ISSN:0007-1641    

DOI:10.1002/pi.4980230302

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980230303

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe abundance and renewability of lignocellulosic materials renders them to be a promising feedstock for production of energy, food and chemicals. Enzymatic hydrolysis of lignocellulose into fermentable sugars has been extensively studied in order to reach a more efficient utilization of renewable biomass energy. Enzymatic hydrolysis of lignocellulose means degradation of cellulose toD‐glucose, but the mechanism of cellulose hydrolysis by enzymes is still not well understood.This paper deals with processes for obtaining lignocellulosic materials, for converting them into fermentables by use of acid and enzyme hydrolysis, and for fermentation of the sugars to useful product

ISSN:0007-1641    

DOI:10.1002/pi.4980230304

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractPoly(5‐(4‐phenylazobenzyl)‐L‐glutamate) was synthesized to study the photoinduced helix coil transition of a unipolymer. The crucial point in the synthesis is the selective esterification of theL‐glutamic acid, which was carried out as an alcoholysis of theN‐protected cyclic anhydride. The 5‐ester was treated with phosgene to óbtain theN‐carboxyanhydride, which was polymerized by base catalysis. The polymer was investigated in dilute dioxane solutions. The photoinduced transition was followed by means of UV spectroscopy for the chromophore and viscosimetric experiments for the configuration of the polymer chain. The changes in viscosity are more complex than expected for a helix coil transition, so aggregates have to be ta

ISSN:0007-1641    

DOI:10.1002/pi.4980230305

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractPoly(adipic anhydride) (PAA), poly(sebacic anhydride) (PSA) and poly(dodecanoic anhydride) (PDA) were prepared from the mixed anhydrides of diacids and ketene (in tetrahydrofuran (THF) solution), the mixed anhydrides being subjected to melt polycondensation. The polymerizations were carried out in the presence of diethyl zinc as a catalyst. The polymers were characterized by means of1H NMR, IR spectroscopy, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The polymer yields and the molecular weights of the polymers increased in the presence of catalyst. From these results a mechanism for the reaction is proposed. The highest melting temperature of the resultant polymers was obtained from PDA (Tpeak= 90°C). The heat of fusion was approximately 100 J/g (PDA). The number‐average and weight‐average molecular weights of the polyanhydrides were 18000 and 33000 respectively (PDA). Poly(anhydride)‐b‐poly(ethylene glycol) and poly(anhydride)‐b‐poly(tetramethylene glycol) copolymers were prepared from the mixed anhydrides of dodecanoic acid, poly(ethylene glycol)‐succinic half‐ester and poly(tetramethylene glycol)‐succinic half‐ester respectively. The block copolymers were characterized by means of1H NMR, IR and GPC. The hydrolytic degradation of PDA has been studied in a buffered salt solution (pH 7·2) at 37°C by examining the changes in molecular weight, heat of fusion, mass loss and surface structure of m

ISSN:0007-1641    

DOI:10.1002/pi.4980230306

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractPreparation, some properties and applications of the bioanalogous poly(alkylene phosphates), obtained according to the methods elaborated in these authors' laboratory, are reviewed. Ring‐opening polymerization, polyaddition, and two‐step polycondensation methods are effective in the synthesis of polymers with various moieties of nucleic and teichoic acids (NA and TA, respectively). The major aim of the work is to find relatively simple methods allowing high molecular weight polymers to be prepared. Thus, preparation of poly(glycerol phosphate) and poly(trimethylene phosphate) bearing NA bases and related polymers withM¯n⩾ 104are des

ISSN:0007-1641    

DOI:10.1002/pi.4980230307

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractSince poly(α‐malic acid) is a biodegradable and bioabsorbable lactic acid type polyester having pendent carboxylic acid groups, it is of interest for application as the polymer carrier to covalently attach both a parent drug and a targeting agent. In order to provide a macromolecular prodrug of 5‐fluorouracil (5FU) with reduced side‐effects and exhibiting high antitumor activity, the covalent attachment of 5FU to poly(α‐malic acid) through hydrophobic spacer groups, ester or amide and carbamoyl groups was carried out. In order to estimate the release behavior of 5FU from poly(α‐malic acid)‐5FU conjugates, the hydrolysis of the pendent ester or amide and carbamoyl groups in the conjugates obtained was investigatedin vitrousing various kinds of aqueous solution at 37°C. The effect on prolongation of life was testedin vivoagainst p‐388lymphocytic leukemiain female CDF1mice by intraperitoneal (i.p.) i.p. injection. These poly(α‐malic acid) 5FU conjugates gave a high survival rate and did not display acute toxicity in the high dose ra

ISSN:0007-1641    

DOI:10.1002/pi.4980230308

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn this study liposomes composed of only dicetylphosphate (DCP), or of a 7:2: 1 (mole ratio) mixture of phosphatidylcholine (PC), dicetylphosphate (DCP) and cholesterol (Chol.( were prepared. Resultant liposomes were coated with varying amounts of poly(1,4‐pyridinium diethylene salt(, P1,4VN. The polymer was shown to be different from poly(4‐vinylpyridine(, P4VN, which is also obtained from the same monomer. The increase in the coating extent (or thickness( was shown by IR and UV through the increase in the peaks due to polymer. The strength of binding was indirectly shown by being able to obtain scanning electron micrographs for the coated liposomes while it was not possible for the uncoated ones. It was shown that the lipid membrane under the polymeric coat can be removed. The resultant structure is highly permeable in comparison to the impermeable, lipid‐containing form. The activity of the enzyme glucose oxidase was demonstrated using the enzyme encapsulated in the polymeri

ISSN:0007-1641    

DOI:10.1002/pi.4980230309

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe ring‐opening polymerization ofD, L‐dilactide and an equimolar dilactide‐diglycolide mixture has been investigated. Conversion and molecular weight in the lactide bulk polymerization are determined not only by the kinetics of the primary ring‐opening reaction, but also by the concentration and extent of consecutive reactions of reactive groups in the polyester formed. High conversions and high molecular weights are obtained only by high polymerization rates. For the characterization of the polymers, viscosity‐molecular weight relationships for monomer‐containing ‘equilibrium’ polymers and reprecipitated polymers were determined. The application of these polymers in parenteral drug delivery systems for a gonadotropin‐releasing hormone agonist has

ISSN:0007-1641    

DOI:10.1002/pi.4980230310

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe kinetics of the controlled release of biocides from simple model systems have been studied. Crosslinked dextran, modified crosslinked dextran and ion‐exchange resin (Wofatit) were used as carriers. Salicylic acid, 2,4,5‐trichlorophenol, 8‐hydroxyquinoline and codeine were used as biocides. Some systems were coated with poly(vinyl acetate), acetylchitin or a copolymer of methyl methacrylate with dimethylaminoethyl methacrylate. An exponential equation was proposed for the description of the release kinetics and checked experimentally. Good correlation with the equation was

ISSN:0007-1641    

DOI:10.1002/pi.4980230311

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY