperse polymethylmethacrylate (PMMA) beads by dispersion polymerization in a methanol/water mixture were proposed. PMMA forming microspheres having an average molecular weight of 55,300 g/mol, 2.6 μm weight-average diameter, with a 5.3% coefficient of variation and 91% conversion, were successfully obtained in the presence of 15 wt.% of polyvinylalcohol (PVA), 100/50 (g/g) of MeOH/water mixtures at 70°C; the reaction lasted for 8 h. Compared to dispersion polymerization using polyvinylpirrolydone, PVA proved to be an extremely stable steric stabilizer in the dispersion polymerization of methylmethacrylate. 相似文献
8.
PVA/PVP共混物的聚集态结构 总被引:2,自引:0,他引:2
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。 相似文献
9.
Jeong Hyun Yeum Byung Chul Ji Chul Joo Lee Ji Youl Lee Sang‐Seob Lee Sam Soo Kim Joon Ho Kim Won Seok Lyoo 《Journal of polymer science. Part A, Polymer chemistry》2002,40(8):1103-1111
To prepare water‐soluble, syndiotacticity‐rich poly(vinyl alcohol) (PVA) microfibrils for various industrial applications, we synthesized syndiotacticity‐rich, low molecular weight PVA by the solution polymerization of vinyl pivalate (VPi) in tetrahydrofuran (THF) at low temperatures with 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN) as an initiator and successive saponification of poly(vinyl pivalate) (PVPi). Effects of the initiator and monomer concentrations and the polymerization temperature were investigated in terms of the polymerization behaviors and molecular structures of PVPi and the corresponding syndiotacticity‐rich PVA. The polymerization rate of VPi in THF was proportional to the 0.91 power of the ADMVN concentration, indicating the heterogeneous nature of THF polymerization. The low‐temperature solution polymerization of VPi in THF with ADMVN proved to be successful in obtaining water‐soluble PVA with a number‐average degree of polymerization (Pn) of 300–900, a syndiotactic dyad content of 60–63%, and an ultimate conversion of VPi into PVPi of over 75%. Despite the low molecular weight of PVA with Pn = 800, water‐soluble PVA microfibrillar fibers were prepared because of the high level of syndiotacticity. In contrast, for PVA with Pn = 330, shapeless and globular morphologies were observed, indicating that molecular weight has an important role in the in situ fibrillation of syndiotacticity‐rich PVA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1103–1111, 2002 相似文献
10.
Zn‐Al‐salicylic nanohybrid layers have been prepared and used as fillers for polyvinyl alcohol (PVA). Nanohybrid layers of a broad absorption area in UV region were completely and uniformly dispersed in a continuous polymer matrix. PVA and PVA nanohybrid composite (NHC) films were exposed to UV irradiation. Thermal properties (diffusivity, effusivity, and conductivity) of both have been measured through photoacoustic technique before and after UV irradiation. Thermal parameters of PVA suffered from a quick deterioration with UV exposure due to reduction of the phonon mean free path as a result of molecular chain scissions. However, significant stability in such parameters of NHC has been obtained under the influence of UV irradiation. This thermal properties stability may be an important step on the way of obtaining photostable polymer NHC. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献