摘要:

AbstractAn enzyme multilayer film composed of glucose oxidase and glucoamylase alternating with a bipolar quaternary ammonium salt was achieved on the surface of a quartz slide or a gold electrode and its application as a bienzyme maltose sensor was studied.

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970111

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractGas‐phase copolymerizations of ethylene with 1‐butene over MgCl2‐supported titanium catalysts after prepolymerization were studied. The activity of a catalyst treated by ethylene/1‐butene prepolymerization “prep‐cat‐2” for the copolymerization is not affected by the monomer composition in the range of 0–10 mol‐% of 1‐butene, but it is higher than that of the homopolymerization of ethylene with a catalyst treated by ethylene prepolymerization “prep‐cat‐1”. Comparative studies of the polymerizations in the gas‐phase and in slurry reactors showed differences in the rate‐time profiles. The higher activities in the early stage and declining kinetics for the gas‐phase polymerizations can be considered to be due to the higher macroparticle diffusivity and to fast deactivation of the active centres which has been confirmed by the determination of the oxidation state of titanium in the catalyst. Data from determinations of monomer reactivity ratios indicated that the gas‐phase process favours the incorporatio

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970112

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractDehalogenation polycondensation of 2,5‐dibromopyridine, 2,5‐Br2‐Py, to poly(pyridine‐2,5‐diyl), PPy, has been achieved under electrochemical reductive conditions mediated by various nickel(II) and palladium(II) complexes (nickel‐2,2′‐bipyridine (bpy) and ‐phosphine complexes and palladium‐bpy complexes). PPy is obtained as a thin smooth film on a platinum electrode in high yield, and among the nickel and palladium complexes [Ni(bpy)3]2Br2serves as the best mediator for the electrochemical reductive polycondensation. Carrying out the electrochemical polycondensation in a two‐compartment cell and in a one‐compartment cell gives almost the same results. The PPy film prepared by using the nickel(II) complex gives the same IR and cyclic voltammogram as chemically prepared authentic PPy shows. When PdCl2(bpy) is used as the mediator, the formation of PPy is accompanied by metalation react

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970113

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe phase separation states of hemicellulose and lignin in their blends were investigated by means of contact angle measurements. The hysteresis behavior in dynamic contact angles suggested that a phase separation of cluster‐state type (not of random dispersion type) took place at hemicellulose‐rich and lignin‐rich mixing ratios. It may be caused by the low cohesive force between hemicellulose and lignin molecules. Further, the total surface tension, and the balance between dispersion and polar forces in the total surface tension were evaluated from the equation of Wu. It was found that in the region of a hemicellulose‐rich mixing ratio, the polar and dispersion forces of the surface tension of the solid were reduced and raised, respectively, and in contrary to this, in the lignin‐rich region, the former were raised and the latter were reduced. The polymer‐polymer interaction parameter of Flory between hemicellulose and lignin depends on the mixing ratio as reported previously; this may be ascribed to a difference of the balancing of polar‐disp

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970114

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractPoly(aryl ether ketone ketone)s (PEKKs) are prepared via a Friedel‐Crafts acylation reaction with diphenyl ether and terephthalic acid (T) and/or isophthalic acid (I). The crystal structure, polymorphism and morphology of three PEKK homopolymers have been investigated using transmission electron microscopy (TEM), electron diffraction (ED) and wide angle X‐ray diffraction (WAXD) experiments. The PEKKs studied consist of either allpara‐phenylene linkages [PEKK(T)], onemeta‐phenylene linkage [PEKK(I)] or alternating T and I isomers [PEKK(T/I)]. PEKK(T) and PEKK(T/I) show crystalline polymorphism depending upon the crystallization conditions and methods. In PEKK(T) two forms (I and II) can be observed, and their unit cell dimensions and symmetry groups are determined via ED experiments. A possible epitaxial relationship between these two forms is proposed when they coexist. PEKK(I) possesses only one crystal unit cell which belongs to the same category as the form I structure in PEKK(T). Thec‐axis dimension of the unit cell has been determined as three phenylenes having a zig‐zag conformation, with themeta‐phenylene lying on the backbone plane. PEKK(T/I) shows a complicated polymorphism. In addition to forms I and II, as in the case of PEKK(T), a possible form III is

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970115

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe thermal degradation of polyisobutylene is characterized by kinetics consisting of four types of intramolecular hydrogen abstraction (back‐biting) of primary (p) and tertiary (t) terminal macroradicals (R p˙and R t˙) and the successive β scission at the inner position of the main chain. This reaction affords four types of terminal monoolefins in the volatile oligomers. Assuming the reaction occurs competitively under a steady state regarding the on‐chain macroradicals, the composition of the monoolefins are represented as the rate ratios of the respective back‐biting processes. The rate ratio between the abstractions of different types of hydrogens (CH2and CH3) from the same type of macroradicals is expressed only by the rate constant ratio. The (TTD)p/(TVD)pand (TTD)t/(TVD)tratios remain constant during degradation, independently of the decreases in volume and molecular weight of the reacting polymers and this tendency agrees fairly well with the kinetic expectation. This result suggests that back‐biting depends only on the local motion of the reacting chain ends. The ratios between the abstractions of the same type of hydrogen from different macroradicals are expressed by the product of the rate constant ratio and the integrated macroradical concentration ratio ([R p˙]/[R t˙]). The observed values of (TTD)p/(TTD)tand (TVD)p/(TVD)tdecrease with reaction time. This decrease results from the decrease in macror

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970116

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractMicrogels were synthesized by intramolecular crosslinking of poly(vinyl alcohol) single chains with glutaraldehyde in dilute aqueous solutions (concentrationc= 0,1 g/100 mL). The degree of crosslinking was varied fromX= 0 toX= 150 (Xis the number of crosslinker molecules per chain). The reaction products were characterized by static and dynamic light scattering and viscosity measurements. A clear shrinking of molecular dimensions could be observed with increasing degree of crosslinking, since the radius of gyrationRg, and with that, thep‐parameter (p=Rg/Rh) decrease with the number of intramolecular crosslinks. A similar behavior is seen from viscosity measurements. The intrinsic viscosity [η] decreases with increasingX‐parameter and depends only very weakly on the temperature which is an indication of a loss in flexibility and therefore for a relatively fixed struc

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970117

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe synthesis of the model compounds 2‐(4‐methoxyphenylazo)anthraquinone (1) and 2‐[4‐(6‐acetoxyhexyloxy)phenylazo]anthraquinone (2), the monomer 2‐[4‐(6‐methacryloyloxyhexyloxy)phenylazo]anthraquinone (3) and the polymethacrylate poly‐3via radical polymerization of3is described. The electrochemical behaviour of poly‐3is studied by cyclic voltammetry in comparison with1and2. Poly‐3can be reduced and oxidized reversibly in solution and in thin films in a two‐step redox process. Therefore, poly‐3is a potential material for a molecular device system using the e

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970118

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe feasibility of synthesizing high‐molecular‐weight amino acid based bioanalogous polymers (AABBPs)‐poly(urethane amide)s (PUA) — via polycondensation (PC) of di‐p‐nitrophenyl ester ofN,N′‐(trimethylenedioxydicarbonyl)bis(L‐phenylalanine) (3) with diamines or their derivatives under mild conditions in organic solvents was studied for the first time. A regular PUA (ηred= 1,53 dL/g) was obtained by PC of3with hexamethylenediamine. A dipeptide (Phe‐Phe) containing regular poly(ester urethane amide) (ηred= 0,58 dL/g) was synthesized by PC of3withp‐toluenesulfonic acid salt of bis(L‐phenylalanine) 1,4‐butylene diester. A tripeptide (Phe‐Lys‐Phe) containing PUA (ηred= 0,38 dL/g) with pendent ester groups was prepared via PC of3withN,N‐bis(trimethylsilyl)‐L‐lysine methyl ester. These novel AABBPs which may be considered as structural analogs of AB type bioanalogous polymers — conventional poly(amino acids) are of interest in enzymology, immunology, pharmacology, and biotechnology (a

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970119

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractIn this feature article we review the synthesis of polymerizable vinyl sugars. Many such syntheses start from isopropylidene‐protected sugars, which still have a free OH‐group. These compounds are then converted to polymerizable monomers by esterification or etherification. Selective reactions at non‐protected sugars, introducing polymerizable groups, can be achieved by enzymatic catalysis. Alternatively, such selective transformations may be accomplished by chemical reaction at the reducing group of the sugar either directly or after transforming the half‐acetal to a more reactive intermediate. Furthermore, results are described on the synthesis of vinyl sugars whose vinyl group is connected with the monosaccharide by a CC bond. Such monomers can be polymerized by radical as well as by anionic initiation. In this case a chemically very stable connection is obtained in the resulting polymers between the sugar moiety and the polymer

ISSN:1022-1352    

DOI:10.1002/macp.1996.021970120

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY